Cancer Stem Cell Frequency Research Articles

Abstract PO1-06-07: EMSY enhances cancer stem cell self-renewal and tumorigenesis by reshaping methionine metabolism in triple-negative breast cancer

Abstract PO1-06-07: EMSY enhances cancer stem cell self-renewal and tumorigenesis by reshaping methionine metabolism in triple-negative breast cancer

Abstract PO2-24-06: Cancer-Associated Fibroblasts Promote Tumor Stemness in Aggressive Breast Cancers via NDRG1

Abstract Background: Inflammatory breast cancer (IBC) and triple negative breast cancer (TNBC) have the lowest 5-year survival rates among breast cancers: 40% for IBC and 77% for TNBC. Effective treatments for these aggressive tumors are urgently needed. To develop better treatments, it is crucial to understand the underlying mechanisms driving their aggressive biology. Our recent research has identified N-myc downstream regulated gene 1 (NDRG1) as a crucial driver of tumor progression and metastasis in aggressive breast cancers. We have also found that NDRG1 expression in tumors is correlated with poorer outcomes in IBC patients. Additionally, we have observed that cancer-associated fibroblasts (CAFs), derived from breast cancer biopsies, stimulate NDRG1 expression and phosphorylation as well as tumor stemness. Based on these findings, we hypothesize that NDRG1 is a key regulator of tumor stemness and progression, and secreted stromal factors regulate tumor stemness through NDRG1. Methods: To assess tumor stemness, we conducted in vitro experiments by quantifying the CD44+/CD24- subpopulation and performing mammosphere assays in NDRG1 control and depleted cells (SUM149, BCX010, MDA-IBC3). In vivo, we employed a limiting dilution transplantation assay, where NDRG1 control and knockdown SUM149 cells were transplanted into the mammary fat pad at different dilutions. We treated NDRG1 control and knockdown breast cancer cells with different patient-derived CAF-conditioned media (CAFs-CM, 50%, 24h) or control medium. The expression of NDRG1/pNDRG1 and CD44+/CD24- cells was evaluated by immunoblotting and flow cytometry. qPCR array was performed to evaluate tumor stemness markers. Results: NDRG1 depletion significantly reduced the CD44+/CD24- subpopulation (p< 0.001) and the efficiency of mammosphere formation (p=0.001). In vivo limiting dilution experiments demonstrated a substantial reduction in the frequency of breast cancer stem cells in NDRG1 knockdown cells (p= 1 x 10-12). Treatment of IBC cells with CAF-CM derived from breast cancer patients stimulated the cancer stem cell subpopulation [CD44+/CD24-: Control medium (43.1 ± 0.1) vs CAF-CM (55.1 ± 0.7); p=0.004] and increased NDRG1 and phospho-NDRG1 expression. However, the stimulation of NDRG1 knockdown cells with CAF-CM did not significantly alter the cancer stem cell population (0.2 ± 0.2 in Control medium versus 0.4 ± 0.3 in CAF-CM) and the expression of NDRG1/phospho-NDRG1. Additionally, qPCR array analysis revealed the upregulation of several cancer stem cell and self-renewal markers in CAF-CM stimulated cells compared to control-medium treated cells. Conclusions: Our data strongly support the role of NDRG1 as a critical regulator of tumor stemness. Moreover, we have discovered that conditioned media from patient-derived CAFs induces tumor stemness in breast cancer cells, and this effect is dependent on the expression NDRG1. Citation Format: Emilly Villodre, Jenny M Hogstrom, Xiaoding Hu, Nina Kozlova, Debu Tripathy, Taru Muranen, Bisrat Debeb. Cancer-Associated Fibroblasts Promote Tumor Stemness in Aggressive Breast Cancers via NDRG1 [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-24-06.

