The clinical values of breast cancer resistance protein mRNA levels in plasma microvesicles predicting breast cancer chemotherapy

Objective To investigate the predictive values of peripheral blood microvesicles(MVs) containing breast cancer resistance protein(BCRP) mRNA on chemotherapy effectiveness in breast cancer. Methods We selected 40 cases of breast cancer(BC)chemotherapy,84 cases of palliative chemotherapy in patients with advanced metastatic breast cancer(mBC),and 40 cases of normal volunteers(NF).Immunofluorescence was used to detect mucin 1(MUC1)expression rate and co- expression rate of MUC1 and BCRP in plasma MVs.Real- time quantitative reverse transcriptase- polymerase chain reaction(RT-qPCR) was used to detect BCRP mRNA level in plasma MVs.The correlations between clinicopathologic features and BCRP mRNA level with chemotherapy effectiveness were analyzed by the Kaplan- Meier method and Cox regression. Results MUC1 expression rate and co- expression rate of MUC1 and BCRPin plasma MVs of mBC group were(11.60±0.76)% and(14.06±0.62)%, and those in BC group were (6.67±1.03)% and(1.83±0.39)%(P< 0.05).The BCRP mRNA relative levels of plasma MVs in NF, BCand mBCgroups were- 2.15±0.66,- 2.32±0.75,and- 5.75±0.38 respectively.The BCRP mRNA relative levels of plasma MVs in mBC group was significantly higher than in BC group(P< 0.01). According to Response Evaluation Criteria in solid tumors, mBC group was subdivided into the stable disease(SD)subgroup and disease control(DCR)[complete remission(CR)/partial remission(PR)/SD] subgroup.BCRP mRNA relative levels in plasma MVs of SD subgroup and DCR subgroup were- 4.03± 0.71, and- 6.30±0.44 respectively with the difference being statistically significant(P< 0.01). The median progression- free survival(mPFS)on high and low BCRP mRNA expression groups was 2.80 and 4.00 months respectively(P< 0.01).Cox regression analysis showed BCRP mRNA level in the plasma MVs was an independent prognostic factor in advanced metastatic breast cancer chemotherapy(P<0.05). Conclusion The BCRP mRNA levels in the plasma MVs may predict the response of breast cancer chemotherapy as potential markers. Key words: Breast cancer resistance protein; Chemotherapy; Microvesicles