Identification of EGFR kinase domain mutations among lung cancer patients in China:implication for targeted cancer therapy

Lung cancer is one of the leading causes of death with one of the lowest survival rates. However, a subset of lung cancer patients who are of Asian origin and carry somatic mutations in epidermal growth factor receptor or EGFR have responded remarkable well to two tyrosine kinase inhibitors, gefitinib and erlotinib. While EGFR mutation profiles have been reported from Japan, South Korea, and Taiwan, there is no such report from mainland of China where the largest pool of patients reside. In this report, we identified ten somatic mutations from a total of 41 lung cancer patients in China. Among them, seven mutations were found in 17 adenocarcinomas. In contrast to previous reports, eight of these mutations are deletions in exon 19 and two of these deletions are homozygous. These results suggest that a large portion of Chinese adenocarcinoma patients could benefit from gefitinib or erlotinib. This unique mutation profile provides a rationale to develop the next generation of EGFR inhibitors more suitable for the Chinese population.

Methylation profile of the promoter CpG islands of 31 genes that may contribute to colorectal carcinogenesis

AIM: To establish the methylation profile of the promoter CpG islands of 31 genes that might play etiological roles in colon carcinogenesis.METHODS: The methylation specific PCR in conjunction of sequendng verification was used to establish the methylationprofile of the promoter CpG islands of 31 genes in colorectal cancer (n = 65), the neighboring non-cancerous tissues (n = 5), colorectal adenoma (n = 8), and normal mucosa (n = 1). Immunohistochemically, expression of 10 genes was assessed on the home-made tissue microarrays of tissues from 58 patients. The correlation of tumor specific changes with each of clinical-pathologic features was scrutinized with relevant statistic tools.RESULTS: In comparison with the normal mucosa of the non-cancer patients, the following 14 genes displayed no tumor associated changes: breast cancer 1, early onset (BRCA1), cadherin 1, type 1, E-cadherin (epithelial) (CDH1),death-associated protein kinase 1 (DAPK1), DNA (cytosine-5-)-methyltransferase 1 (DNMT1), melanoma antigen, family A, 1 (directs expression of antigen MZ2-E) (MAGEA1), tumor suppressor candidate 3 (N33), cyclin-dependent kinase inhibitor 1A (p21, Cipl) (p21^WAF1), cyclin-dependent kinase inhibitor 1B (p27, 10pl) (p27^WAF1), phosphatase and tensin hornolog (mutated in multiple advanced cancers 1) (PTEN), retinoic acid receptor, beta (RAR-, Ras association (RaIGDS/AF-6) domain family 1 C (RASSFIC), secreted frizzled-related protein 1 (SFRP1), tissue inhibitor of metalloproteinase 3 (Sorsby fundus dystrophy, pseudoinfiammatory) (TIMP3),and von HippeI-Lindau syndrome (VHL). The rest 17 targets exhibited to various extents the tumor associated changes.As changes in methylation of the following genes occurred marginally, their impact on the formation of colorectal cancer were trivial: adenomatous polyposis coli (APC) (8%, 5165),Ras association (RaIGDS/AF-6) domain family 1A (RASSFIA) (3%, 2/65) and cyclin-dependent kinase inhibitor 2A,alternated reading frame Co14~) (6%, 4/65). The following genes exhibited moderate changes in rnethylation: O-6rnethylguanine-DNA rnethyltransferase (MGMT) (20%, 13/65),rnutL hornolog 1, colon cancer, nonpolyposis type 2 (E. coli) (hMLH1) (18%, 12/65), cyclin-dependent kinase inhibitor 2A (melanoma, p16, inhibits CDK4) P16^NK4a) (10%, 10/65),rnethylated in tumor 1 (MINT1) (15%, 10/65), methylated in tumor 31 (MINT31) (11%, 7/65). The rest changed greatly in the rnethylation pattern in colorectal cancer (CRC): cyclin A1 (cyclin al) (100%, 65/65), caudal type homeobox transcriptdon factor 1 (CDX1) (100%, 65/65), RAR(85%, 55/65), myogenic factor 3 (MYOD1) (69%, 45/65),cyclin-dependent kinase inhibitor 2B (p15, inhibits CDK4)(p15^INK4b) (68%, 44/65), prostaglandin-endoperoxide synthase 2 (prostaglandin G/H synthase and cyclooxygenase) (COX2) (72%, 47/65), cadherin 13, H-cadherin (heart) (CDH13) (65%, 42/65), CAAX box 1 (OO~/) (58%, 38/65),tumor protein p73 (p73) (63%, 41/65) and Wilrns tumor 1 (WT/) (58%, 38/65). However, no significant correlation of changes in rnethylation with any given clinical-pathological features was detected. Furthermore, the frequent changes in rnethylation appeared to be an early phase event of colon carcinogenesis. The in situ expression of 10 genes was assessed by the irnrnunohistochernical approach at the protein level: CDH1, CDH13, COX2, cyclin A1, hMLH1,MGMT, p14^ARF, p73, RAR-, and TIMP3 genes in the context of the rnethylation status in colorectal cancer. No clear correlation between the hyperrnethylation of the promoter CpG islands and the negative expression of the genes was established.CONCLUSION: The methylation profile of 31 genes was established in patients with colon cancer and colorectal adenornas, which provides new insights into the DNA rnethylation mediated mechanisms underlying the carcinogenesis of colorectal cancer and may be of prognostic values for colorectal cancer.

