How Ribosomal Protein Mutations Translate Cancer

Mutations in different ribosomal proteins have been described in a series of inherited disorders, known as ribosomopathies. These syndromes come with a variety of symptoms, including hematopoietic defects and a predisposition to develop leukemia and solid tumors later in life. This transition from hypo- to hyperproliferation is a long-standing paradox in the field and the underlying mechanisms by which such ribosomal protein mutations promote transition to cancer in these diseases remain poorly understood. In the last decade, somatic ribosomal protein mutations have also been observed in a variety of cancer types, further consolidating the link between ribosomal protein defects and oncogenesis. First, we studied the RPL10 R98S mutation, found in pediatric T-ALL as a first example to explore the oncogenic mechanisms of ribosome-defective cancer cells. By analyzing exome sequencing data from a mouse lymphoid RPL10 R98S model and from ribosome mutant leukemia patients, and by performing cell biological experiments in lymphoid RPL10 R98S cell models, we came to a model in which oxidative stress due to ribosome dysfunction causes hypoproliferation in ribosome-defective cancer and ribosomopathies. This oxidative stress also increases DNA damage levels and promotes the acquisition of rescuing mutations that alleviate oxidative stress and stimulate hyperproliferation (e.g. NOTCH1). This model can thus explain the paradoxical transition from hypo-to hyperproliferation in ribosomopathies. Furthermore, by performing a differential proteomics analysis, we show that mouse lymphoid cells expressing RPL10 R98S as well as RPL10 R98S-positive T-ALL xenograft samples display elevated expression of JAK-STAT signaling components. These cells also display Jak-Stat pathway hyperactivation upon cytokine stimulation, reduced Jak1 degradation and enhanced sensitivity to JAK-STAT inhibitors. Next to transcriptional changes, we observed a reduced activity of the proteasome, increased sensitivity to clinically used proteasome inhibitors in RPL10 R98S expressing cells. We identified modulation of the JAK-STAT signaling cascade as a novel cancer-promoting activity of a ribosomal protein mutation. Finally, we looked with a broader scope at ribosomal lesions by generating an isogenic cell line panel by CRISPR-Cas9, representing the most frequently occurring ribosomal protein mutations associated to cancer. Proteomics and phosphoproteomics analyses revealed several cellular processes that are dysregulated in ribosome-defective cells such as the spliceosome, ribosome biogenesis, cell cycle regulation and the proteasome. These results were used to screen the cell line panel against a rationally designed drug library. We highlight several promising targets including exportin 1 in a Rps15 mutant (P131S/H137Y) background and agents impacting on DNA repair, such as PF477736 and AZ20 targeting CHK1/ATR kinase, in a Rpl5/Rpl10/Rpl11 mutant background. This study provides a strong foundation for further efforts aimed at understanding the oncogenic role of ribosomal protein mutations in cancer and at developing targeted therapy for ribosome-defective cancer.

Jaar van publicatie:2021

Toegankelijkheid:Closed