Department of Surgery, Michigan State University, 1200 East Michigan Ave., Suite 655, Lansing, MI 48912, USA.
Am J Surg. 2011 Nov;202(5):520-3. doi: 10.1016/j.amjsurg.2011.06.019. Epub 2011 Sep 9.
Intratumoral pressure may stimulate cancer proliferation whereas intravascular pressure promotes metastatic adhesion. α-Actinin proteins facilitate focal adhesion formation and link focal adhesion complexes to the cytoskeleton. We hypothesized that α-actinin is the mechanotransducer that mediates the effects of pressure on cancer cell proliferation and adhesion.
We treated SW620 colon cancer cells with specific short interfering RNA to reduce α-actinin-1 and/or α-actinin-4, the 2 key epithelial isoforms. Proliferation was measured in adherent cells by microculture tetrazolium (MTT) assay after 24 hours at ambient or 40 mm Hg increased pressure. For comparison, we evaluated the effects of 30 minutes of ambient or 15-mm Hg increased pressure on adhesion of suspended SW620 cells. Because the transcription factor nuclear factor-κB (NF-κB) influences proliferation, we used co-immunoprecipitation to evaluate NF-κB-α-actinin association and a lentiviral reporter assay for NF-κB activity.
A total of 40 mm Hg increased pressure increased SW620 proliferation 41% ± 6% (n = 10; P < .05) versus ambient pressure controls. Reducing α-actinin-1 and α-actinin-4 together or α-actinin-4 alone blocked this effect, but reducing α-actinin-1 alone did not (n = 6; P < .05). We observed a 72% ± 11% increase in NF-κB activity (n = 6; P < .05), and increased association between NF-κB and α-actinin-4 in adherent cells under pressure. NF-κB and α-actinin-1 did not co-immunoprecipitate. However, reducing α-actinin-4 did not prevent pressure-induced NF-κB activation (n = 8).
α-actinin-4 may mediate pressure stimulation of proliferation within large rapidly growing tumors, perhaps by binding transcription factors such as NF-κB. α-actinins may be important targets to inhibit cancer proliferation and metastasis.
肿瘤内压力可能刺激癌症增殖，而血管内压力则促进转移性黏附。α-辅肌动蛋白蛋白促进黏附斑的形成，并将黏附斑复合物与细胞骨架连接起来。我们假设α-辅肌动蛋白是介导压力对癌细胞增殖和黏附影响的机械转导蛋白。
我们用特异性短干扰 RNA 处理 SW620 结肠癌细胞，以减少 2 种关键上皮同工型的α-辅肌动蛋白-1 和/或α-辅肌动蛋白-4。在环境压力或 40mmHg 升高压力下培养 24 小时后，通过微培养四唑（MTT）测定法测量贴壁细胞的增殖。为了进行比较，我们评估了 30 分钟环境压力或 15mmHg 升高压力对悬浮 SW620 细胞黏附的影响。由于转录因子核因子-κB（NF-κB）影响增殖，我们使用共免疫沉淀法评估 NF-κB-α-辅肌动蛋白的结合，并用慢病毒报告基因测定法评估 NF-κB 的活性。
总共 40mmHg 升高压力使 SW620 增殖增加 41%±6%（n=10；P<.05），而环境压力对照增加。减少α-辅肌动蛋白-1 和α-辅肌动蛋白-4 共同减少或单独减少α-辅肌动蛋白-4 均可阻断此作用，但单独减少α-辅肌动蛋白-1 则不能（n=6；P<.05）。我们观察到黏附细胞中 NF-κB 活性增加 72%±11%（n=6；P<.05），并且在压力下 NF-κB 和α-辅肌动蛋白-4 之间的结合增加。NF-κB 和α-辅肌动蛋白-1 不会共免疫沉淀。然而，减少α-辅肌动蛋白-4 并不能阻止压力诱导的 NF-κB 激活（n=8）。
α-辅肌动蛋白-4 可能通过与 NF-κB 等转录因子结合，介导肿瘤内压力对增殖的刺激作用。α-辅肌动蛋白可能是抑制癌症增殖和转移的重要靶点。
