Adoptively transferred ex vivo activated memory T cells with cyclophosphamide: effective tumor-specific chemoimmunotherapy of advanced metastatic murine melanoma and carcinoma.

Autolymphocyte therapy (ALT) is adoptive cellular therapy of neoplastic disease based upon ex vivo activation of autologous peripheral blood mononuclear cells by either the supernatant derived from a previously prepared one-way mixed lymphocyte culture (MLC) or using low doses of the mitogenic monoclonal antibody anti-CD3 and a mixture of previously prepared autologous cytokines (T3CS). We have previously demonstrated that nonspecific ex vivo activation of splenocytes from murine tumor-bearing hosts (TBH) using an MLC supernatant or T3CS without the use of tumor antigen results in the expansion of the CD44+ (memory) T-cell subset. These memory T cells or autolymphocytes (ALT cells) mediate in vivo specificity when infused into murine TBH. To determine if cyclophosphamide (CY) could enhance the effectiveness of these ALT cells, C57BL/6J TBH with B16 melanoma or Lewis lung (3LL) carcinoma were treated with adoptive chemoimmunotherapy (ACIT) consisting of ALT cells and varying doses of CY. ALT cells were derived from the splenocytes of C57BL/6J TBH with B16 melanoma or 3LL carcinoma and activated ex vivo with T3CS. 3LL or B16 TBH received ALT cells derived from 3LL TBH splenocytes, B16 TBH splenocytes, CY alone, or ACIT with ALT cells and CY. Significantly greater antitumor activity as demonstrated by a decreased number of lung metastases (Day 21) and cure of primary and metastatic disease (Day 100) was seen in B16 or 3LL TBH that received ACIT using CY with B16-derived and 3LL-derived ALT cells, respectively, rather than ALT cells alone, CY alone, or ACIT with CY and reciprocal tumor-derived ALT cells. TBH cured by ACIT using CY and ALT cells derived from syngeneic TBH with the identical tumor displayed tumor-specific immunity as they were able to reject a lethal challenge of their previous B16 or 3LL tumor but not reciprocal tumors. TBH cured by ACIT using CY and ALT cells derived from splenocytes of syngeneic TBH with reciprocal tumors were able to reject lethal challenges of both tumors. These data demonstrate that effective ACIT using CY combined with ex vivo T3CS-activated CD44+ memory T cells from TBH conveys long-term tumor-specific immunity.