Benefits of metronomic therapy targeting muscarinic receptors in breast cancer involves an increment in apoptosis/necrosis ratio and a decrement in ABCG2 expression

ALEJANDRO ESPAÑOL; SALEM , AGUSTINA; SANCHEZ, Y; LASERNA, L; MARÍA E. SALES

Congreso; . LXI Reunión anual de la Sociedad Argentina de Investigación Clínica; 2016

Wedemonstrated that muscarinic acetylcholine receptors (mAChR) are expressed in breasttumor cells while they are absent in non-tumorigenic murine and human breastcells. The addition of carbachol (CARB) during 40h stimulates cell deathsimilarly to paclitaxel (PX), a cytostatic drug frequently used in breastcancer treatment. Applying the principles of metronomic therapy, a combinationof low concentrations of CARB with PX promoted cell cytotoxicity generating aapoptosis/necrosis  ratio2:1 in murinemammary adenocarcinomas. In the human breast tumor cell line MCF-7, derivedfrom a luminal tumor, thetreatment with CARB (10-9M) and PX (10-11M)increased cell death by 47±6% (p <0.001 vs. control) measured by MTTassay, in a similar manner to 10-6M PX, that also induced death inthe non-tumorigenic cell line, normal MCF-10A, an undesirable effect inchemotherapy. By flow cytometry with annexine-V and 7-AAD, we demonstrated thatthe combination reduced necrosis (p<0.05 vs. control) and increasedapoptosis (p<0.05 vs. control). In addition, we observed that aftertreatment with CARB plus PX cells were less sensitive to the stimulation withCARB 10-9M during 1hthat usually induces proliferation in tumorcells.   These effects could be mediatedby a reduction of 92 ± 3.05% (p<0,001 vs. control) in the expression ofABCG2 protein measured by Western blot. This protein is involved in the resistanceto cancer drugs administration because it favors the output of these drugs intothe extracellular space. We can conclude that the treatment of MCF-7 tumorcells with a metronomic combination of CARB plus PX could be as effective aspharmacological concentrations of PX to produce cell death and