Dedifferentiation Of Cancer Cells Research Articles

Transposable elements as drivers of dedifferentiation: Connections between enhancers in embryonic stem cells, placenta, and cancer.

Transposable elements (TEs) have emerged as important factors in establishing the cell type-specific gene regulatory networks and evolutionary novelty of embryonic and placental development. Recently, studies on the role of TEs and their dysregulation in cancers have shed light on the transcriptional, transpositional, and regulatory activity of TEs, revealing that the activation of developmental transcriptional programs by TEs may have a role in the dedifferentiation of cancer cells to the progenitor-like cell states. This essay reviews the recent evidence of the cis-regulatory TEs (henceforth crTE) in normal development and malignancy as well as the key transcription factors and regulatory pathways that are implicated in both cell states, and presents existing gaps remaining to be studied, limitations of current technologies, and therapeutic possibilities.

Abstract 4393: Expression levels of T-cell factor-4 variants in hepato-gastrointestinal cancer cells and tissues

Abstract Background: We previously identified 14 variants of T-cell factor (TCF)-4, a key transcriptional factor in the canonical Wnt signaling pathway, from human liver cancer cell lines (Exp Cell Res 2011). The functional analysis of the variants demonstrated that the SxxSS motif played crucial roles in high tumorigenicity, resistance to hypoxia (PLoS ONE 2012), and EMT (Liver Int 2013). These findings suggest that expression levels and patterns of TCF-4 variants tightly regulate diverse phenotypes of cancer cells. Currently, we developed a novel RT-PCR system to quantitatively evaluate TCF-4 variant expressions by using the peptide nucleic acid (PNA)-directed PCR clamping method. Aim: To assess mRNA expression levels of TCF-4 variants in hepato-gastrointestinal cancer cell lines and colon cancer tissues, focusing on TCF-4J and TCF-4K with the presence (K) or absence (J) of the SxxSS motif. Methods: Thirteen cell lines used in this study were as follows: seven liver cancer; one fetus-derived immortalized hepatocyte; one gastric cancer; two pancreatic cancer; and two colon cancer cell lines. The liver cancer cell lines HAK-1A and HAK-1B are clonally sister cell lines. Sets of three forward primers and four reverse primers were used to generate templates for quantitative PCR (qPCR), and three fluorescence (FAM and Cy5)-tagged primers were applied to detect each variant. Thirty-nine resected human cancer and non-cancerous tissue pairs were used in the IRB-certified study (No. 19192). Results: All TCF-4 variants except TCF-4M and TCF-4X were specifically and reproducibly detected and quantified. Cancer cells derived from the colon and stomach highly expressed the TCF-4 variants, showing the highest expression in TCF-4J, while cancer cells from the liver and pancreas expressed relatively lower levels. There was no remarkable difference in the expression profile of TCF-4 variants between HAK-1A and HAK-1B. In colon cancer tissues, TCF-4J was significantly more expressed than TCF-4K. Conclusion: Although the variants had been identified from liver cancer cells, they were universally expressed in cells of other organs. TCF-4J, a variant responsible for aggressive cell phenotype, was prominently found in cancer cells of the digestive tract, where the canonical Wnt signal pathway is known to be constitutively active. A similar variant profile between two liver cancer cell lines with identical clonal origin suggests that the variant pattern in the cells reflects organ-specific traits rather than dynamic phenotypic changes during cancer cell dedifferentiation. Citation Format: Hironori Koga, Yasuko Imamura, Tomoya Sudo, Hiroyuki Suzuki, Toshimitsu Tanaka, Takahiko Sakaue, Atsutaka Masuda, Hideki Iwamoto, Toru Nakamura, Hirohisa Yano, Takumi Kawaguchi. Expression levels of T-cell factor-4 variants in hepato-gastrointestinal cancer cells and tissues [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4393.

Prevention of Metastasis by Suppression of Stemness Genes Using a Combination of microRNAs.

