Mutational and epigenetic evidence for independent pathways for lung adenocarcinomas arising in smokers and never smokers.

Genetic and epigenetic alterations are considered to play important roles in lung cancer. Recent studies showed that EGFR and K-RAS mutations exhibited a mutually exclusive pattern in adenocarcinoma of the lung, suggesting the presence of two independent oncogenic pathways. However, it is unknown how epigenetic alterations were involved in lung carcinogenesis mediated by EGFR or K-RAS mutation. In this study, we examined the relationship between genetic and epigenetic alterations in 164 cases of lung adenocarcinoma. Somatic mutations were determined by direct sequence of EGFR exons 18 to 21 and K-RAS codons 12 and 13. Methylation status of p16(INK4a), RASSF1A, APC, RARbeta, and CDH13, frequently methylated in lung cancer, was determined by methylation-specific PCR and the degree of methylation was defined as the methylation index. Multivariate analysis adjusted for age, sex, and smoking dose showed that the probability of having EGFR mutation was significantly lower among those with p16(INK4a) and CDH13 methylation than in those without [p16(INK4a): odds ratio (OR), 0.07; 95% confidence interval (95% CI), 0.02-0.33; CDH13: OR, 0.34; 95% CI, 0.15-0.77] and the methylation index was significantly lower in EGFR mutant cases than in wild type (OR, 0.70; 95% CI, 0.52-0.95). By contrast, K-RAS mutation was significantly higher in p16(INK4a) methylated cases than in unmethylated cases (OR, 4.93; 95% CI, 1.54-15.7) and the methylation index was higher in K-RAS mutant cases than in wild type with marginal significance (OR, 1.46; 95% CI, 0.95-2.25). Our results indicate the differences in the evolvement of epigenetic alterations between the EGFR- and K-RAS-mediated tumorigenesis and suggest the specific interaction of genetic and epigenetic changes in tumorigenesis of lung cancer.

[A case of gastric cancer with multiple bone metastasis that responded to S-1 with low-dose cis-platinum].

We report a patient with multiple bone metastasis who was treated successfully using S-1 and low-dose cis-platinum (CDDP). Metastasis was diagnosed 4 years after distal gastrectomy for early gastric cancer in a woman now 68 years old. Surgery was performed on February 9, 1999. The primary tumor was located in the midportion of the gastric body, and had invaded the submucosa with metastasis to lymph nodes in the area of the lesser curvature. She was discharged from our hospital 24 days after surgery. About 4 years after surgery, she experienced a backache and her CEA and CA19-9 levels had risen to 15.30 ng/mL and 996.5 U/mL, respectively. The results of an imaging examination were suggestive of multiple bone metastasis. Treatment with S-1+CDDP was started with the following regimen: daily oral administration of 100 mg/body/day S-1 for 14 days, followed by a 7-days rest and CDDP 20 mg/body infusion on day 1 and 8. Three months after initiation of therapy, the CEA and CA19-9 levels decreased 2.80 ng/mL and 36.8 U/mL, respectively. No severe adverse effects were observed with this therapy. The combination of S-1 and CDDP can be a good tool for the management of gastric cancer with bone metastasis.

The relationship between epidermal growth factor receptor mutations and clinicopathologic features in non-small cell lung cancers.

