堀江 久永

It is well established that nuclear factor κB (NF-κB) acts as one of the most important transcription factors for tumor initiation and progression, as it both protects cells from apoptotic/necrotic signals and accelerates angiogenesis and tumor metastasis, which is mediated via the expression of target genes. However, it has not yet been clarified how oncogenic signals accelerate the activation of NF-κB. In the current study, we utilized untransformed NIH-3T3 cells stably harboring a κB-driven luciferase gene to show that an oncogenic mutant of Ras GTPase augmented TNFα-induced NF-κB activation. Notably, enforced expression of cyclin-dependent kinase inhibitors, such as p27Kip1 and p21Cip1 , effectively canceled the accelerated activation of NF-κB, suggesting that oncogenic Ras-induced cell cycle progression is essential for the hyperactivation of NF-κB. Furthermore, we found that Ras (G12V) augmented the transcriptional activation of NF-κB, and this activation required the p38 MAP kinase. We observed that a downstream kinase of p38 MAP kinase, MSK1, was activated by Ras (G12V) and catalyzed the phosphorylation of p65/RelA at Ser-276, which is critical for its transcriptional activation. Significantly, phosphorylation of the p65/RelA subunit at Ser-276 was elevated in patient samples of colorectal cancer harboring oncogenic mutations of the K-Ras gene, and the expression levels of NF-κB target genes were drastically enhanced in several cancer tissues. These observations strongly suggest that oncogenic signal-induced acceleration of NF-κB activation is caused by activation of the p38 MAP kinase-MSK1 signaling axis and by cell cycle progression in cancer cells.

PURPOSE: The study was designed to evaluate the safety and efficacy of adding oxaliplatin to py (CRT) with S-1 in patients with locally advanced rectal carcinoma (LARC). We report here the final results of the study. PATIENTS AND METHODS: Patients with histopathologically confirmed LARC (cT3-T4, any N) were eligible. They received oral S-1 (80 mg/m2/day on days 1-5, 8-12, 22-26, and 29-33) and infusional oxaliplatin (60 mg/m2/day on days 1, 8, 22, 29) plus radiotherapy (1.8 Gy/day, total dose of 50.4 Gy in 28 fractions), with a chemotherapy gap in the third week of radiotherapy. Primary endpoint of the study was pathological complete response (pCR) rate. Secondary endpoints were rates of R0 resection, down-staging, cumulative 3-year local recurrence, 3-year disease-free survival (DFS), and toxicity. RESULTS: Forty-five patients were enrolled at six centers in Japan. All patients received CRT, and 44 underwent operation. The pCR rate was 27.3% (12/44). The R0 resection rate was 95.5% (42/44). T-down-staging rate was 59.1% (26/44), and N-down staging rate was 65.9% (29/44); the combined pathological down-staging rate was 79.5% (35/44). There were no grade 4 adverse events, but 11.1% of the patients had grade 3 adverse events. Cumulative 3-year local recurrence rate was 0%. However, 13 (30.0%) patients suffered from distant metastasis, and one patient suffered from secondary esophageal cancer that was unrelated to rectal cancer. Eight patients had lung metastasis, 4 had liver metastasis, and 3 patients died of the metastatic disease. The 3-year DFS rate of the 44 patients was 67.5% (median follow-up 36.3 months), and the 3-year overall survival (OS) rate was 93.0% (median follow-up 39.6 months). The patients were then divided into the pCR (12 patients) group and non pCR (32 patients) group. The 3-year rate of DFS for each group was 91.7% and 58.1% and that of OS was 100% and 90.3%, respectively. CONCLUSIONS: The study showed a high pCR rate with no severe toxicity, good follow-up results, and good loco-regional control. Therefore, addition of oxaliplatin to preoperative CRT with S-1 in patients with LARC might be feasible and lead to better local control than standard treatment.