We propose an original strategy for metastasis prevention using a combination of three microRNAs that blocks the dedifferentiation of cancer cells in a metastatic niche owing to the downregulation of stemness genes. Transcriptome microarray analysis was applied to identify the effects of a mixture of microRNAs on the pattern of differentially expressed genes in human breast cancer cell lines. Treatment of differentiated CD44- cancer cells with the microRNA mixture inhibited their ability to form mammospheres in vitro. The combination of these three microRNAs encapsulated into lipid nanoparticles prevented lung metastasis in a mouse model of spontaneous metastasis. The mixture of three microRNAs (miR-195-5p/miR-520a/miR-630) holds promise for the development of an antimetastatic therapeutic that blocks tumor cell dedifferentiation, which occurs at secondary tumor sites and determines the transition of micrometastases to macrometastases.

Essential role of PLD2 in hypoxia-induced stemness and therapy resistance in ovarian tumors.

Hypoxia in solid tumors is an important source of chemoresistance that can determine poor patient prognosis. Such chemoresistance relies on the presence of cancer stem cells (CSCs), and hypoxia promotes their generation through transcriptional activation by HIF transcription factors. We used ovarian cancer (OC) cell lines, xenograft models, OC patient samples, transcriptional databases, induced pluripotent stem cells (iPSCs) and Assay for Transposase-Accessible Chromatin using sequencing (ATAC-seq). Here, we show that hypoxia induces CSC formation and chemoresistance in ovarian cancer through transcriptional activation of the PLD2 gene. Mechanistically, HIF-1α activates PLD2 transcription through hypoxia response elements, and both hypoxia and PLD2 overexpression lead to increased accessibility around stemness genes, detected by ATAC-seq, at sites bound by AP-1 transcription factors. This in turn provokes a rewiring of stemness genes, including the overexpression of SOX2, SOX9 or NOTCH1. PLD2 overexpression also leads to decreased patient survival, enhanced tumor growth and CSC formation, and increased iPSCs reprograming, confirming its role in dedifferentiation to a stem-like phenotype. Importantly, hypoxia-induced stemness is dependent on PLD2 expression, demonstrating that PLD2 is a major determinant of de-differentiation of ovarian cancer cells to stem-like cells in hypoxic conditions. Finally, we demonstrate that high PLD2 expression increases chemoresistance to cisplatin and carboplatin treatments, both in vitro and in vivo, while its pharmacological inhibition restores sensitivity. Altogether, our work highlights the importance of the HIF-1α-PLD2 axis for CSC generation and chemoresistance in OC and proposes an alternative treatment for patients with high PLD2 expression.

TERT accelerates BRAF mutant-induced thyroid cancer dedifferentiation and progression by regulating ribosome biogenesis.

TERT reactivation occurs frequently in human malignancies, especially advanced cancers. However, in vivo functions of TERT reactivation in cancer progression and the underlying mechanism are not fully understood. In this study, we expressed TERT and/or active BRAF (BRAF V600E) specifically in mouse thyroid epithelium. While BRAF V600E alone induced papillary thyroid cancer (PTC), coexpression of BRAF V600E and TERT resulted in poorly differentiated thyroid carcinoma (PDTC). Spatial transcriptome analysis revealed that tumors from mice coexpressing BRAF V600E and TERT were highly heterogeneous, and cell dedifferentiation was positively correlated with ribosomal biogenesis. Mechanistically, TERT boosted ribosomal RNA (rRNA) expression and protein synthesis by interacting with multiple proteins involved in ribosomal biogenesis. Furthermore, we found that CX-5461, an rRNA transcription inhibitor, effectively blocked proliferation and induced redifferentiation of thyroid cancer. Thus, TERT promotes thyroid cancer progression by inducing cancer cell dedifferentiation, and ribosome inhibition represents a potential strategy to treat TERT-reactivated cancers.

TNFR1 and TNFR2, Which Link NF-κB Activation, Drive Lung Cancer Progression, Cell Dedifferentiation, and Metastasis.

