MiR-199a-3p inhibition facilitates cardiomyocyte differentiation of embryonic stem cell through promotion of MEF2C.

MicroRNAs (miRNAs) is a small molecule (19-25 nucleotide) noncoding RNA that inhibits the expression of target messenger RNA (mRNA) at the posttranscriptional level as an endogenous regulator. There is an increasing evidence that miR-199a-3p has a significant effect on the development of multiple tumors. However, the specific roles of miR-199a-3p in myocardial differentiation of embryonic stem cell still need to be investigated. Method of the hanging drop was used to build the model of cardiomyocyte differentiation of stem cell and beating rate of embryoid bodies (EBs) was calculated. The levels of intracellular MEF2C, a-MHC, GATA4, Nkx2.5, and cTnT mRNA were measured by real-time quantitative polymerase chain reaction, while the expressions of miR-199a-3p were detected simultaneously. Protein levels of MEF2C, a-MHC, GATA4, Nkx2.5, and cTnT were quantified by western blot analysis. Immunoreactivities of MEF2C and cTnT were analyzed by immunofluorescence. The interaction between miR-199a-3p and its predicted target (3'-untranslated region of MEF2C mRNA) was verified by luciferase assay. MiR-199a-3p levels increased during cardiogenesis. MiR-199a-3p inhibitor increased the beating rate of EBs and promoted expressions of cardiac-specific markers (GATA4, Nkx2.5, cTnT, and a-MHC). Notably, miR-199a-3p inhibition brought upregulation of MEF2C, which is the target of miR-199a-3p that we predicted and verified experimentally. In addition, MEF2C siRNA decreased miR-199a-3p inhibitor promoted EBs beating and attenuated miR-199a-3p inhibitor-induced cTnT and MEF2C expressions. The results above showed that MEF2C was involved in the process of promoting the differentiation of stem cells into cardiac myocytes by miR-199a-3p inhibitors.

Case report: Remarkable response to sintilimab, lenvatinib, and nab-paclitaxel in postoperative metastatic chemotherapy-resistant combined hepatocellular-cholangiocarcinoma.

Background: Combined hepatocellular-cholangiocarcinoma (cHCC-CCA) is a highly aggressive malignancy with a poor prognosis. However, there are no consensus treatment guidelines, and decisions are usually extrapolated from intrahepatic cholangiocarcinoma (ICC) or hepatocellular carcinoma (HCC). Given that cHCC-CCA owns the unequivocal presence of both hepatocytic and cholangiocytic differentiation, a combination regimen of anti-PD1 antibody, multikinase inhibitor, and chemotherapy targeting against both components might be an optimal choice. Case presentation: We present the case of a patient with postoperative metastatic chemotherapy-resistant cHCC-CCA who exhibited a durable response and reasonable tolerability to a combination therapy consisting of the anti-PD1 antibody sintilimab, multikinase inhibitor lenvatinib, and nab-paclitaxel, despite having a low tumor mutational burden (TMB-L), microsatellite stability (MSS), and negative programmed cell death 1 ligand 1 (PD-L1). Conclusion: The combination regimen of immune checkpoint inhibitor sintilimab, multikinase inhibitor lenvatinib, and chemotherapy with nab-paclitaxel, which targets both the HCC and ICC components, may represent a promising treatment option for patients with cHCC-CCA. Further research is warranted to validate these findings in larger patient cohorts.