Effect of alkaline gradient on clear renal cell carcinoma mortality: role of isoform 1 of Na+/H+ exchanger function

MARINA MAZZOCCHI; DI GIUSTO, GISELA; ALEJANDRO PIZZONI; BELTRAMONE, NATALIA; FORD P; CAPURRO CLAUDIA; VALERIA RIVAROLA

Congreso; SAFIS 2019; 2019

The association between cell death and intracellular pHelicits the possibility that extracellular pH (pHe) maymodify cell survival. Moreover, as tumor extracellular acidity is a hallmark of cancers, is probable that pHeaffects differently cancer or normal cells. Our previousstudies showed that cells derived from renal cellcarcinoma (RCC) were more sensitive to 24h alkalosis thannormal cells. The aim of this study was to investigatefurther the best alkaline condition to kill cancer cellswithout affecting normal ones. We use three renal cellmodels: HK2, derived from normal human proximalepithelial cells, 786-O and Caki-1, both derived fromhuman RCC. We exposed cells to media with differentalkaline pHe during 48 to 96h. Then, we estimated cellsurvival by acrydin orange?ethidium bromideexperiments. Our results show that normal HK2 cells couldsurvive up to 72h in very mild alkaline conditions (4.8mMNaOH, + 0.05 pH units) without being affected (94±16 % ofliving cells respect to control, n=6). At the sameconditions, both RCC derived cell lines had significantfewer % of living cells respect to control (64±5 % for 786-O and 72±7 % for Caki-1 cells, both with n=6). With 72hexposition to 9.6 mM NaOH (+ 0.1 pH units) thepercentage of living RCC cells respect to control becameminimal (23±8 % for 786-O and 16±5 % for Caki-1 cells,both with n=6). However, at this condition HK2 cells werealso affected (28±5 % of living cells respect to control,n=6). NHE1 isoform of Na+/H+ exchanger favors apoptoticprocess in some experimental models. Then, we inhibitedthe transporter during the 72h exposition to 9.6 mMNaOH. NHE1 inhibition partially reverted the effects ofalkalosis only in normal HK2 cells (% of living cells respectto control: +NHE1 28±5 vs ?NHE1 54±6, p