RhoGDIß inhibition via miR-200c/AUF1/SOX2/miR-137 axis contributed to lncRNA MEG3 downregulation-mediated malignant transformation of human bronchial epithelial cells.

Nickel pollution is a recognized factor contributing to lung cancer. Understanding the molecular mechanisms of its carcinogenic effects is crucial for lung cancer prevention and treatment. Our previous research identified the downregulation of a long noncoding RNA, maternally expressed gene 3 (MEG3), as a key factor in transforming human bronchial epithelial cells (HBECs) into malignant cells following nickel exposure. In our study, we found that deletion of MEG3 also reduced the expression of RhoGDIß. Notably, artificially increasing RhoGDIß levels counteracted the malignant transformation caused by MEG3 deletion in HBECs. This indicates that the reduction in RhoGDIß contributes to the transformation of HBECs due to MEG3 deletion. Further exploration revealed that MEG3 downregulation led to enhanced c-Jun activity, which in turn promoted miR-200c transcription. High levels of miR-200c subsequently increased the translation of AUF1 protein, stabilizing SOX2 messenger RNA (mRNA). This stabilization affected the regulation of miR-137, SP-1 protein translation, and the suppression of RhoGDIß mRNA transcription and protein expression, leading to cell transformation. Our study underscores the co-regulation of RhoGDIß expression by long noncoding RNA MEG3, multiple microRNAs (miR-200c and miR-137), and RNA-regulated transcription factors (c-Jun, SOX2, and SP1). This intricate network of molecular events sheds light on the nature of lung tumorigenesis. These novel findings pave the way for developing targeted strategies for the prevention and treatment of human lung cancer based on the MEG3/RhoGDIß pathway.

2-O-Octadecylascorbic acid represses RhoGDIß expression and ameliorates DNA damage-induced abnormal spindle orientations.

The appropriate regulation of spindle orientation maintains proper tissue homeostasis and avoids aberrant tissue repair or regeneration. Spindle misorientation due to imbalance or improper functioning leads to a loss of tissue integrity and aberrant growth, such as tissue loss or overgrowth. Pharmacological manipulation to prevent spindle misorientation will enable a better understanding of how spindle orientation is involved in physiological and pathological conditions and will provide therapeutic possibilities to treat patients associated with abnormal tissue function caused by spindle misorientation. N-terminal-deleted Rho guanine nucleotide dissociation inhibitor ß (RhoGDIß/RhoGDI2/LyGDI) produced by caspase-3 activation perturbs spindle orientation in surviving cells following exposure to either ionizing radiation or UVC. Thus, presumably, RhoGDIß cleaved by caspase-3 activation acts as a determinant of radiation-induced spindle misorientation that promote aberrant tissue repair due to deregulation of directional organization of cell population and therefore becomes a potential target of drugs to prevent such response. The objective of this study was to screen and identify chemicals that suppress RhoGDIß expression. We focused our attention on ascorbic acid (AA) derivatives because of their impact on the maintenance of skin tissue homeostasis. Here, we screened for AA derivatives that suppress RhoGDIß expression in HeLa cells and identified a lipophilic derivative, 2-O-octadecylascorbic acid (2-OctadecylAA), as a novel RhoGDIß inhibitor that ameliorated ionizing radiation-induced abnormal spindle orientations. Among all examined AA derivatives, which were also antioxidative, the inhibition activity was specific to 2-OctadecylAA. Therefore, this activity was not due to simple antioxidant properties. 2-OctadecylAA was previously shown to prevent hepatocellular carcinoma development. Our findings suggest that the anticarcinogenic effects of 2-OctadecylAA are partly due to RhoGDIß inhibition mechanisms by which spindle orientation perturbations are attenuated. Thus, the molecular targeting features of RhoGDIß warrant its further development for the treatment or control of spindle orientation abnormalities that affect epithelial homeostasis.

Comprehensive identification of SUMO2/3 targets and their dynamics during mitosis.