Abstract 5438: Circulating tumor cells exhibit a tumor stemness defense phenotype in Head and Neck cancer subjects undergoing cisplatin based chemotherapy

Abstract Introduction: We have proposed that tumor has its own defense mechanism similar to an organism having its own defense at the population level. We also proposed that the center of this tumor defense is the hypoxic niche of cancer stem cells (CSCs). Our lab has previously characterized the hypoxic niche of CSCs, and demonstrated that these CSCs reprogram to a highly inflammatory, aggressive and embryonic stemness phenotype during oxidative stress (1). These reprogrammed CSCs, the tumor stemness defense (TSD) phenotype is transient, and exert altruistic defense against bacterial invasion in SCC-25 cell line (2). Further, VEGF/VEGFR1 autocrine signaling was found in cisplatin induced TSD phenotype (4) and Myc/Hif2alpha stemness pathway was found in TSD phenotype of a leukemia stem cell model (3). We hypothesize that the platinum-induced stress may also activate TSD phenotype in the dormant CSC fraction of head and neck squamous cell carcinoma (HNSCC), which may mobilize to the distant tissue via circulation as circulating tumor cells (CTCs). Methods: To test the hypothesis, we isolated EpCAM+/ABCG2+ CTCs (blood, n=14) and EpCAM+/ABCG2+ CSCs (tumor tissue, n=6/14) of HNSCC subjects under cisplatin treatment. CTCs were collected from peripheral blood mononuclear cells (PBMNC) by the immunomagnetic sorting of EpCAM+ cells, and then cells were expanded in a defined serum free media that we used to maintain the hypoxic CSCs (1). We evaluated the EpCAM+/ABCG2+ CTCs and EpCAM+/ABCG2+ CSCs for TSD phenotype by performing qPCR gene expression, Boyden chamber assay of invasion, clonogenic assay and serial transplantation assay in NOD/SCID mice. Data was compared with the EpCAM+/ABCG2- cell population. We also developed a pre-clinical model of cisplatin-induced reprogramming of HNSCC derived CSCs to understand the molecular mechanisms. Results: In 8/14 patient derived EpCAM+/ABCG2+ CTCs and EpCAM+/ABCG2+ CSCs showed TSD phenotype associated gene expression, high migration/invasion, self sufficiency (ability to form spheroid when grown in serum free media without growth factors), enhanced secretion of protumorigenic growth factors; VEGF, SDF-1, PIGF, and HMGB1. These CTCs and CSCs have shown tumor formation with significant CSC frequency, when injected to NOD/SCID mice. Finally, using a SCC-25 cell line derived pre-clinical model, we demonstrated that cisplatin therapy reprogram CSCs to TSD phenotype. Conclusion: Our work indicates that CTCs with TSD phenotype may indicate the interaction between cisplatin and CSC niche defense. Using the pre-clinical model, the TSD phenotype based CSC niche defense mechanism may be further explored to develop markers for therapy response, metastasis or recurrence in HNSCC.

Abstract B090: Gut microbial suppression of epithelial ovarian cancer and attenuation of chemoresistance: opportunity for probiotics in patient care to improve survival

Abstract Up to 80% of ovarian cancer patient tumors will recur, become platinum resistant, and require additional treatment. Platinum resistance is correlated with poor overall survival and reduced therapeutic options for epithelial ovarian cancer (EOC) patients, a leading cause of gynecologic cancer death. Our findings identify a microbial tumor suppressive activity that is disrupted by antibiotics including vancomycin, metronidazole, neomycin, and ampicillin. Starting with a retrospective clinical analysis of OC patients, we found antibiotic use during chemotherapy treatment is associated with poor overall survival. In pre-clinical studies, we found that broad spectrum antibiotics (ABX) therapy, including metronidazole, ampicillin, vancomycin, and neomycin, augments tumor growth of EOC and leads to resistance to cisplatin. In follow up studies we determined vancomycin and metronidazole are sufficient to accelerate ovarian cancer growth and response to cisplatin therapy. Mechanistically, we determined that tumors from ABX treated mice exhibited increased proliferation, reduced apoptosis, decreased DNA damage in cisplatin treated specimens, and increased angiogenesis compared to control treated mice. As these are functional indicators of increased cancer stem cells (CSCs), we analyzed the tumors by RNAseq and single cell spheroid analysis for stem cell frequency. Tumors from ABX treated immune competent mice contained a higher frequency of cisplatin-induced CSCs than tumors from control treated mice. Tumors from untreated mice did not show increased CSCs. We determined that ABX treatment unmasked a microbiome dependent immune suppressor of cancer stem cells as tumors from immune deficient mice exhibited cisplatin induced CSCs in presence or absence of ABX. Finally, we determined that repletion of the microbiome via cecal transplants derived from ABX or control treated mice to recolonize the microbiome of ABX treated mice is sufficient to ameliorate the chemoresistance and survival of ABX treated mice indicative of a gut-derived tumor suppressor. We identified microbial metabolites suppressed in ovarian cancer patients and reduced by ABX in mice as candidate compounds that underlie the tumor suppressive activity. Collectively, the findings indicate the gut microbiome delivers a tumor suppressive signal that is unmasked by ABX treatment. We propose a probiotic strategy as a complement to standard of care may yield improved outcomes in ovarian cancer treatment. Citation Format: Ofer Reizes, Laura Chambers, Chad M. Michener, Mark Brown, Justin D. Lathia, Mohammed Dwidar, Naseer Sangwan, Roberto Vargas, Zeneng Wang, Adeline Hajjar. Gut microbial suppression of epithelial ovarian cancer and attenuation of chemoresistance: opportunity for probiotics in patient care to improve survival [abstract]. In: Proceedings of the AACR Special Conference on Ovarian Cancer; 2023 Oct 5-7; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(5 Suppl_2):Abstract nr B090.

