Prothymosin alpha1 effects on IL-2-induced expression of LFA-1 on lymphocytes and their adhesion to human umbilical vein endothelial cells.

Prothymosin alpha1 (Pro alpha1) is known to stimulate in vitro and in vivo natural killer (NK) and lymphokine (IL-2)-activated killer (LAK) cells against tumor cells. In this process, LAK cells first adhere to endothelial cells in vivo, raising the question whether Pro alpha1 affects this interaction as well. The binding ability of peripheral blood lymphocytes (PBL) to human umbilical vein endothelial cells (HUVEC) was increased by incubation with IL-2 in a concentration-dependent manner, reaching a maximal value at 20U/ml IL-2. Although Pro alpha1 alone was without any stimulating effect, it significantly increased PBL binding to unstimulated HUVECs in combination with suboptimal IL-2 (5 and 10 U/ml). The combination of Pro alpha1 (1 microg/ml) and 5 U/ml or 10 U/ml IL-2 is as effective as 10 U/ml or 20 U/ml IL-2 alone. This Pro alpha1 effect on IL-2-activated lymphocytes was found to be augmented on IL-1 or tumor necrosis factor (TNF)-alpha-activated endothelial cells. Analyzing the effect of Pro alpha1 on IL-2-activated lymphocytes by flow cytometry revealed an increase of CD16, CD56, and CD18 surface marker expression, whereas CD3, CD11a/b, CD49d, and CD54 were not affected. In conclusion, Pro alpha1 functions as a mediator of the adhesion of IL-2-activated lymphocytes to HUVECs.

Interleukin-2-activated killer cell activity in colorectal tumor patients: evaluation of in vitro effects by prothymosin alpha1.

The effects of prothymosin alpha1 (Pro alpha1) in combination with interleukin-2 (IL-2) on peripheral blood lymphocytes from 50 colorectal tumor patients at different stages were studied with respect to immunocytotoxicity, adhesion to cultured SW620 colon carcinoma cells, secretion of cytokines and expression of adhesion and surface marker molecules. On average, the patients showed lower natural killer (NK) cell activity than healthy donors, which was associated with a lower adhesion capacity to the tumor target cells. The NK cell activity of the patients was inversely related to the tumor stage. The generation of lymphokine(IL-2)-activated killer (LAK) cell activity was found to be comparable on lymphocytes from healthy individuals and patients and was not correlated to tumor stage. Pro alpha1 stimulated patients' LAK cell activity only, primarily at the early stage (Dukes A/B). The Pro alpha1 effect was associated with an increased adhesion of lymphocytes to tumor target cells and an increased secretion of the deficient IL-2-induced IFN gamma secretion. No significant effects on the low level of TNF alpha secretion was noted. By flow cytometry, Pro alpha1 in combination with IL-2 augmented the expression of the NK cell markers CD56, CD16/56, the subset CD3/16/56 and CD25 on lymphocytes of the patients. In contrast, Pro alpha1 was equally effective by increasing the expression of CD18 and CD11a on lymphocytes from the patients and from normal controls. In conclusion, Pro alpha1, in combination with IL-2, can partially normalize lymphocyte deficiencies of colon cancer patients in vitro. This potential might provide an experimental basis for applying Pro alpha1 or related thymic peptides in selected immunotherapies against colorectal tumors.

Prothymosin alpha 1 effects, in vitro, on the antitumor activity and cytokine production of blood monocytes from colorectal tumor patients.

Recent animal studies demonstrate that prothymosin alpha 1 (ProT alpha) enhances the antitumor response by stimulation of mononuclear phagocyte functions. The present study was aimed at characterizing the in vitro effects by ProT alpha on blood monocytes from human colon cancer patients. Purified peripheral blood monocytes were studied in terms of tumor cytostatic ability and cytokine production after incubation with ProT alpha or interferon (rIFN-gamma) and transforming growth factor-beta (TGF beta), used as reference substances. SW620 colon carcinoma cells were used as tumor target cells in growth inhibition experiments. The level of baseline growth inhibitory activity of unstimulated patient's monocytes was significantly lower than that of normal monocytes. The defective antitumor activity of patient monocytes was associated with a higher production of the inhibitory monokines prostaglandin E2 (PGE2) and TGF beta. The stimulation of monocytes by ProT alpha and/or rIFN-gamma elevated the average antitumor activity in all donor groups. The ProT alpha-induced increase was associated with a significantly higher monocytic secretion of IL-1 beta and TNF-alpha. Moreover, the concentrations of TGF beta and PGE2 in the culture supernatants decreased significantly, when patient's monocytes were treated with ProT alpha and/or rIFN-gamma. Additionally, ProT alpha enhanced the diminished antitumor activity of TGF beta-treated normal monocytes. These results suggest that ProT alpha selectively regulates distinct functions of blood monocytes, the effect of this cytokine varying with the parameter and donor population examined. These data provide a rational and biological endpoint for further studies with ProT alpha as an activator of mononuclear function in colon cancer.