Mutations in ribosomal proteins (RP) often cause bone marrow syndromes associated with increased risk for cancer development. We have shown that Rpl22 is a haploinsufficient tumor suppressor in T acute lymphoblastic leukemia (T-ALL). Indeed, loss of one Rpl22 allele accelerates T-cell lymphomagenesis in the murine Akt transgenic mouse model, by inducing the stem cell factor Lin28B in an NFκB-dependent manner. Moreover, mice lacking both Rpl22 alleles exhibited significantly increased thymic tumor size, which was associated with poor survival and markedly enhanced angiogenesis relative to Rpl22 heterozygous mice or wild type. The increased angiogenesis in the mediastinal mass was linked to upregulation of VEGFA and downregulation of S1P1. Loss of S1P1 is sufficient to block egress of lymphoma cells from thymus. Rpl22-deficient thymic lymphoma lines also exhibit enhanced growth upon adaptation to growth in vitro, and this is reversed by ectopic expression of Rpl22. Rpl22 expression also represses the expression of proteins that promote traversal of the cell cycle. Collectively, the increased tumor growth and angiogenesis, and the blockade of thymic egress contribute to the enlarged mediastinal masses observed in Rpl22-deficient mice. Rpl22-mutant T-ALL are a molecularly distinct subtype exhibiting increased aggression and treatment resistance. Accordingly, our identification of a number of signaling pathways controlled by Rpl22 may enable the development of novel strategies, such as targeting angiogenesis, in such cases of T-ALL.

Citation Format: Shuyun Rao, Jason E. Stadanlick, Kathy Q. Cai, Wiest L. David. Loss of Rpl22 promotes tumor progression through regulation of angiogenesis and dissemination. [abstract]. In: Proceedings of the AACR Special Conference on Hematologic Malignancies: Translating Discoveries to Novel Therapies; Sep 20-23, 2014; Philadelphia, PA. Philadelphia (PA): AACR; Clin Cancer Res 2015;21(17 Suppl):Abstract nr A07.