Dominant negative epidermal growth factor receptor inhibits growth of human gastric cancer cells by inducing cell cycle arrest and apoptosis

Antibody-assisted target identification reveals afatinib, an EGFR covalent inhibitor, down-regulating ribonucleotide reductase

Afatinib, used for the first-line treatment of non-small-cell lung carcinoma (NSCLC) patients with distinct epidermal growth factor receptor (EGFR) mutations, inactivates EGFR by mimicking ATP structure and forming a covalent adduct with EGFR. We developed a method to unravel potential targets of afatinib in NSCLC cells through immunoprecipitation of afatinib-labeling proteins with anti-afatinib antiserum and mass spectrometry analysis. Ribonucleotide reductase (RNR) is one of target proteins of afatinib revealed by this method. Treatment of afatinib at 10-100 nM potently inhibited intracellular RNR activity in an in vitro assay using permeabilized PC-9 cells (formerly known as PC-14). PC-9 cells treated with 10 μM afatinib displayed elevated markers of DNA damage. Long-term treatment of therapeutic concentrations of afatinib in PC-9 cells caused significant decrease in protein levels of RNR subunit M2 at 1-10 nM and RNR subunit M1 at 100 nM. EGFR-null Chinese hamster ovary (CHO) cells treated with afatinib also showed similar effects. Afatinib repressed the upregulation of RNR subunit M2 induced by gemcitabine. Covalent modification with afatinib resulting in inhibition and protein downregulation of RNR underscores the therapeutic and off-target effects of afatinib. Afatinib may serve as a lead compound of chemotherapeutic drugs targeting RNR. This method can be widely used in the identification of potential targets of other covalent drugs.

Plasma membrane proteomic analysis of human Gastric Cancer tissues: revealing flotillin 1 as a marker for Gastric Cancer

Background

Gastric cancer remains the second leading cause of cancer-related deaths in the world. Successful early gastric cancer detection is hampered by lack of highly sensitive and specific biomarkers. Plasma membrane proteins participate and/or have a central role in the metastatic process of cancer cells and are potentially useful for cancer therapy due to easy accessibility of the targets.

Methods

In the present research, TMT method followed by mass spectrometry analysis was used to compare the relative expression levels of plasma membrane proteins between noncancer and gastric cancer tissues.

Results

Of a total data set that included 501 identified proteins, about 35% of the identified proteins were found to be plasma membrane and associated proteins. Among them, 82 proteins were at least 1.5-fold up- or down-regulated in gastric cancer compared with the adherent normal tissues.

Conclusions

A number of markers (e.g. annexin A6, caveolin 1, epidermal growth factor receptor, integrin beta 4) were previously reported as biomarkers of GC. Additionally, several potential biomarkers participated in endocytosis pathway and integrin signaling pathways were firstly identified as differentially expressed proteins in GC samples. Our findings also supported the notion that flotillin 1 is a potential biomarker that could be exploited for molecular imaging-based detection of gastric cancer. Together, the results show that subcellular proteomics of tumor tissue is a feasible and promising avenue for exploring oncogenesis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1343-5) contains supplementary material, which is available to authorized users.

Homozygous deletions at 3p22, 5p14, 6q15, and 9p21 result in aberrant expression of tumor suppressor genes in gastric cancer

Homozygous deletion is a frequent mutational mechanism of silencing tumor suppressor genes in cancer. Therefore, homozygous deletions have been analyzed for identification of tumor suppressor genes that can be utilized as biomarkers or therapeutic targets for cancer treatment. In this study, to elucidate potential tumor suppressor genes involved in gastric cancer (GC), we analyzed the entire set of large homozygous deletions in six human GC cell lines through genome- and transcriptome-wide approaches. We identified 51 genes in homozygous deletion regions of chromosomes and confirmed the deletion frequency in tumor tissues of 219 GC patients from The Cancer Genome Atlas database. We evaluated the effect of homozygous deletions on the mRNA level and found significantly affected genes in chromosome bands 9p21, 3p22, 5p14, and 6q15. Among the genes in 9p21, we investigated the potential tumor suppressive effect of KLHL9. We demonstrated that ectopic expression of KLHL9 inhibited cell proliferation and tumor formation in KLHL9-deficient SNU-16 cell line. In addition, we observed that homozygous focal deletions generated truncated transcripts of TGFBR2, CTNNA1, and STXBP5. Ectopic expression of two kinds of TGFBR2-reverse GADL1 fusion genes suppressed TGF-β signaling, which may lead to the loss of sensitivity to TGF-β tumor suppressive activity. In conclusion, our findings suggest that novel tumor suppressor genes that are aberrantly expressed through homozygous deletions may play important roles in gastric tumorigenesis.

MicroRNA-302b suppresses cell proliferation by targeting EGFR in human hepatocellular carcinoma SMMC-7721 cells

BACKGROUND

MicroRNAs are regulators that can play an essential role in tumorigenesis. Although miR-302 families have been suggested to be tumor repressors in human cancer, the mechanism by which they suppress tumor development remains to be defined. In this study, we discover that miR302b suppresses tumor proliferation may due to directly targeting EGFR in human hepatocellular carcinoma (HCC).

METHODS

QRT-PCR was used to assess miR-302b and EGFR expression in 27 pairs of clinical hepatocellular carcinoma tissues and their corresponding adjacent nontumorous liver tissues. MTT, colony formation, immunofluorescence staining, and cell cycle assays were used to examine the tumor suppressor role of miR302b in cell proliferation. Luciferase assays were performed to assess the EGFR was a novel target of miR-302b. Western blot assay was used to validate the protein expression level.

RESULTS

We demonstrated that miR-302b was frequently down-regulated, whereas EGFR was up-regulated in 27 pairs of clinical HCC and non-tumorous counterparts. The dual-luciferase reporter assays revealed that EGFR was a novel target of miR-302b. Re-expression of miR-302b resulted in the inhibition of proliferation in hepatocellular carcinoma SMMC-7721 cells. The silencing of EGFR by miR-302b or siEGFR led to down-regulation of proliferation-related proteins, such as AKT2, CCND1, and CDK2.

CONCLUSION

miR-302b suppresses HCC growth may due to targeting the EGFR/AKT2/CCND1 pathway.

Prognostic value of epidermal growth factor receptor in patients with gastric cancer: a meta-analysis

BACKGROUND

The epidermal growth factor receptor (EGFR) plays important roles in the development of gastric cancer. This study aims to analyze the prognostic value of EGFR in patients with gastric cancer.

METHODS

A meta-analysis is performed by searching Cochrane Library, PubMed, EMBASE and Science Direct databases from Jan 1970 to May 2013. Data are extracted from studies evaluating the survival of gastric cancer patients with either positive or negative EGFR expression. Pooled hazard ratios (HRs) and 95% confidence intervals (CIs) are calculated.

RESULTS

Totally 1600 cases of gastric cancer patients from five studies are subjected to final analysis. The HR of post-operational survival of patients with positive EGFR expression is 1.16 (95% CI: 0.94-1.43) as compared with those with negative expression, indicating that positive EGFR expression does not significantly predict the poor survival of gastric cancer.

CONCLUSIONS

EGFR expression is not an independent predictor for the survival of gastric cancer patients.