Tumor-associated antigenic differences between the primary and the descendant metastatic tumor cell populations

What the structure of angiostatin may tell us about its mechanism of action

Originally discovered in 1994 by Folkman and coworkers, angiostatin was identified through its antitumor effects in mice and later shown to be a potent inhibitor of angiogenesis. An internal fragment of plasminogen, angiostatin consists of kringle domains that are known to be lysine-binding. The crystal structure of angiostatin was the first multikringle domain-containing structure to be published. This review will focus on what is known about the structure of angiostatin and its implications in function from the current literature.

Selection of liver-colonizing tumor cells from a murine fibrosarcoma induced by methylcholanthrene

An experimental tumor model was developed to study the organ preference of malignant tumors. The primary tumor ER 15-P was induced by inoculation of 1 mg methylcholanthrene in 0.1 ml sesame oil into the left femoral muscle of a female C57/Bl6J mouse. The tumor was palpable 100 days after induction. Spontaneous lung metastases were found at autopsy on day 128. Serial IM transplantation of tumor cells from the primary ER 15-P resulted in pulmonary metastases in all male and female mice. After IV injection of tumor cells from ER 15-P to male mice, colonies were found in lungs, thoracic cavity, liver, kidneys and occasionally also adrenals; female mice sometimes had ovarian metastases in addition, but no hepatic metastases. Liver-colonizing tumor cells were selected in male mice as follows: (a) IV injection of tumor cells from primary ER 15-P; (b) removal of tumor cells from liver tumor nodules, reinjection into mesenteric vein; (c) preparation of resulting tumors in the liver, reinjection of these cells through the portal system in one group of mice, and IV administration into tail vein in another group: (d) IM inoculation of tumor cells of the mesenteric passage in the left gastrocnemius muscle of mice prior to IV injection via tail vein in another group. Steps c and d were repeated three times. The procedure resulted in a highly significant decrease of tumor cell colonization to lungs and other organs, and a preferential increase of liver colonization. The liver preference of cell lines thus selected was obvious. Possible mechanisms for the organ preference of malignant tumors are discussed.

Estrogen and progesterone receptors in prediction of metastatic behavior of breast carcinoma

The relation between estrogen- and progesterone-binding receptors and the metastatic behavior of breast carcinoma was examined by reviewing autopsy findings in 25 subjects with metastatic breast cancer at Johns Hopkins Hospital for whom the results of estrogen- and/or progesterone-binding assays were available. Regardless of receptor status, patients treated with hormone therapy had prolonged survival (p less than 0.05), but had greater tumor burden at autopsy (p less than 0.05). The distributions of metastases differed for receptor-positive versus receptor-negative tumors. Estrogen-positive tumors metastasized more frequently to thyroid and/or parathyroid glands (p less than 0.01). Estrogen-negative tumors metastasized more extensively to the leptomeninges (p less than 0.01). Progesterone-positive tumors metastasized more frequently to myocardium (p less than 0.01), small bowel (p less than 0.01), urothelial structures (p less than 0.05), and thyroid and/or parathyroid glands (p less than 0.05). These differences in the distributions of metastases may reflect different tissue preferences in metastasizing breast carcinoma cells with estrogen- and/or progesterone-binding receptors. In this regard, perhaps patients with estrogen-negative tumors should be monitored closely for the development of carcinomatous meningitis, because this form of central nervous system involvement is a frequent cause of death among patients with breast carcinoma.

Nonrandom distribution of metastases in neuroblastic tumors

Metastatic behavior of neuroblastic tumors was analyzed to determine whether the secondary distribution of tumor was random, or whether the pattern of metastases was predictable and related to tumor type. The authors reviewed the 64 patients subjected to complete autopsy who had metastases from a neuroblastoma, retinoblastoma, medulloblastoma, or pinealoblastoma. The organ and tissue distribution of metastases was recorded in relation to location of primary tumor, type of therapy, survival, and presence of central nervous system metastases. Data were analyzed using chi-square contingency tables, correlation coefficients, and cluster analysis. The results indicate that: (1) the development of central nervous system metastases from neuroblastoma correlates with the pattern of extracentral nervous system metastases; (2) the pattern of tumor metastases is altered by chemotherapy and/or radiation; and (3) regardless of the site of origin, neuroblastic tumors behave in a uniform manner with a nonrandom metastatic distribution in particular tissues within the central nervous system. Cluster analysis demonstrated patterns of neuroblastoma tumor metastases which were consistent with both Hutchison and Pepper syndromes. The findings suggest that a random distribution, as might be secondary to blood flow, does not account for metastatic patterns, but rather that there are preferential patterns of growth, possibly reflecting trophic tendencies in neoplasms.

