BACKGROUND. The implementation of new treatment protocols for locally advanced breast cancer is currently limited by inaccurate evaluation of response to neoadjuvant chemotherapy. A recently developed dedicated breast magnetic resonance imaging (MRI) method (RODEO MRI) was evaluated as a tool for determining tumor response and extent of residual disease after neoadjuvant chemotherapy.

The present investigation was undertaken to determine if an interaction affecting 45Ca release from prelabeled fetal rat long bones could be elicited by the Ca2+ ionophore, A-23187, and the phorbol ester, 12-myristate 13-acetate (PMA). Treatment with either A-23187 at a concentration of 0.3 microM or PMA at concentrations of 10(-6) M, 10(-7) M, and 10(-8) M produced significant 45Ca mobilization. When A-23187 and PMA were combined, enhanced 45Ca release was observed on days 1 and 2 of culture. The stimulation of calcium mobilization noted on day 1 occurred when neither ionophore nor 10(-6) M PMA treatments alone produced significant 45Ca release. On day 2, cumulative 45Ca release elicited by the combination of A-23187 plus 10(-6) M PMA was slightly more than additive (15.9% for combination treatment vs. 13.7% for the sum of the individual treatments). Moreover, when A-23187 was combined with 10(-7) M PMA on day 2, an enhancement of 45Ca release was observed which was clearly more than additive (14.5% for combination treatment vs. 8.8% for the individual treatments), suggesting the possibility of a synergistic interaction between the two agents. These results were in marked contrast to those obtained with the inactive phorbol ester analog, phorbol 13-monoacetate. No stimulation of 45Ca release was observed with 10(-6) M and 10(-7) M phorbol 13-monoacetate alone nor was enhanced 45Ca release noted when the analog was combined with 0.3 microM A-23187.(ABSTRACT TRUNCATED AT 250 WORDS)