Tyrosine kinase inhibitors (TKIs) are the most commonly used targeted therapeutics in clear-cell renal cell carcinoma (ccRCC); however, drug resistance limits their utility and can lead to tumor “flare-up” and progression. In this study, we show that RCC resistance to sunitinib and sorafenib involves different mechanisms and leads to increased malignancy. Sunitinib decreased tumor growth and cell motility along with increased E-cadherin expression and secretion of the proangiogenic cytokines IL6 and IL8, which activated senescence in ccRCC cells and led to VE-cadherin phosphorylation, enhancing tumor angiogenesis. Sorafenib resistance increased the levels of mesenchymal markers and the secretion of MMP9, which cleaved VE-cadherin and disrupted endothelial cell integrity. Both sunitinib resistance and sorafenib resistance led to activation of the c-Met receptor IRAK1 and downregulation of the tumor suppressor MCPIP1, resulting in an increase in the metastasis of resistant cells, possibly due in part to enhanced vascularization of ccRCC. MCPIP1 overexpression partially overcame resistance to these drugs by decreasing micrometastasis and decreasing the expression of factors involved in tumorigenesis. In tumor samples from ccRCC patients, we observed a significant increase in the level of the c-Met receptor, IRAK1 and a decrease in MCPIP1 with respect to normal kidney tissue. Our results indicate separate novel mechanisms for sunitinib and sorafenib resistance, which both lead to MCPIP1 inhibition and ccRCC progression. The presented study suggests caution in the treatment of RCC with TKIs, which may lead to the unintended outcome of tumor progression.

C-Met tyrosine kinase receptor plays an important role under normal and pathological conditions. In tumor cells’ overexpression or incorrect activation of c-Met, this leads to stimulation of proliferation, survival and increase of motile activity. This receptor is also described as a marker of cancer initiating cells. The latest research shows that the c-Met receptor has an influence on the development of resistance to targeted cancer treatment. High c-Met expression and activation in renal cell carcinomas is associated with the progression of the disease and poor survival of patients. C-Met receptor has become a therapeutic target in kidney cancer. However, the therapies used so far using c-Met tyrosine kinase inhibitors demonstrate resistance to treatment. On the other hand, the c-Met pathway may act as an alternative target pathway in tumors that are resistant to other therapies. Combination treatment together with c-Met inhibitor reduces tumor growth, vascularization and pro-metastatic behavior and results in suppressed mesenchymal phenotype and vascular endothelial growth factor (VEGF) secretion. Recently, it has been shown that the acquirement of mesenchymal phenotype or lack of cell differentiation might be related to the presence of the c-Met receptor and is consequently responsible for therapy resistance. This review presents the results from recent studies identifying c-Met as an important factor in renal carcinomas being responsible for tumor growth, progression and metastasis, indicating the role of c-Met in resistance to antitumor therapy and demonstrating the pivotal role of c-Met in supporting mesenchymal cell phenotype.

Nonalcoholic fatty liver disease is defined as the accumulation of excessive fat in the liver in the absence of excessive alcohol consumption or any secondary cause. Although the disease generally remains asymptomatic, chronic liver inflammation leads to fibrosis, liver cirrhosis, and even to the development of hepatocellular carcinoma (HCC). Fibrosis results from epithelial–mesenchymal transition (EMT), which leads to dedifferentiation of epithelial cells into cells with a mesenchymal-like phenotype. During EMT, epithelial cells with high expression of E-cadherin, influenced by growth factors, cytokines, and inflammatory processes, undergo morphological changes via enhanced expression of, e.g., vimentin, fibronectin, and N-cadherin. An inducer of EMT and, consequently, of fibrosis development is transforming growth factor beta (TGFβ), a pleiotropic cytokine associated with the progression of hepatocarcinogenesis. However, the understanding of the molecular events that direct the development of steatosis into steatohepatitis and liver fibrosis remains incomplete. Our study revealed that both prolonged exposure of hepatocarcinoma cells to fatty acids in vitro and high-fat diet in mice (20 weeks) result in inflammation. Prolonged treatment with fatty acids increased the levels of TGFβ, MMP9, and β-catenin, important EMT inducers. Moreover, the livers of mice fed a high-fat diet exhibited features of liver fibrosis with increased TGFβ and IL-1 levels. Increased expression of IL-1 correlated with a decrease in monocyte chemoattractant protein-induced protein 1 (MCPIP1), a negative regulator of the inflammatory response that regulates the stability of proinflammatory transcripts encoding IL-1. Our study showed that a high-fat diet induced EMT by increasing the levels of EMT-activating transcription factors, including Zeb1, Zeb2, and Snail and changed the protein profile to a profile characteristic of the mesenchymal phenotype.

Monocyte chemoattractant protein-induced protein 1 (MCPIP1), encoded by ZC3H12A, is a negative regulator of inflammation and tumorigenesis. While its role has been implicated in various cancers, the function of MCPIP1 in hepatocellular carcinoma (HCC) remains poorly understood. This study explored the contribution of hepatocyte-specific MCPIP1 loss to HCC pathogenesis, highlighting its role in overcoming the inherent tumor resistance observed in female mice. Liver tissues (n ≥5 per group) and primary hepatocytes (n ≥3 per group) were evaluated using western blotting, immunohistochemistry, immunofluorescence, RNA sequencing and pathway-enrichment analysis. The expression levels of MCPIP1 in HCC were measured by quantitative reverse-transcription PCR. The results are presented as mean ± SD, Student's t or Mann‒Whitney U tests were used for statistical analysis of two groups. For more than two groups, ordinary two-way ANOVA was used. The hepatocyte-specific loss of MCPIP1 markedly promoted fibrosis and tumorigenesis, particularly in female mice, disrupting the normal sex-related protection observed in the diethylnitrosamine model. As determined by next-generation sequencing and bioinformatics analysis, oncogenic and fibrotic programs, including the EMT, Wnt/β-catenin, and JAK/STAT3 pathways, were activated in MCPIP1 knockout livers. These molecular events activated β-catenin, c-Met, and IL-6/STAT3/NF-κB signaling, and they enhanced fibrotic remodeling. In MCPIP1-deficient hepatocytes, active β-catenin and CREB1 accumulated in the nucleus, and the expression of protumorigenic targets, such as Spp1, Tgfb2, and Adam17 increased. Moreover, MCPIP1 expression was significantly downregulated in human HCC tissues and correlated with tumor progression. MCPIP1 plays a protective role against inflammation-driven hepatocarcinogenesis, particularly in females, by restraining fibrotic remodeling and oncogenic signaling. The downregulation of MCPIP1 expression promotes a tumor-promoting microenvironment through the coordinated activation of the β-catenin, STAT3, and CREB1 pathways.