Adoptive transfer of ex vivo-activated memory T-cell subsets with cyclophosphamide provides effective tumor-specific chemoimmunotherapy of advanced metastatic murine melanoma and carcinoma.

Autolymphocyte therapy (ALT) is adoptive cellular therapy of neoplastic disease using ex vivo activation of autologous (human) or syngeneic (murine) lymphocytes from tumor-bearing hosts (TBH) by low doses of anti-CD3 monoclonal antibody (MAb) and a mixture of previously prepared autologous cytokines (T3CS). Ex vivo activation by T3CS without tumor antigen results in expansion of CD44+ (memory) T cells. These memory T cells (ALT cells) mediate in vivo anti-tumor specificity and with cyclophosphamide (CY) are capable of curing metastatic disease in murine TBH. To determine whether CY could enhance the effectiveness of CD4+ or CD8+ subsets of ALT cells, C57BL/6J TBH with B16 melanoma or Lewis lung (3LL) carcinoma were treated with adoptive chemoimmunotherapy (ACIT) using CD4-depleted or CD8-depleted ALT cells and CY. ALT cells were derived from splenocytes of B16 or 3LL-TBH and activated ex vivo with T3CS. Depletion of CD4+ or CD8+ T cells was performed before or after activation with T3CS. B16-TBH or 3LL-TBH that received ACIT using CY with B16-derived or 3LL-derived CD8-depleted ALT cells, respectively, demonstrated cure of metastatic disease regardless of whether CD8+ T cells were depleted before or after T3CS activation. B16 or 3LL-TBH that received ACIT using CY with B16 or 3LL-derived CD4-depleted ALT cells also cured metastatic disease but only if CD4+ T cells were depleted after T3CS activation. Interleukin (IL)-2 added to pre-T3CS CD4-depleted ALT cells cultured with T3CS restored anti-tumor activity when combined with CY. TBH cured by ACIT using CY and ALT-cell subsets derived from syngeneic TBH with the identical tumor displayed tumor-specific immunity in rejecting a lethal challenge of identical but not reciprocal tumor. TBH given ACIT using CY and ALT-cell subsets derived from splenocytes of syngeneic TBH with reciprocal tumors rejected lethal challenges of both tumors. Tumor specificity measured by interferon (IFN)-gamma and 51Cr-release assays was demonstrated in pre- or post-T3CS/CD8-depleted, post-T3CS/CD4-depleted and pre-T3CS + IL-2/CD4-depleted ALT-cell subsets. Our data demonstrate that ACIT using CY combined with ex vivo T3CS-activated CD44+ memory T-cell subsets conveys long-term tumor-specific immunity.