QUALITATIVE AND QUANTITATIVE INTRATUMORAL CHANGES IN GENE-EXPRESSION FOLLOWING CYCLOPHOSPHAMIDE INJECTION AND THE ADOPTIVE TRANSFER OF T-CELLS - THE POTENTIAL CONTRIBUTION OF TUMOR-ASSOCIATED MACROPHAGES

Adoptive immunotherapy (AIT) of mice bearing the MCA/76-9 rhabdomyosar coma in combination with cyclophosphamide (CY) injection results in th e permanent regression of tumors. This report is concerned with change s in the tumor-associated macrophage (TAM) population and the influenc e of both CY injection and CY/AIT on their potential functions. Sequen tial analyses of FcR, MAC-I and Class-II mhc antigen expressed by tumo r-associated cells (TAC) showed that CY injection or CY/AIT induced ma rked increases in the proportions of all 3 parameters as compared with the relatively stable levels in progressing tumors. These changes wer e time- and treatment-related. The mean MAC-I fluorescence (antigen de nsity per cell) increased nearly 2-fold by 48 hr after CY injection, r egardless of subsequent AIT. In contrast, the density of Class-II anti gen per cell declined by as much as 75% within 48 hr after CY injectio n and did not recover by 7 days. This initial decline was also seen af ter CY/AIT and was followed by a rapid recovery to near-normal values by day 7. Northern analysis of RNA isolated from whole tumor tissue in dicated wide fluctuations in expression of the typical macrophage gene s encoding the proteins MAC-I, IL-I alpha, IL-I beta, TNF alpha, IA be ta and c-fms. However, with the exception of MAC-I and IL-I alpha/IL-I beta mRNA, the modifications appeared to be qualitative rather than r epresenting changes in the proportions of TAM. The data suggest that t he changes in membrane antigen and gene expression by TAM reflect a co mplex interaction between TAM and their environment, in particular tum or cells and tumor-infiltrating lymphocytes. In addition, it is eviden t that CY injection per se is responsible for defined fundamental chan ges that presumably influence the outcome of AIT. (C) 1994 Wiley-Liss, Inc.