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The efficacy of antineoplastic chemotherapies with anthracyclines or oxaliplatin relies on the induction of immunogenic cell death, thus provoking an anticancer immune response. Recently, we observed that overexpression of CD39, an ATPdegrading enzyme expressed on the cell surface, abolishes the immunogenicity of cell death, thus rendering cancers resistant against chemotherapy [ABSTRACT FROM AUTHOR]

There is ample experimental and clinical evidence that chemotherapies are more efficient if they succeed in (re)activating immune surveillance, hence triggering a long-term immune response against residual tumor cells. Most of the preclinical evidence supporting this notion has been obtained with transplantable cancers, for which it has been shown that chemotherapy-induced autophagy in cancer cells is mandatory for the recruitment of myeloid cells into the tumor bed and the subsequent T lymphocyte-mediated reduction in tumor growth. Here, we characterized the chemotherapeutic response of melanomas caused by 4-hydroxy-tamoxifen-induced expression of the Cre recombinase in melanocytes that results in the activation of oncogenicBraftogether with the inactivation of the tumor suppressorPten, as well as the optional inactivation of the essential autophagy geneAtg7. Systemic chemotherapy with the anthracycline Mitoxantrone (MTX) reduced the growth of autophagy-competent melanomas (genotype:BrafCa/+; Ptenfl/fl;Atg7+/+), yet failed to affect the progression of autophagy-deficient melanomas (genotype:BrafCa/+; Ptenfl/fl; Atg7fl/fl). The growth-inhibitory effect of MTX on autophagy-competent melanomas was abolished by the combined depletion of CD4+or CD8+T lymphocytes. In conclusion, it appears that the success of chemotherapy against “spontaneous,” genetically induced cancers is governed by the same rules as those applicable to transplantable tumors. [ABSTRACT FROM PUBLISHER]

Cis-diamminedichloridoplatinum(II) (CDDP), commonly referred to as cisplatin, is a chemotherapeutic drug used for the treatment of a wide range of solid cancers. CDDP is a relatively poor inducer of immunogenic cell death (ICD), a cell death modality that converts dying cells into a tumor vaccine, stimulating an immune response against residual cancer cells that permits long-lasting immunity and a corresponding reduction in tumor growth. The incapacity of CDDP to trigger ICD is at least partially due to its failure to stimulate the premortem endoplasmic reticulum (ER)-stress response required for the externalization of the “eat-me” signal calreticulin (CRT) on the surface of dying cancer cells. Here, we developed a murine cancer cell line genetically modified to express the ER resident protein reticulon-1c (Rtn-1c) by virtue of tetracycline induction and showed that enforced Rtn-1c expression combined with CDDP treatment promoted CRT externalization to the surface of cancer cells. In contrast to single agent treatments, the tetracycline-mediated Rtn-1c induction combined with CDDP chemotherapy stimulated ICD as measured by the capacity of dying tumor cells, inoculated into syngenic immunocompetent mice, to mount an immune response to tumor re-challenge 1 week later. More importantly, established tumors, forced to constitutively express Rtn-1c in vivo by continuous treatment with tetracycline, became responsive to CDDP and exhibited a corresponding reduction in the rate of tumor growth. The combined therapeutic effects of Rtn-1c induction with CDDP treatment was only detected in the context of an intact immune system and not innu/numice lacking thymus-dependent T lymphocytes. Altogether, these results indicate that the artificial or “synthetic” induction of immunogenic cell death by genetic manipulation of the ER-stress response can improve the efficacy of chemotherapy with CDDP by stimulating anticancer immunity. [ABSTRACT FROM PUBLISHER]