Methylation profile of the promoter CpG islands of 14 “drug-resistance”genes in hepatocellular carcinoma

AIM: To establish the DNA methylation patterns of the promoter CpG islands of 14 'drug-resistance' genes in hepatocellular carcinoma (HCC).METHODS: The methylation specific polymerase chain reaction in conjunction with sequencing verification was used to establish the methylation patterns of the 14 genes in the liver tissues of four healthy liver donors, as well as tumor and the paired non-cancerous tissues of 30 HCC patients.RESULTS: While 11 genes (ATP-binding cassette, sub-family G (WHITE), member 2(ABCG2), activating transcription factor (ATF2), beta-2-microglobulin (B2M), deoxycytidine kinase(DCK, occludin (OCLN, v-raf-1 murine leukemia viral oncogene homolog (RAF/), ralA binding protein 1 (RALBP1),splicing factor (45 kD) (SPF45), S-phase kinase-associated protein 2 (p45) (SKP2), tumor protein p53 (Li-Fraumeni syndrome) (TP53) and topoisomerase (DNA) II beta (TOP2B) maintained the unmethylated patterns, three genes displayed to various extents the hypermethylation state in tumor tissues in comparison with the normal counterparts. The catalase (CAT) was hypermethylated in tumor and the neighboring non-cancerous tissue of one case (3.3%). Both glutathione S-transferase pi (GSTp/) (80%, 24/30 in tumor and 56.7%,17/30 in the paired non-cancerous tissues) and cystic fibrosis transmembrane conductance regulator, ATP-binding cassette (sub-family C, member 7) (CF-FR) (77%, 23/30 in tumor and 50%, 15/30 in the paired non-cancerous tissues) genes were prevalently hypermethylated in HCC as well as their neighboring non-cancerous tissues. No significant difference in the hypermethylation occurrence was observed between the HCC and its neighboring non-cancerous tissues.CONCLUSION: Hypermethylation of promoter CpG islands of both CF-FR and GSTpigenes occurs prevalently in HCC,which may correlate with the low expression of these two genes at the mRNA level and has the profound etiological and clinical implications. It is likely to be specific to the early phase of HCC carcinogenesis.

The altered DNA methylation pattern and its implications in liver cancer

DNA methylation is the most intensively studied epigenetic phenomenon, disturbances of which result in changes ingene transcription, thus exerting drastic imparts onto biological behaviors of cancer. Both the global demethylation andthe local hypermethylation have been widely reported in all types of tumors, providing both challenges and opportunitiesfor a better understanding and eventually controlling of the malignance. However, we are still in the very early stage ofinformation accumulation concerning the tumor associated changes in DNA methylation pattern. A number of excellentrecent reviews have covered this issue in depth. Therefore, this review will summarize our recent data on DNA methy-lation profiling in cancers. Perspectives for the future direction in this dynamic and exciting field will also be given.

A novel protein-DNA interaction involved with the CpG dinucleotide at -30 upstream is linked to the DNA methylation mediated transcription silencing of the MAGE-A1 gene

To understand the DNA-methylation mediated gene silencing mechanisms, we analyzed in cell culture of the promoter function of the MAGE-A1 gene, which is frequently demethylated and over-expressed in human hepatocellular carcinoma. We have established the correlation of the DNA methylation of the promoter CpG island with expression status of this gene in a panel of the established liver cancer cell lines. The crucial CpG dinucleotide(s) within the minimal promoter subjected to the control mediated by DNA methylation with profound biological functions was also delineated.Furthermore, a novel sequence-specific DNA-protein interaction at the -30 CpG dinucleotide upstream of the gene was found having a vital part to play in the DNA methylation mediated transcription silencing of the MAGE-A1 gene. Our results would not only provide new insights into the DNA methylation mediated mechanisms over transcription of the MAGE-A1 gene, but also pave the way for further defining the cross-talk among DNA methylation, histone modification and chromatin remodeling in detail.