Functional analysis of microRNAs in human hepatocellular cancer stem cells

Abstract

MicroRNAs are endogenous small non-coding RNAs that regulate gene expression and cancer development. A rare population of hepatocellular cancer stem cells (HSCs) holds the extensive proliferative and self-renewal potential necessary to form a liver tumour. We postulated that specific transcriptional factors might regulate the expression of microRNAs and subsequently modulate the expression of gene products involved in phenotypic characteristics of HSCs. We evaluated the expression of microRNA in human HSCs by microarray profiling, and defined the target genes and functional effects of two groups of microRNA regulated by IL-6 and transcriptional factor Twist. A subset of highly chemoresistant and invasive HSCs was screened with aberrant expressions of cytokine IL-6 and Twist. We demonstrated that conserved let-7 and miR-181 family members were up-regulated in HSCs by global microarray-based microRNA profiling followed by validation with real-time polymerase chain reaction. Importantly, inhibition of let-7 increases the chemosensitivity of HSCs to sorafenib and doxorubicin whereas silencing of miR-181 led to a reduction in HSCs motility and invasion. Knocking down IL-6 and Twist in HSCs significantly reduced let-7 and miR-181 expression and subsequently inhibited chemoresistance and cell invasion. We showed that let-7 directly targets SOCS-1 and caspase-3, whereas miR-181 directly targets RASSF1A, TIMP3 as well as nemo-like kinase (NLK). In conclusion, alterations of IL-6- and Twist-regulated microRNA expression in HSCs play a part in tumour spreading and responsiveness to chemotherapy. Our results define a novel regulatory mechanism of let-7/miR-181s suggesting that let-7 and miR-181 may be molecular targets for eradication of hepatocellular malignancies.

miRNAs Highlights in Stem and Cancer Cells

“…[203], CDK6, CDC25A [204], HMGA2 [205], KRAS, NRAS [68], MYC [206], SOC-1 [203] TS miR-9 Breast, medulloblastoma, ovarian MYC [207] TS/OG miR-10a/b Breast OG miR-15a/16-1 cluster Lymphoma, multiple myeloma, pituitary adenoma, prostate, pancreatic BCL-2 [176], MCL1 [176], p53 [60] TS miR-17-92 fam Breast, colon, gastric, lung 122, lymphoma, myeloma, medulloblastoma, prostate AIB1 [208], BIM, CDKN1A [209,210], E2F [209], MYC [211,209], PTEN [210] OG miR- 21 Breast, cholangiocarcinoma, gastric, glioblastoma, lymphoma, lung, myelom, prostat, colon PDCD4 [212], GF1alfa [213], IL-6 [214], MASPIN [215], PTEN [216], TPM1 [217], OG miR-22/25 Prostate PTEN [218] OG miR-26a…”

“…Colon, osteosarcoma, pancreatic MMP [231]; RAS [232] TS miR- 155 Breast, colon, lung, lymphoma, pancreatic NF-kB [233], CEBPB and SHIP1 [234] OG/TS miR-181a/b/c Glioblastoma, hepatocellular carcinoma RASSF1A, TIMP3 [203] TS miR- 205 Prostate, bladder, breast, oesophageal, ovarian, lung, melanoma E2F1 [235] TS/OG miR-206 Breast, rhabdomyosarcoma TP53INP1 [236] TS miR- [221][222] Glioblastoma, liver P27(KIP1) [237] OG miR-302 Prostate PTEN [218] OG miR-340 Breast MET [238] TS miR-335 Breast SOX4, TNC [239] TS miR-371/373…”

Primary and Metastatic Tumours of the Liver: Expanding Scope of Morphological and Immunohistochemical Details in the Biopsy

“…MicroRNA-183 inhibits apoptosis [98]. MicroRNA expression can be subjected to regulation with IL-6 [25]. Reduced expression of microRNA-26 in HCC is associated with poor prognosis.…”

“…MicroRNA-181 down-regulates the differentiation and maturation of hepatocytes [96]. Suppression of microRNA-181 expression leads to reduced motility and invasion of HCC stem cells [25]. MicroRNA-182 could promote metastasis [97].…”

“…New technologies as proteomic profiling and genomic marker analysis should be applied in the evaluation of liver tumours [4]. MicroRNA studies can lead to new findings in cancer pathogenesis and prediction of treatment efficacy [24,25].…”