Cdc42 Regulates the Expression of Cytoskeleton and Microtubule Network Proteins to Promote Invasion and Metastasis of Progeny Cells Derived from CoCl2-induced Polyploid Giant Cancer Cells.

Purpose: Our previous studies have shown that CoCl2 can induce the formation of polyploid giant cancer cells (PGCCs) and PGCCs could produce progeny cells via asymmetric division. In this study, the molecular mechanism by which PGCCs generate progeny cells with high invasion and migration abilities was explored. Methods: In this study, PGCCs induced by CoCl2 produced progeny cells via asymmetric division, which was observed dynamically using laser scanning confocal microscopy. Cell cycle in LoVo and Hct116 before and after CoCl2 treatment was analyzed by flow cytometry. Cell function experiments, co-immunoprecipitation, mass spectrometry analysis, ML141 treatment, western blotting, and siRNA transfection experiments were used to demonstrate that Cdc42/PAK1 was involved in the regulation of cytoskeleton expression. The proliferation, migration, and invasion abilities of PGCCs and progeny cells were compared in PGCCs and progeny cells with and without inhibiting the expression of Cdc42 and PAK1. Results: G2/M phase arrest appeared in CoCl2-treated LoVo and Hct116 cells. After CoCl2 treatment, an increased expression of Cdc42 and PAK1 led to a decrease in the expression of stathmin and an increase in the expression of phosphorylated stathmin, which is located in the nucleus of PGCCs and progeny cells. PTPN14 negatively regulates the expression of PAK1 and p38MAPK. Low levels of PTPN14 expression, a downstream regulatory protein of stathmin, endows progeny tumor cells generated by PGCCs with the ability to invade and metastasize. The expression of PKA1α, cathepsin B, and D increased in CoCl2-treated cells compared with that in the control cells, associated with the infiltration and migration of PGCCs with their progeny cells. Conclusion: CoCl2-induced overexpression of Cdc42 plays a critical role in increasing the infiltration and migration abilities of PGCCs and progeny cells by regulating cytoskeleton protein expression.

Fibroblast growth factor 3 promotes spontaneous mammary tumorigenesis in Tientsin albino 2 mice via the FGF3/FGFR1/STAT3 pathway.

Introduction: Tientsin albino 2 (TA2) mice can develop spontaneous breast cancer (SBC), which is associated with multiple pregnancies and infection with the mouse mammary tumor virus (MMTV). In this study, we sought to elucidate the molecular mechanisms underlying the development of SBC in TA2 mice induced by MMTV. Methods: The integration site of MMTV in TA2 SBC was identified using whole-genome sequencing. The expression of fibroblast growth factor 3 (FGF3) in SBCs and normal breast tissues was compared. The primary cell line, TA-1106, derived from SBC, was cultured. The proliferation, cell cycle, migration, invasion, and tumorigenicity abilities, as well as the expression of epithelial-mesenchymal transition-related proteins, phosphorylated STAT3, and phosphorylated Akt, were assessed in MA-891cell line from TA2 and TA-1106 cells after FGF3 knockdown. The binding of FGF3 to FGF receptor 1 (FGFR1) was determined by co-immunoprecipitation. Additionally, the relationship between STAT3 and Akt phosphorylation was investigated using a small molecule inhibitor and STAT3 knockdown. Results: MMTV integrated upstream of the FGF3 gene, and the FGF3 protein was highly expressed in TA2 SBCs. FGF3 knockdown in MA-891 and TA-1106 decreased their proliferation, migration, and invasion abilities, affected the cell cycle and expression of epithelial-mesenchymal transition-related proteins, and inhibited the growth of animal xenografts. FGF3 binds to FGFR1, and either FGF3 or FGFR1 knockdown decreases STAT3 and Akt phosphorylation levels. Inhibition of phosphorylation or expression of STAT3 resulted in decreased Akt phosphorylation levels. Inhibition of Akt phosphorylation also resulted in decreased STAT3 phosphorylation levels. Furthermore, treatment of MA-891 and TA-1106 cells with Wortmannin or Stattic caused FGFR1 upregulation in addition to inhibiting Akt or STAT3 phosphorylation. Conclusion: The results of this study demonstrate that FGF3 plays a significant role in the development of SBC through the FGF3/FGFR1/STAT3 signaling pathway. There is a reciprocal activation between STAT3 and Akt. Inhibition of STAT3 or Akt phosphorylation promoted the expression of FGFR1. Validating the conclusions obtained in this study in human breast cancer (HBC) may contribute to targeted therapy and it is worth exploring whether the homologous sequences of MMTV in HBC have a similar oncogenic effect.

PLK4 is a key molecule in the formation of PGCCs and promotes invasion and migration of progeny cells derived from PGCCs.

