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Tumor initiation represents the first step in tumorigenesis during which normal progenitor cells undergo cell fate transition to cancer. Capturing this process as it occurs in vivo , however, remains elusive. Here we employ cell tracing approaches with spatiotemporally controlled oncogene activation and tumor suppressor inhibition to unveil the processes underlying oral epithelial progenitor cell reprogramming into cancer stem cells (CSCs) at single cell resolution. This revealed the rapid emergence of a distinct stem-like cell state, defined by aberrant proliferative, hypoxic, squamous differentiation, and partial epithelial to mesenchymal (pEMT) invasive gene programs. Interestingly, CSCs harbor limited cell autonomous invasive capacity, but instead recruit myeloid cells to remodel the basement membrane and ultimately initiate tumor invasion. CSC transcriptional programs are conserved in human carcinomas and associated with poor patient survival. These findings illuminate the process of cancer initiation at single cell resolution, thus identifying candidate targets for early cancer detection and prevention., Competing Interests: DECLARATION OF INTERESTS J.S.G. has received other commercial research support from Kura Oncology, Mavupharma, Dracen, Verastem, and SpringWorks Therapeutics, and is a consultant/advisory board member for Domain Therapeutics, Pangea Therapeutics, and io9, and founder of Kadima Pharmaceuticals. The remaining authors declare no competing interests. Additional Declarations: Yes there is potential Competing Interest. J.S.G. has received other commercial research support from Kura Oncology, Mavupharma, Dracen, SpringWorks Therapeutics, is a consultant/advisory board member for Oncoceutics Inc., Vividion Therapeutics, Domain Therapeutics, and Pangea Therapeutics, and io9, and founder of Kadima Pharmaceuticals. The remaining authors declare no competing interests.

Our previous work demonstrated that Piwil2 reactivated by the human papillomavirus oncoproteins E6 and E7 may reprogram somatic cells into tumor-initiating cells (TICs), which contribute to cervical neoplasia lesions. Maintaining the stemness of TICs is critical for the progression of cervical lesions. Here, we determined that canonical Wnt signaling was aberrantly activated in HaCaT cells transfected with lentivirus expressing Piwil2 and in cervical lesion specimens of low-grade squamous intraepithelial lesion, high-grade squamous intraepithelial lesion, and invasive carcinoma. Blocking the β-catenin and CREB binding protein interaction with ICG-001 significantly downregulated the reprogramming factors c-Myc, Nanog, Oct4, Sox2, and Klf4, thus leading to cell differentiation and preventing tumorigenicity in Piwil2-overexpressing HaCaT cells. Similarly, Piwil2 also critically regulated the canonical Wnt signaling pathway in cervical cancer. We further demonstrated that ICG-001 increased cisplatin sensitivity and significantly suppressed tumor growth of cervical cancer alone or in combination with cisplatin both in vitro and in vivo. The β-catenin/ CREB binding protein-mediated transcription activated by Piwil2 is essential for the maintenance of TICs, therefore contributing to the progression of cervical oncogenesis.

Esophageal squamous cell carcinoma (ESCC) is a frequent malignant tumor with low 5-year overall survival. Targeting ESCC tumor-initiating cells (TICs) may provide a new research avenue to achieve better therapeutic effects of ESCC. However, the identity and characteristics of ESCC TICs remain poorly understood. Through genetic lineage tracing approach, we found that a group of Moloney murine leukemia virus insertion site 1- (Bmi1-) expressing cell populations present in the invasive front of the esophageal epithelium, providing a continuous flow of tumor cells for ESCC. Subsequently, we found that ablation of Bmi1+ cells from mice with ESCC led to inhibition of tumor growth. In addition, our results demonstrated that PTC-209, an inhibitor of Bmi1, was able to inhibit ESCC progression when combined with cisplatin. In summary, our data suggest that Bmi1+ cells serve as TICs in ESCC.

