UVB radiation induces apoptosis in murine multidrug resistant cell lines

GARCÍA MG; MAGLIO DG; ALANIZ L; LEONI J; ALVAREZ E; HAJOS S

Córdoba, Argentina

Congreso; VII Congreso Latinoamericano de Inmunología; 2005

Asociación Latinoamericana de Inmunología (ALAI) y Sociedad Argentina de Inmunología (SAI)

Multidrug resistance is the main reason for failure of cancer therapy with resistance to apoptosis being one of the mechanisms involved. UVB radiation causes DNA damage inducing cell cycle arrest and DNA repair. If the damage appears irreversible, cells undergo apoptosis. The Akt kinase, an upstream regulator of apoptosis in many cell types, is activated (pAkt) in keratinocytes by UVB radiation. Besides, survivin, a protein that inhibits apoptosis and regulates cell division is also upregulated. In this work we analyzed the UVB response of murine leukemic cell lines resistant to vincristine (LBRV) or to doxorubicin (LBRD) obtained previously in our laboratory. We evaluated the apoptosis induction after UVB treatment by AnnexinV and acridine orange and ethidium bromide staining. Western Blot was used to investigate the expression of pAkt and survivin. We observed that UVB radiation (5mJ) induced higher levels of apoptosis in the sensitive cell line (LBR) than in LBRD and LBRV (42,7%±0,4%; 25,8%±8,8% and 23,1%±7,8% respectively). pAkt and survivin expression was upregulated after UVB radiation. Due to the increase in pAkt expression we used low doses of wortmannin (a PI3K/Akt inhibitor) that were not able to induce apoptosis per se. We observed that inhibition of PI3K/Akt pathway plus UVB radiation increased apoptosis induction compared with UVB alone in LBR and LBRV (42,7%±0,4% vs. 69%±6,9% and 23,1%±7,8% vs. 37,7±3,9 respectively). We conclude that LBRD and LBRV are more resistant to UVB induced apoptosis than LBR. Radiation upregulated pAkt and survivin while inhibition with wortmannin enhanced apoptosis induction.per se. We observed that inhibition of PI3K/Akt pathway plus UVB radiation increased apoptosis induction compared with UVB alone in LBR and LBRV (42,7%±0,4% vs. 69%±6,9% and 23,1%±7,8% vs. 37,7±3,9 respectively). We conclude that LBRD and LBRV are more resistant to UVB induced apoptosis than LBR. Radiation upregulated pAkt and survivin while inhibition with wortmannin enhanced apoptosis induction.