Project description:The tumor suppressor gene TP53 is the most frequently mutated gene in numerous cancer types, including prostate cancer (PCa). Specifically, missense mutations in TP53 are selectively enriched in PCa, and cluster to particular "hot spots" in the p53 DNA binding domain with mutation at the R273 residue occurring most frequently. While this residue is similarly mutated to R273C-p53 or R273H-p53 in all cancer types examined, in PCa selective enrichment of R273C-p53 is observed. Importantly, examination of clinical datasets indicated that TP53 heterozygosity can either be maintained or loss of heterozygosity (LOH) occurs. Thus, to mimic tumor-associated mutant p53, R273C-p53 and R273H-p53 isogenic PCa models were developed in the presence or absence of wild-type p53. In the absence of wild-type p53, both R273C-p53 and R273H-p53 exhibited similar loss of DNA binding, transcriptional profiles, and loss of canonical tumor suppressor functions associated with wild-type p53. In the presence of wild-type p53 expression, both R273C-p53 and R273H-p53 supported canonical p53 target gene expression yet elicited distinct cistromic and transcriptional profiles when compared to each other. Moreover, heterozygous modeling of R273C-p53 or R273H-p53 expression resulted in distinct phenotypic outcomes in vitro and in vivo. Thus, mutant p53 acts in a context-dependent manner to elicit pro-tumorigenic transcriptional profiles, providing critical insight into mutant p53-mediated prostate cancer progression.
Project description:Transcription factor ZIC2 plays a pro-tumorigenic role in several human cancers. Herein, we demonstrate that elevated ZIC2 expression was associated with lower overall and post-progression survival of epithelial ovarian cancer (EOC) patients. Knockout of ZIC2 in EOC cells attenuated tumorigenic phenotypes in vitro and in vivo, indicating a pro-tumorigenic role for ZIC2 in EOC. On the other hand, however, overexpression of ZIC2 in EOC cells that do not express endogenous ZIC2 promoted cell migration and sphere formation, but inhibited cell growth and colony formation in vitro and tumor growth in vivo, indicating a context-dependent function for ZIC2 in EOC. Transcriptomic study showed that ZIC2-regulated genes were involved in multiple biological processes and signaling pathways associated with tumor progression and that ZIC2 regulated common or distinct genes in ZIC2 knockout and overexpression models, which explains the consistency and discrepancy in ZIC2 functions observed in the two models. In conclusion, our findings reveal a context-dependent role for ZIC2 in regulating tumorigenic phenotypes in EOC, providing evidence that ZIC2 can be a potential therapeutic target for EOCs that express a high level of ZIC2.
Project description:Apart from the constitutive proteasome, the immunoproteasome that comprises the three proteolytic subunits LMP2, MECL-1 and LMP7 is expressed in most immune cells. In this study we describe two opposing roles for immunoproteasomes in regulating the tumor microenvironment. During chronic inflammation, immunoproteasomes modulated the expression of pro-tumorigenic cytokines and chemokines and enhanced infiltration of innate immune cells that led to the onset of colitis-associated carcinogenesies (CAC). In ulcerative colitis (UC) patients with high risk for CAC, immunoproteasome-induced pro-tumorigenic mediators were highly upregulated. Interestingly, the role for the same enzymatic complex in melanoma tumors is relatively unknown. We found that the high expression of immunoproteasomes in human melanoma was associated with better prognosis. Our data revealed that the immunoproteasome has a strong anti-tumorigenic function in cancer types with non-inflammatory microenvironment such as melanoma. CD8+ cytotoxic T lymphocytes (CTLs) from immunoproteasome-deficient mice were reduced during T cell homeostasis and were not able to combat melanoma efficiently. Our results indicate that the immunoproteasome exhibits either pro- or anti-tumoral properties in a context-dependent manner.
Project description:Cyclin D1b is a splice variant of the cell cycle regulator Cyclin D1 and is known to harbor divergent and highly oncogenic functions in human disease. While Cyclin D1b is induced during disease progression in many cancer types, the mechanisms underlying Cyclin D1b function remain poorly understood. Herein, models of human disease were utilized to resolve the downstream pathways requisite for the pro-tumorigenic functions of Cyclin D1b. Specifically, it was shown that Cyclin D1b modulates the expression of a large transcriptional network that cooperates with AR signaling to enhance tumor cell growth and invasive potential. Notably, Cyclin D1b promoted AR-dependent activation of genes associated with metastatic phenotypes. Further exploration determined that transcriptional induction of SNAI2 (Slug) was essential for Cyclin D1b- mediated proliferative and invasive properties, implicating Slug as a critical driver of disease progression. Importantly, Cyclin D1b expression highly correlated with that of Slug in clinical samples of advanced disease. Further, in vivo analyses provided strong evidence that Slug enhances both tumor growth and homing to distal soft tissues. Collectively, these findings reveal the underpinning mechanisms behind the pro-tumorigenic functions of Cyclin D1b, and demonstrate that the convergence of the Cyclin D1b-AR and Slug pathways results in the activation of processes critical for the promotion of lethal tumor phenotypes. Analysis of transcriptomes under the control of individual D-type cyclin isoforms in the hormone dependent prostate cancer cell line LNCaP in the presence and absence of androgen. LNCaP cells cultured in charcoal dextran treated media were transduced with virus encoding Cyclin D1a, Cyclin D1b, or control GFP for 24 hours in biological triplicate. Cells were then stimulated with either 1nM DHT or 0.01% EtOH (vehicle control) for 16 hours and harvested for RNA