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Bortezomib (VELCADE) could sensitize certain human renal cell carcinoma (RCC) lines to the apoptotic effects of tumor necrosis factor–related apoptosis-inducing ligand (TRAIL). Analysis of seven human RCC showed a clear increase in the sensitivity of four of the RCC to TRAIL cytotoxicity following bortezomib (5-20 nmol/L) treatment, whereas the remaining three remained resistant. Tumor cell death following sensitization had all the features of apoptosis. The enhanced antitumor activity of the bortezomib and TRAIL combination was confirmed in long-term (6 days) cancer cell outgrowth assays. The extent of proteasome inhibition by bortezomib in the various RCC was equivalent. Following bortezomib treatment, neither changes in the intracellular protein levels of various Bcl-2 and IAP family members, nor minor changes in expression of TRAIL receptors (DR4, DR5), correlated well with the sensitization or resistance of RCC to TRAIL-mediated apoptosis. However, enhanced procaspase-8 activation following bortezomib pretreatment and subsequent TRAIL exposure was only observed in the sensitized RCC in both cell extracts and death-inducing signaling complex immunoprecipitates. These data suggest that the molecular basis for bortezomib sensitization of RCC to TRAIL primarily involves early amplification of caspase-8 activity. In the absence of this increased caspase-8 activation, other bortezomib-induced changes are not sufficient to sensitize RCC to TRAIL-mediated apoptosis. Mol Cancer Res; 8(5); 729–38. ©2010 AACR.

Supplementary Data from Bortezomib Sensitizes Human Renal Cell Carcinomas to TRAIL Apoptosis through Increased Activation of Caspase-8 in the Death-Inducing Signaling Complex

Screening for sensitizers of cancer cells to TRAIL-mediated apoptosis identified a natural product of the 17β-hydroxywithanolide (17-BHW) class, physachenolide C (PCC), as a promising hit. In this study, we show that PCC was also able to sensitize melanoma and renal carcinoma cells to apoptosis in response not only to TRAIL, but also to the synthetic polynucleotide poly I:C, a viral mimetic and immune activator, by reducing levels of antiapoptotic proteins cFLIP and Livin. Both death receptor and TLR3 signaling elicited subsequent increased assembly of a proapoptotic ripoptosome signaling complex. Administration of a combination of PCC and poly I:C in human M14 melanoma xenograft and a syngeneic B16 melanoma model provided significant therapeutic benefit as compared with individual agents. In addition, PCC enhanced melanoma cell death in response to activated human T cells in vitro and in vivo in a death ligand–dependent manner. Biochemical mechanism-of-action studies established bromo and extraterminal domain (BET) proteins as major cellular targets of PCC. Thus, by targeting of BET proteins to reduce antiapoptotic proteins and enhance caspase-8–dependent apoptosis of cancer cells, PCC represents a unique agent that can potentially be used in combination with various immunotherapeutic approaches to promote tumor regression and improve outcome.Significance:These findings demonstrate that PCC selectively sensitizes cancer cells to immune-mediated cell death, potentially improving the efficacy of cancer immunotherapies.

Supplementary Materials & Methods, Supplementary Figures 1-10 with Figure Legends

Cancer immunotherapy shows great promise but many patients fail to show objective responses, including in cancers that can respond well, such as melanoma and renal adenocarcinoma. The proteasome inhibitor bortezomib sensitizes solid tumors to apoptosis in response to TNF-family death ligands. Because T cells provide multiple death ligands at the tumor site, we investigated the effects of bortezomib on T-cell responses in immunotherapy models involving low-avidity antigens. Bortezomib did not affect lymphocyte or tissue-resident CD11c+CD8+ dendritic cell counts in tumor-bearing mice, did not inhibit dendritic cell expression of costimulatory molecules, and did not decrease MHC class I/II-associated antigen presentation to cognate T cells. Rather, bortezomib activated NF-κB p65 in CD8+ T cells, stabilizing expression of T-cell receptor CD3ζ and IL2 receptor-α, while maintaining IFNγ secretion to improve FasL-mediated tumor lysis. Notably, bortezomib increased tumor cell surface expression of Fas in mice as well as human melanoma tissue from a responsive patient. In renal tumor-bearing immunodeficient Rag2−/− mice, bortezomib treatment after adoptive T-cell immunotherapy reduced lung metastases and enhanced host survival. Our findings highlight the potential of proteasome inhibitors to enhance antitumor T-cell function in the context of cancer immunotherapy. Cancer Res; 75(24); 5260–72. ©2015 AACR.

Supplementary Figure 5 from Antigen Presented by Tumors In vivo Determines the Nature of CD8+ T-Cell Cytotoxicity

Supplementary Figure 3 from Antigen Presented by Tumors In vivo Determines the Nature of CD8+ T-Cell Cytotoxicity

Supplementary Figure 2 from Antigen Presented by Tumors In vivo Determines the Nature of CD8+ T-Cell Cytotoxicity

Supplementary Figure 6 from Antigen Presented by Tumors In vivo Determines the Nature of CD8+ T-Cell Cytotoxicity

Calreticulin expression on bortezomib-treated tumor cells.

Legends for Supplementary Figures S1-S3.

Supplementary Figure 1 from Antigen Presented by Tumors In vivo Determines the Nature of CD8+ T-Cell Cytotoxicity

Supplementary Figure 4 from Antigen Presented by Tumors In vivo Determines the Nature of CD8+ T-Cell Cytotoxicity

Physachenolide C (1) is a 17β-hydroxywithanolide natural product with a unique anticancer potential, as it exhibits potent and selective in vitro antiproliferative activity against prostate cancer (PC) cells and promotes TRAIL-induced apoptosis of renal carcinoma (RC) and poly I:C-induced apoptosis of melanoma cells. To explore the effect of ring A/B modifications of physachenolide C (1) on these biological activities, 23 of its natural and semisynthetic analogues were evaluated. Analogues 4-23 were prepared by chemical transformations of a readily accessible compound, physachenolide D (2). Compound 1 and its analogues 2-23 were evaluated for their antiproliferative activity against PC (LNCaP and 22Rv1), RC (ACHN), and melanoma (M14 and SK-MEL-28) cell lines and normal human foreskin fibroblast (HFF) cells. Most of the active analogues had selective and potent activity in reducing cell number for PC cell lines, some showing selectivity for androgen-independent and enzalutamide-resistant 22Rv1 cells compared to androgen-dependent LNCaP cells. Analogues with IC50s below 5.0 μM against ACHN cells, when tested in the presence of TRAIL, showed a significantly increased ability to reduce cell number, and those analogues active against the M14 and SK-MEL-28 cell lines exhibited enhanced activity when combined with poly I:C. These data provide additional structure-activity relationship information for 17β-hydroxywithanolides and suggest that selective activities of some analogues may be exploited to develop natural products-based tumor-specific agents for cancer chemotherapy.

