Frequent mutations of the CA simple sequence repeat in intron 1 of EGFR in mismatch repair-deficient colorectal cancers

DNMT1 promotes cell proliferation via methylating hMLH1 and hMSH2 promoters in EGFR-mutated non-small cell lung cancer

Aberrant DNA methylation is a common form of epigenetic alterations and it has been proved to be closely related to many cancers, while its role in epidermal growth factor receptor (EGFR)-mutated non-small cell lung cancer (NSCLC) is not clear. This study focuses on the role of DNA methyltransferase 1 (DNMT1) in EGFR-mutated NSCLC pathogenesis. First, the expression of DNMT1 was up-regulated, while the expressions of human mutL homolog 1(hMLH1) and human mutS homolog 2 (hMSH2) were down-regulated in EGFR-mutated NSCLC patients and cell line HCC827. The results of the correlation analysis showed that DNMT1 expression was inversely correlated with the expressions of hMLH1 and hMSH2. Then, we found that DNMT1 enhanced the promoter methylation levels of hMLH1 and hMSH2, thus suppressing their expressions. DNMT1 knockdown inhibited the proliferation of HCC827 cells, while both hMLH1 knockdown and hMSH2 knockdown could eliminate its inhibitory effect on cell proliferation. In xenograft mouse models, lentiviral vector-sh-DNMT1 could significantly reduce tumor volumes, confirmed that DNMT1 inhibited tumor cell proliferation in vivo. In conclusion, DNMT1 suppressed the expressions of hMLH1 and hMSH2 via elevating their promoter methylation, thus promoting cell proliferation in EGFR-mutated NSCLC.

Epidermal growth factor receptor intron 1 polymorphism and microsatellite instability in sporadic colorectal cancer

Epidermal growth factor receptor (EGFR) expression is commonly upregulated in sporadic colorectal cancer (CRC) and its high expression is associated with poor prognosis in patients with CRC. CA-SSR1 is a dinucleotide CA repeat of the EGFR gene that can modulate EGFR transcription and is a potential target of the mismatch repair machinery in tumours with microsatellite instability (MSI). In the present study, 160 sporadic colon cancer samples were analysed for EGFR CA-SSR1 polymorphism and MSI status. Additionally, EGFR mRNA and protein expression levels in the tumour centre and in the invasive tumour front, compared with those in adjacent normal tissue samples, were evaluated in 80 tumour samples. An inverse association was identified between EGFR mRNA levels and the sum of repeats in both alleles of the CA-SSR1 polymorphism in normal tissues. Changes in CA-SSR1 were detected in the tumour centre as well as in the invasive tumour front and metastases in all MSI high (MSI-H) tumours. Analysis of EGFR expression at the mRNA and protein levels according to MSI status revealed lower EGFR mRNA and protein expression in MSI-H tumours than microsatellite-stable (MSS) tumours. Furthermore, higher EGFR levels in the invasive tumour front compared with in the tumour centre in MSS tumours were identified, suggesting a role of EGFR in tumour progression and higher invasive potential of MSS than MSI-H tumours.

Temporal and spatial expression of Muc2 and Muc5ac mucins during rat respiratory and digestive tracts development

Secreted mucins constitute a crucial part of the gel that protects respiratory and digestive epithelia, being MUC2/Muc2 the predominant gel-forming mucin of the intestine while MUC5AC/Muc5ac is one of the gel-forming mucins most expressed at the airways. In this study, we have analyzed Muc2 and Muc5ac during rat development by using immunohistochemistry, Western blotting and RT-PCR. We demonstrated that rat Muc2 was expressed in fetal intestinal goblet cells of surface epithelium of villi and developing Lieberkühn crypts. In neonates and adults, Muc2 was expressed at luminal goblet cells of small and large intestine and at gastric mucous and glandular cells. Muc5ac protein was observed in embryonic gastric and lung samples; expression increased during development and postnatal and adult life. After birth, a low reaction was detected at the tracheal surface epithelium and glands, which increased in adults.

