Metabotropic Glutamate Receptor 8 Is Regulated by miR-33a-5p and Functions as an Oncogene in Breast Cancer

Escape from TGF-β-induced senescence promotes aggressive hallmarks in epithelial hepatocellular carcinoma cells

Transforming growth factor-β (TGF-β) signaling and cellular senescence are key hallmarks of hepatocellular carcinoma (HCC) pathogenesis. Despite provoking senescence-associated growth arrest in epithelial HCC cells, elevated TGF-β activity paradoxically correlates with increased aggressiveness and poor prognosis in advanced tumors. Whether the transition between these dichotomous functions involves modulation of the senescence phenotype during disease progression remains elusive. Exploiting the epithelial HCC cell line Huh7 as a robust model, we demonstrate that chronic exposure to TGF-β prompts escape from Smad3-mediated senescence, leading to the development of TGF-β resistance. This altered state is characterized by an optimal proliferation rate and the acquisition of molecular and functional traits of less-differentiated mesenchymal cells, coinciding with differential growth capacity in 2D and 3D culture conditions, epithelial-to-mesenchymal transition (EMT), and increased invasiveness in vitro, and metastasis in vivo. Mechanistically, resistant cells exhibit defective activation and nuclear trafficking of Smad molecules, particularly Smad3, as ectopic activation of the TGF-β/Smad3 axis is able to reinstate TGF-β sensitivity. An integrated transcriptomic landscape reveals both shared and distinct gene signatures associated with senescent and TGF-β resistant states. Importantly, genetic ablation and molecular studies identify microtubule affinity regulating kinase 1 (MARK1) and glutamate metabotropic receptor 8 (GRM8) as critical modulators of the resistance phenomenon, potentially by impairing spatiotemporal signaling dynamics of Smad activity. Our findings unveil a novel phenomenon wherein epithelial HCC cells may exploit senescence plasticity as a mechanism to oppose TGF-β anti-tumor responses and progress towards more aggressive HCC phenotypes.

Polyphyllin VII enhances the sensitivity of endometrial carcinoma cells to medroxyprogesterone acetate through upregulating miR‑33a‑5p expression

Endometrial carcinoma (EC) often exhibits resistance to hormone therapies, such as medroxyprogesterone acetate (MPA), highlighting the need for novel strategies to enhance therapeutic efficacy. The present study aimed to investigate the effects of polyphyllin VII (PPVII) on the efficacy of MPA in EC, focusing on the regulatory role of microRNA (miR)-33a-5p. Briefly, an MPA-resistant Ishikawa cell line (Ishikawa/MPA-R), maintained with 10 µM MPA, was established and transfected with negative control (NC) and miR-33a-5p inhibitors. Following treatment with PPVII and MPA, the proliferation capacity and apoptosis levels of the Ishikawa and Ishikawa/MPA-R cells were evaluated using reverse transcription-quantitative polymerase chain reaction, MTT assay, clonogenic assay, flow cytometry, western blotting and dual-luciferase assay. Next, the expression levels of miR-33a-5p and F-box and leucine rich repeat protein 16 (FBXL16) were measured, and the regulatory relationship between miR-33a-5p and FBXL16 was analyzed. Significant reductions in cell viability were observed in all groups following treatment with increased concentrations of MPA and PPVII, with the greatest effect observed in the combined MPA + PPVII group (P<0.01). The apoptosis levels of the Ishikawa/MPA-R cells were significantly increased in all drug treatment groups, particularly in the MPA + PPVII group (P<0.05). PPVII treatment significantly increased the expression level of miR-33a-5p in Ishikawa/MPA-R cells (P<0.01). In the PPVII + miR-33a-5p inhibitor group, the Ishikawa/MPA-R cells exhibited an upregulation in the viability (P<0.01), colony formation ability (P<0.01), proportion in the G1 phase (P<0.05) and the protein expression levels of cyclin D1 (P<0.01) and cyclin-dependent kinase 4 (P<0.01), and a reduction in the miR-33a-5p expression (P<0.01), apoptosis levels (P<0.05), proportion in the S (P<0.05) and G2 phases and the levels of Bcl-2-associated X protein (P<0.001). The FBXL16 protein expression in Ishikawa/MPA-R cells was significantly higher compared with Ishikawa cells, and the mRNA and protein expression levels of FBXL16 were markedly elevated in the PPVII + miR-33a-5p inhibitor group compared with the PPVII + NC group (P<0.01). These findings suggested that PPVII upregulated the expression of miR-33a-5p, enhanced the sensitivity of EC cells to MPA and potentially exerted anticancer effects in EC through the synergistic action of the miR-33a-5p/FBXL16 axis in combination with MPA.

Region-Based Analyses of Existing Genome-Wide Association Studies Identifies Novel Potential Genetic Susceptibility Regions for Glioma

SIGNIFICANCE

Further investigation of the potential susceptibility regions identified in our study may lead to a better understanding of glioma genetic risk and the underlying biological etiology of glioma. Our study suggests sex may play a role in genetic susceptibility and highlights the importance of sex-specific analysis in future glioma research.

The role of glutamate receptors in the regulation of the tumor microenvironment

Glutamate, as one of the most important carbon sources in the TCA cycle, is central in metabolic processes that will subsequently influence tumor progression. Several factors can affect the expression of glutamate receptors, playing either a tumor-promoting or tumor-suppressor role in cancer. Thus, the activation of glutamate receptors by the ligand could play a role in tumor development as ample studies have demonstrated the expression of glutamate receptors in a broad range of tumor cells. Glutamate and its receptors are involved in the regulation of different immune cells' development and function, as suggested by the receptor expression in immune cells. The activation of glutamate receptors can enhance the effectiveness of the effector's T cells, or decrease the cytokine production in immunosuppressive myeloid-derived suppressor cells, increasing the antitumor immune response. These receptors are essential for the interaction between tumor and immune cells within the tumor microenvironment (TME) and the regulation of antitumor immune responses. Although the role of glutamate in the TCA cycle has been well studied, few studies have deeply investigated the role of glutamate receptors in the regulation of cancer and immune cells within the TME. Here, by a systematic review of the available data, we will critically assess the physiopathological relevance of glutamate receptors in the regulation of cancer and immune cells in the TME and provide some unifying hypotheses for futures research on the role of glutamate receptors in the immune modulation of the tumor.

Implications of a Neuronal Receptor Family, Metabotropic Glutamate Receptors, in Cancer Development and Progression

Cancer is the second leading cause of death, and incidences are increasing globally. Simply defined, cancer is the uncontrolled proliferation of a cell, and depending on the tissue of origin, the cancer etiology, biology, progression, prognosis, and treatment will differ. Carcinogenesis and its progression are associated with genetic factors that can either be inherited and/or acquired and are classified as an oncogene or tumor suppressor. Many of these genetic factors converge on common signaling pathway(s), such as the MAPK and PI3K/AKT pathways. In this review, we will focus on the metabotropic glutamate receptor (mGluR) family, an upstream protein that transmits extracellular signals into the cell and has been shown to regulate many aspects of tumor development and progression. We explore the involvement of members of this receptor family in various cancers that include breast cancer, colorectal cancer, glioma, kidney cancer, melanoma, oral cancer, osteosarcoma, pancreatic cancer, prostate cancer, and T-cell cancers. Intriguingly, depending on the member, mGluRs can either be classified as oncogenes or tumor suppressors, although in general most act as an oncogene. The extensive work done to elucidate the role of mGluRs in various cancers suggests that it might be a viable strategy to therapeutically target glutamatergic signaling.