The highly aggressive character of melanoma makes it an excellent model for probing the mechanisms underlying metastasis, which remains one of the most difficult challenges in treating cancer. We find that miR-182, member of a miRNA cluster in a chromosomal locus (7q31-34) frequently amplified in melanoma, is commonly upregulated in human melanoma cell lines and tissue samples; this up-regulation correlates with gene copy number in a subset of melanoma cell lines. Moreover, miR-182 ectopic expression stimulates migration of melanoma cells in vitro and their metastatic potential in vivo, whereas miR-182 down-regulation impedes invasion and triggers apoptosis. We further show that miR-182 over-expression promotes migration and survival by directly repressing microphthalmiaassociated transcription factor-M and FOXO3, whereas enhanced expression of either microphthalmia-associated transcription factor-M or FOXO3 blocks miR-182's proinvasive effects. In human tissues, expression of miR-182 increases with progression from primary to metastatic melanoma and inversely correlates with FOXO3 and microphthalmia-associated transcription factor levels. Our data provide a mechanism for invasion and survival in melanoma that could prove applicable to metastasis of other cancers and suggest that miRNA silencing may be a worthwhile therapeutic strategy.microRNA ͉ cancer ͉ invasion M etastasis is a central problem in cancer, yet the mechanisms underlying a cell's ability to extravasate from the primary tumor, circulate, and invade new tissue remain poorly understood. We reasoned that melanoma, one of the most notoriously invasive neoplasia, would provide an excellent model for investigating the alterations that contribute to metastasis. Melanomas are characterized by certain well-defined genetic alterations (reviewed in ref. 1) as well as frequent chromosomal aberrations associated with tumor progression (2). Recent work has also shown that melanomas display genomic alterations involving numerous microRNA genes (3). MicroRNAs (miRNAs) are endogenous noncoding small RNAs that interfere with the translation of coding messenger RNAs (mRNAs) in a sequence-specific manner (4), often to regulate processes involved in development or tissue homeostasis (5-7). Intriguingly, dysregulation of miRNAs has been found to contribute to neoplasia (8). We decided to investigate the possible contributions of miRNA dysregulation to melanoma extravasation, migration, and invasion.We compared the expression of miRNAs in a large cohort of melanoma cell lines with that of normal melanocytes. We found that miR-182, flanked by the c-MET and BRAF oncogenes in the 7q31-34 region that is frequently amplified in melanoma (9, 10), is highly expressed in metastatic melanoma cell lines and tumors, often in association with increased copy number. Moreover, we demonstrate that antisense-mediated repression of miR-182 inhibited invasion and induced melanoma cell death, whereas ectopic miR-182 up-regulation enhanced the oncogenic activity of melanoma cells in vitro ...

Previous studies have shown that key enzymes involved in lipid metabolic pathways are differentially expressed in normal compared with tumor tissues. However, the precise role played by dysregulated expression of lipid metabolic enzymes and altered lipid homeostasis in carcinogenesis remains to be established. Fatty acid synthase is overexpressed in a variety of cancers, including breast and prostate. The purpose of the present study was to examine the expression patterns of additional lipid metabolic enzymes in human breast and prostate cancers. This was accomplished by analysis of published expression databases, with confirmation by immunoblot assays. Our results indicate that the fatty acid-activating enzyme, long-chain fatty acyl-CoA synthetase 4 (ACSL4), is differentially expressed in human breast cancer as a function of estrogen receptor alpha (ER) status. In 10 separate studies, ACSL4 messenger RNA (mRNA) was overexpressed in ER-negative breast tumors. Of 50 breast cancer cell lines examined, 17 (89%) of 19 ER-positive lines were negative for ACSL4 mRNA expression and 20 (65%) of 31 ER-negative lines expressed ACSL4 mRNA. The inverse relationship between ER expression and ACSL4 expression was also observed for androgen receptor status in both breast and prostate cancers. Furthermore, loss of steroid hormone sensitivity, such as that observed in Raf1-transfected MCF-7 cells and LNCaP-AI cells, was associated with induction of ACSL4 expression. Ablation of ACSL4 expression inMDA-MB-231 breast cancer cells had no effect on cell proliferation; however, sensitivity to the cytotoxic effects of triacsin C was increased three-fold in the cells lacking ACSL4.