Melatonin inhibits the stemness of head and neck squamous cell carcinoma by modulating HA synthesis via the FOSL1/HAS3 axis.

Hyaluronic acid (HA) is a glycosaminoglycan and the main component of the extracellular matrix (ECM), which has been reported to interact with its receptor CD44 to play critical roles in the self-renewal and maintenance of cancer stem cells (CSCs) of multiple malignancies. Melatonin is a neuroendocrine hormone with pleiotropic antitumor properties. However, whether melatonin could regulate HA accumulation in the ECM to modulate the stemness of head and neck squamous cell carcinoma (HNSCC) remains unknown. In this study, we found that melatonin suppressed CSC-related markers, such as CD44, of HNSCC cells and decreased the tumor-initiating frequency of CSCs in vivo. In addition, melatonin modulated HA synthesis of HNSCC cells by downregulating the expression of hyaluronan synthase 3 (HAS3). Further study showed that the Fos-like 1 (FOSL1)/HAS3 axis mediated the inhibitory effects of melatonin on HA accumulation and stemness of HNSCC in a receptor-independent manner. Taken together, melatonin modulated HA synthesis through the FOSL1/HAS3 axis to inhibit the stemness of HNSCC cells, which elucidates the effect of melatonin on the ECM and provides a novel perspective on melatonin in HNSCC treatment.

METTL16 promotes liver cancer stem cell self-renewal via controlling ribosome biogenesis and mRNA translation

BackgroundWhile liver cancer stem cells (CSCs) play a crucial role in hepatocellular carcinoma (HCC) initiation, progression, recurrence, and treatment resistance, the mechanism underlying liver CSC self-renewal remains elusive. We aim to characterize the role of Methyltransferase 16 (METTL16), a recently identified RNA N6-methyladenosine (m6A) methyltransferase, in HCC development/maintenance, CSC stemness, as well as normal hepatogenesis.MethodsLiver-specific Mettl16 conditional KO (cKO) mice were generated to assess its role in HCC pathogenesis and normal hepatogenesis. Hydrodynamic tail-vein injection (HDTVi)-induced de novo hepatocarcinogenesis and xenograft models were utilized to determine the role of METTL16 in HCC initiation and progression. A limiting dilution assay was utilized to evaluate CSC frequency. Functionally essential targets were revealed via integrative analysis of multi-omics data, including RNA-seq, RNA immunoprecipitation (RIP)-seq, and ribosome profiling.ResultsMETTL16 is highly expressed in liver CSCs and its depletion dramatically decreased CSC frequency in vitro and in vivo. Mettl16 KO significantly attenuated HCC initiation and progression, yet only slightly influenced normal hepatogenesis. Mechanistic studies, including high-throughput sequencing, unveiled METTL16 as a key regulator of ribosomal RNA (rRNA) maturation and mRNA translation and identified eukaryotic translation initiation factor 3 subunit a (eIF3a) transcript as a bona-fide target of METTL16 in HCC. In addition, the functionally essential regions of METTL16 were revealed by CRISPR gene tiling scan, which will pave the way for the development of potential inhibitor(s).ConclusionsOur findings highlight the crucial oncogenic role of METTL16 in promoting HCC pathogenesis and enhancing liver CSC self-renewal through augmenting mRNA translation efficiency.

