adenosine-5--o-(3-thiotriphosphate) and Colorectal-Neoplasms

Primary cell cultures of human colorectal carcinomas were established and characterized immunocytochemically. In the isolated cancer cells intracellular Ca2+ concentrations ([Ca2+]i) were measured by the fura-2 method. Stimulation with either extracellular ATP or UTP caused a biphasic rise of [Ca2+]i in a dose-dependent manner and cross-desensitization between both nucleotides was observed. The rank order of potency was ATP >== UTP > ATP-gamma-S > ADP > adenosine which is characteristic for a P2U-receptor subtype. Selective agonists of P1-, or P2X- purinoceptors had no effect on [Ca2+]i. The initial rise in [Ca2+]i was independent of extracellular calcium [Ca2+]e, whereas the second phase was not observed under [Ca2+]e-free conditions suggesting a capacitative Ca2+-entry-mechanism. Intracellular Ca2+ mobilization was proven by use of the Ca2+-ATPase inhibitor thapsigargin. P2U-specific mRNA could be detected by RT-PCR in both colorectal tumor tissues and in the human colorectal cancer cell line HT 29. In HT 29 cells, the hydrolysis-resistant ATP analog ATP-gamma-S inhibited cell proliferation and, also, induced apoptosis in a dose-dependent manner. Thus, human colorectal cancer cells express functional P2U-receptors which may play a role in the regulation of cell proliferation and apoptosis.

Topics: Adenosine Triphosphate; Aged; Apoptosis; Calcium; Carcinoma; Cell Division; Colorectal Neoplasms; Dose-Response Relationship, Drug; Female; HT29 Cells; Humans; Male; Polymerase Chain Reaction; Purinergic P1 Receptor Agonists; Purinergic P2 Receptor Agonists; Receptors, Purinergic P2; Receptors, Purinergic P2Y2; RNA, Messenger; Tumor Cells, Cultured; Uridine Triphosphate