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

Abstract

We investigated the in vivo effects of cyclophosphamide (CY) on interleukin-2(IL-2)-induced cytolytic function and spleen cell immunophenotype. Pretreatment of A/J mice with CY (25 mg/kg or 75 mg/kg) i.p. on days -10 and -15 followed by IL-2 (50,000 U i.p. on days 0 to +3) resulted in increased lysis of YAC-1 target cells compared to the group receiving IL-2 without previous CY therapy. In contrast, when CY was given on day -5, the cytotoxicity against YAC-1 was not enhanced. Phenotypic analysis of splenocytes obtained from mice treated with CY on day -10 or -15 revealed a relative decrease in L3T4- and Lyt2-positive T cells. In vivo depletion of natural killer (NK) cells by anti-asialoGM1, prior to IL-2 therapy, abrogated the enhancing effect of CY on cytolysis while in vivo elimination of T cells by anti-L3T4 and anti-Lyt2 monoclonal antibodies did not, indicating that in the absence of T cell antigenic challenge, the increased cytolytic function after CY administration is probably mediated through NK cells. These findings provide evidence that CY may be used more effectively in IL-2-based immunotherapy protocols, if consideration is given to timing of CY and IL-2 administration.

Importance of cyclophosphamide-induced bystander effect on T cells for a successful tumor eradication in response to adoptive immunotherapy in mice.

“…Moreover, an ensemble of experiments indicated that an intact immune system of the recipient host and some soluble factors (IFN-␣ / ␤ ) were essential in mediating the antitumor response to the adoptive immunotherapy in the CTX-injected animals. Altogether, these results may lead to reinterpretation of the mechanisms underlying the synergistic effects of CTX and adoptive immunotherapy observed in various experimental tumor models by others (8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22), largely explained on the assumption of a selective effect of CTX on "suppressor T cells" (24,(26)(27)(28).…”

“…Cyclophosphamide (CTX) 1 is a widely used chemotherapeutic agent in cancer therapy (for review see reference 7). CTX has also been used by several groups as an immunomodulatory agent against murine and human tumors (8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22). Many studies have reported that CTX can increase the efficacy of immunotherapeutic regimens by removing tumor-induced suppressor T cells (23)(24)(25)(26)(27)(28).…”

Correlation between the sensitivity or resistance to IL‐2 and the response to cyclophosphamide of 4 tumors transplantable in the same murine host

“…The possible clinical relevance of our results remains to be established. Although the data discussed so far emphasize the importance of some adverse effects of CTX in mice transplanted with IL-2-responsive tumors, CTX, under some circumstances, can enhance anti-tumor immune responses (Awwad andNorth, 1988, 1989;Abrams et al, 1993;Katsanis et al, 1991). Awwad and North (1989), for instance, reported that CTX can cause immunologically mediated regression of an immunogenic, CTX-resistant lymphoma, transplantable in syngeneic mice.…”

“…Although we have not been able to find any evidence of suppressor T cells in these tumor models, our data indicate that CTX, under some treatment schedules, can efficiently synergize with immune cells in the induction of an effective anti-tumor response. Likewise, CTX can act synergistically with IL-2 to enhance cytolytic function and an anti-tumor response when it is given at an appropriate dose and regimen (Katsanis et a!., 1991;Ootsu et al, 1989;Kedar et aL, 1989;Mitchell, 1989). However, the type of CTX-induced effects can markedly depend on the timing of drug administration with respect to tumor challenge, resulting either in suppression or enhancement of the immune response (Glaser, 1979;Awwad andNorth, 1988,1989;Evans, 1983).…”

Interleukin-2 Secretion by Transduced and Unselected BDL-2 Lymphoma Results in Increased Survival in Mice with Previously Established Disseminated Disease

“…Cells lines: BDL-2, a B cell lineage lymphoma derived from a BALB/c mouse (generously provided by J. Braun), was maintained in culture in Dulbecco's modified Eagle medium (DMEM) (GIBCO BRL, Grand Island, NY) supplemented with 2mM L-glutamine (GIBCO), 100 mg/ml streptomycin (GIBCO), 100 U/ml penicillin (GIBCO), 0.025 mg/ml fungizone (GIBCO), 0.5 x minimal essential medium amino acids (Sigma, St Cytotoxicity Assays 51 Cr release assays were performed as previously describedYork (29). Briefly, target cells (BDL-2, YAC) were suspended at a concentration of 1-2 x 106 cells in 0.5 ml of medium and were incubated with 500 mCi Na51Cr04 (5 mCi/ml, Amersham Corporation, Arlington Heights, IL) for 1 hour at 37°C.…”