EXOSC5 maintains cancer stem cell activity in endometrial cancer by regulating the NTN4/integrin β1 signalling axis.

Endometrial carcinoma (EC) is a common type of uterine cancer in developed countries, originating from the uterine epithelium. The incidence rate of EC in Taiwan has doubled from 2005. Cancer stem cells (CSCs) are a subpopulation of cancer cells that have high tumorigenicity and play a crucial role in the malignant processes of cancer. Targeting molecules associated with CSCs is essential for effective cancer treatments. This study delves into the role of Exosome component 5 (EXOSC5) in EC. Data from The Cancer Genome Atlas suggests a correlation between high EXOSC5 mRNA expression and unfavorable EC prognosis. EXOSC5 knockdown diminished EC-CSC self-renewal and reduced expression of key cancer stemness proteins, including c-MYC and SOX2. Intriguingly, this knockdown significantly curtailed tumorigenicity and CSC frequency in EC tumor spheres. A mechanistic examination revealed a reduction in netrin4 (NTN4) levels in EXOSC5-depleted EC cells. Moreover, NTN4 treatment amplified EC cell CSC activity and, when secreted, NTN4 partnered with integrin β1, subsequently triggering the FAK/SRC axis to elevate c-MYC activity. A clear positive relation between EXOSC5 and NTN4 was evident in 93 EC tissues. In conclusion, EXOSC5 augments NTN4 expression, activating c-MYC via the integrin β1/FAK/SRC pathway, offering potential avenues for EC diagnosis and treatment.

58 In vitro chemosensitivity of patient-derived ovarian cancer samples is not correlated with homologous recombination deficiency, platinum sensitivity, or cancer stem cell frequency

58 In vitro chemosensitivity of patient-derived ovarian cancer samples is not correlated with homologous recombination deficiency, platinum sensitivity, or cancer stem cell frequency

Terminally exhausted CD8+ T cells resistant to PD-1 blockade promote generation and maintenance of aggressive cancer stem cells.

Heterogeneity within the tumor infiltrating lymphocyte (TIL) population limits immunotherapeutic efficacy against cancer. Between two subpopulations of exhausted CD8+ TILs (progenitor-exhausted, TPEX; terminally-exhausted, TTEX), TTEX cells remain unresponsive to anti-PD1 therapy. Deciphering whether and how PD1-resistant TTEX cells engage in tumor promotion could improve the response to immunotherapy. Here, we report that TTEX cells actively participate in tumor progression by modulating cancer stem cells (CSC). TTEX cells strongly correlated with elevated CSC frequency in poorly immune-infiltrated (CD8+ TIL low) advanced human breast and ovarian carcinomas. TTEX directly upregulated CSC frequency in vitro, which was not affected by anti-PD1 treatment. The TTEX-influenced CSCs were highly clonogenic and exhibited a multi-drug resistant phenotype, overexpressing drug efflux pumps like ABCC1 and ABCB1. These CSCs were highly invasive, displaying increased invadopodia development and elevated cofilin, CXCR4, and MMP7 expression. The invasive properties along with epithelial-mesenchymal plasticity of TTEX-educated CSCs increased metastasis in vivo. TTEX increased cell surface levels and activation of VEGFR2 in CSCs, and silencing or inhibition of VEGFR2 reversed the CSC-stimulatory effects of TTEX. LAMP3 and NRP1 on the surface of TTEX stimulated VEGFR2 in CSCs to promote aggressiveness. Cumulatively, these findings suggest that screening carcinoma patients for both CD8+ TIL and TTEX frequency prior to anti-PD1-therapy could improve patient outcomes. Additionally, targeting the LAMP3/NRP1-VEGFR2 axis could be a therapeutic strategy in advanced carcinoma patients with limited CD8+ T cell infiltration and high TTEX frequency.

Cancer stem cell antigen nanodisc cocktail elicits anti-tumor immune responses in melanoma.

