Abstract

Mutation of the essential splicing factor SF3B1 is primarily associated with hematological cancers but also occurs in solid tumors. We edited the most common mutation, K700E, into human embryonic stem (ES) cells to determine the effects of this mutation alone in an undifferentiated/non-cancer background. Unexpectedly, >20% of the significantly upregulated genes in the SF3B1K700E ES lines have immune functions. Thus, SF3B1 may have an additional role in proper expression of immune genes in appropriate cell types. In striking contrast, we found that published RNA-seq data from SF3B1 blood (MDS, CLL, AML) and non-blood (BRCA, UVM) cancers exhibited the opposite, downregulation of a multitude of immune pathways with 7 of the pathways shared among all 5 of the SF3B1 cancers. One of these pathways, "leukocyte migration", is the 1st reported pathway shared among all splicing factor cancers, including the 5 SF3B1 cancers and MDS associated with U2AF1, SRSF2 and ZRSR2. Importantly, we identified CCR1, which is in the leukocyte migration pathway as the only shared downregulated gene in the 5 SF3B1 cancers and in U2AF1MT MDS. We conclude that downregulation of CCR1 and its associated immune pathway may play a key role in pathogenesis of these splicing factor cancers and are thus potential therapeutic targets.