Laboratory of Cancer Biology and Genetics, Center for Cancer Research, National Cancer Institute, Bethesda, MD, USA.
Department of Pharmacology, Yale University School of Medicine, New Haven, CT, USA.
Sci Signal. 2024 May 14;17(836):eadd5073. doi: 10.1126/scisignal.add5073.
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 , rendered - and -mutant CRC and -mutant melanoma cells more resistant to these inhibitors. In the absence of MAPK pathway inhibition, 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. 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 -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 deletion. These findings demonstrate that PP6 constrains the growth of - and -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 -mutant cancer cells.
Ras-丝裂原活化蛋白激酶（MAPK）通路是癌症治疗的主要靶点。为了更好地了解调节癌症细胞对 MAPK 通路抑制剂敏感性的遗传途径，我们在携带突变型 KRAS 的结直肠癌（CRC）细胞系上进行了 CRISPR 敲除筛选，并用 MAPK 通路抑制剂进行筛选。编码蛋白磷酸酶 6（PP6）的催化亚基的基因缺失，使突变型 CRC 和突变型黑色素瘤细胞对这些抑制剂更具抗性。在没有 MAPK 通路抑制的情况下，CRC 细胞中的缺失会降低二维（2D）贴壁培养物中的细胞增殖，但会加速 3D 培养中的肿瘤球体生长和体内肿瘤异种移植。缺失增强了 CRC 和黑色素瘤细胞中核因子 κB（NF-κB）信号的激活，并绕过了 MAPK 通路阻断在 CRC 细胞中诱导的细胞周期停滞和 cyclin D1 丰度降低。通过遗传和药理学手段抑制 NF-κB 活性，恢复了 -缺陷细胞在 CRC 和黑色素瘤细胞中的 MAPK 通路抑制敏感性，以及 CRC 细胞中的敏感性。此外，CRC 细胞中 PPP6C 的 R264 点突变赋予了其功能丧失，模拟了观察到的缺失引起的 NF-κB 激活增强和对 MAPK 通路抑制的抗性。这些发现表明，PP6 限制了 -和 -突变型癌细胞的生长，表明 PP6-NF-κB 轴是 MAPK 通路输出的调节剂，并为在 -突变型癌细胞中靶向 NF-κB 通路提供了依据。
