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Evaluation of antineoplastic activities of SMS 201-995 and Ukrain on human colon cancer cell line, after monotherapy and combination with 5-fluorouracil

Although an early diagnosis and adjuvant chemotherapy have slightly increased the survival of colorectal cancer (CRC) patients, the response to treatment in advanced cases is still generally temporary. Moreover, the development of drug resistance and tumor "tolerance", related to the poor immunogenic nature of CRC, often contributes to disappointing outcome of the different clinical trials. AIMS: To investigate the antiproliferative and apoptotic potential of somatostatin analogue SMS 201-995 (SMS), and Ukrain (UK), in vitro on human CRC cell line. The drugs were tested as singe therapeutics or in the combination with the commonly used chemotherapeutic agent, 5-fluorouracil (5-FU). Methods: Human colorectal carcinoma cell line hCRC WiDr (ATCC, Rockville, USA) was cultured in RPMI with fetal calf serum during the 4 days. Upon the administration of 5-FU, SMS or UK in different concentrations and combinations, in cultures lasted 3, 6, 12, 24, 36, 48 and 72 hours the cell cycle analysis was made using a flow cytometer and CELLFIT Software package program. RESULTS: The data have shown that 5-FU in concentration of 0, 1m g/ml arrested the tumor cells in S phase of cell cycle (after 24h), decreasing at higher concentrations also the proportion of cells in G2+M. In addition, 5-FU stimulated apoptosis, increasing the percentage of subdiploid cells to 24% (after 24 h), and to 60% (after 72 h of cultivation). SMS in monotherapy decreased slightly the proportion of cells in G2+M, inducing also an early apoptosis (after 3 hours), which was not seen after treatment with 5-FU. Given in combination of 5-FU SMS, however, prolonged and potentiated the arresting effects of 5-FU on S phase, decreasing also the proportion of cells in G0/G1 and those in G2+M. Moreover, the combination of 5-FU and SMS, in some intervals, increased the intensity of apoptosis. In contrast to 5-FU and SMS, Ukrain in monotherapy, at the dose of 20 m g/ml arrested the cells in G2+M phase of cycle. The effect was initiated after 12h of cultivation and lasted until the 72h, with maximum at 24h and 36h, when approximately 60% were found in G2+M, compared to 10% of control cells. Ukrain stimulated also, on dose dependent manner, the apoptosis of cells, which started after 12h of cultivation, reaching a very high level after 72h (80%). However, the combination of Ukrain with 5-FU had not additive cell arresting potential, resulting in the predominance of the effect of 5-FU (at 24h), and then, when cells escaped from S-block induced by 5-FU, in greater effect of UK on G2+M phase. The later block, was, however, significantly lower, than that induced by Ukrain in monotherapy. Conclusion: The data point to different mechanisms of action of SMS, 5-FU and UK on cell cycle and apoptosis, suggesting that the proper timing and combination of these therapeutics might be important for successful therapy of human CRC.

octreotid; Chelidonium majus alkaloids; chemotherapy; human colon carcinoma line WiDr; cell-cycle analysis; apoptosis.

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