One of the major reasons for poor cancer outcomes is the existence of cancer stem cells (CSCs). CSCs are a small subpopulation of tumor cells that can self-renew, differentiate into the majority of tumor cells, and maintain tumorigenicity. As CSCs are resistant to traditional chemotherapy and radiation, they contribute to metastasis and relapse. Thus, new approaches are needed to target and eliminate CSCs. Here, we sought to target and reduce the frequency of CSCs in melanoma by therapeutic vaccination against CSC-associated transcription factors, such as Sox2 and Nanog, and aldehyde dehydrogenase (ALDH). Toward this goal, we have identified novel immunogenic peptide epitopes derived from CSC-associated Sox2 and Nanog and synthesized synthetic high-density lipoprotein (sHDL) nanodisc vaccine formulated with Sox2, Nanog, and ALDH antigen peptides together with CpG, a Toll-like receptor 9 agonist. Vaccination with nanodiscs containing six CSC antigen peptides elicited robust T cell responses against CSC-associated antigens and promoted intratumoral infiltration of CD8+ T cells, while reducing the frequency of CSCs and CD4+ regulatory T cells within melanoma tumors. Nanodisc vaccination effectively reduced tumor growth and significantly extended animal survival without toxicity toward normal stem cells. Overall, our therapeutic strategy against CSCs represents a cost-effective, safe, and versatile approach that may be applied to melanoma and other cancer types, as well as serve as a critical component in combined therapies to target and eliminate CSCs.

Graphdiyne oxide nanosheets exert anti-lymphoma effect by killing cancer stem cells and remodeling tumor microenvironment

Inflammatory and immunosuppressive tumor microenvironment (TME) is responsible for accelerating lymphoma initiation and progression. Graphdiyne oxide (GDYO) nanosheets have been shown to restrain tumor inflammation, remodel tumor microenvironment and suppress tumor growth. However, whether GDYO exerts anti-lymphoma effect has been elusive. Here, we first delineated the inflammatory and immunosuppressive signature of lymphoma TME by bioinformatic analysis. We then demonstrated the toxic effects of GDYO on multiple types of lymphoma cells in vitro. Further xenograft experiments showed that GDYO significantly eliminated tumor initiation and growth in vivo. Moreover, single-cell transcriptome sequencing of tumor tissue revealed GDYO treatment remarkably decreased the frequencies of cancer stem cells, immunosuppressive Treg cells and pro-inflammatory myeloid cells. Mechanistically, GDYO treatment markedly inhibited the Mif-Ackr3 signaling in tumor cells and CAFs, reduced expression of inflammatory cytokines in CAFs, mitigated the number of Treg cells and CSCs, which ultimately suppressed the growth of lymphoma. Finally, we showed that GDYO showed excellent biosafety and biocompatibility. Together, our study demonstrates that GDYO exerts the duplex anti-lymphoma effects by simultaneously killing the cancer stem cells and remodeling the lymphoma TME, which provide a reference for the potential application of GDYO nanomaterials as a novel nanomedicine to treat lymphoma in the future.

Abstract 890: DNA deaminase APOBEC3B regulates theresponse to PARP inhibitors of epithelial ovarian cancer stem cells

Abstract The most aggressive types of ovarian cancer is high-grade serous ovarian cancer (HGSOC), and the 5-year survival is less than 20%. Relapsed HGSOC patients often have enrichment of cancer stem cells (CSCs) with enhanced pro-survival and self-renewal capacity, suggesting a potential vulnerable population for effective targeted therapies with less toxicity. APOBEC3 proteins are a family of primate-specific DNA deaminases that catalyze cytidine to uracil (C-to-U) on single-strand DNA thereby introducing C-to-T/G point mutations. This important DNA modification is abundant in a wide array of cancer types including HGSOCs. However, the prevalence and significance of A3-induced DNA deamination in HGSOC CSC is currently unknown. We recently discovered that CSCs maintain a low A3-induced mutation burden. Using patient-sample derived spheroid culture and HGSOC cell lines, we found A3B was the only A3 members differentially expressed between CSC and non-CSC and the expression was significantly reduced in CSCs. In addition, inhibition of A3B leads to elevated frequency of CSCs and enhanced expression of the stemness factors. Important, our data suggest that DNA deaminase activity of A3B leads to induction of DNA damage thereby sensitizing HGSOC CSCs to PARPi. These novel insights suggest that DNA deamination plays a fundamental role in CSC biology and also raises the possibility that A3B activation may sensitize HGSOC CSCs to PARPi by promoting DNA damages. Citation Format: Jane isquith, Jessica Pham, Robert Phavong, Maria Rivera, Kathleen Fisch, Catriona Jamieson, Michael McHale, Ramez Eskander, Qingfei Jiang. DNA deaminase APOBEC3B regulates theresponse to PARP inhibitors of epithelial ovarian cancer stem cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 890.

