Focal adhesion kinase regulates the phosphorylation protein tyrosine phosphatase-α at Tyr789 in breast cancer cells.

Protein tyrosine phosphatase (PTP)­α regulates the phosphorylation of focal adhesion kinase (FAK), which is important in cellular signal transduction and integration of proteins. It has been demonstrated that a FAK­Del33 mutation (deletion of exon 33; KF437463) in breast cancer tissues regulates cell migration through FAK/Src signaling activation. However, the detailed pathway for Src activation with FAK­Del33 remains to be elucidated. The present study used a retroviral expression system to examine changes in PTPα phosphorylation affected by the FAK­Del33 protein in breast cancer cells. Small interfering (si)RNA targeting PTPα interfered with the phosphorylation of Src. Wound­healing and migration assays were performed to identify cell morphology and quantitative analysis was performed by examining band color depth in western blot analysis. Significant differences were observed in the phosphorylation level of PTPα at Tyr789 between the FAK­Del33 and the wild­type breast cancer cells, suggesting that FAK regulated the phosphorylation level of PTPα at Tyr789 in breast cancer mutant FAK­Del33 cells. The gene expression profile with FAK siRNA did not alter the levels of phosphorylation in other mutants, including autophosphorylation disability (Y397F), ATP kinase dominant negative (K454R) and protein 4.1, ezrin, radixin, moesin domain attenuate (Δ375). FAK RNAi inhibited the activity of the FAK­Del33 at the Src site and rescued the elevated cell migration and invasion. The present study demonstrated for the first time, to the best of our knowledge, an increase in the phosphorylation level of PTPα­Tyr789 by its upstream activator, FAK­Del33, leading to Src activation in certain breast cancer cells, which has significant implications for metastatic potential.

Somatic mutational analysis of FAK in breast cancer: a novel gain-of-function mutation due to deletion of exon 33.

Focal adhesion kinase (FAK) regulates cell adhesion, migration, proliferation, and survival. We identified a novel splicing mutant, FAK-Del33 (exon 33 deletion, KF437463), in both breast and thyroid cancers through colony sequencing. Considering the low proportion of mutant transcripts in samples, this mutation was detected by TaqMan-MGB probes based qPCR. In total, three in 21 paired breast tissues were identified with the FAK-Del33 mutation, and no mutations were found in the corresponding normal tissues. When introduced into a breast cell line through lentivirus infection, FAK-Del33 regulated cell motility and migration based on a wound healing assay. We demonstrated that the expression of Tyr397 (main auto-phosphorylation of FAK) was strongly increased in FAK-Del33 overexpressed breast tumor cells compared to wild-type following FAK/Src RTK signaling activation. These results suggest a novel and unique role of the FAK-Del33 mutation in FAK/Src signaling in breast cancer with significant implications for metastatic potential.

Rab5a overexpression promoting ovarian cancer cell proliferation may be associated with APPL1-related epidermal growth factor signaling pathway.

Rab5a is a regulatory guanosine triphosphatase that is associated with the transport and fusion of endocytic vesicles, and participates in regulation of intracellular signaling pathways embraced by cells to adapt to the specific environment. Rab5a is also correlated with lung, stomach, and hepatocellular carcinomas. Here, we detected Rab5a in paraffin-embedded samples of 20 ovarian cysts, 20 benign cystadenomas, and 39 ovarian cancers by immunohistochemistry, and observed that Rab5a expression was significantly higher in ovarian cancer (P = 0.0001). By setting up stable HO-8910 cell lines expressing Rab5a or dominant negative Rab5a (Rab5a:S34N), we found that Rab5a overexpression enhanced the cell growth by promoting G1 into S phase. In contrast, Rab5a:S34N inhibited this process. Additionally, APPL1 (adaptor protein containing PH domain, PTB domain, and Leucine zipper motif), a downstream effector of Rab5a, was also involved in promoting HO-8910 cell cycle progress. But this function was blocked by Rab5a:S34N. Laser scanning confocal microscopy represented the colocalization of APPL1 and Rab5a in the plasmolemma, which changed with the time of epidermal growth factor (EGF) stimulation. We also found APPL1 could transfer from the membranes into the nucleus where it interacted with NuRD/MeCP1 (the nucleosome remodeling and histone deacetylase multiprotein complex). NuRD is reported to be involved in the deacetylation of histone H3 and H4 to regulate nuclear transcription. So Rab5a promoted proliferation of ovarian cancer cells, which may be associated with the APPL1-related epidermal growth factor signaling pathway.

Polymorphisms of the coagulation factor VII gene and its plasma levels in relation to acute cerebral infarction differences in allelic frequencies between Chinese Han and European populations.

BACKGROUND: Coagulation factor VII (FVII) levels in plasma are usually related to ischemic heart disease (IHD) and cerebral infarction shares many of the risk factors related to IHD. Is there any relationship between factor VII and cerebral infarction? We investigated the relationship between FVII and acute cerebral infarction and reported genotype frequencies and allelic frequencies of FVII gene polymorphisms in the Chinese Han population. METHODS: We recruited 62 patients with acute cerebral infarction confirmed by magnetic resonance imaging (MRI) from Ruijin Hospital, and 149 age-matched patients clinically free of vascular disease to act as controls. All of them were unrelated, and were from the Chinese Han population. FVII coagulant activity (FVIIc) was determined using an clotting assay, activated FVII (FVIIa) and FVII Ag were assayed using enzyme immunoassay kits. The FVII gene polymorphisms to be detected included-401G/T, -402G/A, 5'F7A1/A2, IVS7 and R353Q. 5'F7 and IVS7 were revealed by means of a PCR and direct agarose gel electrophoresis. The rest were examined by a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). RESULTS: The results showed that FVIIc, FVIIAg and FVIIa were higher in the acute cerebral infarction group than in the control group (P < 0.01, P < 0.05, P < 0.05, respectively). There were no significant differences in the genotype frequencies of FVII gene polymorphisms between the two groups. The allelic frequencies in the Chinese Han population were as follows: -401G/T (96.64/3.36), -402G/A (52.01/47.99), 5'F7A1/A2 (96.64/3.36), IVS7 H5/H6/H7/H8 (0.34/52.35/46.98/0.34) and R353Q (95.64/4.36). There were significant differences (P < 0.01, P < 0.001, P < 0.001, P < 0.001, P < 0.001, respectively) in these allelic frequencies between the Chinese Han and European populations. CONCLUSIONS: The results indicate that increased plasma FVII levels may contribute to thrombosis in cerebral infarction. And there was no significant difference in genotype frequencies of these five FVII gene polymorphisms between the acute cerebral infarction and control groups. Moreover, these results showed that the frequencies of protective allele, including -401T, 5'F7 A2 and 353Q were lower, but that -402A, which was previously found to be associated with increased plasma FVII levels, is higher in Chinese Han population.