Nimbolide attenuates hepatocellular carcinoma by regulating miRNAs 21, 145 and 221 and their target gene expression

MicroRNAs (miRNAs) are becoming progressively emerging in cancer research from an etiologic and curative point of view. Several miRNAs act as oncogenes or tumor suppressors, which are dysregulated in numerous cancers. Our previous studies have established that nimbolide (a bioactive terpenoid from neem) attenuated hepatocellular carcinoma (HCC) through various mechanisms in mice. Here, we aimed to elucidate the effect of nimbolide in modulating specific miRNAs (21, 145, and 221) and their target genes involved in promoting inflammation and cancer cell proliferation in HCC mice.

Following the induction of HCC in mice at 28 weeks, nimbolide (6 mg/kg b.wt.) was administered orally for four consecutive weeks.

We found significantly increased hepatic expression of miR-21a-3p, miR-21a-5p, miR-221-5p and miR-221-3p whilst significantly decreased miR-145a-5p in HCC mice. Nimbolide treatment to HCC mice substantially reduced the miR-21a-5p and miR-221-3p and improved miR-145a-5p gene expression. Our in-silico study also supports these findings. Moreover, hepatic tight junction (TJ) associated proteins such as claudins 1&5 mRNA and protein were increased considerably, whilst significantly decreased hepatic claudin 2 mRNA and protein expression noted in HCC mice. Nimbolide also regulates cadherins, ROCK 1, MMP 9, cyclin D1, CDK4, NF κB and TNFα mRNA expression in HCC mice.

We identified for the first time that nibmolide treatment to HCC mice significantly attenuated hepatic miRNAs 21 & 221 expressions and sheltered miR-145 expression. These findings were further confirmed with in-silico studies. Moreover, nibmolide treatment in HCC mice regulates miRNA target genes involved in cancer cell proliferation and inflammation, thereby attenuating HCC progression in mice.