Screening for sensitizers of cancer cells to TRAIL-mediated apoptosis identified a natural product of the 17β-hydroxywithanolide (17-BHW) class, physachenolide C (PCC), as a promising hit. In this study, we show that PCC was also able to sensitize melanoma and renal carcinoma cells to apoptosis in response not only to TRAIL, but also to the synthetic polynucleotide poly I:C, a viral mimetic and immune activator, by reducing levels of antiapoptotic proteins cFLIP and Livin. Both death receptor and TLR3 signaling elicited subsequent increased assembly of a proapoptotic ripoptosome signaling complex. Administration of a combination of PCC and poly I:C in human M14 melanoma xenograft and a syngeneic B16 melanoma model provided significant therapeutic benefit as compared with individual agents. In addition, PCC enhanced melanoma cell death in response to activated human T cells in vitro and in vivo in a death ligand–dependent manner. Biochemical mechanism-of-action studies established bromo and extraterminal domain (BET) proteins as major cellular targets of PCC. Thus, by targeting of BET proteins to reduce antiapoptotic proteins and enhance caspase-8–dependent apoptosis of cancer cells, PCC represents a unique agent that can potentially be used in combination with various immunotherapeutic approaches to promote tumor regression and improve outcome. Significance: These findings demonstrate that PCC selectively sensitizes cancer cells to immune-mediated cell death, potentially improving the efficacy of cancer immunotherapies.

Eleven withanolides including six previously undescribed compounds, 16β-hydroxyixocarpanolide, 24,25-dihydroexodeconolide C, 16,17-dehydro-24-epi-dioscorolide A, 17-epi-philadelphicalactone A, 16-deoxyphiladelphicalactone C, and 4-deoxyixocarpalactone A were isolated from aeroponically grown Physalis philadelphica. Structures of these withanolides were elucidated by the analysis of their spectroscopic (HRMS, 1D and 2D NMR, ECD) data and comparison with published data for related withanolides. Cytotoxic activity of all isolated compounds was evaluated against a panel of five human tumor cell lines (LNCaP, ACHN, UO-31, M14 and SK-MEL-28), and normal (HFF) cells. Of these, 17-epi-philadelphicalactone A, withaphysacarpin, philadelphicalactone C, and ixocarpalactone A exhibited cytotoxicity against ACHN, UO-31, M14 and SK-MEL-28, but showed no toxicity to HFF cells.

Investigation of aeroponically grown Physalis peruviana resulted in the isolation of 11 new withanolides, including perulactones I-L (1-4), 17-deoxy-23β-hydroxywithanolide E (5), 23β-hydroxywithanolide E (6), 4-deoxyphyperunolide A (7), 7β-hydroxywithanolide F (8), 7β-hydroxy-17-epi-withanolide K (9), 24,25-dihydro-23β,28-dihydroxywithanolide G (10), and 24,25-dihydrowithanolide E (11), together with 14 known withanolides (12-25). The structures of 1-11 were elucidated by the analysis of their spectroscopic data, and 12-25 were identified by comparison of their spectroscopic data with those reported. All withanolides were evaluated for their cytotoxic activity against a panel of tumor cell lines including LNCaP (androgen-sensitive human prostate adenocarcinoma), 22Rv1 (androgen-resistant human prostate adenocarcinoma), ACHN (human renal adenocarcinoma), M14 (human melanoma), SK-MEL-28 (human melanoma), and normal human foreskin fibroblast cells. Of these, the 17β-hydroxywithanolides (17-BHWs) 6, 8, 9, 11-13, 15, and 19-22 showed selective cytotoxic activity against the two prostate cancer cell lines LNCaP and 22Rv1, whereas 13 and 20 exhibited selective toxicity for the ACHN renal carcinoma cell line. These cytotoxicity data provide additional structure-activity relationship information for the 17-BHWs.

Renal cell carcinoma (RCC) is a cancer with poor prognosis, and the 5-year survival rate of patients with metastatic RCC is 5-10%. Consequently, treatment of metastatic RCC represents an unmet clinical need. Screening of a 50 000-member library of natural and synthetic compounds for sensitizers of RCC cells to TRAIL-mediated apoptosis led to identification of the 17β-hydroxywithanolide (17-BHW), withanolide E (1), as a promising lead. To explore structure-activity relationships, we obtained natural and semisynthetic withanolides 1, 2a, 2c, and 3-36 and compared their ability to sensitize TRAIL-mediated apoptosis in a panel of renal carcinoma cells. Our findings revealed that 17-BHWs with a α-oriented side chain are superior to known TRAIL-sensitizing withanolides belonging to withaferin A class with a β-oriented side chain and demonstrated that the 17-BHW scaffold can be modified to enhance sensitization of RCCs to TRAIL-mediated apoptosis, thereby assisting development of natural-product-inspired drugs to treat metastatic RCC.

O1 IL-15 primes an mTOR-regulated gene-expression program to prolong anti-tumor capacity of human natural killer cells #### Andreas Lundqvist1, Vincent van Hoef1, Xiaonan Zhang1, Erik Wennerberg2, Julie Lorent1, Kristina Witt1, Laia Masvidal Sanz1, Shuo Liang1, Shannon Murray3, Ola Larsson1

Cancer immunotherapy shows great promise but many patients fail to show objective responses, including in cancers that can respond well, such as melanoma and renal adenocarcinoma. The proteasome inhibitor bortezomib sensitizes solid tumors to apoptosis in response to TNF-family death ligands. Because T cells provide multiple death ligands at the tumor site, we investigated the effects of bortezomib on T-cell responses in immunotherapy models involving low-avidity antigens. Bortezomib did not affect lymphocyte or tissue-resident CD11c+CD8+ dendritic cell counts in tumor-bearing mice, did not inhibit dendritic cell expression of costimulatory molecules, and did not decrease MHC class I/II-associated antigen presentation to cognate T cells. Rather, bortezomib activated NF-κB p65 in CD8+ T cells, stabilizing expression of T-cell receptor CD3ζ and IL2 receptor-α, while maintaining IFNγ secretion to improve FasL-mediated tumor lysis. Notably, bortezomib increased tumor cell surface expression of Fas in mice as well as human melanoma tissue from a responsive patient. In renal tumor-bearing immunodeficient Rag2−/− mice, bortezomib treatment after adoptive T-cell immunotherapy reduced lung metastases and enhanced host survival. Our findings highlight the potential of proteasome inhibitors to enhance antitumor T-cell function in the context of cancer immunotherapy. Cancer Res; 75(24); 5260–72. ©2015 AACR.

Cucurbitacins B and D were among the compounds identified as sensitizers of cancer cells to TRAIL-mediated apoptosis in a high-throughput screen. Therefore a series of cucurbitacins was further investigated for TRAIL sensitization and possible mechanisms of action. A total of six cucurbitacins promoted TRAIL-induced apoptosis (B, I, E, C, D, and K) and one (P) was inactive. Sensitization of renal adenocarcinoma cells to TRAIL was apparent after as little as 1–4 h pretreatment and did not require continued presence of cucurbitacin. Active cucurbitacins induced caspase-8 activation only after subsequent TRAIL addition and caspase activation was required for apoptosis suggesting amplified proximal signaling from TRAIL death receptors. Cucurbitacin-sensitized TRAIL-induced cytotoxicity was inhibited by N-acetyl cysteine. Structure–activity relationship analysis in comparison to published studies suggests that TRAIL-sensitizing and general cytotoxic activities of cucurbitacins may be decoupled. Cucurbitacins are reported to be inhibitors of STAT3 activation. However, their TRAIL-sensitizing activity is STAT3-independent. Treatment of renal carcinoma cells with active cucurbitacins produced rapid and dramatic changes in cell morphology and cytoskeletal organization (also prevented by NAC). Therefore, cucurbitacins may be useful as tools for investigating the molecular mechanism(s) of action of TRAIL sensitizers, particularly with regard to temporal aspects of sensitization and modulation of TRAIL signaling by cell morphology, and could form the basis for future therapeutic development in combination with TRAIL death receptor agonists.

