pladienolide-b and Carcinogenesis

A growing body of studies has documented the pathological influence of impaired alternative splicing (AS) events on numerous diseases, including cancer. In addition, the generation of alternatively spliced isoforms is frequently noted to result in drug resistance in many cancer therapies. To gain comprehensive insights into the impacts of AS events on cancer biology and therapeutic developments, this paper highlights recent findings regarding the therapeutic routes of targeting alternative-spliced isoforms and splicing regulators to treatment strategies for distinct cancers.

Topics: Adaptor Proteins, Signal Transducing; Alternative Splicing; Antineoplastic Agents; Carcinogenesis; Caspase 9; Cyclin D1; Cyclohexylamines; Epoxy Compounds; Humans; Macrolides; Neoplasm Proteins; Neoplasms; Nuclear Proteins; Oligonucleotides; Pyrans; RNA Splicing Factors; RNA, Messenger; Spiro Compounds; Spliceosomes; Tumor Suppressor Proteins

RNF6 is a RING finger protein with oncogenic potential. In this study, we established colon-specific RNF6 transgenic (tg) mice, and demonstrated that RNF6 overexpression accelerated colorectal carcinogenesis compared to wild-type littermates in a chemically induced colorectal cancer (CRC) model. To understand whether transcriptional activity of RNF6 underlies its oncogenic effect, we performed integrated chromatin immunoprecipitation (ChIP)-sequencing and RNA-sequencing analysis to identify splicing factor 3b subunit 2 (SF3B2) as a potential downstream target of RNF6. RNF6 binds to the SF3B2 promoter and the overexpression of RNF6 activates SF3B2 expression in CRC cells, primary CRC organoids, and RNF6 tg mice. SF3B2 knockout abrogated the tumor promoting effect of RNF6 overexpression, whereas the reexpression of SF3B2 recused cell growth and migration/invasion in RNF6 knockout cells, indicating that SF3B2 is a functional downstream target of RNF6 in CRC. Targeting of RNF6-SF3B2 axis with SF3B2 inhibitor with pladienolide B suppressed the growth of CRC cells with RNF6 overexpression in vitro and in vivo. Moreover, the combination of 5-fluorouracil (5-FU) plus pladienolide B exerted synergistic effects in CRC with high RNF6 expression, leading to tumor regression in xenograft models. These findings indicate that tumor promoting effect of RNF6 is achieved mainly via transcriptional upregulation of SF3B2, and that RNF6-SF3B2 axis is a promising target for CRC therapy.

Topics: Animals; Antimetabolites, Antineoplastic; Apoptosis; Biomarkers, Tumor; Carcinogenesis; Case-Control Studies; Cell Proliferation; Colorectal Neoplasms; DNA-Binding Proteins; Drug Therapy, Combination; Epoxy Compounds; Fluorouracil; Gene Expression Regulation, Neoplastic; Humans; Macrolides; Male; Mice; Mice, Inbred BALB C; Mice, Nude; Prognosis; RNA Splicing Factors; Survival Rate; Tumor Cells, Cultured; Xenograft Model Antitumor Assays