CA-SSR1 Polymorphism in Intron 1 of the EGFR Gene in Patients with Malignant Tumors Who Develop Acneiform Rash Associated with the Use of Cetuximab

Background and Objective

Epidermal growth factor receptor (EGFR) inhibitors are not equally effective in all cancer patients. One potential clinical factor that could help in selecting patients who may benefit from treatment with cetuximab is acneiform rash, which correlates with the clinical response to EGFR inhibitors. Some previous studies have suggested that the tendency to develop rash may depend on polymorphisms in the EGFR gene. In this investigation, the association of degree of CA dinucleotide polymorphism with skin rash and cetuximab therapy outcome was examined.

Methods

The study included 60 patients treated with cetuximab. For each patient, the severity of acneiform rash was assessed, and the type of polymorphism was determined by genotyping. Associations between genotypes, the acneiform rash, and response to treatment were determined by using the chi-square test and Spearman’s rank correlation. The cutoffs S ≤ 17(CA), L > 17(CA), n(CA) ≤ 35, and n(CA) > 35 were tested, as well as the sum of the two allele repetitions.

Results

A correlation was found between body surface area covered by rash and the sum of the two allele repetitions (p = 0.030). No statistically significant relationship between genotype and response to treatment was observed. However, in patients who have had partial remission, we noticed a higher incidence of polymorphism, with less CA dinucleotide repetitions and early onset of rash.

Conclusion

A correlation between genotype and severity of rash was observed. That is, the severity of rash decreased with an increased number of CA repetitions.

Epidermal growth factor receptor gene polymorphisms are associated with prognostic features of breast cancer

BACKGROUND

The epidermal growth factor receptor (EGFR) is differently expressed in breast cancer, and its presence may favor cancer progression. We hypothesized that two EGFR functional polymorphisms, a (CA)n repeat in intron 1, and a single nucleotide polymorphism, R497K, may affect EGFR expression and breast cancer clinical profile.

METHODS

The study population consisted of 508 Brazilian women with unilateral breast cancer, and no distant metastases. Patients were genotyped for the (CA)n and R497K polymorphisms, and the associations between (CA)n polymorphism and EGFR transcript levels (n = 129), or between either polymorphism and histopathological features (n = 505) were evaluated. The REMARK criteria of tumor marker evaluation were followed.

RESULTS

(CA)n lengths ranged from 14 to 24 repeats, comprehending 11 alleles and 37 genotypes. The most frequent allele was (CA)16 (0.43; 95% CI = 0.40-0.46), which was set as the cut-off length to define the Short allele. Variant (CA)n genotypes had no significant effect in tumoral EGFR mRNA levels, but patients with two (CA)n Long alleles showed lower chances of being negative for progesterone receptor (ORadjusted = 0.42; 95% CI = 0.19-0.91). The evaluation of R497K polymorphism indicated a frequency of 0.21 (95% CI = 0.19 - 0.24) for the variant (Lys) allele. Patients with variant R497K genotypes presented lower proportion of worse lymph node status (pN2 or pN3) when compared to the reference genotype Arg/Arg (ORadjusted = 0.32; 95% CI = 0.17-0.59), which resulted in lower tumor staging (ORadjusted = 0.34; 95% CI = 0.19-0.63), and lower estimated recurrence risk (OR = 0.50; 95% CI = 0.30-0.81). The combined presence of both EGFR polymorphisms (Lys allele of R497K and Long/Long (CA)n) resulted in lower TNM status (ORadjusted = 0.22; 95% CI = 0.07-0.75) and lower ERR (OR = 0.25; 95% CI = 0.09-0.71). When tumors were stratified according to biological classification, the favorable effects of variant EGFR polymorphisms were preserved for luminal A tumors, but not for other subtypes.

CONCLUSIONS

The data suggest that the presence of the variant forms of EGFR polymorphisms may lead to better prognosis in breast cancer, especially in patients with luminal A tumors.