Bortezomib (VELCADE) could sensitize certain human renal cell carcinoma (RCC) lines to the apoptotic effects of tumor necrosis factor–related apoptosis-inducing ligand (TRAIL). Analysis of seven human RCC showed a clear increase in the sensitivity of four of the RCC to TRAIL cytotoxicity following bortezomib (5-20 nmol/L) treatment, whereas the remaining three remained resistant. Tumor cell death following sensitization had all the features of apoptosis. The enhanced antitumor activity of the bortezomib and TRAIL combination was confirmed in long-term (6 days) cancer cell outgrowth assays. The extent of proteasome inhibition by bortezomib in the various RCC was equivalent. Following bortezomib treatment, neither changes in the intracellular protein levels of various Bcl-2 and IAP family members, nor minor changes in expression of TRAIL receptors (DR4, DR5), correlated well with the sensitization or resistance of RCC to TRAIL-mediated apoptosis. However, enhanced procaspase-8 activation following bortezomib pretreatment and subsequent TRAIL exposure was only observed in the sensitized RCC in both cell extracts and death-inducing signaling complex immunoprecipitates. These data suggest that the molecular basis for bortezomib sensitization of RCC to TRAIL primarily involves early amplification of caspase-8 activity. In the absence of this increased caspase-8 activation, other bortezomib-induced changes are not sufficient to sensitize RCC to TRAIL-mediated apoptosis. Mol Cancer Res; 8(5); 729–38. ©2010 AACR.

IL-27 exerts antitumor activity in murine orthotopic neuroblastoma, but only partial antitumor effect in disseminated disease. This study demonstrates that combined treatment with IL-2 and IL-27 induces potent antitumor activity in disseminated neuroblastoma metastasis. Complete durable tumor regression was achieved in 90% of mice bearing metastatic TBJ-IL-27 tumors treated with IL-2 compared with only 40% of mice bearing TBJ-IL-27 tumors alone and 0% of mice bearing TBJ-FLAG tumors with or without IL-2 treatment. Comparable antitumor effects were achieved by IL-27 protein produced upon hydrodynamic IL-27 plasmid DNA delivery when combined with IL-2. Although delivery of IL-27 alone, or in combination with IL-2, mediated pronounced regression of neuroblastoma metastases in the liver, combined delivery of IL-27 and IL-2 was far more effective than IL-27 alone against bone marrow metastases. Combined exposure to IL-27 produced by tumor and IL-2 synergistically enhances the generation of tumor-specific CTL reactivity. Potentiation of CTL reactivity by IL-27 occurs via mechanisms that appear to be engaged during both the initial sensitization and effector phase. Potent immunologic memory responses are generated in mice cured of their disseminated disease by combined delivery of IL-27 and IL-2, and depletion of CD8+ ablates the antitumor efficacy of this combination. Moreover, IL-27 delivery can inhibit the expansion of CD4+CD25+Foxp3+ regulatory and IL-17-expressing CD4+ cells that are otherwise observed among tumor-infiltrating lymphocytes from mice treated with IL-2. These studies demonstrate that IL-27 and IL-2 synergistically induce complete tumor regression and long-term survival in mice bearing widely metastatic neuroblastoma tumors.

We have developed a high-throughput screen (HTS) to search for novel molecules that can synergize with TRAIL, thus promoting apoptosis of ACHN renal tumor cells in a combinatorial fashion. The HTS detects synthetic compounds and pure natural products that can pre-sensitize the cancer cells to TRAIL-mediated apoptosis, yet have limited toxicity on their own. We have taken into account the individual effects of the single agents, versus the combination, and have identified hits that are synergistic, synergistic-toxic, or additive when combined with TRAIL in promoting tumor cell death. Preliminary mechanistic studies indicate that a subset of the synergistic TRAIL sensitizers act very rapidly to promote cleavage and activation of caspase-8 following TRAIL binding. Caspase-8 is an apical enzyme that initiates programmed cell death via the extrinsic apoptotic pathway. Thus, these TRAIL sensitizers may potentially reduce resistance of tumor cells to TRAIL-mediated apoptosis. Two representative sensitizers were found to increase levels of p53 but did not inhibit the proteasome, suggesting that early DNA damage-sensing pathways may be involved in their mechanisms of action.

We have previously reported that withanolide E (WE), a steroidal lactone from Physalis peruviana, was highly active in sensitizing various human carcinoma cell lines to TRAIL-mediated apoptosis. Therefore, over 100 natural and semi-synthetic withanolides were evaluated for their ability to promote caspase-8-dependent cancer cell death. Our studies identified several withanolides that were 4-8 fold more potent than WE in sensitizing the renal carcinoma cells and melanoma cells to caspase-8-dependent apoptosis in response to either TRAIL or the TLR3 ligand poly (I:C). All active withanolides were 17-beta-hydroxywithanolides (17-BHW). The highly active 17-BHWs were more efficient than withanolide E at reducing cellular levels of both cFLIPL and cFLIPS and enhancing caspase-8 activation. Furthermore, immunoprecipitation of the TRAIL death-inducing signaling complex (DISC), or the related ripoptosome, demonstrated enhanced levels of both FADD and RIP1 in these macromolecular apoptosis signaling complexes following treatment with active 17-BHWs. The 17-BHWs used in this work were obtained by the application of an efficient method of plant biomass production involving our innovative and patented soil-less aeroponic cultivation of P. crassifolia and P. peruviana and by chemical modification of natural withanolides produced by these plants. Preliminary structure activity relationship (SAR) studies suggested that the enone moiety in ring A was essential for activity. In addition, acetoxylation at C-18, an alpha orientation of the side-chain lactone group and the double bond at C-24(25) of the lactone ring played important roles in determining the activity of 17-BHWs as apoptosis sensitizers. This suggests that the 17-BHW scaffold is amenable to optimization by a medicinal chemistry approach, which could lead to the identification of highly active natural product-based sensitizers of cancer cells to caspase-8-dependent apoptosis. The cellular molecular target(s) of active 17-BHWs are currently under further investigation. Funded by FNLCR Contract HHSN261200800001E. Citation Format: Alan D. Brooks, Ya-ming Xu, E. M. Kithsiri Wijeratne, Curtis J. Henrich, Poonam Tewary, Leslie Gunatilaka, Thomas J. Sayers. Promoting caspase-8-dependent apoptosis signaling using 17-beta-hydroxywithanolides [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2313. doi:10.1158/1538-7445.AM2017-2313