PURPOSE: Recent studies reported that clinical responsiveness to gefitinib was associated with somatic mutation of epidermal growth factor receptor (EGFR) gene in non-small cell lung cancers (NSCLC). Here, we investigated the relationship between EGFR mutation and clinicopathologic features. EXPERIMENTAL DESIGN: EGFR mutational status of 120 NSCLCs was determined mainly in EGFR exons 18 to 21 by direct sequence and correlated with clinicopathologic parameters. RESULTS: EGFR mutations were present in 38 cases (32%) and the majority of mutations were in-frame deletions of exon 19 (19 cases) and a missense mutation in exon 21 (18 cases). EGFR mutations were frequently associated with adenocarcinoma (P < 0.0001), never smoker (P < 0.0001), and female gender (P = 0.0001). Of interest, increasing smoke exposure was inversely related to the rate of EGFR mutation (P < 0.0001). Multivariate analysis showed that smoking and histology were independent variables. Furthermore, gender difference was observed for the mutational location (P = 0.01) dominance of exon 19 for males and exon 21 for females. Twenty-one cases were treated with gefitinib and found that EGFR mutation was significantly related to gefitinib responsiveness (P = 0.002). In addition, median survival times of patients with and without EGFR mutations treated with gefitinib were 25.1 and 14.0 months, respectively. Patients with EGFR mutations had approximately 2-fold survival advantage; however, the difference was not significant. CONCLUSIONS: We show that EGFR mutations were significantly related to histology and smoke exposure and were a strong predictive factor for gefitinib responsiveness in NSCLC.

Promoter methylation downregulates CDX2 expression in colorectal carcinomas.

CDX2 (caudal type homeobox transcription factor 2) is a homeobox protein, which is expressed in intestinal epithelium. CDX2 has been considered to play a role as a tumor suppressor gene in colorectal cancer because its expression is lacking in colorectal carcinomas, but preserved in adenomas. The point mutations have been found to account for loss of CDX2 expression, but the main mechanism responsible for CDX2 gene inactivation is less understood. We analyzed methylation and expression status of CDX2 in colorectal cancer cell lines and primary tumors. There are two CpG-rich sites in promoter region of CDX2 gene, -1570 to -1200 and -220 to +880. By COBRA (combined bisulfite restriction analysis) assay, the upper CpG-rich site was heavily methylated in all cell lines, but the lower CpG-rich site was methylated in limited cell lines. Bisulfite sequencing analysis and RT-PCR revealed that methylation of the lower CpG site was associated with down-regulation of CDX2. In addition, gene expression was restored in COLO201, a methylated cell line with 5-aza-2'-deoxycytidine, confirming that methylation caused gene down-regulation. We also examined CDX2 promoter methylation of primary tumors by MSP (methylated-allele specific PCR) assay and found that nearly 40% of cases have a methylated CDX2 gene. Our results demonstrate that CDX2 methylation is frequently present in colorectal cancers and may play a key role in inactivating CDX2 expression.

Aberrant promoter methylation of insulin-like growth factor binding protein-3 gene in human cancers.

Insulin-like growth factor binding protein-3 (IGFBP-3) is postulated to be a mediator of growth suppression signals. Here, we examined the methylation status of IGFBP-3 to correlate to clinicopathological factors in human cancers. The methylation status of IGFBP-3 was determined by bisulfite DNA sequencing and was correlated with expression semi-quantified by real-time RT-PCR to develop a methylation-specific PCR (MSP) assay for IGFBP-3. Using the MSP assay, we examined the methylation status of IGFBP-3 in gastric cancer (GC), colorectal cancer (CRC), breast cancer (BC) and malignant mesothelioma (MM). IGFBP-3 methylation was detected in 6 of 13 (46%) and 16 of 24 (67%) GC cell lines and tumors, respectively; 4 of 8 (50%) and 15 of 26 (58%) CRC cell lines and tumors, respectively; 3 of 11 (27%) and 7 of 39 (18%) BC cell lines and tumors, respectively and 1 of 5 (20%) and 18 of 56 (32%) MM cell lines and tumors, respectively. Interestingly, the methylation status of MM specimens from Japanese patients (75%, 12 out of 16 patients) was significantly higher than those from the USA (15%, 6 out of 40 patients) (p < 0.0001), suggesting the presence of ethnic differences in the IGFBP-3 methylation status. We also found that IGFBP-3 methylation was preferentially present in GCs arising in the lower-third of the stomach (p = 0.079). In summary, our results showed that IGFBP-3 methylation played an important role in the silencing of its expression, suggesting that IGFBP-3 may act as a tumor suppressor gene in several human cancers examined.