TP53 Germline Mutations are Associated with HR+/HER2+ in BRCA1/2-Negative Early-Onset Breast Cancer in China

Background: Except for BRCA1/2, there is no data on the relationship between genetic counseling for the range of mutations and early-onset breast cancer populations. We looked for a link between inherited genes and the molecular subtype of early-onset breast cancer.Methods: We genotyped 1214 individuals with early-onset sporadic breast cancer (age≤40 years) who were BRCA1/2-negative in 3 genes: TP53, PALB2, and RECQL. We focus on the immunohistochemistry characteristics that are unique to each patient. Results: The mutation rates of TP53, PALB2, and RECQL in 1214 BRCA-negative young individuals were 4/1214(0.33%), 8/1214(0.66%), 2/1214(0.16%), respectively. The fact that the TP53 mutation rate was 3.49% among estrogen receptor-and/or progesterone receptor-positive, human epidermal growth factor receptor 2 (HER-2) amplification patients under the age of 35 (P<0.001) was particularly noteworthy. Conclusion: According to the findings, TP53 genetic testing should focus on women under 35 with HR-positive and HER2-positve IDC patients.

High prevalence of somatic PIK3CA and TP53 pathogenic variants in the normal mammary gland tissue of sporadic breast cancer patients revealed by duplex sequencing.

The mammary gland undergoes hormonally stimulated cycles of proliferation, lactation and involution. We hypothesized that these factors increase the mutational burden in glandular tissue and may explain high cancer incidence rate in the general population and recurrent disease. Hence, we investigated the DNA sequence variants in the normal mammary gland, tumor and peripheral blood from 52 reportedly sporadic breast cancer patients, including breast-conserving surgery cases. Targeted resequencing of 542 cancer associated genes revealed mosaic somatic pathogenic variants of: PIK3CA, TP53, AKT1, MAP3K1, CDH1, RB1, NCOR1, MED12, CBFB, TBX3 and TSHR in the normal mammary gland, at considerable allelic frequencies (9x10-2 to 5.2x10-1) indicating clonal expansion. Further evaluation of the frequently damaged PIK3CA and TP53 genes by ultra-sensitive duplex sequencing demonstrated a diversified picture of multiple low level-mosaic (in 10-2 to 10-4 alleles) hotspot pathogenic variants. Our results raise a question about the oncogenic potential in non-tumor mammary gland tissue of breast-conserving surgery patients.

The Loss of Heterozygosity of FHIT Gene in Sporadic Breast Cancer

The loss of heterozygosity (LOH) is a genetic event that can change gene function. FHIT is a potential tumor suppressor gene. Although the precise FHIT molecular mechanism of action is not well understood, evidences suggest that Fhit protein reduced levels are involved in mammary carcinogenesis. The aim of this study was to investigate if FHIT LOH could influence on sporadic breast cancer (BC) biological behavior, through its association with prognostic factors for sporadic BC.Tumor tissue and peripheral blood samples were analyzed using the microsatellite marker D3S1300. The findings were associated with clinicopathological parameters including overall survival. LOH was detected in 31.1%(52/167) of the informative BC’ cases. Considering clinical and pathological characteristics we have found no significant association with FHIT LOH status. The mean follow-up time was 80 months. After the Cox regression analysis two parameters remained associated with BC’s risk of death: TNM stage III and IV - HR = 3.74(95% CI, 1.16-12.1) P=0.027 and disease relapse HR = 3.14(CI 95% 1.26-7.80) P =0.014. This study shows that FHIT LOH by itself is not a prognostic factor for sporadic BC. Further researches are required to elucidate the functional role of FHIT LOH concerning to BC.

Germline Mutation Analysis in Sporadic Breast Cancer Cases with Clinical Correlations

Demographics for breast cancers vary widely among nations. The frequency of germline mutations in breast cancers, which reflects the hereditary cases, has not been investigated adequately in Pakistani population. In the present study, germ-line mutations in twenty-seven breast cancer candidate genes were investigated in eighty-four sporadic breast cancer patients along with the clinical correlations. The germ-line variants were also assessed in two healthy controls. The most frequent parameters associated with hereditary cancer cases are age and ethnicity. Therefore, the clinico-pathological features were evaluated by descriptive analysis and Pearson χ2 test (with significant p-value <0.05). The analyses were stratified on the basis of age (<40 years vs >40 years) and ethnicity. The breast cancer gene panel assay was carried out by a genomic capture, massively parallel next generation sequencing assay on Illumina Hiseq2000 assay with 100bp read lengths. Copy number variations were determined by partially-mapped read algorithm. Once the mutation was identified, it was validated by Sanger sequencing. The ethnic analysis stratified on the basis of age showed that the frequency of breast cancer at young age (<40 years) was higher in Sindhis (n=12/19; 64%) in contrast to patients in other ethnic groups. Majority of the patients had stage III (38.1%), grades II and III (46.4%), tumor size 2-5cm (54.8%), and invasive ductal carcinoma (81%). Overall, the analysis revealed germ-line mutations in 11.9% of the patients. The mutational spectrum was restricted to three genes: BRCA1, BRCA2, and TP53. The identified mutations consist of seven novel germ-line mutations, while three mutations have been reported previously. All the mutations are predicted to result in protein truncation. No mutations were identified in the remaining twenty-four candidate breast cancer genes. The present study provides the framework for the development of preventive and treatment strategies against breast cancers in Pakistani population.

Genomic Diversity in Sporadic Breast Cancer in a Latin American Population

Among Latin American women, breast cancer incidences vary across populations. Uruguay and Argentina have the highest rates in South America, which are mainly attributed to strong, genetic European contributions. Most genetic variants associated with breast cancer were described in European populations. However, the vast majority of genetic contributors to breast cancer risk remain unknown. Here, we report the results of a candidate gene association study of sporadic breast cancer in 176 cases and 183 controls in the Uruguayan population. We analyzed 141 variants from 98 loci that have been associated with overall breast cancer risk in European populations. We found weak evidence for the association of risk variants rs294174 (ESR1), rs16886165 (MAP3K1), rs2214681 (CNTNAP2), rs4237855 (VDR), rs9594579 (RANKL), rs8183919 (PTGIS), rs2981582 (FGFR2), and rs1799950 (BRCA1) with sporadic breast cancer. These results provide useful insight into the genetic susceptibility to sporadic breast cancer in the Uruguayan population and support the use of genetic risk scores for individualized screening and prevention.