Recent studies have demonstrated a role of toll-like receptor 3 (TLR3) signaling for the initiation of apoptosis in some malignant cells. We have previously shown that, withanolide E (WE), a 17β-hydroxywithanolide (17-BHW) natural product derived from the medicinal plant Physalis peruviana was capable of sensitizing tumor cells to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-mediated apoptosis by reducing cellular levels of the anti-apoptotic protein cFLIP. Animal studies also revealed that WE sensitized human renal carcinoma cells to apoptosis at concentrations that did not promote apoptosis in normal cells. Thus we further screened a library of 30 natural and semi-synthetic 17-BHWs for their ability to promote death ligand-mediated cancer cell death. Among the 30 compounds tested, LG-02 (physachenolide C) was found to be 4-5 fold more potent than WE in sensitizing some human renal carcinoma and melanoma cells to apoptotic cell death in response not only to TRAIL but also to the synthetic polynucleotide poly (I:C), which is known to mimic anti-viral responses by activating TLR3 signaling. To date there are no withanolides known to have this dual apoptosis sensitizing activity. LG-02 and Poly (I:C) treatment resulted in increased activation of caspase-8, and apoptosis was blocked by the pan caspase inhibitor zVAD-FMK. Poly (I:C)-driven apoptosis signaling was dependent on endosomal acidification, but independent of IRF 3 and Interferon α/β signaling. Molecular studies suggested a role for changes in the anti-apoptotic proteins cFLIP, IAPs, and Livin on apoptosis signaling in LG-02 treated cells. Loss of cIAP activity is reported to promote spontaneous formation of an intracellular death-inducing protein platform the ripoptosome, that can activate either apoptosis or necroptosis. Immunoprecipitation of either the TRAIL death-inducing signaling complex (DISC) or the Poly (I:C) ripoptosome, demonstrated enhanced levels of FADD and RIP1 and decreased levels of cFLIP in these macromolecular apoptosis signaling complexes in LG-02 treated cells. Intratumor administration of LG-02 and Poly (I:C) in a xenograft M14 melanoma model provided therapeutic benefit leading to complete tumor regression in 90 % of the mice as compared to control mice. Further studies with active 17-BHWs could lead to the identification of more potent analogues, and novel and common therapeutic targets involved in apoptosis signaling in response to both TNF death receptor family members as well as TLR3 ligands.Funded by FNLCR Contract HHSN261200800001E Citation Format: Poonam Tewary, Alan D. Brooks, Ya-ming Xu, Kithsiri E.M Wijeratne, Leslie A. Gunatilaka, Thomas J. Sayers. A specific 17-beta-hydroxywithanolide (LG-02) sensitizes cancer cells to apoptosis in response to TRAIL and TLR3 ligands [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2159. doi:10.1158/1538-7445.AM2017-2159

Withanolide E, a steroidal lactone from Physalis peruviana, was found to be highly active for sensitizing renal carcinoma cells and a number of other human cancer cells to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-mediated apoptosis. Withanolide E, the most potent and least toxic of five TRAIL-sensitizing withanolides identified, enhanced death receptor-mediated apoptotic signaling by a rapid decline in the levels of cFLIP proteins. Other mechanisms by which TRAIL sensitizers have been reported to work: generation of reactive oxygen species (ROS), changes in pro-and antiapoptotic protein expression, death receptor upregulation, activation of intrinsic (mitochondrial) apoptotic pathways, ER stress, and proteasomal inhibition proved to be irrelevant to withanolide E activity. Loss of cFLIP proteins was not due to changes in expression, but rather destabilization and/or aggregation, suggesting impairment of chaperone proteins leading to degradation. Indeed, withanolide E treatment altered the stability of a number of HSP90 client proteins, but with greater apparent specificity than the well-known HSP90 inhibitor geldanamycin. As cFLIP has been reported to be an HSP90 client, this provides a potentially novel mechanism for sensitizing cells to TRAIL. Sensitization of human renal carcinoma cells to TRAIL-induced apoptosis by withanolide E and its lack of toxicity were confirmed in animal studies. Owing to its novel activity, withanolide E is a promising reagent for the analysis of mechanisms of TRAIL resistance, for understanding HSP90 function, and for further therapeutic development. In marked contrast to bortezomib, among the best currently available TRAIL sensitizers, withanolide E’s more specific mechanism of action suggests minimal toxic side effects.

The precise molecular mechanisms enabling cancer cells to metastasize from the primary tumor to different tissue locations are still largely unknown. Secretion of some proteins by metastatic cells could facilitate metastasis formation. The comparison of secreted proteins from cancer cells with different metastatic capabilities in vivo might provide insight into proteins involved in the metastatic process. Comparison of the secreted proteins from the mouse breast cancer cell line 4T1 and its highly metastatic 4T1.2 clone revealed a prominent differentially secreted protein which was identified as SLPI (secretory leukocyte protease inhibitor). Western blotting indicated higher levels of the protein in both conditioned media and whole cell lysates of 4T1.2 cells. Additionally higher levels of SLPI were also observed in 4T1.2 breast tumors in vivo following immunohistochemical staining. A comparison of SLPI mRNA levels by gene profiling using microarrays and RT-PCR did not detect major differences in SLPI gene expression between the 4T1 and 4T1.2 cells indicating that SLPI secretion is regulated at the protein level. Our results demonstrate that secretion of SLPI is drastically increased in highly metastatic cells, suggesting a possible role for SLPI in enhancing the metastatic behavior of breast cancer cell line 4T1.

Activated T cells lyse the murine renal cancer Renca. We have examined the mechanism of tumor cell lysis with the use of T cells derived from C57BL/6, BALB/c, B6.gld, and B6.Pfp-/- mice. C57BL/6 and BALB/c T cells can lyse Renca cells through the use of both granule- and Fas ligand (FasL)-mediated pathways. However, B6.gld T cells predominantly use granule-mediated killing, whereas B6.Pfp-/- T cells use FasL. The lysis of Renca by Pfp-/- T cells is only partially inhibited by the caspase inhibitor ZVAD-FMK, suggesting that caspase-independent signaling is also important for Renca cell lysis. When the reactive oxygen scavenger butylated hydroxyanisole was used alone or in combination with ZVAD-FMK a substantial reduction of Renca lysis was observed. Therefore, the caspase-independent generation of reactive oxygen intermediates in Renca after Fas triggering contributes to the lysis of these cells.

The role of Fas in the regulation of solid tumor growth was investigated. Murine renal carcinoma (Renca) cells were constitutively resistant to Fas-mediated killing in vitro, but exhibited increased expression of Fas and sensitivity to Fas-mediated killing after exposure to IFN-γ and TNF. Transfected Renca cells overexpressing Fas were efficiently killed in vitro upon exposure to anti-Fas Ab (Jo2). When Fas-overexpressing Renca cells were injected into syngenic BALB/c mice, there was a consistent and significant delay in tumor progression, reduced metastasis, and prolonged survival that was not observed for Renca cells that overexpressed a truncated nonfunctional Fas receptor. The delay of in vivo tumor growth induced by Fas overexpression was not observed in IFN-γ−/− mice, indicating that IFN-γ is required for the delay of in vivo tumor growth. However, there was a significant increase of infiltrated T cells and in vivo apoptosis in Fas-overexpressing Renca tumors, and Fas-overexpressing Renca cells were also efficiently killed in vitro by T cells. In addition, a strong therapeutic effect was observed on Fas-overexpressing tumor cells by in vivo administration of anti-Fas Ab, confirming that overexpressed Fas provides a functional target in vivo for Fas-specific ligands. Therefore, our findings demonstrate that Fas overexpression on solid tumor cells can delay tumor growth and provides a rationale for therapeutic manipulation of Fas expression as a means of inducing tumor regression in vivo.

