Molecular Cancer Research最新文献

mTOR is a serine/threonine kinase that controls prostate cancer cell growth in part by regulating gene programs associated with metabolic and cell proliferation pathways. mTOR-mediated control of gene expression can be achieved via phosphorylation of transcription factors, leading to changes in their cellular localization and activities. mTOR also directly associates with chromatin in complex with transcriptional regulators, including the androgen receptor (AR). Nuclear mTOR (nmTOR) has been previously shown to act as a transcriptional integrator of the androgen signaling pathway in association with the chromatin remodeling machinery, AR, and FOXA1. However, the contribution of cytoplasmic mTOR (cmTOR) and nmTOR and the role played by FOXA1 in this process remains to be explored. Herein, we engineered cells expressing mTOR tagged with nuclear localization and export signals dictating mTOR localization. Transcriptome profiling in AR-positive prostate cancer cells revealed that nmTOR generally downregulates a subset of the androgen response pathway independently of its kinase activity, while cmTOR upregulates a cell cycle-related gene signature in a kinase-dependent manner. Biochemical and genome-wide transcriptomic analyses demonstrate that nmTOR functionally interacts with AR and FOXA1. Ablation of FOXA1 reprograms the nmTOR cistrome and transcriptome of androgen responsive prostate cancer cells. This works highlights a transcriptional regulatory pathway in which direct interactions between nmTOR, AR and FOXA1 dictate a combinatorial role for these factors in the control of specific gene programs in prostate cancer cells.

Implications: The finding that canonical and nuclear mTOR signaling pathways control distinct gene programs opens therapeutic opportunities to modulate mTOR activity in prostate cancer cells.

Breast cancer is the most common cancer in females, affecting one in every eight women and accounting for the majority of cancer-related deaths in women worldwide. Germline mutations in the BRCA1 and BRCA2 genes are significant risk factors for specific subtypes of breast cancer. BRCA1 mutations are associated with basal-like breast cancers, whereas BRCA2 mutations are associated with luminal-like disease. Defects in mammary epithelial cell differentiation have been previously recognized in germline BRCA1/2 mutation carriers even before cancer incidence. However, the underlying mechanism is largely unknown. Here, we employ spatial transcriptomics to investigate defects in mammary epithelial cell differentiation accompanied by distinct microenvironmental alterations in preneoplastic breast tissues from BRCA1/2 mutation carriers and normal breast tissues from noncarrier controls. We uncovered spatially defined receptor-ligand interactions in these tissues for the investigation of autocrine and paracrine signaling. We discovered that β1-integrin-mediated autocrine signaling in BRCA2-deficient mammary epithelial cells may differ from BRCA1-deficient mammary epithelial cells. In addition, we found that the epithelial-to-stromal paracrine signaling in the breast tissues of BRCA1/2 mutation carriers is greater than in control tissues. More integrin-ligand pairs were differentially correlated in BRCA1/2-mutant breast tissues than noncarrier breast tissues with more integrin receptor-expressing stromal cells.

Implications: These results suggest alterations in the communication between mammary epithelial cells and the microenvironment in BRCA1 and BRCA2 mutation carriers, laying the foundation for designing innovative breast cancer chemo-prevention strategies for high-risk patients.

Exosomal long noncoding RNAs (lncRNA) derived from cancer cells are implicated in various processes, including cancer cell proliferation, metastasis, and immunomodulation. We investigated the role and underlying mechanism of exosome-transmitted lncRNA NEAT1 in the immune escape of multiple myeloma cells from natural killer (NK) cells. Multiple myeloma cells and samples from patients with multiple myeloma were obtained. The effects of multiple myeloma cell-derived exosomes (multiple myeloma exosomes) and exosomal NEAT1 on the functions of NK cells were evaluated using EdU staining, CCK-8, flow cytometry, and ELISA. Chromatin and RNA immunoprecipitation were performed to identify interactions between NEAT1, enhancer of Zeste Homolog 2 (EZH2), and pre-B-cell leukemia transcription factor 1 (PBX1). A xenograft tumor model was constructed to verify the effects of exosomal NEAT1 on tumor growth. qRT-PCR, Western blot analysis, and IHC were conducted to detect related genes. NEAT1 levels were upregulated in multiple myeloma tumor tissues, multiple myeloma cells, and multiple myeloma exosomes. Multiple myeloma exosomes suppressed cell proliferation, promoted apoptosis, reduced natural killer group 2, member D (NKG2D)-positive cells, and the production of TNFα) and interferon-gamma (IFN-γ) in NK cells, whereas NEAT1-silenced exosomes had little effect. NEAT1 silenced PBX1 by recruiting EZH2. PBX1 knockdown abrogated the effects of NEAT1-silenced exosomes on NK and multiple myeloma cells. NEAT1-silenced exosomes inhibited tumor growth in mice, decreased Ki67 and PD-L1, and increased NKG2D, TNFα, and IFNγ in tumor tissues. In summary, multiple myeloma cell-derived exosomal NEAT1 suppressed NK-cell activity by downregulating PBX1, promoting multiple myeloma cell immune escape. This study suggests a potential strategy for treating multiple myeloma.

