Lymphocytotoxic autoantibodies eluted from in vivo propagating sarcoma cells of mice

Tumor-microenvironment interactions: dangerous liaisons

The interaction between microenvironmental components and tumor cells is bidirectional. Tumor cells and their products are capable of regulating and altering gene expression in nontumor cells residing in or infiltrating into the microenvironment and exert selective pressures on such cells, thereby shaping their phenotype. Conversely, microenvironmental components regulate gene expression in tumor cells thereby directing the tumor into one or several possible molecular evolution pathways, some of which may lead to metastasis. This review summarizes six instances in which the tumor liaises with different components of its microenvironment. These liaisons result, in most cases, in enhanced tumor progression. In these cases (responses of tumor and nontumor cells to microenvironmental stress, the interaction of the tumor with fibroblasts, endothelial cells and macrophages, the formation of the metastatic niche, and the interaction of the tumor with immunoglobulins) the tumor, directly or indirectly, alters the phenotype of its interaction partners thereby enlisting them to promote its progression. Does the tumor need all these pathways to form metastasis? Is there a hierarchy of interactions with respect to impact on tumor progression? These questions remain open. They may be answered by approaches employed in the analysis of hypercomplex systems.

Receptors involved in microenvironment-driven molecular evolution of cancer cells

Cells, including cancer cells, communicate with their microenvironment via various types of membrane receptors. An important down-stream effect of such interactions is a change in the molecular phenotype of the cells. The microenvironment-driven molecular evolution of cancer cells may induce either growth arrest or death of the cells or alternatively, boost their malignancy phenotype. In this paper we summarize studies from our own laboratory on interactions of cancer cells with microenvironmental ligands via two types of receptors that are not commonly associated with tumour progression i.e. the receptor for the Fc portion of IgG, and Ly-6 proteins of mouse and human origin. We also review information on interactions of tumour-associated chemokines and chemokine receptors with the corresponding microenvironmental factors. We demonstrate how these interactions may drive the molecular evolution of tumour cells and discuss the possible impact of this evolution on tumour progression.

Possibilities of interference with the immune system of tumor bearers by non-lymphoid Fc gamma RII expressing tumor cells

The ectopic expression of Fc gamma RII by PyV transformed 3T3 cells derived from tumors of long latency has been established. It was suggested that this expression is one of several changes conferring upon the cells an increased capacity for survival. We found that in one case cells expressing a very high level of Fc gamma RII had also a very high metastatic phenotype as compared to FcR negative cells. Direct evidence that Fc gamma RIIbl functions as a progression factor was provided by transfection experiments. The transfected gene conferred an increased malignancy and invasive phenotype upon PyV or c-Ha-ras transformed cells. In the present study we tested the possibility that Fc gamma RII expressing tumor cells could interfere with the immune system. The following subjects were investigated: 1) The ability of Fc gamma R on the tumor cells to bind the ligand and/or release IBF. 2) The effect of a local accumulation of ligand and/or IBF (assumed to take place in situ in the tumor) on Fc gamma RII expressing T cells. It was found that both tumor-derived receptor positive and beta l transfected PyV transformed cells were capable of binding aggregated mouse IgG. The binding of bivalent ligand was followed by an increase in membrane Fc gamma RII expression. Also both types of cells were capable of releasing IBF. We then tested the possibility that a local accumulation of IgG within the tumor could effect Fc gamma R expressing T cells. It was found that aggregated mouse IgG (as well as IgGl) could stimulate the proliferation of the T cell hybridoma (T2D4) and other Fc gamma RII expressing T cells. We also found that the expression of beta Fc gamma RII specific mRNA peaked at the logarithmic phase of T2D4 cultures, in parallel with their maximal potential to release IBF. Several pathways for interference with the immune system are suggested.

The immune system during the precancer period: naturally-occurring tumor reactive monoclonal antibodies and urethane carcinogenesis

Previous results obtained in our laboratory suggested that natural antibodies reactive with L5178Y lymphoma cells play a role in the induction of lung tumors by the chemical carcinogen urethane. In order to characterize some of the naturally-occurring L5178Y reactive antibodies we prepared hybridomas that secreted natural monoclonal IgM antibodies reactive with L5178Y lymphoma cells. In the present study we characterized some of these antibodies and provided further proof as to their role in urethane carcinogenesis. One hybridoma secreted a cytotoxic antibody that reacted only with mouse lymphoma cell lines. Other non-cytotoxic monoclonal L5178Y-reactive antibodies showed various degrees of cross-reactivity with syngeneic, allogeneic and xenogeneic cells of normal or malignant origin. One of these antibodies reacted much better with activated T cells than with resting ones. Four groups of mice were treated with urethane. Three groups were injected twice a week during 5 months with different IgM preparations of natural monoclonal antibodies. The mice in the fourth group were not treated with IgM and served as controls. Five months after the urethane treatment the mice were sacrificed and the number of tumor foci in the lungs of each mouse was determined. The results show that the group treated with the cytotoxic monoclonal antibody 1.80 had a significant decrease, while the group treated with the IgM myeloma protein 104E had a significant increase in the number of tumor foci compared to urethane-treated mice that did not receive any IgM treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Studies on the level of natural antibodies reactive with various tumor cells during urethane carcinogenesis in BALB/c mice

Serum from young normal BALB/c mice was found to contain IgM antibodies able to mediate complement-dependent lysis of certain syngeneic or allogeneic tumor target cells. The titer of such naturally occurring antitumor antibodies ( NATA ) was found to increase with aging. A longitudinal serological study comparing the cytotoxicity potential of NATA from normal and from urethan-treated BALB/c mice was performed. It was found that urethan-treated mice that did not develop primary lung-adenomas within the duration of the experiment had significantly lower NATA titers, against one out of 4 target cells assayed, than urethan-treated animals that developed lung adenomas. This difference was evident in two independent experiments. The results suggested that the lower NATA activity of the urethan-treated mice that did not develop tumors existed even before exposure to the carcinogenic insult. This raises the possibility that certain populations could be segregated according to their natural antibody profile into those individuals which will develop primary tumors within a certain period if exposed to a subthreshold amount of carcinogen, and those which will not.