Mice bearing the experimental murine renal cancer Renca can be successfully treated with some forms of immunotherapy. In the present study, we have investigated the molecular pathways used by NK and T cells to lyse Renca cells. Renca cells normally express low levels of Fas that can be substantially enhanced by either IFN-γ or TNF-α, and the combination of IFN-γ + TNF-α synergistically enhances cell-surface Fas expression. In addition, cells pretreated with IFN-γ and TNF-α are sensitive to lysis mediated by Fas ligand (FasL)-expressing hybridomas (dllS), cross-linking of anti-Fas Abs or soluble Fas (FasL). Lysis via Fas occurs by apoptosis, since Renca shows all the typical characteristics of apoptosis. No changes in levels of bcl-2 were observed after cytokine treatments. We also examined cell-mediated cytotoxic effects using activated NK cells and T cells from gld FasL-deficient mice, and perforin-deficient mice, as well as wild-type C57BL/6 and BALB/c mice. Interestingly, the granule-mediated pathway predominated in killing of Renca by activated NK cells, while the Fas/FasL pathway contributed significantly to cell-mediated killing of Renca by activated T cells. These results suggest that killing of Renca tumor cells by immune effector cells can occur by both granule and Fas-mediated cytotoxicity. However, for the Fas-mediated pathway to function, cell surface levels of Fas need to be increased beyond a critical threshold level by proinflammatory cytokines such as IFN-γ and TNF-α.

We have previously reported that withanolide E (WE), a steroidal lactone from Physalis peruviana, was highly active in sensitizing various human carcinoma cell lines to TRAIL-mediated apoptosis. Treatment of cancer cells with WE induced a reduction in the levels of the antiapoptotic proteins cFLIPL and cFLIPS, resulting in an increased activation of caspase-8 on subsequent TRAIL binding to its death receptors DR4 or DR5. The reduction in cFLIPL and cFLIPS was due to their destabilization and increased degradation by the proteasome. Interestingly, WE (a 17-beta-hydoxywithanolide, 17-BHW) was a far superior TRAIL sensitizer than more widely studied withaferin A (WFA) and its analogues, which lack the 17-beta-hydroxy group and bear an opposite side chain orientation, exhibit more promiscuous reactivity and are much more directly toxic to cells. Therefore, over 30 natural and semi-synthetic 17-BHWs were evaluated for their ability to promote death ligand-mediated cancer cell death. The 17-BHWs used in this work were obtained by the application of an efficient method of plant biomass production involving our innovative and patented soil-less aeroponic cultivation of P. crassifolia and P. peruviana and by chemical modification of natural withanolides produced by these plants. Our studies identified several 17-BHWs that were 4-8 fold more potent than WE in sensitizing the renal carcinoma cells ACHN to TRAIL-mediated apoptosis. These more active 17-BHWs were also more efficient at reducing cellular levels of cFLIPL and cFLIPS and enhancing caspase-8 activation. Preliminary structure activity relationship (SAR) studies suggested that the enone moiety in ring A was essential for activity. In addition acetoxylation at C-18, an alpha orientation of the lactone group and the double bond at C-24(25) of the lactone ring played important roles in determining the activity of 17-BHWs as TRAIL sensitizers. This suggests that the 17-BHW scaffold is amenable to optimization by a medicinal chemistry approach, which could lead to the identification of highly active natural product-based sensitizers of cancer cells to TRAIL-mediated apoptosis. The cellular molecular target(s) of active 17-BHWs are currently under further investigation. Funded by FNLCR Contract HHSN261200800001E Citation Format: Alan D. Brooks, Ya-ming Xu, E. M. Kithsiri Wijeratne, Poonam Tewary, Curtis J. Henrich, Cheryl L. Thomas, A. A. Leslie Gunatilaka, Thomas J. Sayers. Promoting TRAIL apoptosis signaling using 17-beta-hydroxywithanolides. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3513.

Indoleamine 2,3-dioxygenase (IDO), a flavin-dependent enzyme that catalyzes the conversion of tryptophan to kynurenine, is induced in peripheral blood mononuclear cells by interferon-gamma (IFN gamma). Interleukin-4 (IL-4) is a cytokine that modulates the functional properties of monocytes/macrophages, and we investigated the effects of IL-4 on IDO. We showed that IL-4 inhibited the induction of IDO mRNA and IDO activity by IFN gamma in human monocytes. The inhibitory effect was evident with as little as 2 U/mL of IL-4. These results provide the first evidence that a cytokine can provide a negative signal for IDO expression and that IL-4 can influence the catabolism of tryptophan.

The biological relevance of the perforin and Fas ligand (FasL) cytolytic pathways of CD8+ T lymphocytes (CTL) for cancer immunotherapy is controversial. We investigated the importance of these pathways in a murine renal cell carcinoma expressing influenza viral hemagglutinin as a defined surrogate antigen (Renca-HA). Following Renca-HA injection, all FasL-dysfunctional FasLgld/gld mice (n = 54) died from Renca-HA tumors by day 62. By contrast, perforin−/− (51%; n = 45) and Faslpr/lpr (55%; n = 51) mice remained tumor-free at day 360. Blocking FasL in vivo inhibited tumor rejection in these mice. Moreover, established Renca-HA tumors were cleared more efficiently by adoptively transferred HA518-526–specific T-cell receptor–transgenic CTL using FasL rather than perforin. Strikingly, a range of mouse tumor cells presenting low concentrations of immunogenic peptide were all preferentially lysed by the FasL but not the Pfp-mediated effector pathway of CTL, whereas at higher peptide concentrations, the preference in effector pathway usage by CTL was lost. Interestingly, a number of human renal cancer lines were also susceptible to FasL-mediated cytotoxicity. Therefore, the FasL cytolytic pathway may be particularly important for eradicating Fas-sensitive tumors presenting low levels of MHC class I–associated antigens following adoptive T-cell therapy. [Cancer Res 2009;69(16):6615–23]

Hypoxia Inducible Factor-1 (HIF-1) is activated by a variety of stimuli, including inflammatory mediators. In this report we investigated the role that bacterial lipopolysaccharide (LPS) and hypoxia play in the regulation of HIF-1-dependent gene expression in macrophages. We report that murine macrophages stimulated with low concentrations of LPS (1-10 ng/ml) expressed significantly higher levels of inducible nitric oxide synthase (iNOS) mRNA when cultured under hypoxic compared to normoxic conditions. Functional studies of the iNOS promoter demonstrated that the synergistic interaction between LPS and hypoxia was mediated, at least in part, by the NFkappaB and the HIF-1 binding sites. In addition, transient transfection experiments using a Hypoxia Response Element (HRE)-containing plasmid showed that LPS and hypoxia synergistically induced HIF-1-dependent transcriptional activity. Interestingly, LPS did not significantly affect HIF-1alpha protein levels or HIF-1 DNA binding activity relative to hypoxic induction. HIF-1alpha, but not HIF-2alpha, was critical for the synergistic induction of HRE-dependent transcriptional activity in macrophages, as indicated by experiments using siRNA targeting HIF-1alpha or HIF-2alpha. Addition of ROS-scavengers completely abrogated the synergistic induction of HIF-1 transcriptional activity by LPS and hypoxia, but neither inhibited HIF-1 transcriptional activity induced by hypoxia alone nor affected HIF-1alpha protein levels or HIF-1 DNA binding induced by hypoxia alone or hypoxia plus LPS. Taken together, our results demonstrate that LPS and hypoxia act synergistically to induce HIF-1alpha-transcriptional activity and they emphasize the existence of a cross talk between hypoxic and non-hypoxic signaling pathways in the regulation of macrophages gene expression.

