Tyrosine kinase inhibitors induce alternative spliced BCR‐ABLIns35bp variant via inhibition of RNA polymerase II on genomic BCR‐ABL

To elucidate dynamic changes in native BCR‐ABL and alternatively spliced tyrosine kinase inhibitor (TKI)‐resistant but function‐dead BCR‐ABLIns35bp variant, following commencement or discontinuation of TKI therapy, each transcript was serially quantified in patients with chronic myeloid leukemia (CM...

Full description

Saved in:
Bibliographic Details
Published in:Cancer science 2020-07, Vol.111 (7), p.2361-2373
Main Authors: Yuda, Junichiro, Odawara, Jun, Minami, Mariko, Muta, Tsuyoshi, Kohno, Kentaro, Tanimoto, Kazuki, Eto, Tetsuya, Shima, Takahiro, Kikushige, Yoshikane, Kato, Koji, Takenaka, Katsuto, Iwasaki, Hiromi, Minami, Yosuke, Ohkawa, Yasuyuki, Akashi, Koichi, Miyamoto, Toshihiro
Format: Article
Language:English
Subjects:
alternative splicing
BCR‐ABL
BCR‐ABLIns35bp
chronic myeloid leukemia
MRD
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:To elucidate dynamic changes in native BCR‐ABL and alternatively spliced tyrosine kinase inhibitor (TKI)‐resistant but function‐dead BCR‐ABLIns35bp variant, following commencement or discontinuation of TKI therapy, each transcript was serially quantified in patients with chronic myeloid leukemia (CML) by deep sequencing. Because both transcripts were amplified together using conventional PCR system for measuring International Scale (IS), deep sequencing method was used for quantifying such BCR‐ABL variants. At the initial diagnosis, 7 of 9 patients presented a small fraction of cells possessing BCR‐ABLIns35bp, accounting for 0.8% of the total IS BCR‐ABL, corresponding to actual BCR‐ABLIns35bp value of 1.1539% IS. TKI rapidly decreased native BCR‐ABL but not BCR‐ABLIns35bp, leading to the initial increase in the proportion of BCR‐ABLIns35bp. Thereafter, both native BCR‐ABL and BCR‐ABLIns35bp gradually decreased in the course of TKI treatment, whereas small populations positive for TKI‐resistant BCR‐ABLIns35bp continued fluctuating at low levels, possibly underestimating the molecular response (MR). Following TKI discontinuation, sequencing analysis of 54 patients revealed a rapid relapse, apparently derived from native BCR‐ABL+ clones. However, IS fluctuating at low levels around MR4.0 marked a predominant persistence of cells expressing function‐dead BCR‐ABLIns35bp, suggesting that TKI resumption was unnecessary. We clarified the possible mechanism underlying mis‐splicing BCR‐ABLIns35bp, occurring at the particular pseudo‐splice site within intron8, which can be augmented by TKI treatment through inhibition of RNA polymerase II phosphorylation. No mutations were found in spliceosomal genes. Therefore, monitoring IS functional BCR‐ABL extracting BCR‐ABLIns35bp would lead us to a correct evaluation of MR status, thus determining the adequate therapeutic intervention. Dynamic changes were observed in BCR‐ABL and BCR‐ABLIns35bp after TKI discontinuation. BCR‐ABL+ cells responsible for early relapse after cessation of TKI treatment might derive from the residual native BCR‐ABL addicted clones. In contrast, some patients whose MRD mainly consisted of BCR‐ABLIns35bp transiently lost DMR during a relatively late phase after TKI discontinuation and thereafter regained DMR spontaneously without TKI resumption.
ISSN:1347-9032
1349-7006
DOI:10.1111/cas.14424