Ovarian carcinoma consists of a group of histologically heterogeneous diseases involving distinct tumorigenic pathways. High-grade papillary serous carcinoma of the ovary is commonly associated with p53 mutations. HMGA2, an oncofetal protein, is found to be overexpressed in ovarian cancer. To study the function of HMGA2 in ovarian cancer, it is important to know which subtypes of ovarian cancer are associated with HMGA2 overexpression. In this study, we collected six different types of ovarian cancer and examined HMGA2 expression by immunohistochemistry, along with HMGA1, p53 and Ki-67. We found that HMGA2 overexpression was significantly higher in high-grade papillary serous carcinoma (64%) and carcinosarcoma (60%) than in other types of ovarian cancers (7-23%). HMGA2 overexpression was moderately associated with dominant p53 mutations (R ¼ 0.51). In addition, the microRNA in situ analysis revealed that let-7b, the HMGA2-negative regulators, were significantly lost in high-grade serous carcinoma. Our findings suggest that HMGA2 is an important molecular change significantly related to high-grade papillary serous carcinoma and is less common in other histological types of ovarian cancer.

A major obstacle in treating prostate cancer is the development of androgen-independent disease. In this study, we examined LEF1 expression in androgen-independent cancer as well as its regulation of androgen receptor (AR) expression, prostate cancer growth, and invasion in androgenindependent prostate cancer cells. Affymetrix microarray analysis of LNCaP and LNCaP-AI (androgen-independent variant LNCaP) cells revealed 100-fold increases in LEF1 expression in LNCaP-AI cells. We showed that LEF1 overexpression in LNCaP cells resulted in increased AR expression and consequently enhanced growth and invasion ability, whereas LEF1 knockdown in LNCaP-AI cells decreased AR expression and, subsequently, growth and invasion capacity. Chromatin immunoprecipitation, gel shift, and luciferase assays confirmed LEF1 occupancy and regulation of the AR promoter. Thus, we identified LEF1 as a potential marker for androgen-independent disease and as a key regulator of AR expression and prostate cancer growth and invasion. LEF1 is highly expressed in androgen-independent prostate cancer, potentially serving as a marker for androgen-independent disease. [Cancer Res 2009;69(8):3332-8] IntroductionA variety of theories have been proposed regarding the mechanism by which prostate cancer cells progress to aggressive phenotypes, including increased invasive and metastatic potentials, and developing resistance to androgen ablation therapy (1-3). Of great importance, increasing evidence fortify that increased androgen receptor (AR) expression and altered AR function, due to amplification, overexpression and mutation, play a dominant role in the progression and treatment failure of advanced prostate cancer (4-8). The role of AR in the invasive and metastatic potential of prostate cancer is suggested by several studies (9-11), including a recent study by Hara and colleagues (12). However, the direct role that AR plays in the invasion and metastasis of prostate cancer remains understudied.Regulation of AR expression is complex, involving positive (13, 14) and negative (15) control by transcription factors. AR expression is also linked to cross-talk with growth factor receptor or other signaling pathways (16-24). LEF1, lymphoid enhancerbinding factor 1 in the Wnt signaling pathway, has been indicated to regulate AR expression (25). LEF1/TCF is the nuclear transducer on activated the Wnt pathway. Members of the family represent a group of proteins with DNA-binding activities that specifically recognize and bind to a contiguous six-base consensus sequence, 5 ¶-a/ta/t-C-A-A-G-3 ¶ within the 5 ¶ promoter regions of Wnt target genes (26). There are eight putative LEF1 binding sites described at the AR promoter region regulating its expression (25).In addition to its function in a variety of developmental processes including stem cell renewal, embryonic development, and tissue differentiation, more recent evidence indicates that aberrant activity of the Wnt signaling pathway is involved in the tumorigenesis of several organ systems incl...

Androgen receptor (AR), a member of the steroid receptor family, is a transcription factor that has an important role in the regulation of both prostate cell proliferation and growth suppression. AR coactivators may influence the transition between cell growth and growth suppression. We have shown previously that the internally spliced ARA70 isoform, ARA70␤, promotes prostate cancer cell growth and invasion. Here we report that the full length ARA70␣, in contrast, represses prostate cancer cell proliferation and anchorage-independent growth in vitro and inhibits tumor growth in nude mice xenograft experiments in vivo. Further, the growth inhibition by ARA70␣ is ARdependent and mediated through induction of apoptosis rather than cell cycle arrest. Interestingly, AR with T877A mutation in LNCaP cells decreased its physical and functional interaction with ARA70␣, facilitating the growth of LNCaP cells. The tumor suppressor function of ARA70␣ is consistent with our previous findings that ARA70␣ expression is decreased in prostate cancer cells compared with benign prostate. ARA70␣ also reduced the invasion ability of LNCaP cells. Although growth inhibition by ARA70␣ is AR-dependent, the inhibition of cell invasion is an androgen-independent process. These results strongly suggest that ARA70␣ functions as a tumor suppressor gene. Androgen receptor (AR) is a transcription factor that regulates growth and differentiation of prostate cells. It mediates transcriptional activation through a series of events including ligand binding, DNA binding to androgen response elements, and interaction with various cofactors that converge on the general transcription machinery.