Department of Translational Oncology Genentech, MS 50, 1 DNA Way, South San Francisco, CA 94080, USA.
J Natl Cancer Inst. 2013 May 1;105(9):606-7. doi: 10.1093/jnci/djt054. Epub 2013 Mar 27.
Although remarkable clinical response rates in melanoma have been observed using vemurafenib or dabrafenib in patients with tumors carrying oncogenic mutations in BRAF, a substantial unmet medical need remains for the subset of patients with wild-type BRAF tumors.
To investigate the role of p21-activated kinases (PAKs) in melanoma, we determined PAK1 genomic copy number and protein expression for a panel of human melanoma tissues. PAK1 was inhibited in vitro and in vivo using RNA interference or PF-3758309 inhibitor treatment in a panel of melanoma cell lines with known BRAF and RAS (rat sarcoma) genotype to better understand its role in melanoma cell proliferation and migration. Tumorigenesis was assessed in vivo in female NCR nude mice and analyzed with cubic spline regression and area under the curve analyses. All statistical tests were two-sided.
Strong cytoplasmic PAK1 protein expression was prevalent in melanomas (27%) and negatively associated with activating mutation of the BRAF oncogene (P < .001). Focal copy number gain of PAK1 at 11q13 was also observed in 9% of melanomas (n = 87; copy number ≥ 2.5) and was mutually exclusive with BRAF mutation (P < .005). Selective PAK1 inhibition attenuated signaling through mitogen-activated protein kinase (MAPK) as well as cytoskeleton-regulating pathways to modulate the proliferation and migration of BRAF wild-type melanoma cells. Treatment of BRAF wild-type melanomas with PF-3758309 PAK inhibitor decreased tumor growth for SK-MEL23 and 537MEL xenografts (91% and 63% inhibition, respectively; P < .001) and MAPK pathway activation in vivo.
Taken together, our results provide evidence for a functional role of PAK1 in BRAF wild-type melanoma and therapeutic use of PAK inhibitors in this indication.
虽然在携带 BRAF 致癌突变的肿瘤患者中，使用威罗菲尼或达拉非尼治疗可观察到显著的黑色素瘤临床反应率，但对于 BRAF 野生型肿瘤患者亚组，仍存在大量未满足的医疗需求。
为了研究 P21 激活激酶（PAKs）在黑色素瘤中的作用，我们测定了一组人黑色素瘤组织中 PAK1 基因组拷贝数和蛋白表达。在一组已知 BRAF 和 RAS（大鼠肉瘤）基因型的黑色素瘤细胞系中，使用 RNA 干扰或 PF-3758309 抑制剂治疗，以更好地了解 PAK1 在黑色素瘤细胞增殖和迁移中的作用。在雌性 NCR 裸鼠体内进行肿瘤发生评估，并进行立方样条回归和曲线下面积分析。所有统计检验均为双侧检验。
在黑色素瘤中，细胞质 PAK1 蛋白表达强烈（27%），并与 BRAF 致癌基因的激活突变呈负相关（P<0.001）。在 9%的黑色素瘤中也观察到 PAK1 在 11q13 的局灶性拷贝数增益（n=87；拷贝数≥2.5），与 BRAF 突变互斥（P<0.005）。选择性 PAK1 抑制可减弱丝裂原激活的蛋白激酶（MAPK）以及细胞骨架调节途径的信号传导，从而调节 BRAF 野生型黑色素瘤细胞的增殖和迁移。用 PF-3758309 PAK 抑制剂治疗 BRAF 野生型黑色素瘤可使 SK-MEL23 和 537MEL 异种移植瘤的肿瘤生长减少（分别为 91%和 63%的抑制率；P<0.001），并抑制体内 MAPK 途径的激活。
总之，我们的结果为 PAK1 在 BRAF 野生型黑色素瘤中的功能作用提供了证据，并为该适应症中 PAK 抑制剂的治疗用途提供了证据。
