RAF1 amplification drives a subset of bladder tumors and confers sensitivity to MAPK-directed therapeutics
Raie T. Bekele, Amruta S. Samant, Amin H. Nassar, Jonathan So, Elizabeth P. Garcia, Catherine R. Curran, Justin H. Hwang, David L. Mayhew, Anwesha Nag, Aaron R. Thorner, Judit Börcsök, Zsofia Sztupinszki, Chong-Xian Pan, Joaquim Bellmunt, David J. Kwiatkowski, Guru P. Sonpavde, Eliezer M. Van Allen, Kent W. Mouw
Raie T. Bekele, Amruta S. Samant, Amin H. Nassar, Jonathan So, Elizabeth P. Garcia, Catherine R. Curran, Justin H. Hwang, David L. Mayhew, Anwesha Nag, Aaron R. Thorner, Judit Börcsök, Zsofia Sztupinszki, Chong-Xian Pan, Joaquim Bellmunt, David J. Kwiatkowski, Guru P. Sonpavde, Eliezer M. Van Allen, Kent W. Mouw
View: Text | PDF
Research Article Oncology

RAF1 amplification drives a subset of bladder tumors and confers sensitivity to MAPK-directed therapeutics

Abstract

Bladder cancer is a genetically heterogeneous disease, and novel therapeutic strategies are needed to expand treatment options and improve clinical outcomes. Here, we identified a unique subset of urothelial tumors with focal amplification of the RAF1 (CRAF) kinase gene. RAF1-amplified tumors had activation of the RAF/MEK/ERK signaling pathway and exhibited a luminal gene expression pattern. Genetic studies demonstrated that RAF1-amplified tumors were dependent upon RAF1 activity for survival, and RAF1-activated cell lines and patient-derived models were sensitive to available and emerging RAF inhibitors as well as combined RAF plus MEK inhibition. Furthermore, we found that bladder tumors with HRAS- or NRAS-activating mutations were dependent on RAF1-mediated signaling and were sensitive to RAF1-targeted therapy. Together, these data identified RAF1 activation as a dependency in a subset making up nearly 20% of urothelial tumors and suggested that targeting RAF1-mediated signaling represents a rational therapeutic strategy.

Authors

Raie T. Bekele, Amruta S. Samant, Amin H. Nassar, Jonathan So, Elizabeth P. Garcia, Catherine R. Curran, Justin H. Hwang, David L. Mayhew, Anwesha Nag, Aaron R. Thorner, Judit Börcsök, Zsofia Sztupinszki, Chong-Xian Pan, Joaquim Bellmunt, David J. Kwiatkowski, Guru P. Sonpavde, Eliezer M. Van Allen, Kent W. Mouw

×

Figure 7

HRAS and NRAS mutant bladder cancer cell lines are sensitive to RAF-targeted therapies.

Options: View larger image (or click on image) Download as PowerPoint
HRAS and NRAS mutant bladder cancer cell lines are sensitive to RAF-tar...
(A) HRAS and NRAS gene-dependency scores from DepMap CRISPR-Cas9 essentiality screens confirm that the HRAS (G12V) mutant T24 bladder cancer cell line shown in green and the NRAS mutant Ku-19-19 (NRAS Q61R) and BFTC905 (NRAS Q61L) bladder cancer cell lines shown in orange are dependent on the mutant RAS mutation for survival. (B) Unmagnified colony-formation assays demonstrate increased sensitivity to RAF265 and RAF265 plus trametinib in HRAS-mutant T24 cells and NRAS-mutant Ku-19-19 cells compared with the RAS WT J82 cell line. (C) Crystal violet staining of Ku-19-19 cells 3 days following treatment with LXH254 (left) and immunoblot (blots were run in parallel from the same sample) showing LXH254-induced inhibition of RAF/MEK/ERK signaling (right). (D) Tumor volumes of Ku-19-19–engrafted mice treated twice weekly with PEG400 vehicle (n = 9 mice), 15 mg/kg LXH256 (n = 5), 30 mg/kg LXH256 (n = 10), 30 mg/kg LXH254 plus 1 mg/kg trametinib (n = 7), or 30 mg/kg RAF265 plus 1 mg/kg trametinib (n = 9). (E) Average end-of-experiment tumor weights for mice treated with vehicle, 30 mg/kg LXH254, 30 mg/kg LXH254 plus 1 mg/kg trametinib, or 30 mg/kg RAF265 plus 1 mg/kg trametinib. Average tumor weights were significantly lower in all treatment arms compared with those of vehicle-treated tumors. Significant differences in average tumor size and weight in the treatment groups compared with vehicle are denoted with asterisks. ***P < 0.0001, ANOVA with Bonferroni’s post hoc test. (F) Photographs of excised tumors.