ABSTRACT
An oncogenic mutation (G49A:E17K) in the AKT1 gene has been described recently in human breast, colon, and ovarian cancers. The low frequency of this mutation and perhaps other selective pressures have prevented the isolation of human cancer cell lines that harbor this mutation thereby limiting functional analysis. Here, we create a physiologic in vitro model to study the effects of this mutation by using somatic cell gene targeting using the nontumorigenic human breast epithelial cell line, MCF10A. Surprisingly, knock in of E17K into the AKT1 gene had minimal phenotypic consequences and importantly, did not recapitulate the biochemical and growth characteristics seen with somatic cell knock in of PIK3CA hotspot mutations. These results suggest that mutations in critical genes within the PI3-kinase (PI3K) pathway are not functionally equivalent, and that other cooperative genetic events may be necessary to achieve oncogenic PI3K pathway activation in cancers that contain the AKT1 E17K mutation.
Subject(s)
Breast Neoplasms/genetics , Mutation , Phosphatidylinositol 3-Kinases/genetics , Proto-Oncogene Proteins c-akt/genetics , Breast Neoplasms/etiology , Cell Line, Tumor , Cell Proliferation/drug effects , Class I Phosphatidylinositol 3-Kinases , Estrogens/pharmacology , Female , Humans , Intracellular Signaling Peptides and Proteins/antagonists & inhibitors , Phosphatidylinositol 3-Kinases/physiology , Protein Serine-Threonine Kinases/antagonists & inhibitors , Proto-Oncogene Proteins c-akt/physiology , Signal Transduction , TOR Serine-Threonine Kinases , Tamoxifen/pharmacologyABSTRACT
A retrospective survey was performed in 205 cases of gestational trophoblastic neoplasia with the use of routine tissue sections and quinacrine stain after hydrolysis and pronase pretreatment. The method allows scoring of nuclei simultaneously for either Y chromatin or X chromatin (Barr body) and has proved to be a valid test for sex assignment in tissue sections. Y-chromatin positivity (indicating gamete heterozygosity) was found in 16 of 182 cases (9%) of hydatidiform mole, two of four cases (50%) of invasive mole, and 14 of 19 cases (74%) of choriocarcinoma. The cytogenetic literature of 173 cases of complete hydatidiform mole indicates 8.1% have been 46,XY. Our unexpectedly high incidence of Y chromatin in malignant gestational trophoblastic neoplasia would suggest that homozygosity for a recessive mutant oncogene is not an important factor in pathogenesis of choriocarcinoma. The partial allograft theory of pathogenesis after nonmolar antecedents with attendant diminished host immunoreactivity remains a plausible consideration.
