Ezrin mediates c-Myc actions in prostate cancer cell invasion

Parafibromin expression is an independent prognostic factor for colorectal carcinomas

Parafibromin is a protein encoded by hyperparathyroidism 2, and its down-regulated expression is involved in the pathogenesis of parathyroid, breast, and gastric carcinomas. This study aimed to clarify the roles of parafibromin expression in tumorigenesis, progression, and prognosis of colorectal carcinomas. Parafibromin-expressing plasmid was transfected into DLD-1 cells with the phenotypes, and related molecules were examined. Parafibromin expression was examined in colorectal samples by immunohistochemistry, in situ hybridization, Western blot, or reverse transcription polymerase chain reaction. It was found that parafibromin overexpression could cause G1 arrest and enhance differentiation of DLD-1 cells. There was a high expression of p21, p27, and cyclin E, but low expression of cyclin D1 messenger RNA, phospho-cdc2, and phospho-cdc25c proteins. Parafibromin could inhibit c-myc messenger RNA expression by binding to c-myc promoter. Expression levels of nuclear parafibromin and parafibromin messenger RNA were decreased from colorectal nonneoplastic mucosa and adenomas to carcinomas (P < .05). Immunohistochemically, parafibromin expression was inversely correlated with tumor size, depth of invasion, lymph node metastasis, clinicopathologic staging, and poor prognosis of carcinomas (P < .05). It was suggested that parafibromin overexpression might suppress cell cycle progression and promote differentiation of DLD-1 cells. Aberrant parafibromin expression possibly contributes to the pathogenesis, growth, invasion, and metastasis of colorectal carcinomas and could be regarded as an independent factor to indicate a favorable prognosis for patients with colorectal carcinomas.

Changes in cortical cytoskeletal and extracellular matrix gene expression in prostate cancer are related to oncogenic ERG deregulation

Background

The cortical cytoskeleton network connects the actin cytoskeleton to various membrane proteins, influencing cell adhesion, polarity, migration and response to extracellular signals. Previous studies have suggested changes in the expression of specific components in prostate cancer, especially of 4.1 proteins (encoded by EPB41 genes) which form nodes in this network.

Methods

Expression of EPB41L1, EPB41L2, EPB41L3 (protein: 4.1B), EPB41L4B (EHM2), EPB41L5, EPB49 (dematin), VIL2 (ezrin), and DLG1 (summarized as „cortical cytoskeleton" genes) as well as ERG was measured by quantitative RT-PCR in a well-characterized set of 45 M0 prostate adenocarcinoma and 13 benign tissues. Hypermethylation of EPB41L3 and GSTP1 was compared in 93 cancer tissues by methylation-specific PCR. Expression of 4.1B was further studied by immunohistochemistry.

Results

EPB41L1 and EPB41L3 were significantly downregulated and EPB41L4B was upregulated in cancer tissues. Low EPB41L1 or high EPB41L4B expression were associated with earlier biochemical recurrence. None of the other cortical cytoskeleton genes displayed expression changes, in particular EPB49 and VIL2, despite hints from previous studies. EPB41L3 downregulation was significantly associated with hypermethylation of its promoter and strongly correlated with GSTP1 hypermethylation. Protein 4.1B was detected most strongly in the basal cells of normal prostate epithelia. Its expression in carcinoma cells was similar to the weaker one in normal luminal cells. EPB41L3 downregulation and EPB41L4B upregulation were essentially restricted to the 22 cases with ERG overexpression. Expression changes in EPB41L3 and EPB41L4B closely paralleled those previously observed for the extracellular matrix genes FBLN1 and SPOCK1, respectively.

Conclusions

Specific changes in the cortical cytoskeleton were observed during prostate cancer progression. They parallel changes in the expression of extracellular matrix components and all together appear to be associated with oncogenic ERG overexpression. We hypothesize that these alterations may contribute to the increased invasivity conferred to prostate cancer cells by ERG deregulation.

Specific inhibition of a pathogenic receptor tyrosine kinase by its transmembrane domain

The transmembrane (TM) domains of receptor tyrosine kinases (RTKs) are believed to be important players in RTK signal transduction. However, the degree of specificity and promiscuity of RTK TM domain lateral interactions in mammalian membranes has not been assessed in detail in the literature. A technique to probe the occurrence of interactions between TM domains and their biological significance is to evaluate the propensity for formation of heterodimers of a full-length RTK and its TM domain. Here we examine if the inhibition of two RTK pathogenic mutants, Neu/V664E and FGFR3/A391E, can be achieved by the TM domains of Neu, Neu/V664E, FGFR3 and FGFR3/A391E. We show that the TM domain of Neu/V664E specifically inhibits the phosphorylation of full-length Neu/V664E, while the wild-type Neu TM domain does not. In addition, Neu/V664E TM domain does not affect the phosphorylation levels of full-length FGFR3/A391E. The results suggest that TM domain peptides could be exploited in the future for the development of specific inhibitors of mutant RTKs.