Implication of CA repeated tracts on post-transcriptional regulation in Trypanosoma cruzi

In Trypanosoma cruzi gene expression regulation mainly relays on post-transcriptional events. Nevertheless, little is known about the signals which control mRNA abundance and functionality. We have previously found that CA repeated tracts (polyCA) are abundant in the vicinity of open reading frames and constitute specific targets for single stranded binding proteins from T. cruzi epimastigote. Given the reported examples of the involvement of polyCA motifs in gene expression regulation, we decided to further study their role in T. cruzi. Using an in silico genome-wide analysis, we identify the genes that contain polyCA within their predicted UTRs. We found that about 10% of T. cruzi genes carry polyCA therein. Strikingly, they are frequently concurrent with GT repeated tracts (polyGT), favoring the formation of a secondary structure exhibiting the complementary polydinucleotides in a double stranded helix. This feature is found in the species-specific family of genes coding for mucine associated proteins (MASPs) and other genes. For those polyCA-containing UTRs that lack polyGT, the polyCA is mainly predicted to adopt a single stranded structure. We further analyzed the functional role of such element using a reporter approach in T. cruzi. We found out that the insertion of polyCA at the 3' UTR of a reporter gene in the pTEX vector modulates its expression along the parasite's life cycle. While no significant change of the mRNA steady state of the reporter gene could be detected at the trypomastigote stage, significant increase in the epimastigote and reduction in the amastigote stage were observed. Altogether, these results suggest the involvement of polyCA as a signal in gene expression regulation in T. cruzi.

DNA damage response pathways and cell cycle checkpoints in colorectal cancer: current concepts and future perspectives for targeted treatment

Although several drugs have been designed in the last few years to target specific key pathways and functions in colorectal cancer (CRC), the backbone of CRC treatment is still made up of compounds which rely on DNA damage to accomplish their role. DNA damage response (DDR) and checkpoint pathways are intertwined signaling networks that arrest cell cycle, recognize and repair genetic mistakes which arise during DNA replication and transcription, as well as through the exposure to chemical and physical agents that interact with nucleic acids. The good but highly variable activity of DNA damaging agents in the treatment of CRC suggests that intrinsic alterations in DDR pathways and cell cycle checkpoints may contribute differentially to the way cancer cells react to DNA damage. In the present review, our aim is to depict the recent advances in understanding the molecular basis of the activity of DNA damaging agents used for the treatment of CRC. We focus on the known and potential drug targets that are part of these complex and intertwined pathways. We describe the potential role of the checkpoints in CRC, and how their pharmacological manipulation could lead to chemopotentiation or synergism with currently used drugs. Novel therapeutic agents playing a role in DDR and checkpoint inhibition are assessed. We discuss the possible rationale for combining PARP inhibition with DNA damaging agents, and we address the link between DDR and EGFR pathways in CRC.

Epidermal growth factor receptor in pancreatic cancer

Pancreatic cancer is the fourth leading cause of cancer related death. The difficulty in detecting pancreatic cancer at an early stage, aggressiveness and the lack of effective therapy all contribute to the high mortality. Epidermal growth factor receptor (EGFR) is a transmembrane glycoprotein, which is expressed in normal human tissues. It is a member of the tyrosine kinase family of growth factors receptors and is encoded by proto-oncogenes. Several studies have demonstrated that EGFR is over-expressed in pancreatic cancer. Over-expression correlates with more advanced disease, poor survival and the presence of metastases. Therefore, inhibition of the EGFR signaling pathway is an attractive therapeutic target. Although several combinations of EGFR inhibitors with chemotherapy demonstrate inhibition of tumor-induced angiogenesis, tumor cell apoptosis and regression in xenograft models, these benefits remain to be confirmed. Multimodality treatment incorporating EGFR-inhibition is emerging as a novel strategy in the treatment of pancreatic cancer.

Epidermal growth factor receptor (EGFR) intron 1 polymorphism and clinical outcome in pancreatic adenocarcinoma

BACKGROUND

Epidermal growth factor receptor (EGFR) intron 1 has a polymorphic region of CA repeats that is believed to be associated with increased EGFR expression, tumor aggressiveness, and worse survival in cancer patients.

METHODS

A large population of pancreatic adenocarcinoma patients was investigated to evaluate this polymorphism as a potential prognostic marker of clinical outcome. Deoxyribonucleic acid obtained from 50 resected pancreatic adenocarcinomas and from 85 diagnostic endoscopic ultrasound-guided fine-needle aspiration procedures corresponding to patients with unresectable tumors was included. The correlation between CA repeat length and EGFR messenger ribonucleic acid levels was also examined.

