Prostaglandins and metastasis

The inhibitory effect of 4-hydroxyphenyl retinamide (4-HPR) on metastasis of prostate adenocarcinoma-III cells in Lobund-Wistar rats

Tumor cells of transplanted prostate adenocarcinoma-III (PA-III) spread with very high frequency from the extravascular implant site through ipsilateral lymphatic channels to the lungs in which they produce visible focal tumors. The latter enlarge, coalesce and eventually kill the host. This system was used to demonstrate the effect of a retinoid on metastasis. Lobund-Wistar (L-W) rats were administered 1 mmol 4-HPR/kg diet L-485, and control rats received the same diet without 4-HPR. After an interval, all rats were inoculated subcutaneously with PA-III cells. When examined at autopsy, all rats had developed an anticipated tumor at the implant site. However, the numbers of focal PA-III tumors in the lungs were significantly reduced among the 4-HPR-treated rats compared to the control rats (P = 0.002).

Differential role of prostaglandin E1 on tumor metastasis

Previous studies from our laboratory have shown that intravenous (iv) infusion of pharmacologic doses of prostaglandin E1 (PGE1) inhibits "spontaneous" metastases in mice bearing Lewis Lung carcinoma (LLC). This study was done to determine the effect of iv PGE1 on "artificial" metastases. Male hybrid mice (20 g) underwent iv catheterization and were begun on continuous infusions of either PGE1 at 10 micrograms/kg/min or 0.9% NaCl (NS). After 2 days, each mouse received an iv injection of 10(5) viable LLC cells and was continued on the infusion regimens. Pulmonary metastatic nodules were enumerated and measured 12 days after injection. The iv infusion of PGE1 increased the metastatic rate 6-fold, the number of metastases greater than or equal to 2 mm in diameter 7-fold, and the number of metastases greater than or equal to 3 mm in diameter 14-fold. Thus, PGE1 demonstrates differential effects on tumor metastases, acting as a promotor of artificial metastases, in contrast to its antimetastatic effect on an intact primary tumor. When the promotional effect of iv PGE1 on artificial metastases is evaluated in light of our previous studies, it can be concluded that the inhibitory effect of PGE1 on spontaneous metastases from an intact tumor is secondary to the effect of PGE1 at the level of the primary tumor, and not in the circulation or at the target organ of metastases (lung).

Adherent spleen cell production of E series prostaglandins in rats bearing variants of the R3327 Dunning prostatic adenocarcinoma: effect of cyclophosphamide

Prostaglandins of the E series (PGE) have been implicated in many facets of immunoregulation, as well as having a possible role in metastatic dissemination. Variant sublines of the Dunning R3327 rat prostatic adenocarcinoma, differing in growth rate, hormonal responsiveness and in propensity for metastasis, were carried in Fisher X Copenhagen F1 animals. Adherent spleen cells were assayed in vitro for their ability to convert arachidonic acid to prostaglandins of the E series. These glass adherent cells presumably include the monocytic and T cell populations which have been implicated as being immunoregulatory. The results indicated that those spleen cells obtained from animals carrying the metastatic R3327-MAT-LyLu subline tumor converted more arachidonic acid to PGE's than cells derived from animals bearing non-metastatic sublines. Cyclophosphamide therapy did not alter such conversion. Multiple regulatory mechanisms for prostaglandin metabolism are suggested.

Elevation of serum prostaglandin E levels following electrical stimulation of the midbrain

Serum prostaglandin E (PGE) levels were measured in rats immediately following electrical stimulation of the mesencephalic periaqueductal gray (PAG) region and the nucleus raphe magnus (NRM) and compared to controls. An additional group received aspirin prior to PAG stimulation. A significant increase in serum PGE levels was found after stimulation of the PAG, but not the NRM. Aspirin inhibited the stimulation-induced increases in PGE.

Review: prostaglandins and cancer

This paper reviews work on the role of prostaglandins in cancer. A substantial body of evidence demonstrates elevated amounts of E series of prostaglandins in human and experimental tumors. Blockade of prostaglandin synthesis in vitro or in vivo results in inhibition of tumor growth. Involvement of prostaglandins is implicated in the actions of tumor promoters like phorbol and polycyclic aromatic hydrocarbon carcinogens. Symptoms like hypercalcemia, osteolysis and tumor metastasis are discussed where disordered synthesis and/or action of prostaglandins and related substances might have a role in the altered metabolism associated with neoplasia.

Prostaglandin E2 and cyclic AMP levels in human breast tumors

Prostaglandin E2 (PGE2) and cyclic adenosine-3', 5'-monophosphate (cAMP) concentrations were measured in human benign and malignant breast tumors by radioimmunoassay. Two groups were found among the malignant tissues, one with high PGE2 (M = 65.89 pg/mg) and high cAMP (M = 0.704 pmole/mg) concentrations and one with low concentrations (M = 9.24 pg/mg and M = 0.299 pmole/mg, respectively). The low PGE2 levels in the malignant tumors did not differ significantly from the levels found in benign tumors (M = 8.06 pg/mg). cAMP levels were positively and highly correlated (r = +0.81) with PGE2 levels. No bone osteolysis could be discovered in any of the patients a few weeks after mastectomy operation, but PGE2 analysis of breast tumors may have prognostic value for the future.