BackgroundStandard aggressive therapy of glioblastoma (GBM), which includes maximum safe resection, concurrent radiation therapy and temozolomide chemotherapy (RT/TMZ) followed by maintenance TMZ, is associated with a 25% 2-year overall survival (OS). Adding treatment with AV-GBM-1, a vaccine consisting of autologous dendritic cells (DC) pulsed with autologous tumor antigens (ATA) may improve OS by inducing and/or enhancing the host anti-GBM immune response. Methylation of the O-6-methylguanine-DNA methyltransferase (MGMT) gene promoter, and mutation of the gene for isocitrate dehydrogenase (IDH) are favorable prognostic markers in newly diagnosed GBM. An objective of a multi-center phase II clinical trial was to determine whether these markers were still prognostic for OS in patients treated with adjunctive AV-GBM-1.MethodsKey eligibility criteria for intent-to-treat (ITT) enrollment were: (1) confirmation of primary GBM, (2) successful GBM cell culture, (3) collection of sufficient numbers of monocytes (MC) by leukapheresis, (4) Karnofsky Performance Status 70 or greater after recovery from surgery, and (5) plan to treat with concurrent RT/TMZ. AV-GBM-1 was manufactured while patients were being treated with RT/TMZ. Interleukin-4 and granulocyte-macrophage colony stimulating factor (GM-CSF) were used to differentiate DC from MC. Each vaccine consisted of autologous DC incubated with ATA from the lysate of irradiated cultured GBM cells grown in serum-free media with factors that favor survival and proliferation of stem cells and early progenitor cells (tumor-initiating cells). After recovery from RT/TMZ, intent was to vaccinate for up to six months with cryopreserved AV-GBM-1 admixed with 500 mg GM-CSF. All patients had testing for MGMT-methylation and IDH-mutation. OS was calculated from date of ITT enrollment.Results60 patients were enrolled during August 2018 to January 2020. MGMT promoter methylation was detected in 21 (35%), mutated IDH in 7 (12%), and one or both in 25 (42%). At a minimum follow-up of 15 months, median OS had not been reached for patients with a methylated MGMT promotor, IDH mutation, or one or both, compared to 14.6 months for 38 with unmethylated MGMT promotor (p=0.026), 14.7 months for 53 with IDH wild-type (p=0.044), and 14.6 months for 35 who had neither (p=0.017). 18-month OS rates were 59% vs 35% for MGMT promotor methylation, 71% vs 40% for IDH mutation and 58% vs 32% for either.ConclusionsBoth MGMT promotor methylation and IDH mutation were associated with a substantial and similar survival benefit in primary GBM patients treated with AV-GBM-1 in addition to standard aggressive therapy.Trial RegistrationClinicaltrialsgov NCT03400917Ethics ApprovalThis study was approved by the Western IRB, approval number 20182582; all participants gave written informed consent before taking part

FAM3C/Interleukin-like EMT Inducer (ILEI) is an oncogenic member of the FAM3 cytokine family and serves essential roles in both epithelial-mesenchymal transition (EMT) and breast cancer metastasis. ILEI expression levels are regulated through a non-canonical TGFβ signaling pathway by 3′-UTR-mediated translational silencing at the mRNA level by hnRNP E1. TGFβ stimulation or silencing of hnRNP E1 increases ILEI translation and induces an EMT program that correlates with enhanced invasion and migration. Recently, EMT has been linked to the formation of breast cancer stem cells (BCSCs) that confer both tumor cell heterogeneity as well as chemoresistant properties. Herein, we demonstrate that hnRNP E1 knockdown significantly shifts normal mammary epithelial cells to mesenchymal BCSCs in vitro and in vivo. We further validate that modulating ILEI protein levels results in the abrogation of these phenotypes, promoting further investigation into the unknown mechanism of ILEI signaling that drives tumor progression. We identify LIFR as the receptor for ILEI, which mediates signaling through STAT3 to drive both EMT and BCSC formation. Reduction of either ILEI or LIFR protein levels results in reduced tumor growth, fewer tumor initiating cells and reduced metastasis within the hnRNP E1 knock-down cell populations in vivo. These results reveal a novel ligand-receptor complex that drives the formation of BCSCs and represents a unique target for the development of metastatic breast cancer therapies.

Simple Summary Different types of cells with tumor-initiating cell (TIC) activity contribute to colorectal cancer (CRC) progression and resistance to anti-cancer treatment. In this study, we aimed to understand whether different cell types exist within a patient-derived tumor culture, distinguishable by different patterns of their gene expression. By mRNA sequencing of patient-derived CRC cultures at the single-cell level, we defined expression programs that closely resemble differentiated cell populations of the normal intestine. Here, cell type-associated subpopulations showed differences in functional properties such as cell growth and energy metabolism. Subsequent functional analyses in vitro and in vivo demonstrated that metabolic states are linked to TIC activity in primary CRC cultures. We also show that TIC activity is dependent on oxidative phosphorylation, which may therefore represent a target for novel therapies. Abstract Intra-tumor heterogeneity of tumor-initiating cell (TIC) activity drives colorectal cancer (CRC) progression and therapy resistance. Here, we used single-cell RNA-sequencing of patient-derived CRC models to decipher distinct cell subpopulations based on their transcriptional profiles. Cell type-specific expression modules of stem-like, transit amplifying-like, and differentiated CRC cells resemble differentiation states of normal intestinal epithelial cells. Strikingly, identified subpopulations differ in proliferative activity and metabolic state. In summary, we here show at single-cell resolution that transcriptional heterogeneity identifies functional states during TIC differentiation. Furthermore, identified expression signatures are linked to patient prognosis. Targeting transcriptional states associated to cancer cell differentiation might unravel novel vulnerabilities in human CRC.

