Development of systemic immunity to glioblastoma multiforme using tumor cells genetically engineered to express the membrane-associated isoform of macrophage colony-stimulating factor

We investigated the ability of Fischer rat T9 glioblastoma cells transduced with cDNA genes for the secreted (s) or membrane-associated (m) isoform of M-CSF to elicit an antitumor response when implanted into syngeneic animal s, Intracranial (i,c,) implantation of 1 x 10(5) T9 cells expressing mM-CSF (T9/mM-CSF) resulted in 80% tumor rejection. Electron microscopy of the T9 /mM-CSF tumor site, 2-4 days postimplantation, showed marked infiltration b y macrophages, many of which Here in physical contact with the T9/mM-CSF ce lls. Animals that rejected T9/mM-CSF cells a-ere resistant to i,c, rechalle nge with T9 cells, but not syngeneic MadB106 breast adenocarcinoma cells, s uggesting that T9-specific immunity can be generated within the brain via t he endogenous APCs. Intracranial injection of parental T9, vector control ( T9/LXSN), or T9 cells secreting,M-CSF (T9/sM-CSF) was 100% fatal, Subcutane ous injection of 1 x 10(7) T9/sM-CSF, T9/LXSN, or parental T9 cells resulte d ill progressive tumors, In contrast, T9/mM-CSF cells injected s,c. were d estroyed in 7-10 daps and animals developed systemic immunity to parental T 9 cells. Passive transfer of CD3(+) T cells from the spleens of immune mts into naive recipients transferred T9 glioma-specific immunity. In vitro, sp lenocytes from T9/mM-CSF-immunized rats specifically proliferated in respon se to various syngeneic glioma stimulator cells, However, only marginal T c ell-mediated cytotoxicity was observed by these splenocytes in a CTL assay against T9 target cells, regardless of restimulation with T9 cells, Subcuta neous immunization with viable T9/mM-CSF cells was effective in eradicating i,c, T9 tumors.