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  • Protein phosphatase 6 activates NF-κB to confer sensitivity to MAPK pathway inhibitors in KRAS- and BRAF-mutant cancer cells.

Protein phosphatase 6 activates NF-κB to confer sensitivity to MAPK pathway inhibitors in KRAS- and BRAF-mutant cancer cells.

Science signaling (2024-05-15)
Haibo Zhang, Abigail Read, Christophe Cataisson, Howard H Yang, Wei-Chun Lee, Benjamin E Turk, Stuart H Yuspa, Ji Luo
ABSTRACT

The Ras-mitogen-activated protein kinase (MAPK) pathway is a major target for cancer treatment. To better understand the genetic pathways that modulate cancer cell sensitivity to MAPK pathway inhibitors, we performed a CRISPR knockout screen with MAPK pathway inhibitors on a colorectal cancer (CRC) cell line carrying mutant KRAS. Genetic deletion of the catalytic subunit of protein phosphatase 6 (PP6), encoded by PPP6C, rendered KRAS- and BRAF-mutant CRC and BRAF-mutant melanoma cells more resistant to these inhibitors. In the absence of MAPK pathway inhibition, PPP6C deletion in CRC cells decreased cell proliferation in two-dimensional (2D) adherent cultures but accelerated the growth of tumor spheroids in 3D culture and tumor xenografts in vivo. PPP6C deletion enhanced the activation of nuclear factor κB (NF-κB) signaling in CRC and melanoma cells and circumvented the cell cycle arrest and decreased cyclin D1 abundance induced by MAPK pathway blockade in CRC cells. Inhibiting NF-κB activity by genetic and pharmacological means restored the sensitivity of PPP6C-deficient cells to MAPK pathway inhibition in CRC and melanoma cells in vitro and in CRC cells in vivo. Furthermore, a R264 point mutation in PPP6C conferred loss of function in CRC cells, phenocopying the enhanced NF-κB activation and resistance to MAPK pathway inhibition observed for PPP6C deletion. These findings demonstrate that PP6 constrains the growth of KRAS- and BRAF-mutant cancer cells, implicates the PP6-NF-κB axis as a modulator of MAPK pathway output, and presents a rationale for cotargeting the NF-κB pathway in PPP6C-mutant cancer cells.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Monoclonal Anti-Vinculin antibody produced in mouse, clone hVIN-1, ascites fluid
Sigma-Aldrich
IKK-2 Inhibitor IV, The IKK-2 Inhibitor IV, also referenced under CAS 507475-17-4, controls the biological activity of IKK-2. This small molecule/inhibitor is primarily used for Inflammation/Immunology applications.