The selective nature of metastasis

The issue of whether metastases result from the random survival of cells released from a primary tumor or from the selective growth of specialized tumor subpopulations endowed with metastatic properties is important to our understanding of the metastatic process and to the development of therapeutic modalities against metastatic disease. We have found that the tumor cells populating spontaneous metastases are more metastatic than the cells populating the parent neoplasm, clearly indicating that metastasis is selective and not random. The selective nature of metastasis is a consistent observation, however, only when tumor cells are obtained from spontaneous metastases from mice bearing heterogenous, poorly metastatic tumors. Tumor cells from spontaneous metastases from mice bearing tumors that have been selected for metastatic potential or that are homogeneous (cloned) do not differ significantly in metastatic potential from tumor cells populating the parent tumor. Thus, under some conditions the process of metastasis can appear random. Although tumor cells from different individual metastases may be homogeneous with regard to a metastatic phenotype, they may be heterogeneous with regard to their sensitivity to chemotherapeutic agents. Thus, although metastasis selects for metastatic variants, resulting in the population of metastatic foci with tumor cells endowed with metastatic properties, it does not appear to select for phenotypes irrelevant to the process of metastasis such as sensitivity to therapeutic agents.

Immunology of metastasis. Can the immune response cope with disseminated tumor?

The application of immunologic methods to the treatment of neoplasia has been a goal of research in tumor immunology. Unfortunately, no clearly defined success for such therapy has been achieved. However, the most recent advances in tumor biology have provided for a more valid conceptual framework upon which to plan further research in this area. The more general awareness of tumor progression and heterogeneity, particularly in the context of tumor metastasis, while imposing a sense of gloom regarding all therapeutic modalities, shifted immunologic thinking toward the development of nonspecific modalities. We herein propose that this 'shift' may be premature and that immunotherapy using cytolygic T cells could still be feasible. Our views are based on newer approaches for selecting immunogenic variants of malignant tumors and a better understanding of the relationship of the immune response to metastases.

Syngeneic humoral immune responses to tumor-associated antigens expressed by K-1735 UV-induced melanoma and its metastases

An enzyme-linked immunoassay (ELISA) was developed to study syngeneic humoral immune response to a primary tumor and its metastases in the K-1735 ultraviolet light (UV)-induced C3H murine melanoma system. Binding of sera from syngeneic animals previously immunized with primary tumor or metastatic tumor tissue (M-3, M-4) to corresponding 3 M KCl extracts of tumor was significantly greater than binding of control C3H mouse serum. Antibody binding was not significantly reduced by competitive binding with syngeneic murine muscle or liver extracts, indicating the presence of tumor antigen(s) not shared by normal murine tissue. Antibodies to the tumor-associated antigens were selectively removed by competitive binding with syngeneic K-1735 tumor extracts but not by the unrelated 102 murine sarcoma from C57BL/6. However, EL-4 extracts (C57BL/6) did inhibit antibody binding to the primary and both metastases. Further competitive binding studies demonstrated the presence of a common antigen(s) present on the primary tumor and both metastases. We conclude that the K-1735 UV-induced melanoma primary tumor and its metastases express serologically detectable shared antigenic determinate.

Different expression of Lyt differentiation antigens and cell surface glycoproteins by a murine T lymphoma line and its highly metastatic variant

Cloned lines of the methylcholanthrene-induced DBA/2 T lymphoma Eb and its highly metastatic variant line ESb were analyzed for differences in the expression of serologically detectable cell surface differentiation markers. Flow cytofluorographic analysis of cells stained with fluorescein isothiocyanate-conjugated monoclonal rate anti-mouse Thy-1, Lyt-1, Lyt-2 and complement-dependent cytotoxicity with mouse alloantisera against Lyt-3.2 and Ly-6.2 revealed, for the parental low metastasizing line, Eb, a phenotype of Thy-1+, Lyt-1-, Lyt-2+, Lyt-3+, Ly-6+, whereas the highly metastasizing variant line typed as Thy-1-, Lyt-1+, Lyt-2-, Lyt-3-, Ly-6-. Analysis of galactose oxidase/NaB3H4-labeled glycoproteins from Eb and ESb clones by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate showed further phenotypic differences. Selective binding of radiolabeled glycoproteins to Helix pomatia or Vicia villosa-Sepharose, respectively, allowed the identification of T130 to be expressed on Eb cells and T145 to be expressed on some ESb clones. The latter antigen is expressed on murine cytotoxic T lymphocytes. Immune precipitation analysis revealed that Eb and ESb bear different molecular forms of the T200 antigen. Comparisons of iodinated surface proteins derived from tumor cells either treated or untreated with tunicamycin indicated that many of the differences in membrane proteins between Eb and ESb cells could be attributed to differences in glycosylation. Our results, derived from a defined tumor system of lymphoid origin, show that the progression from a low to a high malignant tumor line can be associated with changes in the expression of various defined cell surface differentiation antigens. The question of a possible relationship between tumor progression and cell differentiation or dedifferentiation is discussed.