RESULTS

Analysis of the 135 patients revealed no correlation between EGFR intron 1 CA repeat length and tumor stage. There was no difference in overall patient survival when stratified by allele length. A correlation between EGFR intron 1 length and EGFR transcript and protein levels could not be established.

CONCLUSIONS

The length of the EGFR intron 1 CA repeats does not correlate with levels of EGFR expression and cannot be used as marker of clinical prognosis in pancreatic cancer patients.

An A13 repeat within the 3'-untranslated region of epidermal growth factor receptor (EGFR) is frequently mutated in microsatellite instability colon cancers and is associated with increased EGFR expression

Colorectal cancers (CRC) with microsatellite instability (MSI) have clinical, pathologic, genetic, and epigenetic features distinct from microsatellite-stable CRC. Examination of epidermal growth factor receptor (EGFR) mRNA and protein expression levels in a panel of colon cancer cell lines identified strong expression of EGFR in multiple cell lines with MSI. Although no relationship between EGFR overexpression and the length of a CA dinucleotide repeat in intron 1 was observed, a variant A13/A14 repeat sequence within the 3'-untranslated region (3'-UTR) of the EGFR gene was identified, which was mutated by either mononucleotide or dinucleotide adenosine deletions in 64% of MSI cell lines and 69% of MSI colon tumors. Using a Tet-Off system, we show that this mutation increases EGFR mRNA stability in colon cancer cells, providing a mechanistic basis for EGFR overexpression in MSI colon cancer cell lines. To determine whether this mutation is a driver or a bystander event in MSI colon cancer, we examined the effect of pharmacologic and molecular inhibition of EGFR in EGFR 3'-UTR mutant MSI cell lines. Cell lines with an EGFR 3'-UTR mutation and that were wild-type (WT) for downstream signaling mediators in the Ras/BRAF and PIK3CA/PTEN pathways were sensitive to EGFR inhibition, whereas those harboring mutations in these signaling mediators were not. Furthermore, in cell lines WT for downstream signaling mediators, those with EGFR 3'-UTR mutations were more sensitive to EGFR inhibition than EGFR 3'-UTR WT cells, suggesting that this mutation provides a growth advantage to this subset of MSI colon tumors.

Expression of EGFR, HER-2, VEGF in tumour tissues and their directive significance for the molecular targeting therapy of colorectal carcinoma

AIM: To detect the characteristics of epidermal growth factor receptor (EGFR), human epidermal receptor-2 (HER-2) and vascular endothelial growth factor (VEGF) expression in colorectal carcinoma (CRC) tumor tissues, and to analyze their directive significance for the molecular targeting therapy of colorectal carcinoma (CRC).

METHODS: Seventy eight patients with CRC were randomly selected, who underwent radical surgery in the department of general surgery at our hospital from May 2005 to March 2009. The SP Immunohistochemical staining was used to detect EGFR, HER-2 and VEGF protein expression in 78 CRC tumor tissue samples. And their corresponding clinical data were analysed retrospectively.

RESULTS: The expression rates of EGFR, HER-2 and VEGF protein in CRC tumour tissue were 38.5% (30/78), 53.8% (42/78) and 41.0% (32/78). Positive rates of EGFR, HER-2 and VEGF protein were closely relevant to the tumour size, knubbly invasive depth and lymph node metastasis; but not to the patient's sex, age, tumor site or histology grade. There was a stable positive relationship among EGFR, HER-2 and VEGF expression in CRC tumour tissue samples. The related coefficients were 0.421, 0.484 and 0.469 respectively (P = 0.019, 0.012 and 0.016).

CONCLUSION: The present study demonstrates that the EGFR, HER-2 and VEGF expression participate in the development, invasion and metastasis process of CRC. Their joint detection can be looked as an important symbol for judging the prognosis of CRC, screening the high-risk metastasis patients and guiding the molecular targeting therapy of colorectal carcinoma.