TNFR1 and TNFR2, encoded by TNFRSF1A and TNFRSF1B, respectively, are the most well-characterized members among the TNFR superfamily. TNFR1 is expressed in most cell types, while TNFR2 has been reported to be preferentially expressed in leukocytes. Lung cancer remains the leading cause of cancer mortality worldwide but TNFRs' activities in lung cancer development have not been fully evaluated. Recently, overexpressed TNFR1 was reported in a large proportion of human lung squamous cell carcinomas. Increased TNFR1 coupled with increased UBCH10 caused lung SCC cell dedifferentiation with epithelial-mesenchymal transition features and the metastasis in a combined spontaneous lung SCC and TNFR1 transgenic mouse model. UBCH10, an E2 ubiquitin-conjugating enzyme that is an oncogene, increased Sox2, c-Myc, Twist1, and Bcl2 levels. Increased TNFR1 upregulated UBCH10 expression by activating c-Rel and p65 NF-κB. Lung SCC patients overexpressing TNFRSF1A and one of these target genes died early compared to lung SCC patients expressing lower levels of these genes. Recently, we also revealed that TNFR2 was required for lung adenocarcinoma progression, delivering a signaling pathway of TNF/TNFR2/NF-κB-c-Rel, in which macrophage-produced ROS and TNF converted CD4 T cells to Foxp3 Treg cells, generating an immunosuppressive tumor microenvironment and promoting lung ADC progression. In human lung ADC cohorts, TNFRSF1B expression was highly correlated with TNF, FOXP3, and CD4 expression. Of note, TNF stimulated the activities of TNFR1 and TNFR2, two membrane-binding receptors, which accelerate tumorigenesis through diverse mechanisms. This review focuses on these new findings regarding the roles of TNFR1 and TNFR2 in lung SCC and ADC development in humans and mice, and highlights the potential therapeutic targets of human lung cancers.

Hypoxia-induced cancer cell reprogramming: a review on how cancer stem cells arise.

Cancer stem cells are a subset of cells within the tumor that possess the ability to self-renew as well as differentiate into different cancer cell lineages. The exact mechanisms by which cancer stem cells arise is still not completely understood. However, current research suggests that cancer stem cells may originate from normal stem cells that have undergone genetic mutations or epigenetic changes. A more recent discovery is the dedifferentiation of cancer cells to stem-like cells. These stem-like cells have been found to express and even upregulate induced pluripotent stem cell markers known as Yamanaka factors. Here we discuss developments in how cancer stem cells arise and consider how environmental factors, such as hypoxia, plays a key role in promoting the progression of cancer stem cells and metastasis. Understanding the mechanisms that give rise to these cells could have important implications for the development of new strategies in cancer treatments and therapies.

Interleukin-6 promotes the dedifferentiation of papillary thyroid cancer cells.

Radioiodine treatment is a fundamental therapy for patients with papillary thyroid cancer (PTC). Sodium/iodide symporter (NIS)-mediated iodine uptake is a prerequisite for the efficacy of radioiodine therapy. Interleukin-6 (IL-6) is a pro-tumor cytokine, but its regulation of NIS expression in PTC has not been elucidated. In this study, we found that IL-6 enhanced the proliferation ability of PTC cells. Moreover, the negative association between IL-6 and NIS expression in thyroid cancer tissues was demonstrated. IL-6 downregulated thyroid-specific genes such as NIS, thyroid peroxidase, and thyroid-stimulating hormone receptor and thyroid-specific transcription factors including thyroid transcription factor-1 (TTF-1) and paired box protein-8 (PAX-8). The inhibitory effects of IL-6 on NIS expression were alleviated by mitogen-activated protein kinase and Janus kinase inhibitors. Depletion of c-Jun or STAT3 also rescued IL-6-induced NIS downregulation, with STAT3 depletion exerting a stronger effect. TTF-1 protein expression was also restored by depleting c-Jun or STAT3. STAT3 depletion, but not c-Jun depletion, alleviated the inhibitory effect of IL-6 on PAX-8 expression. Moreover, the downregulation of NIS by IL-6 was rescued by overexpressing TTF-1 and PAX-8. Tocilizumab, an IL-6 receptor blocker, did not have any cytostatic activity in PTC cells, and it also failed to induce redifferentiation in vitro. However, we found that the drug blocked the inhibitory effect of IL-6 on NIS expression. In summary, IL-6 inhibits NIS transcription in PTC cells by activating mitogen-activated protein kinase and Janus kinase signaling.

