The Use Of CXCL4 Monoclonal Antibody In Inhibiting Colon Cancer Regrowth After Chemotherapy

Colon cancer has become the third most common malignant tumor worldwide,it poses a great threat to health and quality of life of patients.Chemotherapy has becoming a conventional therapeutical method to treat the primary and metastatic colon cancer.However,colon cancer re-growth and recurrence after chemotherapy and eventually death of the patients are still the main reasons for chemotherapy failure,therefore they remain as an important and urgent issue to be resolved by the field experts.The detailed mechanism of tumor re-growth after chemotherapy has not yet been elucicated.We proposed that the homeostatically regulated genes during colon cancer re-growth after chemotherapy may participate in this process.Using the CT26 tumor re-growth mouse model after 5-FU chemotherapy,we identified the chemokine CXCL4 was such a homeostatically regulated gene and may serve as a new target for treating tumor re-growth after chemotherapy.Firstly,we confirmed that the CXCL4 expression in both gene and protein level was increased,accompanying the decline of tumor volume,and returned to the basal level thereafter as the tumor rebounded.These results suggest that CXCL4 may be involved in cancer re-growth after chemotherapy.Secondly,we tested the effect of recombinant human CXCL4 protein in vitro alone or in combination with 5-FU on the proliferation of colorectal cancer cell lines.The results showed that CXCL4 either alone or in combination with 5-FU had no effect on the proliferation of colon cancer cells in vitro.However,CXCL4 stimulated tumor growth in the CT26-bearing mice when the mCXCL4 expression plasmid mCXCL4-pcDNA3.1 was constructed to over-express CXCL4.This suggests that the role of CXCL4 is indirect,which supports our proposal that the elevation of CXCL4 expression in the mice may account for tumor re-growth after chemotherapy.Subsequently,we focused on the application of CXCL4-mab in the colon cancer re-growth after 5-FU chemotherapy.The use of CXCL4-mab suppressed the colon tumor re-growth after 5-FU chemotherapy,significantly reduced the mortality of mice bearing tumor.Further study showed that CXCL4-mab inhibited tumor re-growth after 5-FU chemotherapy not only by inhibiting the proliferation of tumor cells,but also by enhancing the apoptosis of tumor cells.The mechanism research revealed that highly expressed CXCL4 from colon tumor cells under the stress of 5-FU treatment,inhibited the CTLs' function by reducing the secretion of anti-tumor factors such as IFN-? and GRAN-b.Meanwhile,CXCL4 also inhibited the M1-like macrophages which also played the anti-tumor role in colon cancer tissues.CXCL4-mab antagonized the high-expressed CXCL4 so that unlocked its inhibition of CTLs' and TAM's antitumor function,which demonstrated the inhibition of colon cancer re-growth after 5-FU treatment.Taken together,our results showed that CXCL4 high expression in tumor cells after 5-FU chemotherapy created a facility for them to escape from immune-suppression.CXCL4 neutralizing antibodies were able to inhibit colon cancer re-growth after 5-FU treatment.Therefore,CXCL4-mab could become a new target for the prevention and treatment of drug resistance and clinical relapse after chemotherapy strategy.