BackgroundDespite standard aggressive therapy (maximum safe surgical resection, concurrent radiation therapy and temozolomide chemotherapy (RT/TMZ), then maintenance TMZ), 2-year survival is only about 25% for patients with newly diagnosed primary glioblastoma (GBM). Adding AV-GBM-1, a vaccine consisting of autologous dendritic cells (DC) pulsed with autologous tumor antigens (ATA) may improve survival. One objective of a multi-center phase II clinical trial was to determine the feasibility of collecting fresh GBM and establishing short-term cell cultures of GBM tumor-initiating cells (TIC) to serve as ATA source.MethodsKey eligibility criteria for tumor collection were (1) clinical suspicion of new primary GBM, (2) age 18 to 70 years (3) tentative agreement to undergo a leukapheresis procedure after recovery from surgery, and (4) tentative plans for RT/TMZ. Fresh tumor was placed in media and shipped in a transport kit by overnight courier to AIVITA where a cell suspension was placed in culture and incubated in serum-free medium with factors that favor survival and proliferation of TICS (stem cells and early progenitor cells). The intent was to produce a patient-specific DC-ATA vaccine by incubating a lysate of irradiated TICs with autologous DC for subsequent subcutaneous injection.ResultsPatients were enrolled from five sites in California, one in Kentucky and one in New Jersey. Tumors were collected between August 2018 and January 2020. 106 patients consented for tumor collection, but 15 were not GBM, 4 had insufficient tissue to send, 2 patients withdrew consent, 4 were ineligible because of age, and 1 was ineligible because of autoimmune disease. Of the 80 GBM tumors that were placed into culture, 7 were discontinued because of patient withdrawal. 71/73 (97%) resulted in a successful cell culture; two were unsuccessful because of contamination. 60/71 subsequently consented for intent-to-treat ; 46/60 (77%) had cells in culture for 28 days or less, 11 were in culture for 30 to 35 days, and the remaining 3 were cultured 46, 54, and 55 days. The average number of cells per culture at the time of irradiation was 14.0 million (range 0.78 to 63.3 million). 58/60 (97%) yielded more than 1 million TICs for irradiation for the tumor cell lysate; 36/60 (60%) had more than 10 million cells irradiated. 57 patients were subsequently treated with AV-GBM-1 after recovery from RT/TMZ.ConclusionsSelf-renewing GBM TIC cultures can be reliably and rapidly established for use as the antigen source for personal DC-ATA vaccines.Trial RegistrationClinicaltrialsgov NCT03400917Ethics ApprovalThis study was approved by the Western IRB, approval number 20182582; all participants gave written informed consent before taking part

BackgroundDespite standard aggressive therapy, including maximum safe surgical resection, concurrent radiation therapy and temozolomide chemotherapy (RT/TMZ) followed by maintenance TMZ, survival is still extremely poor for patients with newly diagnosed primary glioblastoma (GBM). Adding treatment with AV-GBM-1, a personal vaccine consisting of autologous dendritic cells (DC) pulsed with autologous tumor antigens (ATA) may improve survival. One objective of a multi-center phase II clinical trial was to determine changes in blood proteomics before and after injections of AV-GBM-1.MethodsAV-GBM-1 consists of autologous DC incubated with ATA from a lysate of irradiated autologous GBM cells that had been placed in culture and incubated in serum-free medium with factors that favor the survival and proliferation of stem cells and early progenitor cells. After recovery from RT/TMZ, GBM patients were injected subcutaneously with AV-GBM-1 admixed in granulocyte-macrophage colony-stimulating factor (GM-CSF) at weeks 1, 2, 3, 8, 12, 16, 20, and 24. Blood samples obtained at baseline (week-0), just prior to the third injection (week-2) and just prior to the fourth injection (week-8), were cryopreserved and subsequently analyzed for 448 proteomic markers using quantitative, multiplex enzyme-linked immunosorbent assays (Raybiotech, Inc., Norcross, GA.). In this preliminary analysis the averages of paired samples for each time point were determined and compared using the student T-Test with a focus on differences of pResultsPatients were enrolled from five sites in California, and one each in Kentucky and New Jersey. 57 patients were treated during November 2018 to October 2020. Paired samples from all three time points were available for 49 patients. After two weekly injections there were increases in thymus-and activation-regulated chemokine (TARC, CCL17), the chemotactic protein chemerin, lipocalin-2, (expressed by macrophages and epithelium in response to inflammation) and angiopoietin-1 (suppressor of vascular inflammation), and decreases in thrombospondin-5 (possibly involved in synaptogenesis in brain repair), angiotensinogen (a precursor of all angiotensin peptides), and beta-fibroblast growth factor (important in tissue repair). The increase in TARC (pConclusionsIf there were humoral changes in proteins associated with Th1 and Th2 responses, these were no longer present after two weekly vaccinations. More sophisticated analyses of this data set, such as principal component analysis, may be needed to understand the effects of AV-GBM-1.Trial RegistrationClinicaltrialsgov NCT03400917Ethics ApprovalThis study was approved by the Western IRB, approval number 20182582; all participants gave written informed consent before taking part

Although tumor‐initiating cell (TIC) self‐renewal has been postulated to be essential in progression and metastasis formation of human pancreatic adenocarcinoma (PDAC), clonal dynamics of TICs within PDAC tumors are yet unknown. Here, we show that long‐term progression of PDAC in serial xenotransplantation is driven by a succession of transiently active TICs producing tumor cells in temporally restricted bursts. Clonal tracking of individual, genetically marked TICs revealed that individual tumors are generated by distinct sets of TICs with very little overlap between subsequent xenograft generations. An unexpected functional and phenotypic plasticity of pancreatic TICs in vivo underlies the recruitment of inactive TIC clones in serial xenografts. The observed clonal succession of TIC activity in serial xenotransplantation is in stark contrast to the continuous activity of limited numbers of self‐renewing TICs within a fixed cellular hierarchy observed in other epithelial cancers and emphasizes the need to target TIC activation, rather than a fixed TIC population, in PDAC.