During mitosis large alterations in cellular structures occur rapidly, which to a large extent is regulated by post-translational modification of proteins. Modification of proteins with the small ubiquitin-related protein SUMO2/3 regulates mitotic progression, but few mitotic targets have been identified so far. To deepen our understanding of SUMO2/3 during this window of the cell cycle, we undertook a comprehensive proteomic characterization of SUMO2/3 modified proteins in mitosis and upon mitotic exit. We developed an efficient tandem affinity purification strategy of SUMO2/3 modified proteins from mitotic cells. Combining this purification strategy with cell synchronization procedures and quantitative mass spectrometry allowed for the mapping of numerous novel targets and their dynamics as cells progressed out of mitosis. This identified RhoGDIα as a major SUMO2/3 modified protein, specifically during mitosis, mediated by the SUMO ligases PIAS2 and PIAS3. Our data provide a rich resource for further exploring the role of SUMO2/3 modifications in mitosis and cell cycle regulation.

Depletion of RhoGDI2 expression inhibits the ability of invasion and migration in pancreatic carcinoma.

Rho GDP dissociation inhibitor 2 (RhoGDI2) has been identified as a regulator of tumor metastasis, although its role in tumor progression remains controversial. In this study, we examined the expression of RhoGDI2 in PC tissues and cell lines. To investigate the function of RhoGDI2 in PC cells, RhoGDI2 expression was depleted in PANC-1 and Patu8988 cells by small interfering RNA (siRNA). RhoGDI2 was found to be overexpressed in pancreatic carcinoma (PC) tissues and PC cell lines. Additionally, the results showed that depletion of RhoGDI2 significantly inhibited cell motility and invasion in vitro, but did not affect cell proliferation. The clinical study together with the experimental data confirmed that RhoGDI2 modulated the expression of matrix metalloproteinase 2 (MMP2). Taken together, findings of the present study indicated that RhoGDI2 is involved in pancreatic tumor malignancy and metastasis. Thus, RhoGDI2 is a potential target for the gene therapy of PC.

VEGF-C mediates RhoGDI2-induced gastric cancer cell metastasis and cisplatin resistance.

Rho GDP dissociation inhibitor 2 (RhoGDI2) expression is correlated with tumor growth, metastasis and chemoresistance in gastric cancer. However, the mechanisms by which RhoGDI2 promotes tumor cell survival and metastasis remain unclear. In this study, we clearly demonstrate that RhoGDI2 upregulates VEGF-C expression and RhoGDI2 expression is positively correlated with VEGF-C expression in human gastric tumor tissues as well as parental gastric cancer cell lines. VEGF-C depletion suppressed RhoGDI2-induced gastric cancer metastasis and sensitized RhoGDI2-overexpressing cells to cisplatin-induced apoptosis in vitro and in vivo. Secreted VEGF-C enhanced gastric cancer cell invasion and conferred cisplatin resistance to RhoGDI2-overexpressing cells. We also show that RhoGDI2 positively regulates Rac1 activity in gastric cancer cells. Inhibition of Rac1 expression suppressed RhoGDI2-induced VEGF-C expression, and this inhibition was associated with decreased invasiveness and increased sensitivity to cisplatin in RhoGDI2-overexpressing cells. Our results indicate that RhoGDI2 might be a potential therapeutic target for simultaneously reducing metastasis risk and enhancing chemotherapy efficacy in gastric cancer.

Ectopic expression of miR-34a enhances radiosensitivity of non-small cell lung cancer cells, partly by suppressing the LyGDI signaling pathway.

miR-34a is transcriptionally induced by the tumor suppressor gene p53, which is often downregulated in non-small cell lung cancer (NSCLC). To address whether the downstream signal of miR-34a is sufficient to induce apoptosis and to alter cellular radiosensitivity, a chemical synthetic miR-34a mimic was delivered into A549 and H1299 cells, with or without co-treatment of γ-irradiation. Results showed that ectopic expression of miR-34a induced dose-dependent cell growth inhibition and apoptosis in a p53-independent manner in both NSCLC cell lines. Interestingly, LyGDI was discovered as a new target gene of miR-34a, and downregulation of LyGDI promoted Rac1 activation and membrane translocation, resulting in cell apoptosis. Furthermore, restoration of miR-34a indirectly reduced cyclooxygenase-2 (COX-2) expression. Taken together, these results demonstrate that restoration of miR-34a expression enhances radiation-induced apoptosis, partly by suppressing the LyGDI signaling pathway, and miR-34a could possibly be used as a radiosensitizer for non-small cell lung cancer therapy.