The ability of Erwinia chrysanthemi to cause soft-rot diseases involving tissue maceration in many plants has been linked to the production of endo-pectate lyase E. chrysanthemi EC16 mutant UM1005, however, contains deletions in the pel genes that encode the known endopectate lyases, yet still macerates plant tissues. In an attempt to identify the remaining macerating factor(s), a gene library of UM1005 was constructed in Escherichia coli and screened for pectolytic activity. A clone (pPNL5) was identified in this library that contained the structural gene for an exopolygalacturonate lyase (ExoPL). The gene for ExoPL was localized on a 3.3-kb EcoRV fragment which contained an open reading frame for a 79,500-Da polypeptide. ExoPL was purified to apparent homogeneity from Escherichia coli DH5 alpha (pPNL5) and found to have an apparent molecular weight of 76,000 with an isoelectric point of 8.6. Purified ExoPL had optimal activity between pH 7.5 and 8.0 and could utilize pectate, citrus pectin, and highly methyl-esterified Link pectin as substrates. A PL- ExoPL- mutant of EC16 was constructed that exhibited reduced growth on pectate, but retained pathogenicity on chrysanthemum equivalent to that of UM1005. The results indicate that ExoPL does not contribute to the residual macerating activity of UM1005.

The NKG2D receptor on NK cells can recognize a variety of ligands on the tumor cell surface. Using a mouse renal cancer (Renca), we show that NKG2D recognition by NK cells was crucial for their ability to limit tumor metastases in vivo in both liver and lungs using perforin-dependent effector mechanisms. However, for the R331 cell line established from Renca, NKG2D recognition and perforin-dependent lysis played no role in controlling liver metastases. R331 cells were also more resistant to perforin-dependent lysis by NK cells in vitro. We therefore used these phenotypic differences between Renca and R331 to further investigate the crucial receptor:ligand interactions required for triggering lytic effector functions of NK cells. Reconstitution of R331 cells with ICAM-1, but not Rae-1γ, restored NKG2D-mediated, perforin-dependent lysis. Interestingly, R331 cells were efficiently lysed by NK cells using death ligand-mediated apoptosis. This death ligand-mediated killing did not depend on NKG2D recognition of its ligands on tumor cells. This result suggests that the intracellular signaling in NK cells required for perforin and death ligand-mediated lysis of tumor target cell are quite distinct, and activation of both of these antitumor lytic effector functions of NK cells could improve therapeutic benefits for certain tumors.

On testing a panel of different human cancer cell lines, we observed that the proteasome inhibitor bortezomib could dramatically sensitize some lines to the apoptotic effects of Apo2L/TRAIL. Certain renal, colon, or breast tumor cell lines were dramatically sensitized, whereas other tumor lines from the same tissue of origin remained resistant. This sensitization did not correlate with either the p53 status of the individual tumor cell lines or their intrinsic sensitivity to Apo2L/TRAIL. Colon cancer cell lines lacking p53 or Bax were sensitized by bortezomib, suggesting that neither p53 nor Bax levels were crucial for sensitization. Although the molecular basis of bortezomib sensitization of tumor cells to Apo2L/TRAIL remains to be determined, this combination can have an enhanced apoptotic effect over either agent alone for certain human cancer cells.

Human renal carcinoma cells (RCCs) were sensitized to the apoptotic effects of tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL), by treatment with cycloheximide (CHX). In contrast to a previous study, a rapid and dramatic decrease in levels of cellular FLICE (Fas-associated death domain-like IL-1beta-converting enzyme) inhibitory protein (cFLIP) following cycloheximide treatment was observed in all RCCs studied. The unambiguous detection of this decrease in cFLIP was dependent on the quality of the particular antibody preparation used to detect cFLIP. Cycloheximide treatment caused no major change in levels of pro-caspase-8 or cell surface expression of TRAIL receptors. Therefore, cycloheximide treatment resulted in an increase in the pro-caspase-8 to cFLIP ratio, which correlated with sensitization to TRAIL-mediated apoptosis. Furthermore, treatment of human RCCs with small interfering oligoribonucleotides (siRNA) for cFLIP caused a reduction of cFLIP protein and sensitized cells to TRAIL-mediated apoptosis. We concluded that in the presence of an intact TRAIL signaling pathway, a significant reduction of cFLIP alone is sufficient to sensitize human RCCs to TRAIL apoptosis.

Because of the pivotal role the proteasome plays in apoptosis, inhibitors of this enzyme, such as PS-341, provide a great opportunity for exploring synergy between proteasome inhibition and other apoptosis-inducing agents. Tumor necrosis factor—related apoptosis-inducing ligand (TRAIL) can selectively induce apoptosis in tumor cells. In overnight assays, combinations of PS-341 and TRAIL were much more effective than either agent alone in promoting apoptosis of a murine myeloid leukemia, C1498, and a murine renal cancer, Renca. For C1498 cells, apoptosis sensitization by PS-341 affected neither the activity of nuclear factor κB (NF-κB) nor the levels of most antiapoptotic proteins. However, reductions in the antiapoptotic protein c-FLIP in response to PS-341 were observed in both C1498 and Renca cells. Treatment of normal bone marrow mixed with C1498 tumor cells for 18 hours with a combination of PS-341 and TRAIL resulted in a specific depletion of the tumor cells. Upon transfer to irradiated syngeneic recipient mice, mixtures treated with the PS-341 plus TRAIL combination resulted in enhanced long-term tumor-free survival of mice. These data therefore support the targeting of apoptotic pathways in tumor cells, using combinations of agents such as PS-341 and TRAIL that interact synergistically to preferentially promote tumor cell apoptosis. (Blood. 2003;102:303-310)

Recent reports have suggested that the death ligand tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) may partially limit the formation of hepatic metastases of a variety of mouse tumors, and the major source of TRAIL in the liver was shown to be local natural killer cells. We isolated a clone (R331) of the murine renal cancer cell line Renca that was strikingly more sensitive to both Fas and TRAIL death receptor-mediated apoptosis in vitro. R331 grew in tissue culture in vitro at a rate similar to that of the parental Renca cell line but formed larger and more numerous colonies than parental Renca in soft agar. After s.c. implantation, R331 tumors progressed more rapidly than parental Renca tumors. However, R331 formed far fewer lung and liver metastases in wild-type (WT) BALB/c mice. Administration of antibodies that neutralized TRAIL dramatically increased the number of R331 liver metastases. Furthermore, numbers of R331 liver metastases were much greater in TRAIL(-/-) than in WT BALB/c mice. In contrast, no difference was seen in numbers of lung metastases when comparing TRAIL(-/-) and WT mice, suggesting that the antitumor effects of TRAIL in vivo were compartment specific. Transfection of cellular Fas-associated death domain-like interleukin-1beta-converting enzyme inhibitory protein into R331 increased the numbers of liver metastases in BALB/c mice by up to 10-fold, indicating that local TRAIL in the liver was directly mediating tumor cell apoptosis. These organ-specific differences in the endogenous levels of death ligands may apply different selective pressures on the development of liver or lung metastases. Consequently, the efficacy of TRAIL therapy may vary depending on the location of the tumor metastases.

