Study of leukemia inhibitory factor (LIF) system in a murine mammary tumor comprising luminal and myoepithelial cells

KRASNAPOLSKI MARTÍN; QUAGLINO ANA; KORDON EDITH CLAUDIA; DE KIER JOFFÉ ELISA BAL

orlando

Congreso; American Association for Cancer Research Annual Meeting; 2011

AACR

The presence of LIF, a cytokine that activates JAK/STAT and ERK pathways, its receptor (LIFRb) and the constitutive activation of Stat3 (a molecule downstream LIFRb) have been described in tumors, primary cultures and several cancer-derived cell lines, suggesting a role for this pathway in tumor progression. Also, Stat3 activation was widely related to an immunosuppressive phenotype in many tumor models. From the murine mammary adenocarcinoma M38 comprising luminal (LEP) and myoepithelial (MEP) cells (both transformed) we derived LM38-LP (LEP & MEP), LM38-HP (epithelioid) and LM38-D2 (MEP) cell lines. While the mixed cell line presents a malignant behavior, the last two show a lower growth rate and metastatic potential than the parental tumor. Previously we demonstrated that this lower malignancy is partially caused by their inability to suppress the host’s immune system, underscoring the importance of cellular interactions in complex tumor behaviors. Our purpose was to evaluate LIF and LIFRb mRNA expression levels and to study LIF effects on Stat3 and ERK activation, as well as on the proliferation and clonogenic capacity in the LM38 family of cell lines. Using RT-PCR we could see that LM38-LP cell line expresses high LIF and LIFRb mRNA levels, LM38-HP expresses LIF mRNA but not it receptor’s mRNA and LM38-D2 has low levels of both molecules. By Western blot we studied LIF (80 ng/ml) effect over Stat3 and ERK activation. While in LM38-LP and LM38-D2 cells Stat3 and ERK phosphorylation was rapidly induced at 5 min, in LM38-HP cells, that don’t express LIFRb, no response was detected. Then, we evaluated the effect of a prolonged 48 h treatment with LIF (1, 5, 20 and 80 ng/ml) on cell viability using MTS assay. While LIF slightly reduced cell viability (20%) in LM38-LP and LM38-D2 cell lines, LM38-HP cells were not affected. Finally, since LIF is also involved in stem cell maintenance, the effect of LIF in a low density/clonogenic setting was evaluated. While in LM38-LP and LM38-D2 cell lines LIF significatively (p