alitretinoin and Lymphoma--Mantle-Cell

Mantle cell lymphoma (MCL) is an aggressive haematological malignancy in which the response to therapy can be limited by aberrantly activated molecular and cellular pathways, among which autophagy was recently listed. Our study shows that the 9-cis-retinoic acid (RA)/Interferon(IFN)-α combination induces protective autophagy in MCL cell lines and primary cultures reducing the extent of drug-induced apoptosis. The treatment significantly up-regulates phospholipid scramblase 1 (PLSCR1), a protein which bi-directionally flips lipids across membranes. In particular, RA/IFN-α combination concomitantly increases PLSCR1 transcription and controls PLSCR1 protein levels via lysosomal degradation. Herein we describe a new function for PLSCR1 as negative regulator of autophagy. Indeed, PLSCR1 overexpression reduced MCL cell susceptibility to autophagy induced by RA/IFN-α, serum deprivation or mTOR pharmacological inhibition. Moreover, PLSCR1 can bind the ATG12/ATG5 complex preventing ATG16L1 recruitment and its full activation, as indicated by co-immunoprecipitation experiments. The combination of doxorubicin or bortezomib with RA/IFN-α strengthened PLSCR1 up-regulation and enhanced apoptosis, as a likely consequence of the blockade of RA/IFN-α-induced autophagy. Immunohistochemical analysis of 32 MCL biopsies revealed heterogeneous expression of PLSCR1 and suggests its possible implication in the response to anticancer therapies, especially to drugs promoting protective autophagy.

Topics: Aged; Alitretinoin; Antineoplastic Agents; Apoptosis; Autophagy; Bortezomib; Cell Line, Tumor; Doxorubicin; Drug Synergism; Female; Gene Expression Regulation, Neoplastic; Humans; Interferon-alpha; Lymphoma, Mantle-Cell; Male; Middle Aged; Phospholipid Transfer Proteins; Tretinoin

Mantle cell lymphoma (MCL) is characterized by a profound deregulation of the mechanisms controlling cell-cycle progression and survival. We herein show that the combination of 9-cis-retinoic acid (RA) and IFN-α induces marked antiproliferative and proapoptotic effects in MCL cells through the modulation of critical targets. Particularly, IFN-α enhances RA-mediated G(0)-G(1) cell accumulation by downregulating cyclin D1 and increasing p27(Kip1) and p21(WAF1/Cip1) protein levels. Furthermore, RA/IFN-α combination also induces apoptosis by triggering both caspases-8 and -9 resulting in Bax and Bak activation. In particular, RA/IFN-α treatment downregulates the antiapoptotic Bcl-xL and Bfl-1 proteins and upregulates the proapoptotic BH3-only Noxa protein. Sequestration of Mcl-1 and Bfl-1 by upregulated Noxa results in the activation of Bid, and the consequent induction of apoptosis is inhibited by Noxa silencing. Noxa upregulation is associated with nuclear translocation of the FOXO3a transcription factor as consequence of RA/IFN-α-induced Akt inhibition. Pharmacologic suppression of Akt, but not of TORC1, increases Noxa protein levels and downregulates Bfl-1 protein supporting the conclusion that the inhibition of the Akt pathway, the resulting FOXO3a activation and Noxa upregulation are critical molecular mechanisms underlying RA/IFN-α-dependent MCL cell apoptosis. These results support the potential therapeutic value of RA/IFN-α combination in MCL management.

Topics: Aged; Alitretinoin; Antineoplastic Combined Chemotherapy Protocols; Apoptosis; Cell Line, Tumor; Cell Proliferation; Female; Forkhead Box Protein O3; Forkhead Transcription Factors; Humans; Interferon-alpha; Lymphoma, Mantle-Cell; Male; Middle Aged; Phosphoinositide-3 Kinase Inhibitors; Proto-Oncogene Proteins c-akt; Proto-Oncogene Proteins c-bcl-2; Receptors, Retinoic Acid; Retinoic Acid Receptor alpha; Retinoid X Receptors; Tretinoin