Dysregulation of miR-126/Crk protein axis predicts poor prognosis in gastric cancer patients.

BACKGROUND: miR-126 functions as a tumor suppressor in gastric cancer (GC) by negatively regulating Crk protein expression post-transcriptionally. OBJECTIVE: The aim of this study was to investigate the associations of miR-126 and Crk protein expression levels, alone or in combination, with the clinicopathological characteristics and prognosis of GC patients. METHODS: The expression levels of miR-126 and Crk protein in 338 GC patients were analyzed by quantitative real-time polymerase chain reaction and immunohistochemistry, respectively. The relationship of miR-126 and Crk protein expression with clinicopathologic characteristics and clinical outcome was evaluated. RESULTS: Compared with matched adjacent non-tumor tissues, miR-126 was significantly down-regulated while Crk protein was significantly up-regulated in tumor tissues. A reduced miR-126 expression and an elevated Crk protein expression, alone or in combination, statistically correlated with aggressive clinicopathological characteristics, such as larger tumor size, deeper local invasion, more lymph node metastasis, advanced TNM stage, and poorer prognosis. Multivariate analysis showed that combined miR-126-low/Crk protein-high expression was an independent unfavorable prognostic factor of GC. CONCLUSIONS: These results indicate for the first time that miR-126 down-regulation and Crk protein up-regulation may be synergistically associated with tumor progression in GC and may predict unfavorable prognosis of GC.

Contribution of Crk adaptor proteins to host cell and bacteria interactions.

The Crk adaptor family of proteins comprises the alternatively spliced CrkI and CrkII isoforms, as well as the paralog Crk-like (CrkL) protein, which is encoded by a different gene. Initially thought to be involved in signaling during apoptosis and cell adhesion, this ubiquitously expressed family of proteins is now known to play essential roles in integrating signals from a wide range of stimuli. In this review, we describe the structure and function of the different Crk proteins. We then focus on the emerging roles of Crk adaptors during Enterobacteriaceae pathogenesis, with special emphasis on the important human pathogens Salmonella, Shigella, Yersinia, and enteropathogenic Escherichia coli. Throughout, we remark on opportunities for future research into this intriguing family of proteins.

MiR-126 inhibits the invasion of gastric cancer cell in part by targeting Crk.

OBJECTIVE: Accumulating evidence has shown that microRNAs (miRNAs) are aberrantly expressed in human gastric cancer and crucial to tumorigenesis. Herein, we identified the role of miR-126 in human gastric cancer (GC) growth and development in vitro. MATERIALS AND METHODS: MiR-126 expression was investigated in GC tissue samples and cell lines by real-time PCR. Crystal violet test and Transwell assay were conducted to explore the effects of miR-126 on the proliferation and invasion of human GC cell lines, respectively. The impaction of miR-126 over expression on putative target Crk (v-crk sarcoma virus CT10 oncogene homolog) was subsequently confirmed via Western blot. Crk specific siRNA was used to suppress Crk expression. RESULTS: MiR-126 expression was frequently and markedly downregulated (p < 0.05) in human gastric cancer tissues. Overexpression of miR-126 inhibited GC cells invasion but did not affect its proliferation in vitro. Moreover, overexpression of miR-126 significantly decreased (p < 0.05) the protein levels of Crk, which has previously been identified as a direct target of miR-126. Knockdown of Crk also markedly suppressed GC cells invasion. CONCLUSIONS: Our results demonstrated that overexpression of miR-126 inhibited GC cells invasion in part by targeting Crk. These findings suggested that miR-126 played major roles in the malignant behavior of GC and it might be a promising therapeutic target of GC.

Expression of miR-126 and Crk in endometriosis: miR-126 may affect the progression of endometriosis by regulating Crk expression.

PURPOSE: To evaluate the relationship between miR-126 and Crk and discuss the role of miR-126 in the development and progression of endometriosis (EMs). METHODS: The expression levels of miR-126 and Crk mRNA were quantified using real time fluorescent quantitative polymerase chain reaction (real time PCR) in ectopic endometrium (ECs) and eutopic endometrium (EUs) in patients with EMs and normal endometrium (ENs) in EMs-free subjects. The expression levels of Crk protein in all samples were evaluated by Western blot. RESULTS: The expression level of miR-126 was significantly downregulated in ECs versus EUs (p = 5.45E(-5)) in the experimental group and in EUs versus ENs (p = 0.019). The expression level of Crk mRNA did not distinguish ECs from EUs (p = 0.995) but was overexpressed in EUs versus ENs (p = 0.006). Crk protein was overexpressed in ECs versus EUs (p = 0.002) in the experimental group and in EUs versus ENs (p = 1.13E(-6)). The expression level of miR-126 had no correlation with Crk mRNA (p = 0.496) but was negatively correlated with Crk protein (p = 3.134E(-5)). The expression level of miR-126 in EUs and ECs was negatively correlated with American Fertility Society (AFS) stage (p = 0.022, p = 0.025) and AFS score (p = 0.002, p = 0.007). miR-126 expression decreased with the progression of EMs, but the decrease was not significantly different. CONCLUSIONS: miR-126 may play an initial role in the development and progression of EMs. Crk may be regulated by miR-126, and synergism between abnormal expressions may play an important role in the pathogenesis of EMs.

Overexpression of CRKII increases migration and invasive potential in oral squamous cell carcinoma.

CT10 regulator of kinase (CRK) was originally identified as an oncogene product of v-CRK in a CT10 chicken retrovirus system. Overexpression of CRKII has been reported in several human cancers. CRKII regulates cell migration, morphogenesis, invasion, phagocytosis, and survival; however, the underlying mechanisms are not well understood. In the present study, we evaluated the possibility of CRKII as an appropriate molecular target for cancer gene therapy. The expression of CRKII in 71 primary oral squamous cell carcinomas and 10 normal oral mucosal specimens was determined immunohistochemically, and the correlation of CRKII overexpression with clinicopathological factors was evaluated. Overexpression of CRKII was detected in 41 of 70 oral squamous cell carcinomas, the frequency being more significant than in normal oral mucosa. In addition, CRKII overexpression was more frequent in higher-grade cancers according to the T classification, N classification, and invasive pattern. Moreover, RNAi-mediated suppression of CRKII expression reduced the migration and invasion potential of an oral squamous cell carcinoma cell line, OSC20. Downregulation of CRKII expression also reduced the expression of Dock180, p130Cas, and Rac1, and the actin-associated scaffolding protein cortactin. These results indicate that the overexpression of CRKII is tightly associated with an aggressive phenotype of oral squamous cell carcinoma. Therefore, we propose that CRKII could be a potential molecular target of gene therapy by RNAi-targeting in oral squamous cell carcinoma.

miR-126 functions as a tumour suppressor in human gastric cancer.

MicroRNAs have emerged as important gene regulators and are recognised as key players in carcinogenesis. In the present study, we show that miR-126 was significantly down-regulated in gastric cancer tissues compared with matched normal tissues and was associated with clinicopathological features, including tumour size, lymph node metastasis, local invasion and tumour-node-metastasis (TNM) stage. Ectopic expression of miR-126 in SGC-7901 gastric cancer cells potently inhibited cell growth by inducing cell cycle arrest in G0/G1 phase, migration and invasion in vitro as well as tumorigenicity and metastasis in vivo. Mechanistically, we identified the adaptor protein Crk as a target of miR-126. Taken together, our results suggest that miR-126 may function as a tumour suppressor in gastric cancer, with Crk as a direct target.