Activation of natural resistance against lung metastasis of an adenocarcinoma in T-cell depressed spontaneously hypertensive rats by infection with Listeria monocytogenes

Enhanced effect of epidermal growth factor on pulmonary metastasis and in vitro invasion of rat mammary carcinoma cells

We examined the effects of epidermal growth factor (EGF) on metastatic and in vitro invasive capacity of weakly malignant ER-1 cells derived from a rat mammary carcinoma cell line, c-SST-2. EGF enhanced the metastatic capacity and in vitro invasiveness to reconstituted basement membrane, Matrigel, of ER-1 cells in a dose-dependent fashion. EGF-stimulated invasiveness was inhibited by anti-EGF antibody, which is able to neutralize the binding of EGF to EGF receptor, in the invasion assay system. EGF stimulated chemotactic migration toward fibronectin, laminin or newborn rat fibroblast-conditioned medium which was used as a chemoattractant in the in vitro invasion assay, but showed neither adhesion to Matrigel nor production of gelatinase and plasminogen activators. These results suggested that the increased metastatic and invasive capacity of ER-1 cells by EGF might be due to the increase in cell motility.

Inhibition of pulmonary metastases and tumor cell invasion in experimental tumors by sodium D-glucaro-delta-lactam (ND2001)

Sodium D-glucaro-delta-lactam (ND2001) inhibited spontaneous pulmonary metastases of the highly metastatic B16 melanoma variant with a maximal inhibition rate of 99.5%, and 6 of 7 animals remained metastasis-free. Likewise, ND2001 inhibited the spontaneous pulmonary metastases of both Lewis lung carcinoma (3LL) with a rate of 98.0% (3 of 5 animals remaining metastasis-free) and rat KDH-8 liver carcinoma with a rate of 82.5% (3 of 7 animals remaining metastasis-free), although it was unable to inhibit the metastases of mouse BMT-11 fibrosarcoma and rat SST-2 breast carcinoma. Pretreatment with ND2001 in vitro inhibited the pulmonary metastases of the B16 variant and 3LL cells, which indicates direct action upon the cancer cells. When the invasive activity of cancer cells was measured by the Boyden chamber method, the number of invading B16 variant or 3LL cells was reduced with maximal inhibition rates of 93.0% or 89.9%, respectively, but pretreatment with ND2001 failed to reduce the invasive activity of BMT-11 or SST-2 cells. ND2001 showed neither cytocidal nor antitumor activity. These results suggest that ND2001 inhibited pulmonary metastases at the invasive step into the basement membrane by directly changing some property of the tumor cells.

Establishment of highly metastatic tumor clones derived from a skin squamous cell carcinoma (SqC-NH), D-1 and F-3, with distinct features of pulmonary metastases

We have established two highly metastatic tumor clones, D-1 and F-3, which have the distinct features of undergoing pulmonary metastases. Both clones were derived from a skin squamous cell carcinoma (SqC-NH), which had spontaneously occurred in DS-Nh mice. F-3 was morphologically spindle-shaped in tumor mass and adherent in culture, while D-1 was round and non-adherent. In in vitro growth, there was no significant difference between them. When the clonal tumor cells were implanted intradermally into syngeneic mice, however, the growth of D-1 was slower than that of F-3. As for the metastatic ability, both D-1 and F-3 were highly metastatic compared with the original tumor. Interestingly, the pulmonary metastases of these two clones were apparently different. In F-3-bearing mice, some round nodules were detected and no tumor cells were seen in the surrounding area around the nodules (nodule-type). In contrast, D-1 cells had initially grown from the periphery of lobes, and interstitially infiltrated the lung parenchyma area without forming nodules (diffuse-type) and the appearance was similar to lymphagitis carcinomatosa. Histologically, a remarkably smaller number of metastatic foci formed around the blood vessel for D-1 as compared with F-3. It should also be noted that some localized nodules (nodule-type both visually and histologically) were seen in the lung, when D-1 cells were inoculated in the tail vein. In addition, D-1 showed markedly higher lymphatic metastasis than F-3. These observations show that the pulmonary metastases of D-1 and F-3 differ in the mechanisms underlying the processes of tumor dissemination. We suppose a possibility that D-1 may preferentially metastasize via the lymphatics and F-3 may metastasize via the bloodstream.

Age-related decrease of pulmonary metastasis of rat mammary carcinoma by activated natural resistance

We found that the number of pulmonary metastatic foci of spontaneously developed rat mammary carcinoma (SST-2), when transplanted subcutaneously in spontaneously hypertensive (SH) rats, decreased with aging. In the SST-2-bearing SH rats, it was observed that T cell functions progressively declined while activities of macrophages and natural killer cells were non-specifically activated by increasing age. To examine the mechanisms of the age-related decrease of pulmonary metastasis in SH rats, we treated the SST-2-bearing rats with anti-(asialo-GM1) antibody and/or carrageenan, which are known to suppress the functions of macrophages and natural killer cells, or with poly(I).poly(C), which is a stimulator to natural killer cells. The anti-(asialo-GM1) treatment significantly increased the number of pulmonary metastatic foci in both young and old SH rats, while poly(I).poly(C) significantly decreased the lung nodules in the old SH rats. These result suggest that the decrease of pulmonary metastasis in the SH rats with aging may be closely correlated with non-specifically activated natural killer cells and macrophages, though it should be also considered that non-immunological tumor-host interactions may be involved in the differences between the young and the old SH rats.