Usefulness of Daily Fractionated Administration of Wortmannin Combined With gamma-Ray Irradiation in Terms of Local Tumor Response and Lung Metastasis

Abstract

Background: To evaluate the usefulness of fractionated administration of wortmannin combined with gamma-ray irradiation in terms of local tumor response and lung metastatic potential, referring to the response of intratumor quiescent (Q) cells. Methods: B16-BL6 melanoma tumor-bearing C57BL / 6 mice were continuously given 5-bromo-2 ' -deoxyuridine (BrdU) to label all proliferating (P) cells. The tumor-bearing mice then received gamma -ray irradiation after wortmannin treatment through a single or 4 consecutive daily intraperitoneal administrations up to a total dose of 4 mg / kg in combination with an acute hypoxia-releasing agent (nicotinamide) or mild temperature hyperthermia (MTH). Immediately after the irradiation, cells from some tumors were isolated and incubated with a cytokinesis blocker. The responses of the Q and total ( = P + Q) cell populations were assessed based on the frequency of micronuclei using immunofluorescence staining for BrdU. In other tumor-bearing mice, 17 days after irradiation, macroscopic lung metastases were enumerated. Results: Wortmannin raised the sensitivity of Q cells more remarkably than the total cell population in both single and daily administrations. Daily administration of wortmannin elevated the sensitivity of both the total and Q cell populations, but especially the total cell population, compared with single administration. Daily administration, especially combined with MTH, decreased the number of lung metastases. Conclusion: Daily fractionated administration of wortmannin in combination with gamma -ray irradiation was thought to be more promising than single administration because of its potential to enhance local tumor response and repress lung metastatic potential. World J Oncol. 2013;4(1):26-36 doi: https://doi.org/10.4021/wjon640w