// Joseph Dosch 1, * , Elizabeth Ziemke 1, * , Shanshan Wan 2 , Kathryn Luker 1 , Theodore Welling 2 , Karin Hardiman 2 , Eric Fearon 3 , Suneetha Thomas 4 , Matthew Flynn 4 , Jonathan Rios-Doria 4 , Robert Hollingsworth 4 , Ronald Herbst 4 , Elaine Hurt 4, # and Judith Sebolt-Leopold 1, # 1 Department of Radiology, University of Michigan, Ann Arbor, MI 48109, USA 2 Department of Surgery, University of Michigan, Ann Arbor, MI 48109, USA 3 Department of Internal Medicine, University of Michigan, Ann Arbor, MI 48109, USA 4 Department of Oncology Research, MedImmune, LLC, Gaithersburg, MD 20878, USA * These authors contributed equally to this work # Co-senior authors Correspondence to: Judith Sebolt-Leopold, email: jssl@med.umich.edu Keywords: ADAM17, TACE, colorectal, stem cell, Notch Received: November 24, 2016 Accepted: April 03, 2017 Published: May 10, 2017 ABSTRACT ADAM17 (a disintegrin and metalloproteinase 17)/TACE (TNFα converting enzyme) has emerged as a potential therapeutic target in colorectal cancer (CRC) and other cancers, due in part to its role in regulating various tumor cell surface proteins and growth factors and cytokines in the tumor microenvironment. The emergence of MEDI3622, a highly potent and specific antibody-based ADAM17 inhibitor, has allowed testing of the concept that targeting ADAM17 may be an important new therapeutic approach for CRC patients. We demonstrate that MEDI3622 is highly efficacious on tumor growth in multiple human CRC PDX models, resulting in improved survival of animals bearing tumor xenografts. MEDI3622 was further found to impact Notch pathway activity and tumor-initiating cells. The promising preclinical activity seen here supports further clinical investigation of this treatment approach to improve therapeutic outcome for patients diagnosed with metastatic CRC, including patients with KRAS-mutant tumors for whom other therapeutic options are currently limited.

In solid tumors, cancer stem cells (CSCs) or tumor-initiating cells (TICs) are often found in hypoxic niches. Nevertheless, the influence of hypoxia on TICs is poorly understood. Using previously established, TIC-enrichedpatient-derived colorectal cancer (CRC) cultures, we show that hypoxia increases the self-renewal capacity of TICs while inducing proliferation arrest in their more differentiated counterpart cultures. Gene expression data revealed macroautophagy/autophagy as one of the major pathways induced by hypoxia in TICs. Interestingly, hypoxia-induced autophagy was found to induce phosphorylation of EZR (ezrin) at Thr567 residue, which could be reversed by knocking down ATG5, BNIP3, BNIP3L, or BECN1. Furthermore, we identified PRKCA/PKCα as a potential kinase involved in hypoxia-induced autophagy-mediated TIC self-renewal. Genetic targeting of autophagy or pharmacological inhibition of PRKC/PKC and EZR resulted in decreased tumor-initiating potential of TICs. In addition, we observed significantly reduced in vivo tumor initiation and growth after a stable knockdown of ATG5. Analysis of human CRC samples showed that p-EZR is often present in TICs located in the hypoxic and autophagic regions of the tumor. Altogether, our results establish the hypoxia-autophagy-PKC-EZR signaling axis as a novel regulatory mechanism of TIC self-renewal and CRC progression. Autophagy inhibition might thus represent a promising therapeutic strategy for cancer patients. Abbreviations ATG: autophagy related; BECN1: beclin 1; BNIP3: BCL2 interacting protein 3; BNIP3L: BCL2 interacting protein 3 like; CQ: chloroquine; CSC: cancer stem cells; CRC: colorectal cancer; HIF1A/HIF-1α: hypoxia inducible factor 1 subunit alpha; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; PRKC/PKC: protein kinase C; SQSTM1/p62: sequestosome 1; TICs: tumor-initiating cells.

In cancer, the deregulation of growth signaling pathways drives changes in the cell¿s architecture and its environment that allow autonomous growth of tumors. These cells then acquire a tumor-initiating ¿stemness¿ phenotype responsible for disease advancement to more aggressive stages. Here, we show that high levels of the actin cytoskeleton-associated protein WIP (WASP-interacting protein) correlates with tumor growth, both of which are linked to the tumor-initiating cell phenotype. We find that WIP controls tumor growth by boosting signals that stabilize the YAP/TAZ complex via a mechanism mediated by the endocytic/endosomal system. When WIP levels are high, the ß-catenin Adenomatous polyposis coli (APC)-axin-GSK3 destruction complex is sequestered to the multi-vesicular body compartment, where its capacity to degrade YAP/TAZ is inhibited. YAP/TAZ stability is dependent on Rac, p21-activated kinase (PAK) and mammalian diaphanous-related formin (mDia), and is Hippo independent. This close biochemical relationship indicates an oncogenic role for WIP in the physiology of cancer pathology by increasing YAP/TAZ stability., MINECO (SAF2013-45937-R to I.M.A.) and MINECO/FEDER (SAF2015-70368-R to I.M.A. and F.W.), the European Union (EU-FP7-2009-CT222887 to F.W.), the Instituto de Salud Carlos III Centro de Investigación Biomédica en Red (CIBERNED to F.W.) and by a grant from ISCIII-RETIC (RD12/0036/0009 to R.G.E.)

