A predictor of pathological complete response to neoadjuvant chemotherapy in triple-negative breast cancer patients with the DNA repair genes

Background

We conducted this study to investigate the prevalence of potential chemo-response-related gene mutations in triple-negative breast cancer (TNBC) patients and to evaluate the potential relationship between these gene mutations and neoadjuvant chemotherapy response in TNBC patients.

Methods

One hundred sixty-two TNBC patients in Fudan University Shanghai Cancer Center who received NAC with 4 cycles of paclitaxel and carboplatin were enrolled in this study. Fifty-six pathological complete response (pCR) patients and 56 non-pCR patients were enrolled in this retrospective study for the training set. Clinical assessments of postoperative residual tumors were performed according to Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 criteria. Forty chemo-response-related genes were screened in each tumor specimen by second-generation sequencing analysis. Fifty TNBC patients who received neoadjuvant chemotherapy with paclitaxel and carboplatin were enrolled in the validation group.

Results

Fifty-seven of 112 (50.9%) TNBCs contained at least one detected somatic mutation. As expected, TP53 mutation was the most common alteration, which was observed in 21.4% of patients. BRCA1, BRCA2, RET, PI3KCA, and PTEN mutations were each observed in 11.6%, 4.5%, 5.4%, 2.7% and 3.6% of all cases, respectively. No significant differences in any gene mutation frequency between pCR and non-pCR groups were identified. We found that the mutation status of 10 DNA repair genes involved in homologous recombination (HR) pathway successfully discriminated between responding and nonresponding tumors in the training group. Up to 18 patients who were mutation-positive experienced pCR compared to only 6 in the non-pCR group (P=0.006), and 75% the HR related gene mutation patients achieved pCR. In the validation group, TNBC patients with DNA repair gene mutations achieved 77.8% pCR.

Conclusions

A subset of TNBC patients carry deleterious somatic mutations in 10 HR-related genes. The mutation status of this expanded gene panel is likely to effectively predict respond rate to neoadjuvant chemotherapy based on paclitaxel and carboplatin. Our findings need to be validated through follow-up studies in this and additional cohorts.

[A preliminary study on the molecular characteristics of D-cycloserine resistance of Mycobacterium tuberculosis]

Objective: To investigate the relationship between D-cycloserine resistance and the gene mutations of alrA, ddlA and cycA of Mycobacterium (M.) tuberculosis, as well as the association between D-cycloserine resistance and spoligotyping genotyping. Methods: A total of 145 M. tuberculosis strains were selected from the strain bank. D-cycloserine resistant phenotypes of the strains were determined by the proportion method and the minimal inhibitory concentration was determined by resazurin microtiter assay. PCR amplification and DNA direct sequencing methods were used for the analysis of gene mutations. Relationship between the resistance phenotype and genotype was analyzed by chi-square test. Results: Of the 145 clinically collected strains, 24 (16.6%) of them were D-cycloserine resistant and 121 (83.4%) were sensitive. There were only synonymous mutations noticed on alrA, ddlA and cycA in sensitive strains. Of the 24 D-cycloserine resistant strains, 3 (12.5%) isolates' cycA and 1 (4.2%) isolates' alrA happened to be non-synonymous mutations, in which the codes were 188, 318 and 508 of cycA, and 261 of alrA, respectively. Results on drug sensitivity tests confirmed the minimal inhibitory concentration of the mutant strains were all increased to some degrees. The D-cycloserine resistant rates of 88 Beijing genotype and 57 non-Beijing genotype strains were 20.5% and 10.5% , respectively, but with no statistically significant difference (χ(2) =2.47, P>0.05). Conclusions: The non-synonymous mutations of alrA and cycA might contribute to one of the mechanisms of M. tuberculosis D-cycloserine resistance. M. tuberculosis Beijing genotype or non-Beijing genotype was not considered to be associated with the D-cycloserine resistance.