Smad4 and p53 synergize in suppressing autochthonous intestinal cancer.

BackgroundSmad4 and p53 mutations are the most common mutations in human colorectal cancers (CRCs). We evaluated whether and how they are synergistic in intestinal carcinogenesis using novel autochthonous mouse models.MethodTo recapitulate human CRCs, we generated Villin‐Cre;Smad4F / F ;Trp53F / F mice. We then compared the intestinal phenotype of Villin‐Cre;Smad4F / F ;Trp53F / F mice (n = 40) with Villin‐Cre;Smad4F / F (n = 30) and Villin‐Cre;Trp53F / F mice (n = 45).ResultsTwenty‐week‐old Villin‐Cre;Smad4F / F ;Trp53F / F mice displayed spontaneous highly proliferative intestinal tumors, and 85% of mice developed adenocarcinomas. p21 was downregulated in the intestinal mucosa in Villin‐Cre;Smad4F / F ;Trp53F / F mice than in Villin‐Cre;Smad4F / F and Villin‐Cre;Trp53F / F mice. Villin‐Cre;Smad4F / F ;Trp53F / F mice displayed multistep intestinal tumorigenesis and Wnt activation. Long‐term CWP232291 (small‐molecule Wnt inhibitor) treatment of Villin‐Cre;Smad4F / F ;Trp53F / F mice suppressed intestinal tumorigenesis and progression. CWP232291 treatment downregulated cancer stem cell (CSC) tumor markers including CD133, Lgr‐5, and Sca‐1. CWP232291 treatment reduced the CSC frequency. Small‐molecule Wnt inhibitors reduced intestinal CSC populations and inhibited their growth, along with Bcl‐XL downregulation. Furthermore, BH3I‐1, a Bcl‐XL antagonist, increasingly inhibited intestinal CSCs than bulk tumor cells.ConclusionSmad4 loss and p53 loss are synergistic in autochthonous intestinal carcinogenesis, by downregulating p21 and activating Wnt/β‐catenin pathway.

Niclosamide induces miR-148a to inhibit PXR and sensitize colon cancer stem cells to chemotherapy.

SummaryTumor recurrence is often attributed to cancer stem cells (CSCs). We previously demonstrated that down-regulation of Pregnane X Receptor (PXR) decreases the chemoresistance of CSCs and prevents colorectal cancer recurrence. Currently, no PXR inhibitor is usable in clinic. Here, we identify miR-148a as a targetable element upstream of PXR signaling in CSCs, which when over-expressed decreases PXR expression and impairs tumor relapse after chemotherapy in mouse tumor xenografts. We then develop a fluorescent reporter screen for miR-148a activators and identify the anti-helminthic drug niclosamide as an inducer of miR-148a expression. Consequently, niclosamide decreased PXR expression and CSC numbers in colorectal cancer patient-derived cell lines and synergized with chemotherapeutic agents to prevent CSC chemoresistance and tumor recurrence in vivo. Our study suggests that endogenous miRNA inducers is a viable strategy to down-regulate PXR and illuminates niclosamide as a neoadjuvant repurposing strategy to prevent tumor relapse in colon cancer.

The Influence of Cancer Stem Cells on the Risk of Relapse in Adenocarcinoma and Squamous Cell Carcinoma of the Lung: A Prospective Cohort Study.