// Dingqing Feng 1 , Keqin Yan 1 , Ying Zhou 2 , Haiyan Liang 1 , Jing Liang 1 , Weidong Zhao 2,3 , Zhongjun Dong 4 and Bin Ling 1 1 Department of Obstetrics and Gynecology, China-Japan Friendship Hospital, Beijing, China 2 Department of Obstetrics and Gynecology, Anhui Provincial Hospital Affiliated to Anhui Medical University, Hefei, China 3 Department of Gynecology and Oncology, Anhui Provincial Cancer Hospital, Hefei, China 4 School of Medicine, Tsinghua University, Beijing, China Correspondence to: Bin Ling, email: // Keywords : Piwil2, cell reprogramming, tumor initiating cell, HPV oncoprotein, cervical cancer Received : April 04, 2016 Accepted : July 19, 2016 Published : September 01, 2016 Abstract The human papillomavirus (HPV) oncoproteins E6 and E7 are risk factors that are primarily responsible for the initiation and progression of cervical cancer, and they play a key role in immortalization and transformation by reprogramming differentiating host epithelial cells. It is unclear how cervical epithelial cells transform into tumor-initiating cells (TICs). Here, we observed that the germ stem cell protein Piwil2 is expressed in pre-cancerous and malignant lesions of the cervix and cervical cancer cell lines with the exception of the non-HPV-infected C33a cell line. Knockdown of Piwil2 by shRNA led to a marked reduction in proliferation and colony formation, in vivo tumorigenicity, chemo-resistance, and the proportion of cancer stem-like cells. In contrast, Piwil2 overexpression induced malignant transformation of HaCaT cells and the acquisition of tumor-initiating capabilities. Gene-set enrichment analysis revealed embryonic stem cell (ESC) identity, malignant biological behavior, and specifically, activation targets of the cell reprogramming factors c-Myc , Klf4 , Nanog , Oct4 , and Sox2 in Piwil2 -overexpressing HaCaT cells. We further confirmed that E6 and E7 reactivated Piwil2 and that E6 and E7 overexpression resulted in a similar gene-set enrichment pattern as Piwil2 overexpression in HaCaT cells. Moreover, Piwil2 overexpression or E6 and E7 activation induced H3K9 acetylation but reduced H3K9 trimethylation, which contributed to the epigenetic reprogramming and ESC signature maintenance, as predicted previously. Our study demonstrates that Piwil2 , reactivated by the HPV oncoproteins E6 and E7, plays an essential role in the transformation of cervical epithelial cells to TICs via epigenetics-based cell reprogramming.

// Cristina Richichi 1 , Daniela Osti 1 , Massimiliano Del Bene 2 , Lorenzo Fornasari 1 , Monica Patane 3 , Bianca Pollo 3 , Francesco DiMeco 2, 4 , Giuliana Pelicci 1, 5 1 Department of Experimental Oncology, European Institute of Oncology, 20139, Milan, Italy 2 Department of Neurosurgery, IRCCS Foundation Neurological Institute “C. Besta”, 20133, Milan, Italy 3 Department of Neuropathology, IRCCS Foundation Neurological Institute “C. Besta”, 20133, Milan, Italy 4 Department of Neurosurgery, Johns Hopkins University, Baltimore, MD 21218, USA 5 Department of Translational Medicine, Piemonte Orientale University “Amedeo Avogadro”, 28100 Novara, Italy Correspondence to: Giuliana Pelicci, email: giuliana.pelicci@ieo.eu Keywords: glioblastoma, tumor-initiating cell frequency, neurosphere, limiting dilution assay, tumorigenicity Received: March 03, 2016 Accepted: August 13, 2016 Published: August 25, 2016 ABSTRACT Glioblastoma (GBM) is maintained by a small subpopulation of tumor-initiating cells (TICs). The arduous assessment of TIC frequencies challenges the prognostic role of TICs in predicting the clinical outcome in GBM patients. We estimated the TIC frequency in human GBM injecting intracerebrally in mice dissociated cells without any passage in culture. All GBMs contained rare TICsand were tumorigenic in vivo but only 54% of them grew in vitro as neurospheres. We demonstrated that neurosphere formation in vitro did not foretell tumorigenic ability in vivo and frequencies calculated in vitro overestimated the TIC content. Our findings assert the pathological significance of GBM TICs. TIC number correlated positively with tumor incidence and inversely with survival of tumor-bearing mice. Stratification of GBM patients according to TIC content revealed that patients with low TIC frequency experienced a trend towards a longer progression free survival. The expression of either putative stem-cell markers or markers associated with different GBM molecular subtypes did not associate with either TIC content or neurosphere formation underlying the limitations of TIC identification based on the expression of some putative stem cell-markers.

