Inhibition of tumor implantation at sites of trauma by Arg-Gly-Asp containing proteins and peptides

The potential role of integrin receptor subunits in the formation of local recurrence and distant metastasis by mouse breast cancer cells

BACKGROUND

The mechanisms by which surgical injury fosters tumor growth are examined.

METHODS

TA3Ha mouse breast tumor line and its subline (TA3AD) differing in their metastatic abilities as tested by two models were used. In model a, TA3Ha/TA3AD tumors were grown in the mammary fat pads of mice and then surgically removed with a curative intent. In model b, TA3Ha/TA3AD cells were injected intravenously into mice subjected to liver or spleen wedge resection. Frequency of tumor formation at various sites was assessed. Expression of integrin, immunoglobulin, and proteoglycan cell adhesion receptors on TA3Ha and TA3AD cells was examined by flow cytometry. The roles of these receptors in metastasis were examined by blocking them by selected ligands and/or antibodies.

RESULTS

Frequencies of local recurrence and axillary metastasis after surgical resection, were 43% (32/74), and 37% (27/74) with TA3Ha tumors and 4% (1/29) at both sites with TA3AD tumors. Tumors at surgically injured spleen and the liver were seen in 75% (141/189) and 45% (107/240) of the mice with TA3Ha cells and in 8% (3/38) and 10% (4/42) of the mice with TA3AD cells. alpha 5 and CD44 receptors were expressed by TA3Ha cells but not by TA3AD cells. Other receptors examined were similarly expressed by both cell lines. Blocking of alpha 5 receptor by fibronectin reduced tumor implantation in a dose-dependent manner.

CONCLUSIONS

The data suggest a correlation among the ability to implant at surgically injured sites, to form local recurrence, and to express the fibronectin receptor subunit.

Treatment of immune cell-mediated liver damage by nonpeptidic mimetics of the extracellular matrix-associated Arg-Gly-Asp epitope

The etiology of T-cell-mediated liver injury involves the migration of immune cells, notably CD4+ T lymphocytes, into liver tissues. This process is mediated primarily by integrin-recognition of the sub-endothelium basement membranes and the extracellular matrix. The Arg-Gly-Asp-containing peptide, a major cell-adhesive ligand of extracellular matrix, is present in various plasma- and matrix-glycoproteins, such as fibronectin. Recently, we have described the design and usage of nonpeptide mimetics of Arg-Gly-Asp which bind specifically to integrins, and thereby, inhibit T cell immunity in vivo. We examined the efficacy of Arg-Gly-Asp-mimetics as potential therapeutic compounds for the treatment of experimental T-cell-mediated liver injury induced in mice by injection of Concanavalin-A. We now report that the Arg-Gly-Asp-mimetics specifically inhibited the binding of murine T cells to fibronectin, but did not affect the proliferative response of these cells in vitro. Intraperitoneal or oral administration of the Arg-Gly-Asp-mimetics but not the Arg-Gly-Asp-containing peptide, inhibited liver damage in mice if given before their inoculation with Con-A, as manifested by a lesser elevation in their serum levels of hepatic enzymes. The inhibitory effect of the Arg-Gly-Asp-mimetics was dose-dependent, the ED50 of the tested molecules being in the range of 100 micrograms per mouse and reaching maximal effect, e.g. approximately 95% inhibition, at 500 micrograms per mice. Thus, the Arg-Gly-Asp-mimetics described here may be used therapeutically to prevent immune-cell-mediated acute or chronic pathological reactions in the liver.

Growth and metastasis of human breast cancers in athymic nude mice

To evaluate critically the merit of utilizing a wound model for growing human tumors, a series of increasingly difficult human tumor types were tested for growth at sites of trauma in athymic nude mice. In vitro tumor lines as well as fresh tumors from the breast, colon, rectum, lung, and a metastasis from an unknown primary were intraperitoneally injected into mice subjected to intra-abdominal organ injury. Successful xenografts were obtained from nine of 10 cell lines and 14 of 24 fresh tumors. The latter included five of six (83%) colon cancers, one lung tumor, metastatic tumor of unknown primary, three of four (75%) metastatic breast cancers and four of six (67%) estrogen receptor (ER)-negative breast primary tumors. Six ER-positive breast tumors tested failed to grow in mice without estrogen supplementation. Xenografts from two breast, two colon and the lung cancers formed spontaneous metastases and all xenografts tested were able to yield serial transplants in the surgical wound model. Histologically, all xenografts and their metastases were identical to their respective donor tumors. Transplantability in mice without exogenous estrogen supplementation was linked to the absence of estrogen and progesterone receptors in breast tumors. Transplantability of the cell lines was associated with the expression of cell surface receptors for fibronectin and hyaluronic acid. Receptors for other extracellular matrix components, namely, laminin, vitronectin, collagen, fibrinogen or von Willebrand factor were not associated with transplantability. These results demonstrate that a large proportion of human tumors, including the breast tumors, can be successfully xenografted into athymic mice by providing them with a healing wound environment, and that such xenografts grown at ectopic sites exhibit metastatic ability.