HIF1α and HIF2α regulate non-small-cell lung cancer dedifferentiation via expression of Sox2 and Oct4 under hypoxic conditions

ObjectiveTo explore HIF1α and HIF2α regulate the dedifferentiation of lung cancer cells under hypoxic conditions through Sox2 and Oct4. Materials and methods: HIF1α, HIF2α, Sox2 and Oct4 expression was analysed in lung cancer tissues. We analysed sphere formation by single-cell of differentiated lung cancer under hypoxia, and detected the expression of CD133, CD44, Sox2, Oct4, HIF1α and HIF2α. We knocked out HIF1α, HIF2α, Sox2 or Oct4 in cells, cultured the cells under hypoxic conditions and detected CD133 and CD44 using western blotting. We also detected the apoptosis rate of cells with HIF1α, HIF2α, Sox2 or Oct4 knockout. Results: There was more sphere formation of differentiated lung cancer cells under hypoxic conditions than of control cells under normoxic conditions. These newly formed spheres highly expressed CD133 and CD44. TCGA database showed high expression of HIF1α and HIF2α in lung cancer tissues. After knocking out HIF1α and HIF2α, the expression of Sox2, Oct4, CD133 and CD44 decreased significantly, and after knocking out Sox2 or Oct4, the expression of CD133 and CD44 decreased. Conclusion: HIF1α and HIF2α regulate non-small-cell lung cancer dedifferentiation through Sox2 and Oct4 under hypoxic conditions.

Methods for assessing the effect of microRNA on stemness genes

According to the latest concepts, for micrometastasis to develop into macrometastasis, differentiated cancer cells must revert to a dedifferentiated state. Activation of stemness genes plays a key role in this transition. Suppression of stemness gene expression using microRNAs can become the basis for the development of effective anti-metastatic drugs. This article provides an overview of the existing methods for assessing the effect of microRNAs on stemness genes and cancer cell dedifferentiation.

Cancer Cell De-Differentiation: Plasticity-Driven Stratagem For Tumor Metastasis and Recurrence.

Tumor recurrence is a colossal challenge in clinical oncology. This multifactorial problem is attributed to the emergence of additional genetic mutations and the presence of dormant cancer cells. However, the plasticity of non-stem cancer cells and the acquisition of cancer stem cell (CSC) functionality is another contributing factor to tumor recurrence. Herein, I focus attention on the mechanisms that fuel cancer cell de-differentiation and the interplay between intra-cellular regulators and tumor microenvironment (TME) landscape that promotes cancer cell stemness. Our understanding of the mechanisms underlying tumor cell de-differentiation is crucial for developing innovative therapeutic strategies that prevent cancer from ever recurring.

Linear and nonlinear rheology of liberase-treated breast cancer tumors.

