In this study,we found that the expression level of VHL in the tumor tissue of NSCLC patients plays an important role in predicting the risk of granulocytopenia in platinum-based chemotherapy. According to IHC staining result, we confirmed that granulocytopenia is more likely to happen in the person whose pathological tissue is lack or weak expression of VHL. Previous result has suggested that VHL is a classic tumor suppressor gene, which plays a significant role in the occurrence and progression of many cancers including clear-cell renal cell carcinoma(ccRCC),colon cancer,pancreatic cancer and so on. Early research showed that the absence of VHL led to the continuous accumulation of HIF-1α, which in turn leads to the continuous opening of HIF pathway.(6-8,15,16) This results in continuous overexpression of downstream factors such as vascular endothelial growth factor (VEGF), which causes to high vascularization in normal tissues and promotes the production of erythropoietin (EPO), ultimately evolking the growth and proliferation of carcinoma and hindering the degradation of tumor cells. Furthermore, recent studies have shown that the HIF pathway mediated by VHL is closely associated with the resistance of multiple chemotherapeutic drugs and radiotherapy.(7,16) VHL regulates the HIF pathway, and leads to the overexpression of MDR (multi-drug resistance) gene, which has been widely proved to be related with the resistance of cisplatin, vinblastine, anthracycline, taxane and other chemotherapy drugs treated with some hypoxic carcinomas. However, the correlation between VHL gene and NSCLC chemoradiotherapy and prognosis has rarely been reported.(10-13,17,18)
For this reason, we evaluated the relationship between clinical characteristics of NSCLC patients and the expression level of VHL in their carcinoma tissues. Then, we explored the association among the protein expression level, granulocytosis and OS/DFS. In current study, we found that VHL was more likely to be absent or poorly expressed in NSCLC tissues and Age could influence the expression level of VHL(P-value=0.024). This finding may further support the description of VHL low expression or lack in tumor cells in previous studies. We also discovered that the expression of VHL was related to the neutropenia after platinum-based therapy(P-value=0.005), further multivariate regression analysis showed that lack or low expression of VHL increased the risk of neutropenia after platinum-based chemotherapy. At present, the mechanism of VHL expression level affecting hemotoxicity is still under study. We speculate that the reason for this phenomenon may be related to the regulation of VHL-mediated HIF pathway and its downstream genes on apoptosis in vivo, which is closely similar to the mechanism of MMP2 gene mediating NSCLC granulocyte toxicity.(21,22) In addition, we found that the expression of VHL(X2=5.044,P-value=0.025) and gender(X2=4.632,P-value=0.031) may be related with leukopenia caused by platinum-based chemotherapy. Many recent studies have shown that VHL gene plays an important role in the generation of resistance to platinum chemotherapy by blocking drug entry into cells, enhancing DNA damage repair, and inhibiting cell apoptosis. Based on these studies, we suspect that the negative or weak expression of VHL in NSCLC patients increase the reaction of granulocytopenia through hindering the drugs into the tumor cells and increasing the DNA damage repair ability,which make platinum drugs ineffectively kill cancer tissues and increase the accumulation of drugs in normal tissues.(19,20,23-25) While, multivariate regression analysis didn’t support this in an individual prognostic factor, we planned to increase the sample cohort to verify it.
Furthermore, through the Kaplan-Meier curves, we explored the relationship between the expression level of VHL and DFS or OS. The conclusion showed that VHL expression level(Logrank test:P-value= 0.007,HR= 4.219,95%CI: 1.75-10.174, P-value=0.001) was correlated with OS (Logrank test:P-value= 0.007, while it did not related with DFS(Logrank test:P-value=0.256,HR=1.334,95%CI:0.642-2.769, P-value=0.440).The person who had negative or weak expression in his tumor tissue could live longer than the one who had moderate or high expression in the tissue.Therefore, the expression of VHL in the pathological tissue may be a useful tool for early prediction of the hematotoxicity of platinum-based chemotherapy and the outcome of NSCLC patients. Unlike our study, a previous trial showed that loss of VHL might cause the poor survival of lung adenocarcinoma. However, unlike the previous trial, our study had a considerably larger population and more various patients with different pathological pattern.(26) The difference in patient group may account for the different results. Because the expression level of VHL was effective in predicting the risk of neutropenia in platinum-based chemotherapy, it clearly that the polymorphisms of VHL in blood has potential as a prediction site for the hemotoxicity of platinum-based chemotherapy. Further studies need to be done, however, to firmly establish its place as a predictive marker for hematotoxicity of platinum-based chemotherapy in NSCLC patients.
In summary, severe neutropenia caused by platinum-based chemotherapy often results in severe infection, greatly destroying the patient's quality of life and effecting the subsequent treatment. In this study, we found that the expression level of VHL gene intumor tissues could be used as a biomarker to predict the risk of neutropenia. If clinical transformation could be achieved, it would be of great significance for individual therapy with platinum drugs. At the same time, VHL expression level could indicate the prognosis of NSCLC patients receiving chemotherapy, which can be used to evaluate the long-term prognosis of patients receiving chemotherapy.