Effect of trauma on implantation of metastatic tumor in bone in mice

We studied the influence of surgical trauma to the iliac bone on the implantation of I.V. injected tumor cells, which formed tumor in the surgical wounds of 27/84 mice (32%). None of these mice or nonsurgical mice developed tumor in the opposite or uninjured pelvic bone (P < 0.0001). When different numbers (10(5), 5 x 10(5), and 10 x 10(5)) of TA3Ha cells were injected I.V. immediately after surgery, the frequency of tumor formation showed an increase (respectively, 32%, 63%, 71%). As the interval between induction of trauma and tumor cell injection was increased from 0 to 15 days, the frequency of tumor formation declined from 32% to 0%. These results suggest that the healing wound is a privileged site for experimental metastasis, particularly in the early stages. It is likely that the proteins in the blood clotting cascade are involved in local tumor implantation.

Adhesion molecules and their role in cancer metastasis

This article describes various adhesion molecules and reviews evidence to support a mechanistic role for adhesion molecules in the process of cancer metastasis. A variety of evidence supports the involvement of specific adhesion molecules in metastasis. 1. For example, some cancer cells metastasize to specific organs, irrespective of the first organ encountered by the circulating cancer cells. This ability to colonize a specific organ has been correlated with the preferential adhesion of the cancer cells to endothelial cells derived from the target organ. This suggests that cancer cell/endothelial cell adhesion is involved in cancer cell metastasis and that adhesion molecules are expressed on the endothelium in an organ-specific manner. 2. Further, inclusion of peptides that inhibit cell adhesion, such as the YIGSR- or RGD-containing peptides, is capable of inhibiting experimental metastasis. 3. Metastasis can be enhanced by acute or chronic inflammation of target vessels, or by treatment of animals with inflammatory cytokines, such as interleukin-1. In vitro, cancer cell/endothelial cell adhesion can be enhanced by pretreating the endothelial cell monolayer with cytokines, such as interleukin-1 or tumor necrosis factor-alpha. This suggests that, in addition to organ-specific adhesion molecules, a population of inducible endothelial adhesion molecules is involved and is relevant to metastasis. 4. Further support for this model is found in the comparison to leukocyte/endothelial adhesion during leukocyte trafficking. Convincing evidence exists, both in vivo and in vitro, to demonstrate an absolute requirement for leukocyte/endothelial adhesion before leukocyte extravasation can occur. The relevance of this comparison to metastasis is reinforced by the observation that some of the adhesion molecules involved in leukocyte/endothelial adhesion are also implicated in cancer cell/endothelial adhesion. The involvement of adhesion molecules suggests a potential therapy for metastasis based on interrupting adhesive interactions that would augment other treatments for primary tumors.

The role of fibronectin in tumor implantation at surgical sites

Fibronectins are a family of glycoproteins with modular functional domains. They mediate cell-cell and cell-matrix interactions which are important in embryogenesis, wound healing, metastasis and other processes. We present data on the influence of fibronectin on wound implantation of a murine mammary carcinoma line, TA3Ha. Fibronectin used in these studies was derived from bovine plasma, human serum, human foreskin fibroblasts, and mouse embryo cultures. TA3Ha cells rarely form tumors in the liver of syngeneic mice when injected intravenously but after hepatic wedge resection, 45% (107/240) of the mice develop tumors in the hepatic wound. Wound implantation is markedly reduced when the cells are pre-exposed to 200 micrograms/ml bovine plasma fibronectin (13%, P = 0.007), human serum fibronectin (0%, P = 0.02), human cellular fibronectin (0%, P = 0.02), or mouse cellular fibronectin (0%, P = 0.04). Lung colonization is also reduced by these fibronectins. These effects are not due to a cytotoxic action of fibronectin, since intraperitoneally injected fibronectin-treated cells form ascites tumor as effectively as do control untreated cells. Local application of a solution containing 0.25 mg/ml mouse cellular fibronectin to the hepatic wound reduces the frequency of tumor implantation from 45% to 5% (1/21, P = 0.001). No tumor implantation inhibition is seen when only suspending medium or albumin in suspending medium is used. The mechanism by which topical application of fibronectin reduces hepatic wound implantation of tumor cells is unclear, but this finding raises an exciting possibility of preventing local recurrence of cancer.