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 FAK‑Del33 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 FAK‑Del33 remains to be elucidated. The present study used a retroviral expression system to examine changes in PTPα phosphorylation affected by the FAK‑Del33 protein in breast cancer cells. Small interfering (si)RNA targeting PTPα interfered with the phosphorylation of Src. Wound‑healing 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 FAK‑Del33 and the wild‑type breast cancer cells, suggesting that FAK regulated the phosphorylation level of PTPα at Tyr789 in breast cancer mutant FAK‑Del33 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 FAK‑Del33 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 PTPα‑Tyr789 by its upstream activator, FAK‑Del33, 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.

[The transcription levels of linker for activation of T cell and its upstream regulatory factors in T cells of asthmatic patients]

OBJECTIVE

To examine the mRNA expression of the linker for activation of T cell (LAT) and its upstream regulatory factors (Syk, Lck and ZAP-70) in the peripheral blood T cells of asthmatic patients.

METHODS

Reverse transcription polymerase chain reaction (RT-PCR) was used to detect the mRNA expression of LAT and its upstream regulatory factors (Syk, Lck and ZAP-70) in 20 asthmatic patients and 20 nonallergic subjects. The results of LAT transcription level were confirmed by real-time RT-PCR Results were expressed as x +/- s. Differences between groups were assessed for significance by t test.

RESULTS

Compared with nonallergic subjects, a significant decrease of mRNA expression of LAT gene was observed in T cells of asthmatic patients (0.54 +/- 0.14 vs 0.72 +/- 0.17, t = 3.11, P <0.01), which was verified by real-time RT-PCR (0.0065 +/- 0.0066 vs 0.0124 +/- 0.0045, t =0.0022, P <0.01). The Lck and ZAP-70 gene transcription levels were significantly up-regulated (Lck: 0.71 +/- 0.16 vs 0.53 +/- 0.17, t = 3.18, P<0.01; ZAP-70: 1.05 +/- 0.41 vs 0.82 +/- 0.27, t = 2.10, P < 0.05).

CONCLUSION

A significant decrease of mRNA expression of LAT gene in T cells of asthmatic patients may be due to the up-regulation of its upstream regulatory factors (Lck and ZAP-70). The abnormal mRNA expression of LAT, Lck and ZAP-70 genes may be involved in the pathogenesis of asthma.

[Activation related genes of memory CD(4)(+) T cells in asthma patients]

OBJECTIVE

To screen and identify the genes of activated memory CD(4)(+) T cells in asthma.

METHODS

Differential display polymerase chain reaction (DDPCR) was utilized to identify genes of memory CD(4)(+) T cells after activation from asthmatic patients and normal individuals, and the mRNA levels of the differentially expressed genes were analyzed by reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS

Nineteen differentially expressed cDNA fragments were isolated. The homology analysis indicated that two fragments possessed a high degree of homology with interleukin-7 (IL-7) mRNA and MM-1 mRNA. RT-PCR confirmed that IL-7 mRNA and MM-1 mRNA levels were increased in memory CD(4)(+) T cells after activation in asthmatic patients (0.390 +/- 0.029, 0.629 +/- 0.047, F = 983, 1264 respectively, all P < 0.05).

CONCLUSION

The up-regulated expression of IL-7 and MM-1 genes in memory CD(4)(+) T cells after activation may be a molecular mechanism that differentiates the response to allergens of asthma patients from normal individuals.

[Cloning, expression of the lectin-EGF domain of P-selectin, and preparation of its monoclonal antibody]

To prepare monoclonal antibody specific to P-selectin lectin-EGF domain, the gene for lectin-EGF domain of P-selectin L-EGF was amplified from normal human platelets by RT-PCR, then was cloned into prokaryotic vector pET42b(+). The recombinant plasmid was transformed into E. coli DH5 alpha strain for further screening and characterization, and was expressed in E. coli BL21 strain. Expressed protein was purified by chromatography on a Ni(2+)-NTA superflow agarose column and eluted with pH 8.0-4.5 urea gradient. Then the mAb anti-lectin-EGF was prepared with classical hybridoma technique, and 3 hybridoma cell lines (B10, F3 and H5) were obtained with Ig subclasses of these mAbs were IgG(2), IgG(1), and IgG(3) respectively, and their light chains were all kappa chain. Immuofluorescence and FACS assays demonstrated that mAbs could specifically recognize P-selectin expressed on ECV (endothelial cell line) stimulated by LPS. Meanwhile, the role of mAbs to P-selectin lectin-EGF domain was studied, and it was proved that the mAbs markedly inhibited adhesion between platelets and neutrophils in vitro. These monoclonal antibodies can specifically recognize the natural P-selectin and markedly inhibit adhesion between platelets and neutrophils in vitro.

Effect of N-desulfated heparin on hepatic/renal ischemia reperfusion injury in rats

AIM: To investigate the effect of N-desulfated heparin on hepatic/renal ischemia and reperfusion injury in rats.

METHODS: Using rat models of 60 min hepatic or renal ischemia followed by 1 h, 3 h, 6 h and 24 h reperfusion, animals were randomly divided into following groups, the sham operated controls, ischemic group receiving only normal saline, and treated group receiving N-desulfated heparin at a dose of 12 mg/kg at 5 min before reperfusion. P-selectin expression was detected in hepatic/renal tissues with immunohistochemistry method.

RESULTS: P-selectin expression, serum ALT, AST, BUN and Cr levels were significantly increased during 60 minute ischemia and 1 h, 3 h, 6 h and 24 h reperfusion, while the increment was significantly inhibited, and hepatic/renal pathology observed by light microscopy was remarkably improved by treatment with the N-desulfated heparin. Furthermore, the heparin was found no effects on PT and KPTT.

CONCLUSION: P-selectin might mediate neutrophil infiltration and contribute to hepatic/renal ischemia and reperfusion. The N-desulfated heparin might prevent hepatic/renal damage induced by ischemia and reperfusion injury without significant anticoagulant activity.