Deletions of multidrug resistance gene loci in XXXX leads to the down-regulation of its expression and predict @entity5 response to neoadjuvant chemotherapy.

@entity1 @entity1262 @entity0 @entity5 @entity10430 @entity22477 @entity2033 @entity17609 @entity11092 @entity7737
UNASSIGNED: Neoadjuvant chemotherapy (NAC) is intensively used for the treatment of primary @entity0 . In our previous studies, we reported that clinical @entity5 response to NAC is associated with the change of multidrug resistance (MDR) gene expression in @entity5 after chemotherapy. In this study we performed a combined analysis of MDR gene locus deletions in @entity5 DNA, MDR gene expression and clinical response to NAC in 73 BC @entity1 . Copy number variations (CNVs) in biopsy specimens were tested using high-density microarray platform CytoScanTM @entity2033 Array (Affymetrix, USA). 75%-100% @entity1 having deletions of MDR gene loci demonstrated the down-regulation of MDR gene expression. Expression of MDR genes was 2-8 times lower in @entity1 with deletion than in @entity1 having no deletion only in post-NAC @entity5 samples but not in @entity5 tissue before chemotherapy. All @entity1 with deletions of @entity1262 ABCB 3 @entity22477 gene loci - 7q21.1, 6p21.32, 3q27 correspondingly, and most @entity1 having deletions in @entity11092 (16p13.1), @entity7737 (10q24), @entity17609 (21q22.3), @entity10430 (4q22.1), responded favorably to NAC. The analysis of all CNVs, including both amplification and deletion showed that the frequency of 13q14.2 deletion was 85% among @entity1 @entity5 with the deletion at least in one MDR gene locus versus 9% in @entity1 with no deletions. Differences in the frequency of 13q14.2 deletions between the two groups were statistically significant (p = 2.03 *10-11, Fisher test, Bonferroni-adjusted p = 1.73 * 10-8). In conclusion, our study for the first time demonstrates that deletion MDR gene loci can be used as predictive marker for @entity5 response to NAC.
