Role of retinoids and protein kinase C (PKC) activity in proliferation, survival, and differentiation of murine mammary tumor stem cells

DAMIAN E. BERARDI; CAROLINA FLUMIAN; MARIA I. DIAZ BESSONE; STÉFANO M. CIRIGLIANO; ELISA D. BAL DE KIER JOFFÉ; ALEJANDRO J. URTREGER; LAURA B. TODARO

San Pablo

Congreso; Advances in Molecular Oncology: Translating Molecular Biology into Cancer Treatment; 2013

Sao Paulo School of Advances Sciences

Tumor stem cells are considered responsible of chemoresistance and metastatic spread of many breast tumors. In this work, we used stem cell enriched mammospheres of LM38-LP cell line in order to study: A) The gene expression profile and the ability to regenerate the parental tumor and B) The ability to form secondary mammospheres and 3D colonies after the treatment with retinoids (ATRA 1 uM ) and/or PKCa/d inhibitors (Gö6976 2.5 uM / Rottlerin 1 uM). By RT-PCR we determined that mammospheres express high levels of Nanog, Sox2, Slug, Sox9, c-Myc and p16 with respect to the original line and were able to regenerate the M38 tumor in vivo. Atra o Gö6976 treatment reduced LM38-LP mammospheres growth rate (Diameter at 96h: Control: 200±63 um vs ATRA/Gö6976: 100±25 um). Rottlerin treatment did not induce changes. Mammosphere pre-treatment with ATRA/PKC inhibitor for 96h reduced mammosphere secondary formation (Percentage respect to control values: Gö6976: 14,81%; Rottlerin and ATRA: 75,3%, ATRA/Gö6976: 0% and ATRA/Rottlerin: 40,7%). Furthermore, in 3D matrigel culture assay ATRA pre-treatment induced organized structures with lumen. On the other hand, Gö6976 pre-treatment induced small colonies with apoptotic death signs while Rottlerin pre-treatment induced irregular structures as the control. Finaly only ATRA/Gö6976 clearly decreased mammospheres mRNA levels of Nanog, Slug and C-Myc. Our results confirm that LM38-LP cell line presents pluripotent cells and the inhibition of PKCa activity plus ATRA treatment reduce this stem subpoblation possibly through the downregulation of Nanog, Slug and C-myc and the induction of apoptosis.