Cytotoxic lymphocytes kill tumor or virus-infected target cells utilizing two mechanisms—(1) release of lytic granules (containing perforin and granzymes), and (2) Fas ligand (FasL)/Fas or TNF-initiated apoptosis. We have examined mechanisms of target cell lysis by effector T cells from gene-targeted and mutant mice using a new Flow Cytometric Cytotoxicity Assay (FC Assay). Target cells were labeled with PKH67 dye. Cell death was estimated by 7-AAD inclusion and annexin V-PE binding. A direct correlation has been found between the percentage of dead target cells in FC Assay and the results of 111 In release cytotoxicity assay when effector T cells from either Pfp −/− (perforin knockout) or gld (non-functional Fas Ligand) mice were used. As shown by the 4 h FC assay, the granule-mediated mechanism was utilized by T cells from gld mice. In contrast, T cells from Pfp −/− mice used death receptor-mediated lysis. Therefore, cytotoxic cells from gene-targeted and mutant mice can serve as valuable tools for studying different mechanisms of cell-mediated cytotoxicity, and the FC assay could be applied irrespective of which cytotoxic effector pathway is involved.

Kidney cancer is a devastating disease; however, biological therapies have achieved some limited success. The murine renal cancer Renca has been used as a model for developing new preclinical approaches to the treatment of renal cell carcinoma. Successful cytokine-based approaches require CD8+ T cells, but the exact mechanisms by which T cells mediate therapeutic benefit have not been completely identified. After successful biological therapy of Renca in BALB/c mice, we generated CTLs in vitro using mixed lymphocyte tumor cultures. These CTL mediated tumor-specific H-2Kd-restricted lysis and production of IFN-γ, TNF-α, and Fas ligand (FasL) in response to Renca. CTL used both granule- and FasL-mediated mechanisms to lyse Renca, although granule-mediated killing was the predominant lytic mechanism in vitro. The cytokines IFN-γ and TNF-α increased the sensitivity of Renca cells to CTL lysis by both granule- and FasL-mediated death pathways. Adoptive transfer of these anti-Renca CTL into tumor-bearing mice cured most mice of established experimental pulmonary metastases, and successfully treated mice were immune to tumor rechallenge. Interestingly, we were able to establish Renca-specific CTL from mice gene targeted for perforin (pfp−/−) mice. Although these pfp−/− CTL showed reduced cytotoxic activity against Renca, their IFN-γ production in the presence of Renca targets was equivalent to that of wild-type CTL, and adoptive transfer of pfp−/− CTL was as efficient as wild-type CTL in causing regression of established Renca pulmonary metastases. Therefore, although granule-mediated killing is of paramount importance for CTL-mediated lysis in vitro, some major in vivo effector mechanisms clearly are independent of perforin.

Many tumors have been demonstrated to contain cancer stem cells (CSC). We hypothesized that expression of transcription factors that are required for induction and maintenance of pluripotency would be a possible alternative to cell surface phenotype for identification of CSC populations. Therefore we evaluated Nanog expression in 4T1.2 murine breast carcinoma cells, as a biomarker for CSC sub-populations. Introduction of a Nanog promoter reporter that drives destabilized GFP into 4T1.2 cells resulted in a stable expression of GFP in about 1-3% of the cells. On in vitro cell culture of FACS sorted GFP+ populations, up to 80% of the cells became GFP- over a period of 4 weeks, whereas GFP- populations remained 100% GFP-. In vitro CSC surrogate assays show that Nanog-GFP+ cells exhibited CSC characteristics, with enhanced colony formation in methylcellulose and increased survival in serum-free media. Nanog-GFP+ cells were also more efficient at generating experimental lung metastases following intravenous injection. In addition Nanog-GFP+ cells were also more resistant to the chemotherapeutic drugs paclitaxel and bortezomib. However targeting the extrinsic apoptosis pathway in vitro with a combination of bortezomib and agonist antibodies to the TRAIL death receptor DR5 was equally effective against both Nanog-GFP+ and Nanog-GFP- cell populations. To monitor Nanog expression in human breast cancer cells (SUM159), we used lentiviral vectors to introduce DNA constructs of the Nanog response element driving GFP and luciferase. About 0.5% of the SUM159 cells were GFP+ by FACS, and these cells also demonstrated some CSC characteristics such as enhanced colony formation in methylcellulose. Levels of GFP were increased in the SUM159 cells following cell culture under hypoxic conditions. These findings suggest that Nanog activity may be useful as surrogate marker of aggressive breast CSC subpopulations. Funded by NCI Contract HHSN261200800001E Citation Format: Thomas J. Sayers, Rachel de Kluyver, Marcella Kaddoura, Jim Stauffer, Poonam Tewary, Alan D. Brooks. Can Nanog activity identify aggressive breast cancer stem cell populations. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3876. doi:10.1158/1538-7445.AM2014-3876

Many tumors have been demonstrated to contain a subpopulation of cancer stem cells (CSC) whose epigenetic modifications convey resistance to conventional therapies. Furthermore, tumor expression of genes associated with pluripotent embryonic cells, such as Oct-4, Sox-2 and Nanog, often correlates with poor prognosis. We hypothesized that expression of transcription factors that are required for induction and maintenance of pluripotency (Oct-4, Sox-2 and Nanog) would be a possible alternative to cell surface phenotype for identification of CSC populations. Therefore we evaluated Nanog expression in 4T1.2 murine breast carcinoma cells, as a biomarker for CSC sub-populations. Introduction of a Nanog promoter reporter that drives destabilized GFP into 4T1.2 cells resulted in a stable expression of GFP in about 1% of the cells. These GFP+ cell could be easily isolated by FACS cell sorting. On subsequent in vitro cell culture of GFP+ populations, up to 80% of the cells became GFP- over a period of 4 weeks. This would be consistent with a subsequent differentiation of these cells. By contrast GFP- populations remained 100% GFP-. In vitro CSC surrogate assays show that Nanog-GFP+ cells produced more spheroids in soft agar and under non-adherent growth conditions. More importantly, in vivo cell transfer studies demonstrated that Nanog-GFP+ cells were more efficient at generating experimental lung metastases when compared to Nanog-GFP-cells. Interestingly Nanog-GFP+ cells were more resistant to the chemotherapeutic drugs paclitaxel and bortezomib. However targeting the extrinsic apoptosis pathway with a combination of bortezomib and agonist antibodies to the TRAIL death receptor DR5 was equally effective against both Nanog-GFP+ and Nanog-GFP- cells. These findings suggest that Nanog promoter activity is a robust marker of highly metastatic 4T1.2 CSC subpopulations, and suggests that eradication of such cells may be required for improved anti-cancer therapies. Funded by NCI Contract HHSN261200800001E Citation Format: Alan D. Brooks, Rachel L. de Kluyver, Jimmy K. Stauffer, Marcella Kaddoura, Thomas J. Sayers. Using Nanog expression to identify breast cancer stem cell populations. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2656. doi:10.1158/1538-7445.AM2013-2656