PurposeLung cancer relapse may be associated with the presence of a small population of cancer stem cells (CSCs) with unlimited proliferative potential. Our study assessed the relationship between CSCs and the relapse rate in patients harboring adenocarcinoma (ADL) and squamous cell carcinoma of the lung (SCCL).Experimental designThis is an observational prospective cohort study (NCT04634630) assessing the influence of CSC frequency on relapse rate after major lung resection in 35 patients harboring early (I-II) (n = 21) and locally advanced (IIIA) (n = 14) ADL and SCCL. There was a 2-year enrollment period followed by a 1-year follow-up period. Surgical tumor specimens were processed, and CSCs were quantified by cytofluorimetric analysis.ResultsCancer stem cells were expressed in all patients with a median of 3.1% of the primary cell culture. Primary analysis showed no influence of CSC frequency on the risk of relapse (hazard ratio [HR] = 1.05, 95% confidence interval [CI] = 0.85-1.30). At secondary analysis, patients with locally advanced disease with higher CSC frequency had an increased risk of relapse (HR = 1.26, 95% CI = 1.14-1.39), whereas this was not observed in early-stage patients (HR = 0.90, 95% CI = 0.65-1.25).ConclusionNo association was found between CSC and relapse rates after major lung resection in patients harboring ACL and SCCL. However, in locally advanced-stage patients, a positive correlation was observed between CSC frequency and risk of relapse. These results indicate a need for further molecular investigations into the prognostic role of CSCs at different lung cancer stages.Clinical Trial Registration NCT04634630.

Dissecting Tumor Growth: The Role of Cancer Stem Cells in Drug Resistance and Recurrence.

Simple SummaryCancer is one of the most debated problems all over the world. Cancer stem cells are considered responsible of tumor initiation, metastasis, drug resistance, and recurrence. This subpopulation of cells has been found into the tumor bulk and showed the capacity to self-renew, differentiate, up to generate a new tumor. In the last decades, several studies have been set on the molecular mechanisms behind their specific characteristics as the Wnt/β-catenin signaling, Notch signaling, Hedgehog signaling, transcription factors, etc. The most powerful part of CSCs is represented by the niches as “promoter” of their self-renewal and “protector” from the common oncological treatment as chemotherapy and radiotherapy. In our review article we highlighted the primary mechanisms involved in CSC tumorigenesis for the setting of further targets to control the metastatic process.Emerging evidence suggests that a small subpopulation of cancer stem cells (CSCs) is responsible for initiation, progression, and metastasis cascade in tumors. CSCs share characteristics with normal stem cells, i.e., self-renewal and differentiation potential, suggesting that they can drive cancer progression. Consequently, targeting CSCs to prevent tumor growth or regrowth might offer a chance to lead the fight against cancer. CSCs create their niche, a specific area within tissue with a unique microenvironment that sustains their vital functions. Interactions between CSCs and their niches play a critical role in regulating CSCs’ self-renewal and tumorigenesis. Differences observed in the frequency of CSCs, due to the phenotypic plasticity of many cancer cells, remain a challenge in cancer therapeutics, since CSCs can modulate their transcriptional activities into a more stem-like state to protect themselves from destruction. This plasticity represents an essential step for future therapeutic approaches. Regarding self-renewal, CSCs are modulated by the same molecular pathways found in normal stem cells, such as Wnt/β-catenin signaling, Notch signaling, and Hedgehog signaling. Another key characteristic of CSCs is their resistance to standard chemotherapy and radiotherapy treatments, due to their capacity to rest in a quiescent state. This review will analyze the primary mechanisms involved in CSC tumorigenesis, with particular attention to the roles of CSCs in tumor progression in benign and malignant diseases; and will examine future perspectives on the identification of new markers to better control tumorigenesis, as well as dissecting the metastasis process.

SIRT1 coordinates with the CRL4B complex to regulate pancreatic cancer stem cells to promote tumorigenesis

Pancreatic cancer is a common malignant tumor with poor prognosis. Recently, cancer stem cells (CSCs) were identified in several solid tumors, including pancreatic cancer. Although accumulating evidence indicates that sirtuin 1 (SIRT1) exerts biological functions in various cancers, how it contributes to tumorigenesis and metastasis of pancreatic cancer, as well as its role in CSCs, is still poorly defined. Here we show that SIRT1 interacts with the Cullin 4B (CUL4B)-Ring E3 ligase (CRL4B) complex, which is responsible for H2AK119 monoubiquitination (H2AK119ub1), collaborating as a functional unit. Genome-wide analysis of SIRT1/CUL4B targets identified a cohort of genes, including GRHL3 and FOXO3, critically involved in cell differentiation, growth, and migration. Furthermore, we found that SIRT1 and CUL4B collectively promote the proliferation, autophagy, and invasion of pancreatic cancer cells. Remarkably, we demonstrate that SIRT1/CUL4B promotes CSC-like properties, including increased stemness marker expression and sphere formation. In vivo experiments implied that SIRT1 promoted established tumor xenograft growth, increased tumor-initiating capacity in NOD/SCID mice, and increased CSC frequency. Strikingly, SIRT1 and CUL4B expression is markedly upregulated in a variety of human cancers, including pancreatic cancer. Our data provide a molecular basis for the functional interplay between histone deacetylation and ubiquitination. The results also implicate the SIRT1/CRL4B complex in pancreatic cancer metastasis and stem cell properties, thus supporting SIRT1 as a promising potential target for cancer therapy development.

