The relationship between 99m-Tc-MIBI uptakes and tumor cell death/proliferation state under Irradiation

Aim: Quick evaluation to therapeutic response of tumor tissue in cancer patients is a challenge in oncology nowadays. The present study was undertaken to evaluate the potential of 99Tcm-MIBI imaging to monitor the biological response of tumor cell cellular post-irradiation. Methods: 1. Isolated cell study: Ehrlich carcinoma cells were kept in culture for 48h after irradiation at a single dose of 0, 2, 10, 20Gy, respectively or kept in culture for 24, 48, 72h after irradiation at a single dose of 10Gy. 99Tcm-MIBI uptake, apoptosis index (AI) and plating efficiency (PE) were measured. 2. Animal study: Ehrlich carcinoma bearing model was established in 120 mice. The tumor tissues were irradiated at a single dose of 0, 5, 10, 15, 20Gy, respectively. The following protocols were undertaken at 6h pre-irradiation and at 24, 72, 144h post-irradiation respectively: 99Tcm-MIBI planar scintigraphy was performed and differential uptake ratio (DUR) and tumor-to-nontarget ratio (T/NT) were then calculated to represent the 99Tcm-MIBI uptake; the tumor tissue were taken to observe AI, percentage of necrosis area (PNA) and proliferating cell nuclear antigen integral absorbance (PCNA-IA) simultaneously. Results: 1. Isolated cell study showed that 99Tcm-MIBI uptake decreased with dose escalating and time prolonging. 99Tcm-MIBI uptake was inversely correlated with AI (r -0.91 n 20 P<0.01) and positively correlated with PE ( r 0.86 n 20 P<0.01) at 48h post-irradiation in each group. 2.In animal study DUR and T/NT decreased with dose escalating and time prolonging. At 24h post-irradiation, DUR or T/NT was inversely correlated with AI or PNA (r= -0.849, -0.829; -0.883, -0.855; respectively, n=33, P<0.01) and positively correlated with PCNA-IA (r=0.789, 0.742, respectively, n=33, P<0.01). At 72 and 144h post-irradiation, DUR or T/NT was only inversely correlated with PNA (r= -0.967, -0.956; -0.915, -0.886; respectively, n=33, P<0.01). Conclusion: 99Tcm-MIBI uptake of tumor cell correlated with the changes of cell viability after irradiation. Thus 99Tcm-MIBI imaging may be potentially helpful to monitor the biological response of tumor cell after radiotherapy, although further study remains to be carried out