Background For glioblastoma (GBM) treatments to be effective in vivo, understanding the effects of the tumor microenvironment is imperative. In traditional cell culture conditions, glucose concentrations do not model physiologic levels, nor the diminished concentrations found in tumor niches. We therefore sought to profile the differences in kinase activity in GBM cells cultured in restricted glucose to identify pathways that could be targeted with small molecule inhibitors. Methods Using the PamStation12 platform, we examined the ability of GBM lysates from cells cultured in standard or low glucose conditions to phosphorylate 144 tyrosine and 144 serine/threonine peptides that correspond to known protein phosphorylation sites. Potential kinase targets were identified and validated using small molecule kinase inhibitors in GBM spheroid cultures. Results Using results from two GBM patient-derived xenografts, we determined common changes to peptides derived from Phospholipase C, Gamma 1 (PLCG1) and Raf-1. Using PLC and Raf inhibitors, we found a significantly stronger growth inhibitory effect of the PLC inhibitor U73122 under restricted glucose conditions. In contrast, Raf inhibitors were significantly growth inhibitory regardless of the nutrient level tested. Conclusions Together, our data demonstrate that kinase activity is altered in low glucose conditions and that kinomic profiling can assist with the identification of effective strategies to target GBM growth. Our data further suggest the importance of accurately modeling the tumor microenvironment to reproduce cancer cell signaling and develop drug screens for anti-cancer agents.

For the first time new treatments in melanoma have produced significant responses in advanced diseases, but 30–90% of melanoma patients do not respond or eventually relapse after the initial response to the current treatments. The resistance of these melanomas is likely due to tumor heterogeneity, which may be explained by models such as the stochastic, hierarchical, and phenotype-switching models. This review will discuss the recent advancements in targeting BCL-2 family members for cancer treatments, and how this approach can be applied as an alternative option to combat melanoma, and overcome melanoma relapse or resistance in current treatment regimens.

// Qi Xie 1 , Qiulian Wu 1 , Stephen C. Mack 1 , Kailin Yang 1, 2 , Leo Kim 1 , Christopher G. Hubert 1 , William A. Flavahan 1, 3, 4, 5 , Chengwei Chu 1, 6 , Shideng Bao 1, 2 , Jeremy N. Rich 1, 2 1 Department of Stem Cell Biology and Regenerative Medicine, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA 2 Department of Molecular Medicine, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, OH 44195, USA 3 Department of Pathology and Center for Cancer Research, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114, USA 4 Broad Institute of Harvard and Massachusetts Institute of Technology (MIT), Cambridge, MA 02142, USA 5 Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA 6 Division of Neurosurgery, Department of Surgery, Kaohsiung Medical University Hospital, Kaohsiung 80756, Taiwan Correspondence to: Jeremy N. Rich, e-mail: drjeremyrich@gmail.com Keywords: cancer stem cell, glioblastoma, glioma, tumor initiating cell, CDC20 Received: March 05, 2015 Accepted: April 16, 2015 Published: April 28, 2015 ABSTRACT Glioblastoma is the most prevalent and lethal primary intrinsic brain tumor. Glioblastoma displays hierarchical arrangement with a population of self-renewing and tumorigenic glioma tumor initiating cells (TICs), or cancer stem cells. While non-neoplastic neural stem cells are generally quiescent, glioblastoma TICs are often proliferative with mitotic control offering a potential point of fragility. Here, we interrogate the role of cell-division cycle protein 20 (CDC20), an essential activator of anaphase-promoting complex (APC) E3 ubiquitination ligase, in the maintenance of TICs. By chromatin analysis and immunoblotting, CDC20 was preferentially expressed in TICs relative to matched non-TICs. Targeting CDC20 expression by RNA interference attenuated TIC proliferation, self-renewal and in vivo tumor growth. CDC20 disruption mediated its effects through induction of apoptosis and inhibition of cell cycle progression. CDC20 maintains TICs through degradation of p21 CIP1/WAF1 , a critical negative regulator of TICs. Inhibiting CDC20 stabilized p21 CIP1/WAF1 , resulting in repression of several genes critical to tumor growth and survival, including CDC25C, c-Myc and Survivin. Transcriptional control of CDC20 is mediated by FOXM1, a central transcription factor in TICs. These results suggest CDC20 is a critical regulator of TIC proliferation and survival, linking two key TIC nodes – FOXM1 and p21 CIP1/WAF1 — elucidating a potential point for therapeutic intervention.

Glioblastoma (GBM), or grade IV astrocytoma, is a deadly disease due in part to the high degree of intratumoral heterogeneity that contributes to treatment failures. One cellular subset enriched for the capacity to propagate tumor growth and promote therapeutic resistance is brain tumor initiating cells (BTICs). The aim of the study was to define the roles of GTP cyclohydrolase 1 (GCH1) in regulation of BTIC phenotypes via reactive species. We examined GCH1 mRNA and protein expression in patient-derived xenografts, clinical samples and glioma gene expression datasets. GCH1 levels were modulated using lentiviral expression systems, and effects on cell growth, self-renewal, reactive species production and in vitro animal survival were determined. We found that GCH1 RNA and protein expression were increased in BTICs in comparison to non-BTICs, but that GCH1 was not exclusive to the BTIC fraction. Indeed, GCH1 was elevated in GBM in comparison to normal brain. Overexpression of GCH1 in GBM cells increased cell growth in vitro and decreased survival in an intracranial GBM mouse model. In contrast, GCH1 knockdown with short hairpin RNA in GBM cells led to growth inhibition in vitro as well as increased survival in animal models. Mechanistically, GCH1 increased CD44 expression and was critical for controlling reactive species balance, including suppressing reactive oxygen species production. In silico analyses demonstrated that higher GCH1 levels in glioma patients correlate with higher glioma grade, recurrence and worse survival. Together, our data suggest that upregulation of GCH1 in BTICs promotes tumor maintenance and is a key regulator of reactive oxygen species in GBM.

