Genome-wide Association Study On Platinum-based Hepatotoxicity In Non-small Cell Lung Cancer Patients

Lung cancer has been the most common cancer in the world for several decades, with top incidence among all cancers. It was also the most common cause of death from cancers. Due to the continuous growth of tobacco consumption, severe environment contamination and lifestyle changes, the incidence and mortality of lung cancer trend to ascend straightly in our country, and it has been a serious problem of public health. Lung cancer is mainly divided into small cell lung cancer and non-small cell lung cancer(NSCLC), and the latter accounts for about 80 to 85 percent of the total number of lung cancer. Despite the advance of diagnostic and treatment technologies, NSCLC has a very bad prognosis, with the estimated five-year survival rate at about 15%, 10%, and 8.9% in America, Europe, and developing countries. Clinically, about two-thirds of the NSCLC patients are advanced when they first visit, which loss the opportunities of radical surgery for the early stage, and chemotherapy is the main treatment for them. Platinum-based chemotherapy, such as cisplatin- and carboplatin- based, have been considered as the most effective treatment for advanced NSCLC, and its cytotoxicity is primarily ascribed to its interaction with DNA to form DNA-protein and DNA-DNA interstrand crosslinks. However, the clinical use of platinum-based chemotherapy is often hampered by its severe side effects including hepatotoxicity, which is characterized mainly by elevation of serum transaminases(AST and ALT), bilirubin, and alkaline phosphatase(ALP). NSCLC individuals have different susceptibility to platinum-induced hepatotoxicity even under the same risk factors exposure, and this susceptibility is to be determined by genetics, which is mainly focused on single nucleotide polymorphisms(SNPs).Genome-wide Association Study(GWAS) is one of the powerful tools for genetic susceptibility study of complex diseases, and has been used widely. In 2011, our group reported the first multistage GWAS of lung cancer in the Chinese population, and based on these GWAS data, we conduct the first GWAS among NSCLC patients receiving platinum-based chemotherapy to identify some specific susceptibility loci for platinum-induced liver injury.The study was designed as a 2-stage case-only study. The 334 NSCLC patients in GWAS scan were from the Affiliated Cancer Hospital and the First Affiliated Hospital of Nanjing Medical University, and the replication study included 375 patients from Nanjing Thoracic Hospital, the Affiliated Cancer Hospital and the First Affiliated Hospital of Nanjing Medical University. Subjects in the discovery phase and the replication phase were all unrelated Han Chinese. All patients had histopathologically or cytologically confirmed NSCLC, which was reviewed by at least two local pathologists. Before chemotherapeutic treatment, the liver function was tested and criteria for the inclusion were as follows:(1) Bilirubin level between 1.7μmol/L and 17.1μmol/L;(2) AST< 40 U/L;(3) ALT< 40 U/L;(4) ALP level between 40 U and 110 U. All patients were treated with first-line platinum-based chemotherapy. Chemotherapeutic regimens included cisplatin/carboplatin/oxaliplatin/ nedaplatin plus gemcitabine(GP), cisplatin/carboplatin plus paclitaxel(TP), cisplatin/carboplatinplus docetaxel(DP), and cisplatin plus vinorelbine(NP). Patients who accepted radiation or chemotherapy other than platinum-based drugs were excluded. All patients accepted liver toxicity assessment after 2 or 3 cycles of platinum treatment, according to Common Terminology Criteria Adverse Events Version 3.0(CTCAE v3.0), and was classified into grade 1 to grade 4 according to the peak value of bilirubin, AST, ALT, and ALP.Fisrt, we performed the association study between macro factors and platinum-induced hepatotoxicity in pooled population, including age, gender, smoking status, histology, stage, surgical operation, and platinum compounds. The ordinal logistic regression analysis showed that the risk of liver injury decreased with age(OR=0.69, 95%CI=0.51~0.93, P=0.016), and other factors above showed no effect on hepatotoxicity(P>0.05).For the analysis of SNPs,we found 20 SNPs with P value less than 1.0×10-4 in additive model. After the linkage disequilibrium(LD) analysis, 11 SNPs were selected for replication among 375 NSCLC patients. In the replication stage, only the SNP rs2838566 G>A at 21q22.3(25kb downstream of TRPM2) was found to be significantly associated with platinum-induced hepatotoxicity in the same direction as the GWAS scan, as the minor A allele of rs2838566 could significantly increase the risk of liver injury(OR=3.78, P=4.90×10-5 in GWAS scan and OR=1.89, P =0.039 in replication, both in additive model) among NSCLC patients receiving platinum-based treatment, compared to G allele. When we pooled the subjects of GWAS scan and replication cohorts, rs2838566 was still associated with platinum-induced hepatotoxicity(pooled OR=2.56, P=2.55×10-5 in additive model). We then performed stratification analyses of rs2838566 in the pooled population to evaluate the effects of the variant genotype on risk of platinum-induced hepatotoxicity in NSCLC patients by age, gender, smoking status, histology, stage, surgical operation, and platinum compounds. The results showed that the associations between variant allele of rs2838566 and susceptibility to liver injury were significant in every stratum except in female-only population. Heterogeneity test showed that there was no significant heterogeneity in every two stratums.This is the first GWAS of platinum-induced hepatotoxicity and we identified new specific susceptibility loci at 21q22.3. Our findings are valuable in detecting more susceptibility factors and illustrating potential mechanisms on platinum-induced liver injury in NSCLC patients. Meanwhile, our newly identified susceptibility SNP might be applied in hepatotoxicity high risk population screening among NSCLC patients who receiving platinum-base chemotherapy and promising molecular therapy targets in controlling adverse effects of platinum. In summary, our findings are very important in understanding of the etiology and mechanisms of platinum-induced hepatotoxicity development, which in turn is important for early prevention and control of this adverse effect, and furthermore improves the outcomes of NSCLC patients.