Tetraploidy constitutes a genomically metastable state that can lead to aneuploidy and genomic instability. Tetraploid cells are frequently found in preneoplastic lesions, including intestinal cancers arising due to the inactivation of the tumor suppressor adenomatous polyposis coli (APC). Using a phenotypic screen, we identified resveratrol as an agent that selectively reduces the fitness of tetraploid cells by slowing down their cell cycle progression and by stimulating the intrinsic pathway of apoptosis. Selective killing of tetraploid cells was observed for a series of additional agents that indirectly or directly stimulate AMP-activated protein kinase (AMPK) including salicylate, whose chemopreventive action has been established by epidemiological studies and clinical trials. Both resveratrol and salicylate reduced the formation of tetraploid or higher-order polyploid cells resulting from the culture of human colon carcinoma cell lines or primary mouse epithelial cells lacking tumor protein p53 (TP53, best known as p53) in the presence of antimitotic agents, as determined by cytofluorometric and videomicroscopic assays. Moreover, oral treatment with either resveratrol or aspirin, the prodrug of salicylate, repressed the accumulation of tetraploid intestinal epithelial cells in the ApcMin/+ mouse model of colon cancer. Collectively, our results suggest that the chemopreventive action of resveratrol and aspirin involves the elimination of tetraploid cancer cell precursors. [ABSTRACT FROM AUTHOR]

Summary: The therapeutic efficacy of anthracyclines relies on antitumor immune responses elicited by dying cancer cells. How chemotherapy-induced cell death leads to efficient antigen presentation to T cells, however, remains a conundrum. We found that intratumoral CD11c+CD11b+Ly6Chi cells, which displayed some characteristics of inflammatory dendritic cells and included granulomonocytic precursors, were crucial for anthracycline-induced anticancer immune responses. ATP released by dying cancer cells recruited myeloid cells into tumors and stimulated the local differentiation of CD11c+CD11b+Ly6Chi cells. Such cells efficiently engulfed tumor antigens in situ and presented them to T lymphocytes, thus vaccinating mice, upon adoptive transfer, against a challenge with cancer cells. Manipulations preventing tumor infiltration by CD11c+CD11b+Ly6Chi cells, such as the local overexpression of ectonucleotidases, the blockade of purinergic receptors, or the neutralization of CD11b, abolished the immune system-dependent antitumor activity of anthracyclines. Our results identify a subset of tumor-infiltrating leukocytes as therapy-relevant antigen-presenting cells. [ABSTRACT FROM AUTHOR]

Cancer cells accommodate multiple genetic and epigenetic alterations that initially activate intrinsic (cell-autonomous) and extrinsic (immune-mediated) oncosuppressive mechanisms. Only once these barriers to oncogenesis have been overcome can malignant growth proceed unrestrained. Tetraploidization can contribute to oncogenesis because hyperploid cells are genomically unstable. We report that hyperploid cancer cells become immunogenic because of a constitutive endoplasmic reticulum stress response resulting in the aberrant cell surface exposure of calreticulin. Hyperploid, calreticulin-exposing cancer cells readily proliferated in immunodeficient mice and conserved their increased DNA content. In contrast, hyperploid cells injected into immunocompetent mice generated tumors only after a delay, and such tumors exhibited reduced DNA content, endoplasmic reticulum stress, and calreticulin exposure. Our results unveil an immunosurveillance system that imposes immunoselection against hyperploidy in carcinogen- and oncogene-induced cancers. [ABSTRACT FROM AUTHOR]

The success of anticancer chemotherapy relies at least in part on the induction of an immune response against tumor cells. Thus, tumors growing on mice that lack the pattern recognition receptor TLR4 or the purinergic receptor P2RX7 fail to respond to chemotherapy with anthracyclins or oxaliplatin in conditions in which the same neoplasms growing on immunocompetent mice would do so. Similarly, the therapeutic efficacy (measured as progression-free survival) of adjuvant chemotherapy with anthracyclins is reduced in breast cancer patients bearing loss-of-function alleles of TLR4 or P2RX7. TLR4 loss-of-function alleles also have a negative impact on the therapeutic outcome of oxaliplatin in colorectal cancer patients. Here, we report that loss-of-function TLR4 and P2RX7 alleles do not affect overall survival in non-small cell lung cancer (NSCLC) patients, irrespective of the administration and type of chemotherapy. The intrinsic characteristics of NSCLC (which near-to-always is chemoresistant and associated with poor prognosis) and/or the type of therapy that is employed to treat this malignancy (which near-to-always is based on cisplatin) may explain why two genes that affect the immune response to dying cells fail to influence the clinical progression of NSCLC patients. [ABSTRACT FROM AUTHOR]

