Abstract 1802: Thyroid hormones maintain the proliferative phenotype in T cell lymphomas through nuclear and membrane-initiated transcriptional programs.

Proceedings: AACR 104th Annual Meeting 2013; Apr 6-10, 2013; Washington, DC T cell non-Hodgkin lymphomas (T-NHL) are a heterogeneous group of lymphoproliferative disorders with aggressive clinical course and no specific treatments. Thyroid Hormones (TH) are crucial regulators of differentiation, growth and metabolism. TH modulate these functions by activating canonical nuclear (TR) and membrane receptors (mTR, for most cells represented by RGD integrin dimers). Recent studies of us showed that TH stimulate the proliferation of T-NHLs through complimentary intracellular pathways involving both TH receptors, thus suggesting that both pathways are co-opted by malignant T cells to maintain proliferation and survival. This could represent a specific way to target these lymphoma subtypes. To characterize their participation on the T-NHL malignant phenotype, we analyzed the effect of TH through TR and mTR in 8 human cell lines representing the spectrum of immature and peripheral T-NHLs (CUTLL-1, Jurkat, Hut78, Mac-2A, OCI-Ly12, OCI-Ly13.2, SUDHL-1, Karpas299). Compared to normal T cells, T-NHL expressed higher levels of TRα and TRβ, and mTR (integrins with RGD site). To discriminate between nuclear vs. membrane-initiated effects, T-NHL cells were treated with physiological concentrations of free and cell impermeable agarose-bound T3/T4 (TH-AG), for 1 to 5 days. In these conditions, both free and TH-AG increased the proliferation of T-NHL (doubling time increased between 24 to 43%), PCNA and CCNDs proliferation markers and ERK phosphorylation. To further characterize TR and mTR initiated transcriptional programs, CUTLL1 cells were exposed to Free TH and TH-AG for 24 h and 96 h and mRNA extracted for RNA-sequencing in triplicates. We found 16 and 174 transcripts were significantly (p<0.05) regulated at 24 h in free TH vs. TH-AG, respectively; and 27 and 31 at 96 h in free TH vs TH-AG, respectively. Among the top programs regulated by free TH we found activation of TR, TNFR and IL2 pathways. While activation of the mTR caused activation of genes involved in mitochondrial respiration, fatty-acid synthesis, angiogenesis and DNA replication. Common pathways activated by TR and mTR included the TNFR/ASK1/ERK and WNT/CCND signaling pathways. Transcripts of interest were validated by RT-qPCR. These data suggest that both TR and mTR regulate T-NHL proliferation to distinct yet complimentary programs. To determine whether abrogation of the mTR causes decrease in cell proliferation, we treated our panel of T-NHLs with siRNA for ITGAV, ITGB1, ITGB3 and mTR inhibitors. We found that mTR inhibition affected the mTR-induced transcriptional program and abrogated TH-induced proliferative effect. All these data suggest that (i) TH are important inducers of T-NHLs proliferation by transcriptionally regulating major survival pathways, and (ii) inhibition of mTR could constitute a selective chemotherapy-free treatment for T-NHLs. Citation Format: Florencia Cayrol, Tharu Fernando, Maria Celeste Diaz Flaque, Ana Maria Genaro, Ricardo Farias, Leandro Cerchietti, Graciela Cremaschi. Thyroid hormones maintain the proliferative phenotype in T cell lymphomas through nuclear and membrane-initiated transcriptional programs. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1802. doi:10.1158/1538-7445.AM2013-1802