Extracellular matrix (ECM) rigidity has been shown to increase the invasive properties of breast cancer cells, promoting transformation and metastasis through mechanotransduction. Reducing ECM stiffness via enzymatic digestion could be a promising approach to slowing breast cancer development by de-differentiation of breast cancer cells to less aggressive phenotypes and enhancing the effectiveness of existing chemotherapeutics via improved drug penetrance throughout the tumor. In this study, we examine the effects of injectable liberase (a blend of collagenase and thermolysin enzymes) treatments on the linear and nonlinear rheology of allograft 4T1 mouse mammary tumors. We perform two sets of in vivo mouse studies, in which either one or multiple treatment injections occur before the tumors are harvested for rheological analysis. The treatment groups in each study consist of a buffer control, free liberase enzyme in buffer, a thermoresponsive copolymer called LiquoGel (LQG) in buffer, and a combined, localized injection of LQG and liberase. All tumor samples exhibit gel-like linear rheological behavior with the elastic modulus significantly larger than the viscous modulus and both independent of frequency. Tumors that receive a single injection of localized liberase have significantly lower tumor volumes and lower tissue moduli at both the center and edge compared to buffer- and free liberase-injected control tumors, while tissue viscoelasticity remains relatively unaffected. Tumors injected multiple times with LQG and liberase also have lower tissue volumes but possess higher tissue moduli and lower viscoelasticities compared to the other treatment groups. We propose that a mechanotransductive mechanism could cause the formation of smaller but stiffer tumors after repeated, localized liberase injections. Large amplitude oscillatory shear (LAOS) experiments are also performed on tissues from the multiple injection study and the results are analyzed using MITlaos. LAOS analysis reveals that all 4T1 tumors from the multiple injection study exhibit nonlinear rheological behavior at high strains and strain rates. Examination of the Lissajous-Bowditch curves, Chebyshev coefficient ratios, elastic moduli, and dynamic viscosities demonstrate that the onset and type of nonlinear behavior is independent of treatment type and elastic modulus, suggesting that multiple liberase injections do not affect the nonlinear viscoelasticity of 4T1 tumors.

The Revelation of Continuously Organized, Co-Overexpressed Protein-Coding Genes with Roles in Cellular Communications in Breast Cancer

Many human cancers, including breast cancer, are polygenic and involve the co-dysregulation of multiple regulatory molecules and pathways. Though the overexpression of genes and amplified chromosomal regions have been closely linked in breast cancer, the notion of the co-upregulation of genes at a single locus remains poorly described. Here, we describe the co-overexpression of 34 continuously organized protein-coding genes with diverse functions at 8q.24.3(143437655-144326919) in breast and other cancer types, the CanCord34 genes. In total, 10 out of 34 genes have not been reported to be overexpressed in breast cancer. Interestingly, the overexpression of CanCord34 genes is not necessarily associated with genomic amplification and is independent of hormonal or HER2 status in breast cancer. CanCord34 genes exhibit diverse known and predicted functions, including enzymatic activities, cell viability, multipotency, cancer stem cells, and secretory activities, including extracellular vesicles. The co-overexpression of 33 of the CanCord34 genes in a multivariant analysis was correlated with poor survival among patients with breast cancer. The analysis of the genome-wide RNAi functional screening, cell dependency fitness, and breast cancer stem cell databases indicated that three diverse overexpressed CanCord34 genes, including a component of spliceosome PUF60, a component of exosome complex EXOSC4, and a ribosomal biogenesis factor BOP1, shared roles in cell viability, cell fitness, and stem cell phenotypes. In addition, 17 of the CanCord34 genes were found in the microvesicles (MVs) secreted from the mesenchymal stem cells that were primed with MDA-MB-231 breast cancer cells. Since these MVs were important in the chemoresistance and dedifferentiation of breast cancer cells into cancer stem cells, these findings highlight the significance of the CanCord34 genes in cellular communications. In brief, the persistent co-overexpression of CanCord34 genes with diverse functions can lead to the dysregulation of complementary functions in breast cancer. In brief, the present study provides new insights into the polygenic nature of breast cancer and opens new research avenues for basic, preclinical, and therapeutic studies in human cancer.

A MYC-ZNF148-ID1/3 regulatory axis modulating cancer stem cell traits in aggressive breast cancer

The MYC proto-oncogene (MYC) is one of the most frequently overexpressed genes in breast cancer that drives cancer stem cell-like traits, resulting in aggressive disease progression and poor prognosis. In this study, we identified zinc finger transcription factor 148 (ZNF148, also called Zfp148 and ZBP-89) as a direct target of MYC. ZNF148 suppressed cell proliferation and migration and was transcriptionally repressed by MYC in breast cancer. Depletion of ZNF148 by short hairpin RNA (shRNA) and CRISPR/Cas9 increased triple-negative breast cancer (TNBC) cell proliferation and migration. Global transcriptome and chromatin occupancy analyses of ZNF148 revealed a central role in inhibiting cancer cell de-differentiation and migration. Mechanistically, we identified the Inhibitor of DNA binding 1 and 3 (ID1, ID3), drivers of cancer stemness and plasticity, as previously uncharacterized targets of transcriptional repression by ZNF148. Silencing of ZNF148 increased the stemness and tumorigenicity in TNBC cells. These findings uncover a previously unknown tumor suppressor role for ZNF148, and a transcriptional regulatory circuitry encompassing MYC, ZNF148, and ID1/3 in driving cancer stem cell traits in aggressive breast cancer.

