Some aspects of the immune defense against cancer. I. In vitro studies on animal tumors

Where is the immunology in cancer?

Whether the common human cancers possess tumour-specific antigens which produce an immune response in the host still remains the crucial question in tumour immunology. Recent reports and discussions at the Third International Congress of Immunology suggested that much of the previously published work was not valid. The reasons for this have been analysed by comparing the well-established experimental data with human cancer. It is suggested that much of the current confusion in tumour immunology stems from the poor models used to study human cancer and the inadequate assessment of in vitro assays which have measured the host response. The present methods require refinement, or new techniques need to be developed, before this question can be answered. The field has been well researched, and there do not appear to be any recent major advances in tumour immunology which can be applied in clinical practice.

Nodal response in medullary carcinoma of the breast

From 1954 to 1970, ninety-five patients with medullary carcinoma of the breast were evaluated in terms of immunologic activity based on the histologic changes seen within the tumor and regional nodes. Each patient was studied for the degree of lymphocytic infiltration in the tumor as well as the extent of sinus histiocytosis present within the regional nodes. Contrary to what would normally be expected, those nodes with increased sinus histiocytosis were associated with the larger tumors. In addition, lymph node metastasis increased from 26 to 75 per cent as the degree of sinus histiocytosis became more pronounced. There was no evidence that increased lymphocytic infiltration in the tumor resulted in a statistically significant improvement in the five and ten year survival rates. Similarly, sinus histiocytosis activity did not seem to enhance the survival rate among this particular group of patients. There is a suggestion that a correlation exists between sinus histiocytosis and lymphocytic infiltration in the tumor and that, whatever the stimulus present, its effect is on both the lymph node and the degree of lymphocyte response within the tumor. The antigenic substance in the tumor, which initiates the immune response, possibly produces an abortive reaction, which may result in the induction of blocking factors rather then those factors necessary for destruction. It appears that histologic evidence of immunologic enhancement does not necessarily signify improved survival, at least with those patients having carcinoma of the breast.

Changes in host immunity following excision of a murine melanoma

Changes in cell mediated and humoral immunity following the excision of a transplantable melanoma growing in the footpad of its syngeneic host, as measured by an in vitro cytotoxicity test, were assessed. Spleen cell cytotoxicity did not change significantly. Cells from the regional lymph nodes stimulated tumour growth before tumour excision. Three days following tumour excision this stimulatory effect was undetectable. Loss of serum factors capable of blocking the cytotoxicity of spleen cells occurred 24 h after tumour excision. Serum cytotoxicity increased after tumour excision to a maximum of the third day. Following tumour excision the rise in serum cytotoxicity and loss of regional lymph node tumour stimulation were concomitant with the loss of blocking activity.

Immune response to a syngeneic rat tumour: development of regional node lymphocyte anergy

The development of cellular immunity to a syngeneic squamous cell carcinoma in Wistar rats was studied by in vitro microcytotoxicity assay. Reactivity of lymphocytes from lymph nodes, spleen and blood was tested throughout the period of tumour growth. Maximum lymphocyte cytotoxicity against the tumour was observed at 2 weeks in regional lymph nodes, 4 weeks in intermediate nodes, spleen and blood, and 6 weeks in distant nodes; the intensity of these cytotoxic responses subsequently declined. In the regional nodes, lymphocytes became totally unresponsive despite the maintenance of significant cytotoxicity in intermediate nodes, spleen and blood. Local anergy may account for tumour spread to the regional node in an otherwise immunocompetent host. This anergy may be due to high local concentration of tumour antigen or antigen-antibody complexes, but it was not associated with selective changes in T and B cell proportions.

Cancer--the elusive enemy

The evolution of multicellular organisms involves the possibility that what Professor Stoker in his recent Leeuwenhoek lecture (Stoker 1972) referred to as asocial cells may arise, i.e. cells which possess selective advantages in respect of their own survival but are disadvantageous as regards survival of the organism as a whole. Cancer provides a striking, though not unique, example of this phenomenon. The label enemy , which would certainly not be challenged by a patient with cancer or a clinician, seems therefore not inappropriate even in a strictly biological context. The reasons for the qualification elusive , which according to the O.E.D. connotes among other things the capacity ‘to escape adroitly from ’, will, I hope, become apparent in the course of the lecture, the main purpose of which is to consider where conventional methods of treating cancer fail and how they might be improved. In the course of this inquiry we shall have to consider also the question of the existence and nature of homeostatic mechanisms for the elimination or immobilization of asocial cells because, in so far as such mechanisms do exist, the risk of weakening them, and, on the other hand, the possibility of strengthening or supplementing them, become important considerations both in assessing existing therapeutic procedures and developing new ones.