Implications: This study reveals that exosomal NEAT1 regulates EZH2/PBX1 axis to inhibit NK-cell activity, thereby promoting multiple myeloma cell immune escape, which offers a novel therapeutic potential for multiple myeloma.

11q13 amplification is a frequent event in human cancer and in particular in squamous cell carcinomas (SCC). Despite almost invariably spanning 10 genes, it is unclear which genetic components of the amplicon are the key driver events in SCC. A combination of computational, in vitro, ex vivo, and in vivo models leveraging efficient primary human keratinocyte genome editing by Cas9-RNP electroporation, identified ORAOV1, CCND1, and MIR548K as the critical drivers of the amplicon in head and neck SCC. CCND1 amplification drives the cell cycle in a CDK4/6/RB1-independent fashion and may confer a novel dependency on RRM2. MIR548K contributes to epithelial-mesenchymal transition. Finally, we identify ORAOV1 as an oncogene that acts likely via its ability to modulate reactive oxygen species. Thus, the 11q13 amplicon drives SCC through at least three independent genetic elements and suggests therapeutic targets for this morbid and lethal disease.

Implications: This work demonstrates novel mechanisms and ways to target these mechanisms underlying the most common amplification in squamous cell carcinoma, one of the most prevalent and deadly forms of human cancer.

The transcription factor, SOX10, plays an important role in the differentiation of neural crest precursors to the melanocytic lineage. Malignant transformation of melanocytes leads to the development of melanoma, and SOX10 promotes melanoma cell proliferation and tumor formation. SOX10 expression in melanomas is heterogeneous, and loss of SOX10 causes a phenotypic switch toward an invasive, mesenchymal-like cell state and therapy resistance; hence, strategies to target SOX10-deficient cells are an active area of investigation. The impact of cell state and SOX10 expression on antitumor immunity is not well understood but will likely have important implications for immunotherapeutic interventions. To this end, we tested whether SOX10 status affects the response to CD8+ T cell-mediated killing and T cell-secreted cytokines, TNFα and IFNγ, which are critical effectors in the cytotoxic killing of cancer cells. We observed that genetic ablation of SOX10 rendered melanoma cells more sensitive to CD8+ T cell-mediated killing and cell death induction by either TNFα or IFNγ. Cytokine-mediated cell death in SOX10-deficient cells was associated with features of caspase-dependent pyroptosis, an inflammatory form of cell death that has the potential to increase immune responses.

Implications: These data support a role for SOX10 expression altering the response to T cell-mediated cell death and contribute to a broader understanding of the interaction between immune cells and melanoma cells.

Irradiation (IR) is a highly effective cancer therapy; however, IR damage to tumor-adjacent healthy tissues can result in significant comorbidities and potentially limit the course of therapy. We have previously shown that protein kinase C delta (PKCδ) is required for IR-induced apoptosis and that inhibition of PKCδ activity provides radioprotection in vivo. Here we show that PKCδ regulates histone modification, chromatin accessibility, and double-stranded break (DSB) repair through a mechanism that requires Sirtuin 6 (SIRT6). Overexpression of PKCδ promotes genomic instability and increases DNA damage and apoptosis. Conversely, depletion of PKCδ increases DNA repair via nonhomologous end joining (NHEJ) and homologous recombination (HR) as evidenced by increased formation of DNA damage foci, increased expression of DNA repair proteins, and increased repair of NHEJ and HR fluorescent reporter constructs. Nuclease sensitivity indicates that PKCδ depletion is associated with more open chromatin, while overexpression of PKCδ reduces chromatin accessibility. Epiproteome analysis reveals increased chromatin associated H3K36me2 in PKCδ-depleted cells which is accompanied by chromatin disassociation of KDM2A. We identify SIRT6 as a downstream mediator of PKCδ. PKCδ-depleted cells have increased SIRT6 expression, and depletion of SIRT6 reverses changes in chromatin accessibility, histone modification and DSB repair in PKCδ-depleted cells. Furthermore, depletion of SIRT6 reverses radioprotection in PKCδ-depleted cells. Our studies describe a novel pathway whereby PKCδ orchestrates SIRT6-dependent changes in chromatin accessibility to regulate DNA repair, and define a mechanism for regulation of radiation-induced apoptosis by PKCδ.

Implications: PKCδ controls sensitivity to irradiation by regulating DNA repair.