A happy cell stays home: When metabolic stress creates epigenetic advantages in the tumor microenvironment.

A paradox of fast-proliferating tumor cells is that they deplete extracellular nutrients that often results in a nutrient poor microenvironment in vivo. Having a better understanding of the adaptation mechanisms cells exhibit in response to metabolic stress will open new therapeutic windows targeting the tumor’s extreme nutrient microenvironment. Glutamine is one of the most depleted amino acids in the tumor core and here, we provide insight into how important glutamine and its downstream by-product, α-ketoglutarate (αKG), are to communicating information about the nutrient environment. This communication is key in the cell’s ability to foster adaptation. We highlight the epigenetic changes brought on when αKG concentrations are altered in cancer and discuss how depriving cells of glutamine may lead to cancer cell de-differentiation and the ability to grow and thrive in foreign environments. When we starve cells, they adapt to survive. Those survival “skills” allow them to go out looking for other places to live and metastasize. We further examine current challenges to modelling the metabolic tumor microenvironment in the laboratory and discuss strategies that consider current findings to target the tumor’s poor nutrient microenvironment.

Abstract 3325: ERK inhibitor increases cancer stem cell population in NSCLC through Slug-Mediated epithelial-to-mesenchymal transition

Abstract The aberrant activation of the Mitogen-activated protein kinase pathway (MAPK/ERK pathway) has been found to play an important role in many cancers including non-small-cell lung cancer (NSCLC). Multiple inhibitors targeting this pathway have been developed to treat cancer patients harboring the aberrant MAPK pathway genes. ERK inhibitors (ERKi) have been shown to be effective in a variety of solid-tumor malignancies, but like other MAPK inhibitors, they rarely confer complete and durable responses. Therefore, it is important to define the mechanism underlying potential tumor relapse following ERKi treatment. In this study, we found that ERKi treatment expanded the cancer stem cell (CSC) population in various NSCLC cell lines and a NSCLC patient-derived xenograft (PDX) harboring aberrant MAPK signaling. Such expansion of the CSC population is mainly caused by enhanced epithelial-to-mesenchymal transition (EMT)-mediated cancer cell dedifferentiation. Mechanistically, we revealed that ERK inhibition induces EMT via pSTAT3-mediated upregulation of EMT-transcription factor Slug. Specifically, we found that ERK inhibition increased phosphorylation of STAT3 at Y705, which further increased the expression of miR-204. Increased miR-204 then downregulated expression of SPDEF, a transcriptional repressor of Slug, thereby derepressing Slug expression. Moreover, we found that a low expression of Slug is necessary for maintaining stemness properties of CSCs. Thus, ERKi treatment-increased Slug must be downregulated to allow these cells to fully acquire stemness, and this process is mediated by a Slug-miR-200c negative feedback loop. Finally, we demonstrated that the JAK/STAT pathway inhibitor Ruxolitinib can block the ERK inhibitor-induced EMT and CSCs expansion, providing a feasible combination inhibitor approach for treating NSCLC patients. Overall, these studies provide a better understanding of the tumor relapse following ERKi treatment, and define the role of Slug in de novo production of CSCs and their maintenance. Citation Format: Shurui Cai, Na Li, Xuetao Bai, Ananya Banerjee, Lavudi Kousalya, Qi-en Wang. ERK inhibitor increases cancer stem cell population in NSCLC through Slug-Mediated epithelial-to-mesenchymal transition [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 3325.