We have previously shown that the proteasome inhibitor bortezomib (Velcade/PS-341) specifically sensitized certain human renal carcinoma (RCC) lines to apoptosis induced by the TNF family-member TRAIL. A high-throughput screen conducted by the Molecular Targets Laboratory identified several promising new TRAIL sensitizers. One of these novel TRAIL sensitizers was the natural product withanolide E. Withanolide E, in contrast to bortezomib, had no activity as a proteasome inhibitor. Also withanolide E could sensitize some human RCC to TRAIL that were resistant to the effects of bortezomib. Furthermore sensitizing concentrations of bortezomib were also cytostatic to the RCC, whereas those of withanolide E were not. Bortezomib treatment of RCC resulted in the appearance of various proteins associated with a stress response, yet these proteins were not elevated by withanolide E treatment. By contrast the antioxidant n-acetyl cysteine completely blocked the TRAIL-sensitizing effects of withanolide E but not those of bortezomib. This suggests that changes in cellular redox are important for the sensitizing effects of withanolide E but not those of bortezomib. In order to study the molecular basis for increased TRAIL-mediated apoptosis, we investigated proximal apoptosis signaling events at the death-inducing signaling complex (DISC). Both bortezomib and withanolide E treatments resulted in an enhanced activation of the apoptosis signaling enzyme caspase-8 following exposure of the RCC to TRAIL. However, immunoprecipitation of the DISC revealed that bortezomib treatment resulted in a 4-5 fold increase in the amount of DISC formed. By contrast withanolide E treatment did not significantly alter the amount of the DISC, but reduced levels of the antiapoptotic DISC component c-FLIP. Therefore, both compounds amplified the apoptotic signal from the DISC via distinct molecular mechanisms of action. Funded in part by HHSN261200800001E Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4102. doi:10.1158/1538-7445.AM2011-4102

We have previously shown that the proteasome inhibitor bortezomib (Velcade/PS-341) specifically sensitized certain human renal carcinoma (RCC) lines to apoptosis induced by the TNF family-member TRAIL. A comparison of RCC sensitized by bortezomib with those that remained resistant revealed no major bortezomib-induced changes in the levels of many apoptosis proteins. Also, when bortezomib treatment induced specific changes in protein levels (mcl-1, Bik and survivin) these changes did not directly correlate with subsequent sensitization or resistance to TRAIL apoptosis. In addition changes in surface expression of TRAIL receptors (DR4, DR5, DcR1, DcR2) following bortezomib treatment also did not correlate well with sensitization or resistance. By contrast, enhanced procaspase 8 activation following bortezomib pretreatment and TRAIL exposure was only observed in the sensitized RCC. This increase in procaspase 8 activation in cell extracts of sensitized RCC was observed using both enzyme assays as well as western blotting for activated (cleaved) caspase 8. Use of the apoptosis-resistant MCF-7 cell line demonstrated that bortezomib pretreatment increased caspase-8 activation on exposure to TRAIL even in the absence of subsequent downstream caspase activation and apoptosis. This suggests that bortezomib increases caspase-8 activation upstream at the death-inducing signaling complex (DISC). Furthermore, immunoprecipitation of the DISC demonstrated higher levels of active caspase 8 in the DISC of sensitized but not resistant RCC. Interestingly ACHN (a bortezomib-sensitized RCC) was also sensitized to TRAIL apoptosis when adherence was prevented by coating cell culture dishes with poly-HEMA. In parallel this loss of adherence abolished the sensitizing effects of bortezomib treatment. Bortezomib and poly-HEMA treatment of RCC both result in reduced cellular proliferation, and may change cell adherence properties. Whether both of these treatments sensitize RCC to TRAIL using common or distinct molecular pathways is under further investigation. Funded in part by DHSS #NO1-CO-12400 Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1269.

Worldwide the incidence of hepatocellular carcinoma (HCC) resulting from hepatitis C infection and chronic inflammation is increasing. Poor prognosis HCC is characterized by over-expression of Ep-CAM and alpha-fetoprotein (AFP) which define a population of tumor-initiating cells with stem/progenitor features. Current evidence supports the view that cancer stem cells (CSCs) constitute the primary pathogenic component of both metastases and minimal residual disease, and that elimination of CSCs is required for cure. Typically cell surface markers have been used to identify CSCs, however cell surface phenotype alone does not identify CSC in all tumors from the same tissue or in all patients. Therefore there is a need to define and test more reliable markers of CSCs. Oct-4, Sox-2 and Nanog transcription factors are key regulatory factors in maintenance of pluripotency and have been demonstrated to be robust intracellular biomarkers for tissue and cancer stem cells. A GFP-based reporter driven by a promoter responsive to Nanog or Oct-4 was used to mark pluripotent tumor cells from in vitro cultured, cancer cell lines (breast cancer- 4T1.2), and from autochthonous hepatocellular carcinoma induced by hydrodynamics-based gene transfer of constituitively active Akt and β-Catenin. This tumorigenesis model allows tumor initiation by delivery of clinically relevant oncogenes whose sporadic distribution reflects spontaneous cancer. The molecular profile of primary Akt/β-Cat-induced murine HCC recapitulates that observed in poor prognosis Ep-CAM+/AFP+ human HCC. Further, in vitro functional analyses suggest that Ep-CAM and CD133 (surface markers) and Nanog and Oct-4 (transcription factors required for maintenance and regulation of pluripotency in undifferentiated cells) are CSC markers in this model of HCC. Directly ex vivo, murine HCC stem cells express abundant CD1d and MHC class II in addition to TNF-R2, lymphotoxin-β receptor (LTβR) and DR5. The functional significance of CD1d, MHC class II, TNF-R2, LTβR and DR5 expression will be assessed in future studies using in vitro apoptosis and cytotoxicity assays and transplantation at orthotypic sites prior to adoptive transfer of tumor-specific T cells. Studies of freshly isolated CSCs have demonstrated that a variety of mechanisms combine to render CSC resistant to conventional chemo- and radiotherapies. This study has combined in vitro and in vivo approaches to address whether CSC can be rendered sensitive to T cell-mediated apoptosis, and will provide valuable proof-of-principle data to the merits of CSCs as targets for curative anti-cancer therapies. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4251.

The resistance of tumors to cell death poses a major clinical problem. Bortezomib (Velcade/PS-341), a specific and reversible proteasome inhibitor, sensitized renal (Renca) and mammary (4T1) mouse carcinomas to apoptosis induced by the TNF family ligand TRAIL or its receptor (DR5) agonist antibody. The molecular basis of the tumoritoxicity of the combination of bortezomib and TRAIL seemingly involved amplification of the extrinsic cell death pathway as increased expression of DR5, activation of caspase-8 and -3, and decreased apoptosis inhibitory proteins cFLIP, cIAP-1 and XIAP were observed in bortezomib-treated tumors. In an established tumor setting, anti-DR5 administration to mice pre-treated with bortezomib not only reduced lung metastases of Renca and 4T1 tumors but also significantly increased long-term survival in mice bearing Renca as compared to either agent alone. Encouragingly, no evidence of any overt tissue damage was noted in the treated mice. This provides the first experimental evidence that proteasome inhibition can be combined with DR5 agonist antibody for successful cancer therapy. Moreover, bortezomib administration 24 hours prior to adoptive transfer of T cells did not block their anti-tumor effector function. This suggests that tumor sensitization with bortezomib may also be combined with tumor-specific T cell immunotherapy of cancer. Funded in part by NCI contract N01-CO-12400.