Abstract
Growth of syngeneic transplants of a 3-methylcholanthrene induced rat sarcoma was suppressed when tumour cells were injected in admixture with BCG. Rejection of these mixed inocula resulted in the suppression of growth of a simultaneous challenge with cells of the same tumour at a contralateral subcutaneous site and conditions for immunotherapy were evaluated with respect to the maximum tumour cell challenge rejected and the optimum time of treatment. These studies established that viable tumour cells were more effective than radiation attenuated cells for the immunizing stimulus. Also, the maximum tumour challenge totally rejected in this way was of the order of 10(6) cells, and with this rapidly growing tumour, treatment had to be initiated within 4 days of tumour injection. These observations are relevant to current proposals for adjuvant immunotherapy of human malignant disease where conditions of minimal residual disease are not being fulfilled.
Highlights
Summary.-Growth of syngeneic transplants of a 3-methylcholanthrene induced rat sarcoma was suppressed when tumour cells were injected in admixture with Bacillus Calmette-Guerin (BCG)
In addition to Corynebacterium parvum has been used to the retardation of localized tumour deinduce rejection or to retard growth of velopment, BCG infection of subcutanesyngeneic transplants of a number of ous grafts of a transplanted guinea-pig experimental animal tumours (Mathe, hepatoma prevented the development of Pouillart and Lapeyraque, 1969; Parr lymph node metastases (Zbar et al, 1972) 1972; Bansal and Sj6gren, 1973; Currie and similar treatment of a rat epithelioma and Bagshawe, 1970; Woodruff and Boak, restricted or retarded the formation of 1966)
The rationale of directly direct contact between viable BCG organ- contacting BCG with tumour cells has isms and tumour cells produces a more been used to suppress the development of marked suppression of tumour growth pulmonary metastases produced artificia]ly than that elicited by general immuno- in rats by intravenous injection of sarco
Summary
Rejection of sarcoma-BCG mixed inocula is known to induce suppression of growth of the same tumour implanted at another site (Baldwin and Pimm, 1971) and the conditions for active immunotherapy have been defined in terms of the maximum tumour cell challenge which could be controlled and the optimum time of treatment. In this way it has been possible to define conditions whereby subcutaneous growth of this tumour can be controlled, these observations being relevant in defining conditions where adjuvant immunotherapy of human malignant disease might be appropriate
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