All-trans retinoic acid and protein kinase C \u03b1/\u03b21 inhibitor combined treatment targets cancer stem cells and impairs breast tumor progression

Breast cancer is the leading cause of cancer death among women worldwide. Blocking a single signaling pathway is often an ineffective therapy, especially in the case of aggressive or drug-resistant tumors. Since we have previously described the mechanism involved in the crosstalk between Retinoic Acid system and protein kinase C (PKC) pathway, the rationale of our study was to evaluate the effect of combining all-trans-retinoic acid (ATRA) with a classical PCK inhibitor (Gö6976) in preclinical settings. Employing hormone-independent mammary cancer models, Gö6976 and ATRA combined treatment induced a synergistic reduction in proliferative potential that correlated with an increased apoptosis and RARs modulation towards an anti-oncogenic profile. Combined treatment also impairs growth, self-renewal and clonogenicity potential of cancer stem cells and reduced tumor growth, metastatic spread and cancer stem cells frequency in vivo. An in-silico analysis of “Kaplan–Meier plotter” database indicated that low PKCα together with high RARα mRNA expression is a favorable prognosis factor for hormone-independent breast cancer patients. Here we demonstrate that a classical PKC inhibitor potentiates ATRA antitumor effects also targeting cancer stem cells growth, self-renewal and frequency.

The small molecule drug CBL0137 increases the level of DNA damage and the efficacy of radiotherapy for glioblastoma.

Glioblastoma (GBM) is an incurable brain tumor with inevitable recurrence. This is in part due to a highly malignant cancer stem cell (CSC) subpopulation of tumor cells that is particularly resistant to conventional treatments, including radiotherapy. Here we show that CBL0137, a small molecule anti-cancer agent, sensitizes GBM CSCs to radiotherapy. CBL0137 sequesters the FACT (facilitates chromatin transcription) complex to chromatin, resulting in cytotoxicity preferentially within tumor cells. We show that when combined with radiotherapy, CBL0137 inhibited GBM CSC growth and resulted in more DNA damage in the CSCs compared to irradiation or drug alone. Using an in vivo subcutaneous model, we showed that the frequency of GBM CSCs was reduced when tumors were pretreated with CBL0137 and then exposed to irradiation. Survival studies with orthotopic GBM models resulted in significantly extended survival for mice treated with combinatorial therapy. As GBM CSCs contribute to the inevitable recurrence in patients, targeting them is imperative. This work establishes a new treatment paradigm for GBM that sensitizes CSCs to irradiation and may ultimately reduce tumor recurrence.

CDK5 Inhibition Abrogates TNBC Stem-Cell Property and Enhances Anti-PD-1 Therapy.

Triple‐negative breast cancer (TNBC) is the most aggressive subtype of breast cancer, in which the higher frequency of cancer stem cells (CSCs) correlates with the poor clinical outcome. An aberrant activation of CDK5 is found to associate with TNBC progression closely. CDK5 mediates PPARγ phosphorylation at its Ser 273, which induces CD44 isoform switching from CD44s to CD44v, resulting in an increase of stemness of TNBC cells. Blocking CDK5/pho‐PPARγ significantly reduces CD44v+ BCSCs population in tumor tissues, thus abrogating metastatic progression in TNBC mouse model. Strikingly, diminishing stemness transformation reverses immunosuppressive microenvironment and enhances anti‐PD‐1 therapeutic efficacy on TNBC. Mechanistically, CDK5 switches the E3 ubiquitin ligase activity of PPARγ and directly protects ESRP1 from a ubiquitin‐dependent proteolysis. This finding firstly indicates that CDK5 blockade can be a potent strategy to diminish stemness transformation and increase the response to PD‐1 blockade in TNBC therapy.