Abstract 1587: Multi region single cell sequencing reveals dedifferentiation programs, angiogenic heterogeneity and the effect of microenvironmental hypoxia in ccRCC tumors

Abstract Kidney cancer is the seventh most common malignancy in the Western world and 80% of these are clear cell renal cell cancers (ccRCC). ccRCC arises following inactivation of the VHL gene, which negatively regulates HIF (hypoxia-inducible factor) transcription factors. Therefore, in ccRCC, HIF is constitutively active and drives a gene expression program that is central to tumorigenesis. Whilst this is necessary for ccRCC formation, it is not sufficient, and other mutations must also occur in combination with VHL inactivation to drive ccRCC tumorigenesis. The mechanisms underlying their synergy with VHL inactivation remain poorly understood. These secondary driver mutations are often subclonal in nature, suggesting the presence of phenotypically distinct malignant cells within an individual tumor. This intratumor heterogeneity renders it difficult to study the functional impact of driver mutations in ccRCC by conventional ‘bulk’ analyses such as RNA-seq. Consequently, the molecular mechanisms underlying ccRCC initiation are not known. Furthermore, non-malignant stromal cells (including the vasculature and immune response) can support tumor growth, and little is known as to how they interact with malignant cells in ccRCC. This is particularly important since current therapeutic strategies in kidney cancer target the stromal compartment. Therefore, there is an unmet need to better-understand transcriptional heterogeneity and cellular diversity in ccRCC. To that end, we have sampled multiple regions from ccRCC tumors (and tumor-adjacent kidney tissue) and performed single cell RNA-seq (10x Genomics) on approximately 150,000 individual cells. These encompass malignant cells as well as non-malignant cells (including fibroblasts, endothelial cells, pericytes and immune cells), both of which exhibit pronounced transcriptional heterogeneity within and between tumors. Analysis of these transcriptomes has identified evolutionary gene expression programs underlying cancer cell dedifferentiation. In addition, we observe concurrent heterogeneity in angiogenic signaling between malignant cells and non-malignant blood vessel cells within these tumors. Lastly, we have explored the effect of microenvironmental hypoxia across different ccRCC tumor cell types. In summary, we present a single cell atlas derived from multi-region heterogenous ccRCC samples. This sheds light on the mechanisms underlying tumor evolution and progression, as well as angiogenic heterogeneity (which may contribute to the variable response to receptor tyrosine kinase inhibition) and the effect of hypoxia on ccRCC biology. Citation Format: Olivia Lombardi, Ran Li, Lisa Browning, Peter J. Ratcliffe, David R. Mole. Multi region single cell sequencing reveals dedifferentiation programs, angiogenic heterogeneity and the effect of microenvironmental hypoxia in ccRCC tumors [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 1587.

Redox Homeostasis in Thyroid Cancer: Implications in Na+/I- Symporter (NIS) Regulation.

Radioiodine therapy (RAI) is a standard and effective therapeutic approach for differentiated thyroid cancers (DTCs) based on the unique capacity for iodide uptake and accumulation of the thyroid gland through the Na+/I− symporter (NIS). However, around 5–15% of DTC patients may become refractory to radioiodine, which is associated with a worse prognosis. The loss of RAI avidity due to thyroid cancers is attributed to cell dedifferentiation, resulting in NIS repression by transcriptional and post-transcriptional mechanisms. Targeting the signaling pathways potentially involved in this process to induce de novo iodide uptake in refractory tumors is the rationale of “redifferentiation strategies”. Oxidative stress (OS) results from the imbalance between ROS production and depuration that favors a pro-oxidative environment, resulting from increased ROS production, decreased antioxidant defenses, or both. NIS expression and function are regulated by the cellular redox state in cancer and non-cancer contexts. In addition, OS has been implicated in thyroid tumorigenesis and thyroid cancer cell dedifferentiation. Here, we review the main aspects of redox homeostasis in thyrocytes and discuss potential ROS-dependent mechanisms involved in NIS repression in thyroid cancer.

A Novel Estrogen Receptor β Agonist Diminishes Ovarian Cancer Stem Cells via Suppressing the Epithelial-to-Mesenchymal Transition.

