Major advances in the understanding of clinical tumour biology occurred with the appreciation that tumour-associated substances circulated in the blood of
cancer patients. In this study their origin and immunogenic function have been investigated. Whole tumour cells (WTC) and
cancer cell membrane fractions (CMF) of 24 patients with lung, colon, and
breast cancer were investigated for their antigenic effect upon the patients' own lymphocytes and upon healthy allogeneic ones. The antigenicity of whole lung and
breast cancer cells to stimulate lymphocyte
DNA synthesis, and the ineffectiveness of colon cells were confirmed. CMF had little stimulating effect upon autologous lymphocytes; however, they were able to augment lymphocyte response to
PPD and PHA in high dilution and to suppress it in high concentration. The serum of
cancer patients exerted similar biphasic activity upon
PPD and PHA stimulated lymphocytes ("lymphosuppressive-stimulatory factors", or LSSF).
Sephadex studies confirmed that LSSF activity in
cancer serum correlated with circulating CMF. These substances modulate lymphocyte
nucleic acid synthesis in vitro; it is likely that they similarly modulate the patient tumour-host cell relationship.