Tetraploidy can constitute a metastable intermediate between normal diploidy and oncogenic aneuploidy. Here, we show that the absence of p53 is not only permissive for the survival but also for multipolar asymmetric divisions of tetraploid cells, which lead to the generation of aneuploid cells with a near-to-diploid chromosome content. Multipolar mitoses (which reduce the tetraploid genome to a sub-tetraploid state) are more frequent when p53 is downregulated and the product of the Mos oncogene is upregulated. Mos inhibits the coalescence of supernumerary centrosomes that allow for normal bipolar mitoses of tetraploid cells. In the absence of p53, Mos knockdown prevents multipolar mitoses and exerts genome-stabilizing effects. These results elucidate the mechanisms through which asymmetric cell division drives chromosomal instability in tetraploid cells. [ABSTRACT FROM AUTHOR]

P-glycoprotein (P-gp) is the most well-known ATP-binding cassette (ABC) transporter involved in unidirectional substrate translocation across the membrane lipid bilayer, thereby causing the typical multidrug resistance (MDR) phenotype expressed in many cancers. We observed that in human CEM acute lymphoblastic leukemia cells expressing various degrees of chemoresistance and where P-gp was the sole MDR-related ABC transporter detected, the amount of esterified cholesterol increased linearly with the level of resistance to vinblas tine while the amounts of total and free cholesterol increased in a nonlinear way. Membrane cholesterol controlled the ATPase activity of P-gp in a linear manner, whereas the P-gp-induced daunomycin efflux decreased nonlinearly with the depletion of membrane cholesterol. All these elements suggest that cholesterol controls both the ATPase and the drug efflux activities of P-gp. In addition, in CEM cell lines that expressed increasing levels of elevated chemoresistance, the amount of P-gp increases to a plateau value of 40% of the total membrane proteins and remained unvaried while the amount of membrane cholesterol increased with the elevation of the MDR level, strongly suggesting that cholesterol may be directly involved in the typical MDR phenotype. Finally, we showed that the decreased daunomycin efflux by P-gp due to the partial depletion of membrane cholesterol was responsible for the efficient chemosensitization of resistant CEM cells, which could be totally reversed after cholesterol repletion. [ABSTRACT FROM AUTHOR]

Tumor cells succumb to chemotherapy while releasing ATP. We have found that extracellular ATP attracts dendritic cell (DC) precursors into the tumor bed, facilitates their permanence in the proximity of dying cells and promotes their differentiation into mature DCs endowed with the capacity of presenting tumor-associated antigens. [ABSTRACT FROM AUTHOR]

Retrospective clinical data indicate that cardiac glycosides (CGs), notably digoxin, prolong the survival of carcinoma patients treated with conventional chemotherapy. CGs are known to influence the immune response at multiple levels. In addition, recent results suggest that CGs trigger the immunogenic demise of cancer cells, an effect that most likely contributes to their clinical anticancer activity. [ABSTRACT FROM AUTHOR]

Immunogenic cell death (ICD) inducers can be defined as agents that exert cytotoxic effects while stimulating an immune response against dead cell-associated antigens. When initiated by anthracyclines, ICD is accompanied by stereotyped molecular changes, including the pre-apoptotic exposure of calreticulin (CRT) on the cell surface, the lysosomal secretion of ATP during the blebbing phase of apoptosis, and the release of high mobility group box 1 (HMGB1) from dead cells. By means of genetically engineered human osteosarcoma U2OS cells, we screened the 879 anticancer compounds of the National Cancer Institute (NCI) Mechanistic Diversity Set for their ability to promote all these hallmarks of ICD in vitro. In line with previous findings from our group, several cardiac glycosides exhibit a robust propensity to elicit the major manifestations of ICD in cultured neoplastic cells. This screen pointed to septacidin, an antibiotic produced byStreptomyces fibriatus, as a novel putative inducer of ICD. In low-throughput validation experiments, septacidin promoted CRT exposure, ATP secretion and HGMB1 release from both U2OS cells and murine fibrosarcoma MCA205 cells. Moreover, septacidin-killed MCA205 cells protected immunocompetent mice against a re-challenge with living cancer cells of the same type. Finally, the antineoplastic effects of septacidin on established murine tumors were entirely dependent on T lymphocytes. Altogether, these results underscore the suitability of the high-throughput screening system described here for the identification of novel ICD inducers. [ABSTRACT FROM PUBLISHER]