Predictors of survival outcome following radical gastrectomy for gastric cancer

BACKGROUND

Radical surgery with adjuvant therapy is now the standard treatment for locally advanced gastric cancer. However, the best regimen for adjuvant therapy remains controversial. We aim to determine the predictors of survival outcome of gastric cancer patients who underwent curative surgery with or without adjuvant therapy in our institution.

METHODS

All patients who received surgery for gastric cancer from years 2000 to 2015 were studied using a prospective gastric cancer database at the National University Hospital, Singapore.

RESULTS

A total of 405 patients underwent radical gastrectomy with curative intent. Seventy-eight percent received extended lymphadenectomy (≥D1). R0 resection was achieved in 377 patients (93%) with 30-day mortality rate of 1.7%. There was no significant difference in the complication rate between D1 and extended lymphadenectomy group. One hundred and forty-five patients (36%) received adjuvant therapy. With a median follow-up of 5.9 years, the 5-year disease-free survival for stage I to IV patients were 78%, 58%, 27% and 9%, respectively. Among the 141 patients with known recurrences, the first site of recurrence was 38% distant, 24% locoregional, 20% peritoneal and the rest were multiple sites. Stage of disease, adjuvant therapy, extent of lymphadenectomy, post-operative complication and approach of surgery were independent risk factors for long-term survival.

CONCLUSIONS

Stage of disease, adjuvant therapy, extent of lymphadenectomy, post-operative complication and approach of surgery are significant predictors for long-term survival. Adequate and safe surgery to allow adjuvant therapy should be the goal of all surgeons for our gastric cancer patients.

Discovering novel SNPs that are correlated with patient outcome in a Singaporean cancer patient cohort treated with gemcitabine-based chemotherapy

Background

Single Nucleotide Polymorphisms (SNPs) can influence patient outcome such as drug response and toxicity after drug intervention. The purpose of this study is to develop a systematic pathway approach to accurately and efficiently predict novel non-synonymous SNPs (nsSNPs) that could be causative to gemcitabine-based chemotherapy treatment outcome in Singaporean non-small cell lung cancer (NSCLC) patients.

Methods

Using a pathway approach that incorporates comprehensive protein-protein interaction data to systematically extend the gemcitabine pharmacologic pathway, we identified 77 related nsSNPs, common in the Singaporean population. After that, we used five computational criteria to prioritize the SNPs based on their importance for protein function. We specifically selected and screened six candidate SNPs in a patient cohort with NSCLC treated with gemcitabine-based chemotherapy.

Result

We performed survival analysis followed by hematologic toxicity analyses and found that three of six candidate SNPs are significantly correlated with the patient outcome (P < 0.05) i.e. ABCG2 Q141K (rs2231142), SLC29A3 S158F (rs780668) and POLR2A N764K (rs2228130).

Conclusions

Our computational SNP candidate enrichment workflow approach was able to identify several high confidence biomarkers predictive for personalized drug treatment outcome while providing a rationale for a molecular mechanism of the SNP effect.

Trial registration

NCT00695994. Registered 10 June, 2008 ‘retrospectively registered’.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-4471-x) contains supplementary material, which is available to authorized users.

Position effect variegation and epigenetic modification of a transgene in a pig model

Sequences proximal to transgene integration sites are able to regulate transgene expression, resulting in complex position effect variegation. Position effect variegation can cause differences in epigenetic modifications, such as DNA methylation and histone acetylation. However, it is not known which factor, position effect or epigenetic modification, plays a more important role in the regulation of transgene expression. We analyzed transgene expression patterns and epigenetic modifications of transgenic pigs expressing green fluorescent protein, driven by the cytomegalovirus (CMV) promoter. DNA hypermethylation and loss of acetylation of specific histone H3 and H4 lysines, except H4K16 acetylation in the CMV promoter, were consistent with a low level of transgene expression. Moreover, the degree of DNA methylation and histone H3/H4 acetylation in the promoter region depended on the integration site; consequently, position effect variegation caused variations in epigenetic modifications. The transgenic pig fibroblast cell lines were treated with DNA methyltransferase inhibitor 5-Aza-2'-deoxycytidine and/or histone deacetylase inhibitor trichostatin A. Transgene expression was promoted by reversing the DNA hypermethylation and histone hypoacetylation status. The differences in DNA methylation and histone acetylation in the CMV promoter region in these cell lines were not significant; however, significant differences in transgene expression were detected, demonstrating that variegation of transgene expression is affected by the integration site. We conclude that in this pig model, position effect variegation affects transgene expression.

Transgene insertion affects transcription and epigenetic modification of flanking host sequence in transgenic pigs

Transgenic technology has been used for years to study gene function, produce important proteins, and generate models for the study of human diseases. However, the efficiency of producing transgenic animal lines that retain normal function is extremely low. The low efficiency can be mainly attributed to the integrated transgene. A further understanding of the effects of transgene integration on transcription and epigenetic modification of the host genome would improve the transgenic efficiency. Therefore, we utilized three transgenic pigs produced by SCNT expressing GFP, to identify alterations of transcription, DNA methylation and histone acetylation resulting from integration of the GFP gene. Multiple copies of the transgene integrated into a single site of the three transgenic pigs were verified by TAIL&mdash;PCR and the integration sites were different in each pig. We observed that the integrated transgene frequently resulted in significantly low transcription of flanking sequences in various tissues of transgenic pigs in comparison with wild&mdash;type pigs. Corresponding with the low transcription, DNA hypermethylation and loss of acetylation of histone H3 and H4 were detected. Our results demonstrate that the abnormal transcription and epigenetic modification of sequences flanking the transgene were not correlated with the expression of the transgene. However, the disturbance caused by the insertion of the transgene, was dependent upon the integration site. This suggests that some sequences in the host genome could permit integration and expression of transgene without causing defects in the host.

[Antiarrhythmic effects of crebanine]

Crebanine (Cre) iv 5 mg/kg could convert BaCl2-induced arrhythmia into sinus rhythm in rats, and could significantly increase the tolerant dose of aconitine to produce ventricular fibrillation (VF) and cardiac arrest (CA) in rats. The drug could also decrease the incidence of VF and CA by CaCl2 in rats and by chloroform in mice, but had no protective effects on ouabain-induced arrhythmias in guinea pigs.