Search

Non-coding RNA (ncRNA) has been shown to regulate diverse cellular processes and functions through controlling gene expression. Long non-coding RNAs (lncRNAs) act as a competing endogenous RNAs (ceRNAs) where microRNAs (miRNAs) and lncRNAs regulate each other through their biding sites. Interactions of miRNAs and lncRNAs have been reported to trigger decay of the targeted lncRNAs and have important roles in target gene regulation. These interactions form complicated and intertwined networks. Certain lncRNAs encode miRNAs and small nucleolar RNAs (snoRNAs), and may regulate expression of these small RNAs as precursors. SnoRNAs have also been reported to be precursors for PIWI-interacting RNAs (piRNAs) and thus may regulate the piRNAs as a precursor. These miRNAs and piRNAs target messenger RNAs (mRNAs) and regulate gene expression. In this review, we will present and discuss these interactions, cross-talk, and co-regulation of ncRNAs and gene regulation due to these interactions.

Silibinin is the major active constituent of silymarin, an extract of milk thistle seeds. Silibinin has been shown to have significant anti-cancer effects in a variety of malignancies. However, the molecular mechanisms of silibinin action in bladder cancer have not been studied extensively. In the present study, we found that silibinin (10 μM) significantly suppressed proliferation, migration, invasion and induced apoptosis of T24 and UM-UC-3 human bladder cancer cells. Silibinin down-regulated the actin cytoskeleton and phosphatidylinositide 3-kinase (PI3K)/Akt signaling pathways in these cancer cell lines. These pathways were found to crosstalk through RAS cascades. We found that silibinin suppressed levels of trimethylated histone H3 lysine 4 and acetylated H3 at the KRAS promoter. Furthermore, silibinin targets long non-coding RNA: HOTAIR and ZFAS1, which are known to play roles as oncogenic factors in various cancers. This study shows that silibinin exerts anti-cancer effects through down-regulation of actin cytoskeleton and PI3K/Akt pathways and thus suppresses bladder cancer growth and progression.

Prostate carcinogenesis involves alterations in several signaling pathways, the most prominent being the PI3K/AKT pathway. This pathway is constitutively active and drives prostate cancer (PCa) progression to advanced metastatic disease. PTEN, a critical tumor and metastasis suppressor gene negatively regulates cell survival, proliferation, migration and angiogenesis via the PI3K/Akt pathway. PTEN is mutated, downregulated/dysfunctional in many cancers and its dysregulation correlates with poor prognosis in PCa. Here, we demonstrate that microRNA-4534 (miR-4534) is overexpressed in PCa and show that miR-4534 is hypermethylated in normal tissues and cell lines compared to PCa tissues/cells. miR-4534 exerts its oncogenic effects partly by downregulating the tumor suppressor PTEN gene. Knockdown of miR-4534 impaired cell proliferation, migration/invasion and induced G0/G1 cell cycle arrest and apoptosis in PCa. Suppression of miR-4534 and its effects on tumor growth was confirmed in a xenograft mouse model. We performed parallel experiments in non-cancer RWPE1 cells by overexpessing miR-4534 followed by functional assays. Overexpression of miR-4534 induced pro-cancerous characteristics in this non-cancer cell line. Statistical analyses revealed that miR-4534 has potential to independently distinguish malignant from normal tissues and positively correlated with poor overall and PSA recurrence free survival. Taken together, our results show that depletion of miR-4534 in PCa induces a tumor suppressor phenotype partly through induction of PTEN. These results have important implications for identifying and defining the role of new PTEN regulators such as microRNAs in prostate tumorigenesis. Understanding aberrantly overexpressed miR-4534 and its downregulation of PTEN will provide mechanistic insight and therapeutic targets for PCa therapy.

