Signaling pathways involved in apoptosis-resistance against doxorubicin analogs in murine mammary cells. Role of protein kinase C delta (PKCd)

MARIA INES DÍAZ BESSONE; DAMIAN E. BERARDI; PAOLA B. CAMPODÓNICO; LEONARD LOTHSTEIN; LAURA B. TODARO; ELISA D. BAL DE KIER JOFFÉ; ALEJANDRO J. URTREGER

Orlando

Congreso; 102nd Annual Meeting of the American Associaton for Cancer Research; 2011

American Associaton for Cancer Research (AACR)

In this work we have analyzed whether the overexpression of PKCd in murine mammary cells (NMuMG) is able to alter cell death susceptibility to two chemotherapeutic drugs derived from doxorubicin (AD198 and AD288), and evaluate the signaling pathways involved in this process. Similarly to doxorubicin, the mechanism of action of AD288 involves the generation of DNA damage whereas, it has been proposed that AD198 induces apoptosis by activating PKC isoforms, in particular PKCd. By western blot we could determine that NMuMG-PKCd cells showed an increase in the activation and/or expression of different molecules and signaling pathways involved in cell survival such as Bcl-2, pBad, PI3K/Akt y NFkB. Therefore PKCd overexpression induced an increase in cell death resistance against both ADs (survival: AD198: 80±10% vs. 41±8% and AD288: 90±15% vs. 60±10% in NMuMG-PKCd and NMuMG-vector cells respectively). In order to evaluate the role of PI3K/Akt pathway in cell death resistance induced by both ADs, cells were treated with LY294002, a PI3K inhibitor. The inhibition of this signaling pathway in NMuMG-PKCd cells increased 3-fold AD198 cytotoxic effect, whereas did not alter AD288 effect. The role of NFkB signaling pathway in the resistance against cell death induced by each AD was determined by transient transfection with a variant of its repressor IkB. The inhibition of this signaling pathway significantly increased cell death susceptibility to both drugs (P<0.05 student´s t test). In this work we have demonstrated that the anti-apoptotic signals generated by PKCd in NMuMG mammary cells could be reverted by inhibiting PI3K/Akt and/or NFkB signaling pathways. In addition, it was shown that the pathway involved was dependent on the mechanism of action of the cytotoxic drug used.