The phosphatidylinositol 3V-kinase (PI3K) pathway is frequently activated in thyroid carcinomas through the constitutive activation of stimulatory molecules (e.g., Ras) and/or the loss of expression and/or function of the inhibitory PTEN protein that results in Akt activation. Recently, it has been reported that somatic mutations within the PI3K catalytic subunit, PIK3CA, are common (25-40%) among colorectal, gastric, breast, ovarian cancers, and high-grade brain tumors. Moreover, PIK3CA mutations have a tendency to cluster within the helical (exon 9) and the kinase (exon 20) domains. In this study, 13 thyroid cancer cell lines, 80 well-differentiated thyroid carcinomas of follicular (WDFC) and papillary (WDPC) type, and 70 anaplastic thyroid carcinomas (ATC) were investigated, by PCR-direct sequencing, for activating PIK3CA mutations at exons 9 and 20. Nonsynonymous somatic mutations were found in 16 ATC (23%), two WDFC (8%), and one WDPC (2%). In 18 of the 20 ATC cases showing coexisting differentiated carcinoma, mutations, when present, were restricted to the ATC component and located primarily within the kinase domain. Three cell lines of papillary and follicular lineage (K1, K2, and K5) were also found mutated. In addition, activation of Akt was observed in most of the ATC harboring PIK3CA mutations. These findings indicate that mutant PIK3CA is likely to function as an oncogene among ATC and less frequently well-differentiated thyroid carcinomas. The data also argue for a role of PIK3CA targeting in the treatment of ATC patients. (Cancer Res 2005; 65(22): 10199-207)
KRAS is one of the most frequently mutated oncogenes in cancer, being a potent initiator of tumorigenesis, a strong inductor of malignancy, and a predictive biomarker of response to therapy. Despite the large investment to understand the effects of KRAS activation in cancer cells, pharmacologic targeting of KRAS or its downstream effectors has not yet been successful at the clinical level. Recent studies are now describing new mechanisms of KRAS-induced tumorigenesis by analyzing its effects on the components of the tumor microenvironment. These studies revealed that the activation of KRAS on cancer cells extends to the surrounding microenvironment, affecting the properties and functions of its constituents. Herein, we discuss the most emergent perspectives on the relationship between KRAS-mutant cancer cells and their microenvironment components. .
We suggest that H. pylori alters the E-cadherin-catenin complex, leading to formation of a multiproteic complex composed of CagA, c-Met, E-cadherin, and p120-catenin. This complex abrogates c-Met and p120-catenin tyrosine phosphorylation and suppresses the cell-invasive phenotype induced by H. pylori.
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