Temporo-spatial cell-cycle kinetics in HeLa cells irradiated by Ir-192 high dose-rate remote afterloading system (HDR-RALS).

BACKGROUND: Intracavitary irradiation plays a pivotal role in definitive radiotherapy for cervical cancer, and the Ir-192 high dose-rate remote afterloading system (HDR-RALS) is often used for this purpose. Under this condition, tumor tissues receive remarkably different absorption doses, with a steep gradient, depending on distance from the radiation source. To obtain temporo-spatial information regarding cell-cycle kinetics in cervical cancer following irradiation by Ir-192 HDR-RALS, we examined HeLa cells expressing the fluorescence ubiquitination-based cell cycle indicator (Fucci), which allowed us to visualize cell-cycle progression. METHODS: HeLa-Fucci cells, which emit red and green fluorescence in G1 and S/G2/M phases, respectively, were grown on 35-mm dishes and irradiated by Ir-192 HDR-RALS under normoxic and hypoxic conditions. A 6 French (Fr) catheter was used as an applicator. A radiation dose of 6 Gy was prescribed at hypothetical treatment point A, located 20 mm from the radiation source. Changes in Fucci fluorescence after irradiation were visualized for cells from 5 to 20 mm from the Ir-192 source. Several indices, including first green phase duration after irradiation (FGPD), were measured by analysis of time-lapse images. RESULTS: Cells located 5 to 20 mm from the Ir-192 source became green, reflecting arrest in G2, in a similar manner up to 12 h after irradiation; at more distant positions, however, cells were gradually released from the G2 arrest and became red. This could be explained by the observation that the FGPD was longer for cells closer to the radiation source. Detailed observation revealed that FGPD was significantly longer in cells irradiated in the green phase than in the red phase at positions closer to the Ir-192 source. Unexpectedly, the FGPD was significantly longer after irradiation under hypoxia than normoxia, due in large part to the elongation of FGPD in cells irradiated in the red phase. CONCLUSION: Using HeLa-Fucci cells, we obtained the first temporo-spatial information about cell-cycle kinetics following irradiation by Ir-192 HDR-RALS. Our findings suggest that the potentially surviving hypoxic cells, especially those arising from positions around point A, exhibit different cell-cycle kinetics from normoxic cells destined to be eradicated.

A case of extramedullary plasmablastic plasmacytoma successfully treated using a combination of thalidomide and dexamethasone and a review of the medical literature.

A 56-year-old man developed epistaxis, hoarseness, and swelling of a finger in March 2010. On the basis of biopsies of the masses in the pharynx and finger, he was diagnosed with extramedullary plasmablastic plasmacytoma, with somewhat immature CD45(+), MPC-1(-), and CD49e(-). CHOP (cyclophosphamide, doxorubicin, vincristine, and prednisolone) and VCAP (vincristine, cyclophosphamide, doxorubicin, and prednisolone) therapy was ineffective, but combination therapy with thalidomide and dexamethasone was highly effective. Thalidomide monotherapy successfully maintained partial remission for approximately 7 months. A mass appeared in the right neck in February 2011, and a biopsy confirmed recurrence. Changes to CD45 negativity and MPC-1 partial positivity were seen, while CD49e negativity persisted, suggesting that the plasmablastic plasmacytoma had reverted to a more immature state. Bortezomib therapy was started in March 2011 and was effective. However, during the second round of treatment, the patient developed acute lung injury, which was improved by steroid pulse therapy. After the discontinuation of bortezomib, the extramedullary mass increased rapidly, and the patient died of multiple organ failure. An autopsy showed that plasmablastic plasmacytomas had infiltrated into multiple organs. Extramedullary plasmacytomas and those that revert to an immature state are associated with a poor prognosis, so further treatment improvements are needed in the future.