Tumor escape in a Wnt1-dependent mouse breast cancer model is enabled by p19Arf/p53 pathway lesions but not p16 Ink4a loss.
Breast cancers frequently progress or relapse during targeted therapy, but the molecular mechanisms that enable escape remain poorly understood. We elucidated genetic determinants underlying tumor escape in a transgenic mouse model of Wnt pathway-driven breast cancer, wherein targeted therapy is simulated by abrogating doxycycline-dependent Wnt1 transgene expression within established tumors. In mice with intact tumor suppressor pathways, tumors typically circumvented doxycycline withdrawal by reactivating Wnt signaling, either via aberrant (doxycycline-independent) Wnt1 transgene expression or via acquired somatic mutations in the gene encoding beta-catenin. Germline introduction of mutant tumor suppressor alleles into the model altered the timing and mode of tumor escape. Relapses occurring in the context of null Ink4a/Arf alleles (disrupting both the p16 Ink4a and p19 Arf tumor suppressors) arose quickly and rarely reactivated the Wnt pathway. In addition, Ink4a/Arf-deficient relapses resembled p53-deficient relapses in that both displayed morphologic and molecular hallmarks of an epithelial-to-mesenchymal transition (EMT). Notably, Ink4a/Arf deficiency promoted relapse in the absence of gross genomic instability. Moreover, Ink4a/Arf-encoded proteins differed in their capacity to suppress oncogene independence. Isolated p19 Arf deficiency mirrored p53 deficiency in that both promoted rapid, EMT-associated mammary tumor escape, whereas isolated p16 Ink4a deficiency failed to accelerate relapse. Thus, p19 Arf/p53 pathway lesions may promote mammary cancer relapse even when inhibition of a targeted oncogenic signaling pathway remains in force.
Jake Gittlen Cancer Research Foundation, Pennsylvania State University College of Medicine, Hershey, Pennsylvania 17033, USA.
Michael T
MT
Debies
Shelley A
SA
Gestl
Jessica L
JL
Mathers
Oliver R
OR
Mikse
Travis L
TL
Leonard
Susan E
SE
Moody
Lewis A
LA
Chodosh
Robert D
RD
Cardiff
Edward J
EJ
Gunther
D000483:Alleles; D000818:Animals; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000235:genetics / Q000378:metabolism*; D005260:Female; D042822:Genomic Instability / Q000235:genetics; D008325:Mammary Neoplasms, Experimental / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D051379:Mice; D008822:Mice, Transgenic; D009154:Mutation; D012008:Recurrence; D015398:Signal Transduction / Q000235:genetics; D019139:Tumor Escape / Q000235:genetics*; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*; D051155:Wnt1 Protein / Q000235:genetics / Q000378:metabolism*
C417743:Cdkn2a protein, mouse; D019941:Cyclin-Dependent Kinase Inhibitor p16; D016159:Tumor Suppressor Protein p53; D051155:Wnt1 Protein; C495246:Wnt1 protein, mouse