The Mutational Hotspots Of PIK3CA、kRAS And BEAF Genes In Breast Cancer

As one of the most frequently malignant cancer, breast cancer has a badinfluence on both physiological and psychological health of women, and evenresults in death. With the development of theory and technique on cell andmolecular biology, it is known that the abnormity and disorder of cellular signalingpathway plays a fateful role in breast cancer. Gene mutation is also very importantin the occurrence and development of breast cancer. Till now, it has beendemonstrated multiple genes have great significance on the early diagnosis andprognosis.PIK3CA is a key member of PI3Ks family. The gene is34Kb and locates onchromosome3q26.3. It composes of20exons, coding the p110alpha subunit with1068Aa. PIK3CA is an oncogene, and has mutations in many kinds of tumor,which results in disordered regulation in different level of PI3K signaling pathway,unlimited growth and proliferation of invasive cells, and inhibition of apoptosis.Recently, there are many reports of high frequency mutation of PIK3CA gene incarcinoma of colon, ovarian, breast, stomach and liver. It was discovered that themutation of PIK3CA is most common beyond HER2gene replication and p53mutation in breast cancer.KRAS belongs to RAS family, and locates on the short arm of chromosome12,with a length of35kb. KRAS is a downstream molecule of EGF receptor. Itpossesses four exons and one5’ end non-coding exon, which coding to the189AaRAS protein. This gene mainly serves in the membrane receptor cAMP signalingpathway. KRAS has the worst influence on malignant cancer in the RAS family, andit is detected in almost30%of tumor tissue. BRAF gene was found in Human ewing’s sarcoma, and was confirmed toinfect NIH3T3cells. This gene locates on chromosome7q34, with a length of190kb. BRAF is a very important transduction factor in the Ras-Raf-MEK-ERKsignaling pathway.7-8%of malignant cancer tissues have BRAF mutation. Thepositions of mutation mainly locate on the11th and the15th exon, and mostcommonly is V600E. Recently, the mutation state of BRAF gene was proved topredict and have influence on EGFR negative therapy, and the prognosis of breastcancer. So BRAF gene can be a very important target of breast cancer research.Till now, most researches on gene mutation in breast cancer were based onCaucasians, while there were rare researches based on the patients of breast cancerin China. However, tumor is a complexity process with multi-factor, multi-stageand multi-gene mutation accumulation. There is also diversity of frequency andpoints of gene mutation in different race and multitude. So this issue aims atanalysis of hot spot gene mutation of breast cancer patient in china, to investigatethe relationship among mutation, phenotype of breast cancer and clinic pathologicfeatures.This study collect female breast cancer specimens from Huaibei MinerGeneral Hospital, and performs PCR amplification, followed by sequencinganalysis of hot spot mutations in PIK3CA, KRAS and BRAF gene. As a result: in the26breast cancer samples collected,8samples have PIK3CA gene mutation with afrequency of30%.1sample has the9th exon mutation (G1633A);7samples havemutation (A3140G) on the exon20, one of them was found possessing a new pointmutation A3134C besides A3140G.6samples of KRAS gene mutations, with afrequency of23%, mutation points in both of them locate in the2nd exon of hotspot mutation region (C100A).5samples have mutation of BRAF gene, with afrequency of19%, the mutation points locates in the15th exon of hot spot mutation region (G1808C). Both one PIK3CA gene mutation and one KRAS mutation werefound in1case of invasive ductal carcinoma tissue sample.