// Jing Liu 1 , Zhijie Xiao 1 , Sunny Kit-Man Wong 1 , Vicky Pui-Chi Tin 1 , Ka-Yan Ho 1 , Junwen Wang 2 , Mai-Har Sham 2 , Maria Pik Wong 1 1 Department of Pathology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR China 2 Department of Biochemistry, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR China Correspondence: Maria Pik Wong, email: // Keywords : lung cancer, tumor initiating cell, aldehyde dehydrogenase, CD44, drug resistance Received : August 5, 2013 Accepted : August 28, 2013 Published : August 30, 2013 Abstract Limited improvement in long term survival of lung cancer patients has been achieved by conventional chemotherapy or targeted therapy. To explore the potentials of tumor initiating cells (TIC)-directed therapy, it is essential to identify the cell targets and understand their maintenance mechanisms. We have analyzed the performance of ALDH/CD44 co-expression as TIC markers and treatment targets of lung cancer using well-validated in vitro and in vivo analyses in multiple established and patient-derived lung cancer cells. The ALDH hi CD44 hi subset showed the highest enhancement of stem cell phenotypic properties compared to ALDH hi CD44 lo , ALDH lo CD44 hi , ALDH lo CD44 lo cells and unsorted controls. They showed higher invasion capacities, pluripotency genes and epithelial-mesenchymal transition transcription factors expression, lower intercellular adhesion protein expression and higher G2/M phase cell cycle fraction. In immunosuppressed mice, the ALDH hi CD44 hi xenografts showed the highest tumor induction frequency, serial transplantability, shortest latency, largest volume and highest growth rates. Inhibition of sonic Hedgehog and Notch developmental pathways reduced ALDH + CD44 + compartment. Chemotherapy and targeted therapy resulted in higher ALDH hi CD44 hi subset viability and ALDH lo CD44 lo subset apoptosis fraction. ALDH inhibition and CD44 knockdown led to reduced stemness gene expression and sensitization to drug treatment. In accordance, clinical lung cancers containing a higher abundance of ALDH and CD44-coexpressing cells was associated with lower recurrence-free survival. Together, results suggested the ALDH hi CD44 hi compartment was the cellular mediator of tumorigenicity and drug resistance. Further investigation of the regulatory mechanisms underlying ALDH hi CD44 hi TIC maintenance would be beneficial for the development of long term lung cancer control.

// Jeff C. Liu 1,* , Sean E. Egan 2 and Eldad Zacksenhaus 1,* 1 Division of Cell & Molecular Biology, Toronto General Research Institute - University Health Network, Toronto, Canada 2 Program in Developmental and Stem Cell Biology, The Hospital for Sick Children, Toronto Correspondence: Jeff Liu, email: // Eldad Zacksenhaus, email: // Keywords : HER2 breast cancer; Prognostic signature; Tumor initiating cell; Cancer stem cells; Mouse models Received : July 10, 2013 Accepted : July 24, 2013 Published : July 26, 2013 Abstract The high intra- and inter-tumor heterogeneity of many types of cancers, including breast cancer (BC), poses great challenge to development of subtype-specific prognosis. In BC, the classification of tumors as either ERα + (Luminal A and Luminal B), HER2 + (ERα + or ERα - ) or triple-negative (TNBC)(Basal-like, claudin-low) guides both prognostication and therapy. Indeed, prognostic signatures for ERα + BC are being incorporated into clinical use. However, these signatures distinguish between luminal A (low risk) and Luminal B (high risk) BC; signatures that identify low/high risk patients with luminal B BC are yet to be developed. Likewise, no signature is in clinical use for HER2 + or TNBC. The major obstacles to development of robust signatures stem from diversity of BC, clonal evolution and heterogeneity within each subtype. We have recently generated a prognostic signature for HER2 + :ERα - BC based on the identification of genes that were differentially expressed in a tumor-initiating cell (TIC)-enriched fraction versus non-TIC fraction from a mouse model of HER2 + BC (MMTV-Hers/Neu). Here we describe the rationale behind development of this prognosticator, and present new features of the signature, including elevated PI3K pathway activity and low TNFalpha and IFNgamma signaling in high-risk tumors. In addition, we address controversies in the field such as whether random gene expression signatures significantly associate with cancer outcome. Finally, we suggest a guideline for development of prognostic signatures and discuss future directions.

