Chemoimmunotherapy with cyclophosphamide and bestatin in experimental metastasis in mice

Abstract

Bestatin has significant therapeutic activity (even following oral administration) for the treatment of metastatic disease, an activity which is limited by tumor burden. Therefore, the therapeutic potential of bestatin was examined in combination with chemotherapy to determine if there is additive activity for heavy tumor burdens. Bestatin significantly increased therapeutic activity and decreased the myelotoxicity of cyclophosphamide following a single injection of cyclophosphamide or split daily doses. In immune function studies, in tumor-bearing animals, bestatin increased the number of colony-forming units (granulocyte-macrophage) (CFU) and alveolar macrophage tumoricidal activity. However, when bestatin was combined with cyclophosphamide, which depressed bone marrow and macrophage activity, it did not show apparent augmentation of macrophage and NK cell activity, but did significantly increase bone marrow CFU activity. Thus, in combined chemoimmunotherapy, bestatin appears to enhance therapeutic activity by accelerating the recovery of hematopoiesis. We suggest, therefore, that a combination chemotherapy protocol, with oral bestatin, may facilitate myelorestoration following aggressive chemotherapy. The majority of biological response modifiers require parental administration; thus, the identification of an orally active, synthetic immunoaugmenting agent with a defined receptor is of particular interest.

Importance in timing of cyclophosphamide on the enhancement of interleukin-2-induced cytolysis

“…Furthermore, Lafreniere showed that pretreatment of mice 1 day prior to spleen harvest increased expansion and cytotoxicity of TIL cultures [14]. CY has also been combined with interleukin-2 (IL-2) and has proved to be synergistic against a variety of murine tumor models [1,7,12,17,23].…”

Experimental immunology Modulatory effects of bestatin on T and B lymphocyte subsets and the concentration of cytokines released by Th1/Th2 lymphocytes in cyclophosphamide-treated mice

“…The drug exerts antitumor [4][5][6], antiviral [7] antibacterial [8] and antifungal [9] action, by modulating the functions of immune cells. The immunomodulatory action of bestatin on lymphocytes has been reported in earlier studies by the same authors [10].…”

Effects of bestatin on myelopoietic stem cells in normal and cyclophosphamide-treated mice

“…Bestatin also has significant therapeutic activity against experimental and autochthonous tumors in animals [1,4,15,42,45,46] and clinically for acute nonlymphocytic leukemia in adults [13,35]. Recently we have reported the chemoimmunotherapy potential of cyclophosphamide and bestatin using an animal model of "bulky" (day 14) experimental B16 melanoma metastases [5]. In the present study, we examined the effect of bestatin on hematopoietic activity in Cell suspension.…”

“…The number of CFU-GM was determined as described previously [5,43]. Briefly, fractionated bone marrow cells (5000, 1000, 100, and 33 per well) or spleen (30 000, 10000, 3000, and 1000 per well) were suspended with the modified CMRL-1066 medium supplemented with sodium pyruvate, equine serum (5%), fetal bovine serum (10%), and tryptic soy broth (0.3%).…”

“…We have undertaken a variety of systematic analyses to characterize the immunomodulatory and therapeutic properties of bestatin [4,5,41,45,46], and have demonstrated that bestatin is a macrophage-augmenting agent without activity to stimulate natural killer cells. In addition, it has a slight blastogenic activity for mixed lymphocyte response and a potent adjuvant activity for the induction of cytotoxic T lymphocytes when admixed with a suboptimal tumor vaccine.…”