Cervical cancer severely affects women's health with increased incidence and poor survival for patients with metastasis. Our study aims to investigate the mechanism by which lncRNA LRRC75A-AS1 regulates the epithelial-mesenchymal transition (EMT) of cervical cancer through modulating m6A and ubiquitination modification. In this study, tumor tissues were collected from patients to analyze the expression of LRRC75A-AS1 and SYVN1. Migratory and invasive capacities of HeLa and CaSki cells were evaluated with wound healing and transwell assays. CCK-8 and EdU incorporation assays were employed to examine cell proliferation. The interaction between LRRC75A-AS1, IGF2BP1, SYVN1, and NLRP3 was evaluated through RNA immunoprecipitation, RNA pull-down, FISH, and Co-IP assays, respectively. MeRIP-qPCR was applied to analyze the m6A modification of SYVN1 mRNA. A subcutaneous tumor model of cervical cancer was established. We showed LRRC75A-AS1 was upregulated in tumor tissues, and LRRC75A-AS1 enhanced EMT through activating NLRP3/IL-1β/Smad2/3 signaling in cervical cancer. Furthermore, LRRC75A-AS1 inhibited SYVN1-mediated NLRP3 ubiquitination by destabilizing SYVN1 mRNA. LRRC75A-AS1 competitively bound to IGF2BP1 protein and subsequently impaired the m6A modification of SYVN1 mRNA and its stability. Knockdown of LRRC75A-AS1 repressed EMT and tumor growth via inhibiting NLRP3/IL-1β/Smad2/3 signaling in mice. In conclusion, LRRC75A-AS1 competitively binds to IGF2BP1 protein to destabilize SYVN1 mRNA, subsequently suppresses SYVN1-mediated NLRP3 ubiquitination degradation and activates IL-1β/Smad2/3 signaling, thus promoting EMT in cervical cancer. Implications: LRRC75A-AS1 promotes cervical cancer progression, and this study suggests LRRC75A-AS1 as a new therapeutic target for cervical cancer.

Specificity protein 4 transcription factor (SP4), a member of the Sp/Krüppel-like family (KLF), could bind to GT and GC box promoters, and plays an essential role in transcriptional activating. Despite SP4 having been detected to be highly expressed in a variety of human tumors, its biological effect and underlying molecular mechanism in esophageal squamous cell carcinoma (ESCC) remains unclear. Our research discovered that high SP4 expression is detected in primary ESCC specimens and cell lines and is strongly associated with the ESCC tumor grade and poor prognosis. In vitro, knockdown of SP4 suppressed cell proliferation and cell-cycle progression and promoted apoptosis, whereas overexpression of SP4 did the opposite. In vivo, inhibiting SP4 expression in ESCC cells suppresses tumor growth. Subsequently, we demonstrated that SP4 acts as the transcriptional upstream of PHF14, which binds to PHF14 promoter region, thus promoting PHF14 transcription. PHF14 was also significantly expressed in patient tissues and various ESCC cell lines and its expression promoted cell proliferation and inhibited apoptosis. Moreover, knockdown of SP4 inhibited the Wnt/β-catenin signaling pathway, whereas overexpression of PHF14 eliminated the effects of SP4 knockdown in ESCC cells. These results demonstrate that SP4 activates the Wnt/β-catenin signaling pathway by driving PHF14 transcription, thereby promoting ESCC progression, which indicates that SP4 might act as a prospective prognostic indicator or therapeutic target for patients with ESCC.

Implications: This study identified SP4/PH14 axis as a new mechanism to promote the progression of ESCC, which may serve as a novel therapeutic target for patients with ESCC.

RNF185 is a RING finger domain-containing ubiquitin ligase implicated in ER-associated degradation. Prostate tumor patient data analysis revealed a negative correlation between RNF185 expression and prostate cancer progression and metastasis. Likewise, several prostate cancer cell lines exhibited greater migration and invasion capabilities in culture upon RNF185 depletion. Subcutaneous inoculation of mouse prostate cancer MPC3 cells stably expressing short hairpin RNA against RNF185 into mice resulted in larger tumors and more frequent lung metastases. RNA-sequencing and Ingenuity Pathway Analysis identified wound-healing and cellular movement among the most significant pathways upregulated in RNF185-depleted lines, compared with control prostate cancer cells. Gene Set Enrichment Analyses performed in samples from patients harboring low RNF185 expression and in RNF185-depleted lines confirmed the deregulation of genes implicated in epithelial-to-mesenchymal transition. Among those, COL3A1 was identified as the primary mediator of RNF185's ability to impact migration phenotypes. Correspondingly, enhanced migration and metastasis of RNF185 knockdown (KD) prostate cancer cells were attenuated upon co-inhibition of COL3A1. Our results identify RNF185 as a gatekeeper of prostate cancer metastasis, partly via its control of COL3A1 availability.

Implications: RNF185 is identified as an important regulator of prostate cancer migration and metastasis, in part due to its regulation of COL3A1. Both RNF185 and COL3A1 may serve as novel markers for prostate tumors.

Receptor tyrosine kinase KIT is frequently activated in acute myeloid leukemia (AML). While high PRL2 (PTP4A2) expression is correlated with activation of SCF/KIT signaling in AML, the underlying mechanisms are not fully understood. We discovered that inhibition of PRL2 significantly reduces the burden of oncogenic KIT-driven leukemia and extends leukemic mice survival. PRL2 enhances oncogenic KIT signaling in leukemia cells, promoting their proliferation and survival. We found that PRL2 dephosphorylates CBL at tyrosine 371 and inhibits its activity toward KIT, leading to decreased KIT ubiquitination and enhanced AKT and ERK signaling in leukemia cells.

Implications: Our studies uncover a novel mechanism that fine-tunes oncogenic KIT signaling in leukemia cells and will likely identify PRL2 as a novel therapeutic target in AML with KIT mutations.