Purpose: Cancer stem cells (CSCs) are the evil source of tumor metastasis and recurrence. Polyploid giant cancer cells (PGCCs) that exhibit the characteristics of CSCs produced daughter cells via asymmetric division. The molecular mechanisms of daughter cells derived from PGCCs with high migration, invasion, and proliferation abilities in colorectal cancer (CRC) are explored in this paper based on the bioinformatics analysis. Materials and Methods: We characterized the expression of CSC-related genes in CRCs by analyzing the mRNAsi of The Cancer Genome Atlas and survival time. Weighted gene co-expression network analysis was performed to identify the modules of the hub and key genes. The migration, invasion, and proliferation abilities of cells, the expression of epithelial-mesenchymal transition (EMT)-related proteins and polo-like kinase 4 (PLK4) were compared in LoVo and Hct116 cells with and without bufalin treatment. In addition, the expression and subcellular location of cell division cycle 25C (CDC25C) in cells before and after PLK4 knockdown were assessed. Results: Eight hub genes were screened out and positively association with mRNAsi in CRCs based on bioinformatic analysis. Among them, checkpoint Kinase-1 (CHEK1), budding uninhibited by benzimidazoles 1 Homolog Beta (BUB1B) and PLK4 were closely associated with the prognosis of CRC patients. Bufalin could induce the formation of PGCCs in LoVo and Hct116 cell lines. PLK4 was overexpressed in PGCCs with progeny cells and progeny cells derived from PGCCs had strong migration and invasion abilities by expressing epithelial-mesenchymal transition (EMT)-related proteins. PLK4 could interact with CDC25C and promote CDC25C phosphorylation which was associated with the formation of PGCCs. Decreasing CDC25C expression in both LoVo and Hct116 PGCCs with progeny cells, while levels of pCDC25C-ser216 and pCDC25C-ser198 were increased in LoVo and decreased in Hct116 PGCCs with progeny cells. pCDC25C-ser216 located in the cytoplasm and pCDC25C-ser198 located in the nucleus in cells after bufalin treatment. Furthermore, expression of CDC25C, pCDC25C-ser216, and pCDC25C-ser198 was downregulated after PLK4 knockdown. Furthermore, the expression level of PLK4 was associated with differentiated degree, and lymph node metastasis in human CRC tissues. Conclusion: PLK4 contributes to the formation of PGCCs by regulating the expression of CDC25C and is associated with the expression and subcellular location of CDC25C, pCDC25C-ser216 and pCDC25C-ser198.

Connexin 43 contributes to the sensitization of colorectal cancer cells to photodynamic therapy through Akt inhibition.

BACKGROUND: Photodynamic therapy could be one approach to treat colorectal cancer though resistance leads to failure of therapy. Akt activation is a cellular survival response to photodynamic therapy and is also a reason for resistance. Thus, inhibition of Akt is a strategy to decrease resistance. Akt interacts with connexin 43, another protein involved in photodynamic therapy resistance. Connexin 43 is widely expressed in different human tissues and has a complex role in tumor development. However, the mechanism of inhibition of Akt by connexin 43 that sensitizes colorectal cancer cells to photodynamic therapy needs further investigation. METHODS: In this study, two colorectal cancer cells with low phosphorylated connexin 43 level were used to explore this mechanism. LY294002 was used as an Akt inhibitor, and connexin 43-pCMV3 was transfected into cells to increase connexin 43 expression. RESULTS: Akt and connexin 43 inhibit each other in both colorectal cancer cell lines. In vitro and in vivo experiments showed that LY294002 and connexin 43 transfection sensitized cells to hematoporphyrin-Photodynamic therapy. LY294002 increased the sensitivity of cells to photodynamic therapy with a pronounced effect in cells with high expression levels of connexin 43. CONCLUSIONS: Connexin 43 should be considered an important factor in increasing the phototoxicity of photodynamic therapy in colorectal cancer through Akt inhibition.

Intestinal Immune System and Amplification of Mouse Mammary Tumor Virus.

Mouse mammary tumor virus (MMTV) is a virus that induces breast cancer in mice. During lactation, MMTV can transmit from mother to offspring through milk, and Peyer's patches (PPs) in mouse intestine are the first and specific target organ. MMTV can be transported into PPs by microfold cells and then activate antigen-presenting cells (APCs) by directly binding with Toll-like receptors (TLRs) whereas infect them through mouse transferrin receptor 1 (mTfR1). After being endocytosed, MMTV is reversely transcribed and the cDNA inserts into the host genome. Superantigen (SAg) expressed by provirus is presented by APCs to cognate CD4+ T cells via MHCII molecules to induce SAg response, which leads to substantial proliferation and recruitment of related immune cells. Both APCs and T cells can be infected by MMTV and these extensively proliferated lymphocytes and recruited dendritic cells act as hotbeds for viral replication and amplification. In this case, intestinal lymphatic tissues can actually become the source of infection for the transmission of MMTV in vivo, which results in mammary gland infection by MMTV and eventually lead to the occurrence of breast cancer.