The Inhibitory Effects And Mechanisms Of T Peptides On The Growth Of Post-operative Tumors

As an important disease threat anthropohealth, the incidence of cancer rises every year. Surgery, radiotherapy and chemotherapy are major methods for clinical patients with malignancy. Currently, although immunotherapies for the treatment of cancer are now gaining wider acceptance as viable alternative therapies for treating certain tumor types, such was not always the case. Surgery is still the main curative therapeutic modality for many solid tumors, and reduces the primary tumor burden maximumly. But the process of surgery could increase the risk of recurrence and metastases of residual cancer cells to other sites. Furthermore, there is severe toxicity of radiotherapy and chemotherapy as postoperative therapies, that patients can't suffer from. It is well known that major surgery are associated with severe alterations of the host defense mechanisms, making the patients hightly susceptible inflammatory responses, which intimately correlated with tumor recurrence. A few studies indicated that surgical removal of tumors is insufficient to conquer the profound immunosuppression in patients. Thus, immunotherapy as a promising approaches is used for postoperative cancer patiens.The immunomodulator tuftsin is a nature tetrapeptide (Thr-Lys-Pro-Arg)derived from spleen,isolated at Tufts University by Najjara and co-workers in 1970s. It binds specifically to macrophages, monocytes, and polymorpho-nuclear leukocytes and stimulates them to evoke immunomodulatory activity and tumoricidal properties. The features of tuftsin, coupled with its low toxicity, make the peptide an attractive candidate for immunotherapy. A few studies have reported that tuftsin prevented spontaneous tumor development, after administered for 6 months at the dose of 10μg once a week. However, tuftsin, short half-life (CL = 0.34 L/h,t1/2 = 2.8 h) was degraded in vivo by carboxypeptidase B easily. So tuftsin is less likely to be a novel medicine. In our laboratory in cooperation with a company, the structure of tuftsin has been transformed to obtain a new tuftsin derivative, named T-peptide (TP), which maintained the original function of tetrapeptide, increased anti-enzyme capacity and stability, andextended in vivo half-life.Currently, preclinical oncological evaluation models, including murine xenografts models, nude murine xenograft models that are short of T lymphocytes, and SCID murine xenograft models that are short of T and B lymphocytes, all confine the anticancer evaluation of many immunoagents. Because tumor microenvironment is a deep immunodepression area, in which functions of many immunocytes can be inhibited or changed, such as Type M1 and Type M2 macrophages. Currently, immunotherapy is used for postsurgerical intervention. It is important that a kind of murine model is established, which is close to clinical status and used for the pharmacodynamic evaluation of immunoagents.B ased on the studies mentioned above, we successfully established a novel murine pharmacodynamics model---mice with a postsurgery residual tumor. Our present studies demonstrated surgery had a promoting effect on tumor growth, if postsurgery residual tumor still remained in body. As a immunotherapeutic drugs, the effect of TP on traditional murine xenograft model and directly killing tumor cells was not conspicuous. Because of some anticancer effects of TP administated before tumors grew out and no effects administrated after tumor volumes reached 150mm3,the experiments suggested that many factors possibly confined TP to play actions, such as immune escape, tumor microenvironment, cytokines and immunosuppression. Before the formation of tumor environment,TP could activate macrophages,T lymphocyte,NK, etc. to play anticancer effects. Perhaps, tumor environment as a screen or a black hole, limited drugs to penetrate tumor tissue and to reach all of the tumor cells, in which the anticancer functions of immunocytes were severely inhibited. Based on the studies of traditional murine models in vivo, we researched the anticancer effects of TP on murine mice with postsurgery residual tumors. The results displayed better effcts that the inhibition rate reached above 80% maximally, and almost no toxicity.C ompared with clinical conditions,many tumor patients may have postsurgery residual tumors and metastasis that is not discovered. TP can apparently inhibit the growth of postsurgery residual tumors,and can it inhibit the growth of distant metastasis? We designed another murine model with a postsurgery residual tumor on right and a nonsurgery tumor on left. Suprisingly,TP is also able to inhibite the growth of nonsurgery tumor on left. The effects of surgery on nonsurgery tumors may be attributed to a number of factors, including immunodepression after surgical stress, action of cytokines or changes of tumor microenvironment.To deplete the inflence of surgery stress on the anticancer effects of TP, we designed a murine model with a pseudosurgery tumor mentioned above. The results certified surgery stress did not apperently affect the anticancer action of TP.T he anticancer effects might be related to the postoperative interaction of TP and immunocytes that result in the changes of immune state and the production of cytokines, such as Tumour necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6). Based on anticancer pharmacodynamic action of TP in vitro and in vivo, we furtherly studied the effects of TP on T lymphocytes and macrophages by flow cytometry, RT-PCR, immunohistochemistry, ELISA, and so on. As one of the most important and perplexing immunocytes residing in tumor microenvironment for long terms, macrophage gradually formed its distinct phenotypes and functions, being type M2 macrophage, i.e. tumor- associated macrophages. TAMs are also associated with increased angiogenesis in cancer tissues. Macrophage inflammatory protein 1α(MIP-1α) is from the CC (cysteinecystein) chemokine subfamily, known to be secreted from monocytes, activated macrophages, lymphocytes, and other cell types. Meanwhile, MIP-1αrelates with tumor metastases and angiogenesis.We are interested in the decrease in MIP-1αof tumor tissues and the increase expression of spleen tissues by RT-PCR and immunohistochemistry analysis.The results indicated TP might inhibite the functions of TAMs, but promote phagocytosis of macrophages.And then,we also measured the level of mouse vascular endothelial growth factor (VEGF)in tumor and Ana-1 cells by Western blotting.In conclusion,we successfully established a novel murine model with a postsurgery residual tumors for anticancer pharmacodynamics evaluation. And we researched the anticancer effects of TP on this novel murine model in vivo and in vitro. On the basis of the new model, we studied the mechanisms of TP on macrophages, TAMs and T leukomonocytes. The results and the known low toxicity are clues that TP might be a promising candidate drug for the treatment of clinical patients with postsurgery residual tumors or micrometastasis.