// Loreto Boix 1 , Juan Manuel Lopez-Oliva 1 , Ana Carolina Rhodes 1 , Jordi Bruix 1 1 Barcelona Clinic Liver Cancer (BCLC) Group, Liver Unit, Hospital Clinic of Barcelona, University of Barcelona, Institut d'Investigacions Biomediques August Pi i Sunyer (IDIBAPS), Fundacio Clinic per a la Recerca Biomedica (FCRB), CIBERehd, 08036 Barcelona, Spain Correspondence to: Loreto Boix, email: lboix@clinic.ub.es Keywords: hepatocellular carcinoma, miR122, cancer stem cell, tumor initiating cell, tumor dormancy Received: February 05, 2016 Accepted: June 29, 2016 Published: September 07, 2016 ABSTRACT miR122 is the prevalent miRNA in adult healthy liver and it is responsible for liver stem cell differentiation towards hepatocyte lineage. Its expression is frequently lost in hepatocellular carcinoma (HCC). We studied the effects of restoring miR122 expression in a distinctive cell line derived from human HCC-BCLC9 cells-with a solid stem-like cell profile, high tumor initiating ability and undetectable miR122 expression. We generated a stable BCLC9 cell line that expresses miR122 (BCLC9-miR122). Restitution of miR122 in BCLC9 cells, decreases cell proliferation rate and reduces significantly tumor size in vivo . BCLC9-miR122 cells down-regulate expression of MYC, KLF4, FOXM1, AKT2 and AKT3 genes and up-regulate FOXO1 and FOXO3A gene expression. In addition, miR122 transfected cells decreased AKT2 kinase activation while decreased FOXO1 and FOXO3A protein inactivation. Reduction in tumor size in BCLC9-miR122 associated with an increase in p38MAPK protein expression and activation leading to a low phospho-ERK1/2 to phospho-p38 ratio. Treatment of miR122 positive cells with an inhibitor of TGFBR1 activation, abolished tumor dormancy program and recovered cell proliferation rate through a Smad-independent TGF-β response. HCC stem-like cells can be directed towards cell differentiation and tumor dormancy by restoring miR122 expression. We demonstrate, for the first time, that dormancy program is achieved through a Smad-independent TGF-β pathway. Reestablishing miR122 expression is a promising therapeutic strategy that would work concurrently reducing tumor aggressiveness and decreasing disease recurrence.

Originally adapted from the neurosphere assay, the nonadherent mammosphere assay has been utilized to assess early progenitor/stem cell frequency in a given population of mammary epithelial cells. This method has also been used to measure the frequency of tumorsphere initiating cells in both primary mammary tumors as well as in tumor cell lines. Although, the mammosphere assay has been used extensively in the mammary gland field, a standard method of quantifying and analyzing sphere growth in this assay has remained undefined. Here, we discuss the use and benefit of using a limiting dilution analysis to quantify sphere-forming frequency in primary mammary epithelial cells grown in nonadherent conditions.

The role of TGF-β signaling in tumorigenesis is paradoxical: it can be tumor suppressive or tumor promotional, depending on context. The metastatic regulator, Six1, was recently shown to mediate this switch, providing a novel means to explain this elusive “TGF-β paradox”. Herein, we identify a mechanism by which Six1 activates the tumor promotional arm of TGF-β signaling, via its ability to upregulate the miR-106b-25 microRNA cluster, and further identify a novel function for this cluster of microRNAs. While expression of the miR-106b-25 cluster is known to overcome TGF-β-mediated growth suppression via targeting p21 and BIM, we demonstrate for the first time that this same cluster can additionally target the inhibitory Smad7 protein, resulting in increased levels of the TGF-β type I receptor (TβRI) and downstream activation of TGF-β signaling. We further show that the miR-106b-25 cluster is sufficient to induce an epithelial to mesenchymal transition and a tumor initiating cell phenotype, and that it is required downstream of Six1 to induce these phenotypes. Finally, we demonstrate a significant correlation between miR-106b, Six1, and activated TGF-β signaling in human breast cancers, and further show that high levels of miR-106b and miR-93 in breast tumors significantly predicts shortened time to relapse. These findings expand the spectrum of oncogenic functions of miR-106b-25, and may provide a novel molecular explanation, through the Six1 regulated miR-106b-25 cluster, by which TGF-β signaling shifts from tumor suppressive to tumor promoting.

Tumors are thought to be sustained by a reservoir of self-renewing cells, termed tumor-initiating cells or cancer stem cells. Osteosarcomas are high-grade sarcomas derived from osteoblast progenitor cells and are the most common pediatric bone malignancy. In this report we show that the stem cell transcription factor Sox2 is highly expressed in human and murine osteosarcoma (mOS) cell lines as well as in the tumor samples. Osteosarcoma cells have increased ability to grow in suspension as osteospheres, that are greatly enriched in expression of Sox2 and the stem cell marker, Sca-1. Depletion of Sox2 by short-hairpin RNAs in independent mOS-derived cells drastically reduces their transformed properties in vitro and their ability to form tumors. Sox2-depleted osteosarcoma cells can no longer form osteospheres and differentiate into mature osteoblasts. Concomitantly, they exhibit decreased Sca-1 expression and upregulation of the Wnt signaling pathway. Thus, despite other mutations, these cells maintain a requirement for Sox2 for tumorigenicity. Our data indicate that Sox2 is required for osteosarcoma cell self renewal, and that Sox2 antagonizes the pro-differentiation Wnt pathway that can in turn reduce Sox2 expression. These studies define Sox2 as a survival factor and a novel biomarker of self renewal in osteosarcomas, and support a tumor suppressive role for the Wnt pathway in tumors of mesenchymal origin. Our findings could provide the basis for novel therapeutic strategies based on inhibiting Sox2 or enhancing Wnt signaling for the treatment of osteosarcomas.