Cytochrome P450 (CYP) 1A1 is a phase I enzyme that can activate various compounds into reactive forms and thus, may contribute to carcinogenesis. In this study, we investigated the expression, methylation status, and functional role of CYP1A1 on prostate cancer cells. Increased expression of CYP1A1 was observed in all cancer lines (PC-3, LNCaP, and DU145) compared to BPH-1 (P < 0.05); and was enhanced further by 5-aza-2'-deoxycytidine treatment (P < 0.01). Methylation-specific PCR (MSP) and sequencing of bisulfite-modified DNA of the xenobiotic response element (XRE) enhancer site XRE-1383 indicated promoter methylation as a regulator of CYP1A1 expression. In tissue, microarrays showed higher immunostaining of CYP1A1 in prostate cancer than normal and benign prostatic hyperplasia (BPH; P < 0.001), and methylation analyses in clinical specimens revealed significantly lower methylation levels in cancer compared to BPH at all enhancer sites analyzed (XRE-1383, XRE-983, XRE-895; P < 0.01). Interestingly, smoking affected the XRE-1383 site where the methylation level was much lower in cancer tissues from smokers than non-smokers (P < 0.05). CYP1A1 levels are thus increased in prostate cancer and to determine the functional effect of CYP1A1 on cells, we depleted the gene in LNCaP and DU145 by siRNA. We observe that CYP1A1 knockdown decreased cell proliferation (P < 0.05) and increased apoptosis (P < 0.01) in both cell lines. We analyzed genes affected by CYP1A1 silencing and found that apoptosis-related BCL2 was significantly down-regulated. This study supports an oncogenic role for CYP1A1 in prostate cancer via promoter hypomethylation that is influenced by tobacco smoking, indicating CYP1A1 to be a promising target for prostate cancer treatment.

Background/Aims: Genistein, a soy isoflavone, has been shown to have anti-cancer effects in various cancers including renal cancer. Long non-coding RNA, HOX transcript antisense RNA (HOTAIR), is involved in cancer progression and metastasis, such as renal cancer. Our aim was to investigate the effects of genistein on HOTAIR chromatin remodeling functions. Methods: We used MTS assays and Transwell migration assays to study the effects of genistein on cell proliferation and migration respectively in human renal cell carcinoma (RCC) cell lines. We used Western blots to analyze SNAIL and ZO-1 expression. We performed chromatin immunoprecipitation (ChIP) assays to study recruitment of the polycomb repressive complex 2 (PRC2) to the ZO-1 promoter. We performed RNA immunoprecipitation (RIP) assays to study interaction between HOTAIR and PRC2, SMARCB1 or ARID1A. We also performed transfection experiments to overexpress EED, HOTAIR and knockdown SMARCB1. Results: Genistein reduced cell proliferation and migration of human renal cell carcinoma cell lines. ChIP assays indicated that genistein reduces recruitment of the PRC2 to the ZO-1 promoter and increased its expression. RIP assays showed that genistein inhibits HOTAIR interaction with PRC2, leading to tumor suppression. Immunoprecipitation also revealed that genistein reduced EED levels in PRC2, suggesting that decreased EED levels suppress HOTAIR interaction with PRC2. EED overexpression in the presence of genistein restored PRC2 interaction with HOTAIR and reduced ZO-1 transcription, suggesting genistein activates ZO-1 by inhibiting HOTAIR/PRC2 functions. RIP assays also showed that HOTAIR interacts with SMARCB1 and ARID1A, subunits of the human SWI/SNF chromatin remodeling complex and genistein reduces this interaction. Combination of HOTAIR overexpression and SMARCB1 knockdown in the presence of genistein revealed that genistein inhibits SNAIL transcription via the HOTAIR/SMARCB1 pathway. Conclusion: Genistein suppresses EED levels in PRC2 and inhibits HOTAIR/ PRC2 interaction. Genistein suppresses HOTAIR/PRC2 recruitment to the ZO-1 promoter and enhances ZO-1 transcription. Genistein also inhibits SNAIL transcription via reducing HOTAIR/SMARCB1 interaction. We demonstrate that the reduction of HOTAIR interaction with chromatin remodeling factors by genistein represses HOTAIR/chromatin remodeling pathways to suppress RCC malignancy. [ABSTRACT FROM AUTHOR]