Asparaginase Induces Autophagy In Small Cell Lung Cancer Cells While Inhibiting Their Growth

Background and objectiveIn recent years,the incidence of lung cancer keeps increasing and has already been ranked first in male malignancy.In order to overcome this kind of cancer,human beings have been exploring more effective therapy actively.However its mortality rate is still in the forefront among all the tumor disease.Although small cell lung cancer(SCLC)accounts for only about one-fifth of the proportion of lung cancer,however its degree of malignancy is relatively higher for its early metastasis,wider range of diffusion and recurrence.Radiotherapy and chemotherapy is the main treatment which is not satisfactory because of their obvious side effects,secondary resistance and limited efficacy.In view of this situation,developing an absolutely new and effective drug is clearly imminent.Asparaginase(AN)is a representative drug of amino acid metabolism therapy which has been reported in a number of tumor-related literature report.What's more,it has been applied to the first half of the clinical treatment of leukemia as early as 1970 s.Since AN has such a curative effect on tumors(including a variety of solid tumors).Then,would AN have the any medicinal value for SCLC? No specific reports have been found yet.In order to verify the anti-cancer effect of AN for small cell lung cancer and to explore the possible mechanism,two SCLC cell lines-H1688 and H446 were selected as test subject.Hope that we could make a contribution to clinical treatment.MethodsAfter treatment of AN alone or combined with autophagy inhibitor chloroquine(CQ)in H1688 and H446 cells,MTT assay was applied to assess cell viability while trypan blue exclusion assay was applied to assess cell mortality rate.Then the formation of autophagy marker LC 3 and autophagosome was observed by immunofluorescence method.Western blot analysis was taken to determine the expression of LC 3 and AKT /mTOR signal pathway proteins.ResultIn this study we found that,AN inhibited cell growth in dose-dependent manner(p<0.05),and significantly upregulated the quantity of autophagosome and the expression of LC3 II in H1688 and H446 cells.The inhibition effect of AN to H1688 and H446 cells was promoted when combined with CQ(p<0.05).In H1688 cells,AN suppressed the protein expression of p-AKT,p-mTOR and p-70S6 K.Conclusion(1)AN can inhibit the growth of H1688 and H446 cells;(2)AN can induce autophagy of H1688 and H446 cells;(3)Blocking autophagy can enhance the potency of AN on H1688 and H446 cells;(4)AKT / mTOR was involved in AN-induced autophagy of H1688 and H446 cells.