Simple SummaryEstrogen receptors α (ERα) and β (ERβ) show distinct contributions to tumor initiation and progression. Given that ERβ mainly functions as a “tumor suppressor”, activation of ERβ using its specific agonist should be able to inhibit tumor progression. In this study, we show that a newly developed ERβ agonist, OSU-ERb-12, can not only impede ovarian cancer cell expansion and tumor growth but also reduce the cancer stem cell (CSC) population. OSU-ERb-12 could inhibit epithelial-to-mesenchymal transition (EMT) in ovarian cancer cells by increasing Snail expression, thereby, blocking EMT-mediated cancer cell dedifferentiation. We also found that OSU-ERb-12 inhibits ovarian cancer expansion in an ERα-independent manner while limiting the CSC population in an ERα-dependent manner. Taken together, our data suggest that the newly developed ERβ agonist OSU-ERb-12 can be used not only to hinder tumor growth but also has the potential to prevent tumor relapse and metastasis by depleting CSCs.Epithelial ovarian cancer is the most lethal malignancy of the female reproductive tract. A healthy ovary expresses both Estrogen Receptor α (ERα) and β (ERβ). Given that ERα is generally considered to promote cell survival and proliferation, thereby, enhancing tumor growth, while ERβ shows a protective effect against the development and progression of tumors, the activation of ERβ by its agonists could be therapeutically beneficial for ovarian cancer. Here, we demonstrate that the activation of ERβ using a newly developed ERβ agonist, OSU-ERb-12, can impede ovarian cancer cell expansion and tumor growth in an ERα-independent manner. More interestingly, we found that OSU-ERb-12 also reduces the cancer stem cell (CSC) population in ovarian cancer by compromising non-CSC-to-CSC conversion. Mechanistically, we revealed that OSU-ERb-12 decreased the expression of Snail, a master regulator of the epithelial-to-mesenchymal transition (EMT), which is associated with de novo CSC generation. Given that ERα can mediate EMT and facilitate maintenance of the CSC subpopulation and that OSU-ERb-12 can block the transactivity of ERα, we conclude that OSU-ERb-12 reduces the CSC subpopulation by inhibiting EMT in an ERα-dependent manner. Taken together, our data indicate that the ERβ agonist OSU-ERb-12 could be used to hinder tumor progression and limit the CSC subpopulation with the potential to prevent tumor relapse and metastasis in patients with ovarian cancer.

MUC1-C integrates type II interferon and chromatin remodeling pathways in immunosuppression of prostate cancer

ABSTRACT The oncogenic MUC1-C protein drives dedifferentiation of castrate resistant prostate cancer (CRPC) cells in association with chromatin remodeling. The present work demonstrates that MUC1-C is necessary for expression of IFNGR1 and activation of the type II interferon-gamma (IFN-γ) pathway. We show that MUC1-C→ARID1A/BAF signaling induces IFNGR1 transcription and that MUC1-C-induced activation of the NuRD complex suppresses FBXW7 in stabilizing the IFNGR1 protein. MUC1-C and NuRD were also necessary for expression of the downstream STAT1 and IRF1 transcription factors. We further demonstrate that MUC1-C and PBRM1/PBAF are necessary for IRF1-induced expression of (i) IDO1, WARS and PTGES, which metabolically suppress the immune tumor microenvironment (TME), and (ii) the ISG15 and SERPINB9 inhibitors of T cell function. Of translational relevance, we show that MUC1 associates with expression of IFNGR1, STAT1 and IRF1, as well as the downstream IDO1, WARS, PTGES, ISG15 and SERPINB9 immunosuppressive effectors in CRPC tumors. Analyses of scRNA-seq data further demonstrate that MUC1 correlates with cancer stem cell (CSC) and IFN gene signatures across CRPC cells. Consistent with these results, MUC1 associates with immune cell-depleted “cold” CRPC TMEs. These findings demonstrate that MUC1-C integrates chronic activation of the type II IFN-γ pathway and induction of chromatin remodeling complexes in linking the CSC state with immune evasion.