Tumor-elicited polymorphonuclear cells, in contrast to "normal" circulating polymorphonuclear cells, stimulate invasive and metastatic potentials of rat mammary adenocarcinoma cells.

Abstract

Circulating polymorphonuclear cell (PMN) levels rise in proportion to the metastatic potential of the tumor in 13762NF mammary adenocarcinoma tumor-bearing rats. These tumor-elicited PMNs (tcPMNs) secrete high levels of the basement-membrane-degrading enzymes, type IV collagenase and heparanase, suggesting that metastatic tumor cells stimulate neutrophilia so that the tcPMNs might assist tumor cell extravasation during metastasis. To test this hypothesis, purified proteose peptone-elicited PMNs from peritoneal exudate, circulating normal PMNs, and tcPMNs were evaluated for their effects on in vitro invasive and in vivo metastatic potentials of syngeneic 13762NF mammary adenocarcinoma tumor cells. tcPMNs caused a dose-dependent increase in invasion through a reconstituted basement membrane barrier in an in vitro invasion assay. At PMN:tumor cell ratios of 30:1, invasion potential significantly (P < 0.05) rose to 26-fold, 40-fold, and 37-fold for poorly metastatic MTLn2 cells, higly metastatic MTLn3 cells, and moderately metastatic MTF7 cells, respectively. In contrast, purified proteose peptone-elicited PMNs and circulating normal PMNs did not sgificantly alter invasive potential. Intravenous coij'ections of purified proteose peptone-elicited PMNs did not change the number of experimental lung metastases, but tcPMNs at ratios to 50:1 significantly raised the mean number of metasass 23-fold for MTLn2, 3-to 4-fold for MTLn3, and 1.6-to 1.8-fold for MTF7. These results demonstrate that tcPMNs contribute to the metastatic propensity of mammary adeocarcinoma clones by increasing efficiency of invasion through basement membrane. Although polymorphonuclear cells (PMNs) are not the predominant circulating leukocyte population in normal rats, PMNs are the predominant population in humans. Neutrophils have been seen in close association with metastatic human and animal tumor cells in vivo at the primary tumor (10) and within the vasculature (17). The observation that the level of circulating PMNs increases to 50-fold as the primary tumor proliferates and the observation that tumor-elicited PMNs (tcPMNs) secrete high levels of type IV collagenase and heparanase and are noncytotoxic and noncytostatic (9), combine to suggest that tcPMNs may enhance the ability of tumor cells to extravasate, hence to metastasize.The results presented here demonstrate that tcPMNs, but not normal circulating PMNs (cPMNs), augment the ability of a tumor cell to penetrate a basement membrane-like matrix in vitro and to form lung colonies in vivo.MATERIALS AND METHODS Animals. Cell Lines and Tissue Culture. 13762NF rat mammary adenocarcinoma clones MTLn2, MTLn3, and MTF7 were grown and maintained as described (10, 18). Briefly, cells were grown in a-modified minimum essential medium (aMEM) supplemented with 5% fetal bovine serum. Cells were subcultured when the plates became 70-80% confluent by using 0.25% trypsin solution.Isolation and Purification of PMN. Purified proteose peptone-elicited PMNs (ppPMNs) were obtained by injecting syngen...

The Multifaceted Roles Neutrophils Play in the Tumor Microenvironment

“…co-injections of tumor-elicited neutrophils caused a dose-dependent increase in extrapulmonary metastases that was associated with increased production of heparanase and type IV collagenolytic enzymes by the neutrophils [164]. In contrast to tumor-elicited neutrophils, normal or proteose peptone-elicited neutrophils did not alter the invasive potential [166].…”

Neutrophils in cancer: neutral no more

“…Neutrophils actively participate in different steps of the metastatic cascade: cancer cell escape from the primary tumor, intravasation into the blood and/or the lymphatic vascular system, survival in circulation, extravasation into distant organs and outgrowth of metastases (Figure 4). As early as the late 1980s -before the importance of neutrophils in primary tumor growth was established 117-119 -co-injection of cancer cells and neutrophils from tumor-bearing rodents intravenously was shown to increase experimental lung metastases 141,142 . Although these studies substantiated the pro-metastatic ability of neutrophils, this research area is surrounded by controversy, as opposing roles for neutrophils exist in the literature and often within the same model system.…”

It is possible that tumour-infiltrating granulocytes promote tumour progression

“…Granulocyte effects on tumour cells represent opposite sides of a double-edged sword (6). In some experimental tumours, granulocytes are cytolytic and can eliminate tumour cell populations (7), whereas in others, granulocytes contribute to the invasive potential (6,8) and induce tumour growth by direct promotion of vessel generation under both physiological (wound healing) and pathological (cancer, psoriasis) conditions (9-13). Therefore, the presence of tumour-infiltrating granulocytes (TIGs) might be indicative for a better or worse host antitumoural response.…”