Genetic amplication of the NOTCH modulator LNX2 upregulates the WNT/β-catenin pathway in colorectal cancer
Menée sur des lignées cellulaires de cancer colorectal, cette étude met en évidence un mécanisme par lequel, en régulant l'expression du gène NOTCH, une amplification du gène LNX2 induit une activation aberrante de la voie de signalisation WNT/β-caténine
Chromosomal copy number alterations (aneuploidy) define the genomic landscape of most cancer cells, but identification of the oncogenic drivers behind these imbalances remains an unfinished task. In this study, we conducted a systematic analysis of colorectal carcinomas that integrated genomic copy number changes and gene expression profiles. This analysis revealed 44 highly overexpressed genes mapping to localized amplicons on chromosome 13, gains of which occur often in colorectal cancers. RNAi-mediated silencing identified 8 candidates whose loss of function reduced cell viability 20% or more in colorectal cancer cell lines. The functional space of the genes NUPL1, LNX2, POLR1D, POMP, SLC7A1, DIS3, KLF5, and GPR180 was established by global expression profiling after RNAi exposure. One candidate, LNX2, not previously known as an oncogene, was involved in regulating NOTCH signaling. Silencing LNX2 reduced NOTCH levels but also downregulated the transcription factor TCF7L2 and markedly reduced WNT signaling. LNX2 overexpression and chromosome 13 amplification therefore constitutively activates the WNT pathway, offering evidence of an aberrant NOTCH-WNT axis in colorectal cancer.