Combining radiation with hyperthermia: a multiscale model informed by in vitro experiments

Combined radiotherapy and hyperthermia offer great potential for the successful treatment of radio-resistant tumours through thermo-radiosensitization. Tumour response heterogeneity, due to intrinsic, or micro-environmentally induced factors, may greatly influence treatment outcome, but is difficult to account for using traditional treatment planning approaches. Systems oncology simulation, using mathematical models designed to predict tumour growth and treatment response, provides a powerful tool for analysis and optimization of combined treatments. We present a framework that simulates such combination treatments on a cellular level. This multiscale hybrid cellular automaton simulates large cell populations (up to 107 cells) in vitro, while allowing individual cell-cycle progression, and treatment response by modelling radiation-induced mitotic cell death, and immediate cell kill in response to heating. Based on a calibration using a number of experimental growth, cell cycle and survival datasets for HCT116 cells, model predictions agreed well (R2 > 0.95) with experimental data within the range of (thermal and radiation) doses tested (0-40 CEM43, 0-5 Gy). The proposed framework offers flexibility for modelling multimodality treatment combinations in different scenarios. It may therefore provide an important step towards the modelling of personalized therapies using a virtual patient tumour.

Global spatiotemporal order and induced stochastic resonance due to a locally applied signal

We study the phenomenon of spatiotemporal stochastic resonance (STSR) in a chain of diffusively coupled bistable oscillators. In particular, we examine the situation in which the global STSR response is controlled by a locally applied signal and reveal a wave-front propagation. In order to deepen the understanding of the system dynamics, we introduce, on the time scale of STSR, the study of the effective statistical renormalization of a generic lattice system. Using this technique we provide a criterion for STSR, and predict and observe numerically a bifurcationlike behavior that reflects the difference between the most probable value of the local quasiequilibrium density and its mean value. Our results, tested with a chain of nonlinear oscillators, appear to possess some universal qualities and may stimulate a deeper search for more generic phenomena.

Expression of differentiated functions in hepatoma cell hybrids: reappearance of tyrosine aminotransferase inducibility after the loss of chromosomes

HYBRIDS FROM A CROSS OF RAT HEPATOMA CELLS WITH DIPLOID EPITHELIAL CELLS FROM RAT LIVER HAVE BEEN STUDIED WITH RESPECT TO KARYOTYPE AND EXPRESSION OF TWO FUNCTIONS LIMITED TO THE HEPATOMA PARENT: high level of the enzyme tyrosine aminotransferase (EC 2.6.1.5; L-tyrosine:2-oxoglutarate aminotransferase) and its inducibility with steroid hormones. The hybrids that contain the complete chromosomal complements from both parents show low enzyme activity and no inducibility. One hybrid clone, and all of its derivatives, which have lost 30-40% of the chromosomes initially present, show enzyme inducibility. Induction of tyrosine aminotransferase in the hepatoma and hybrid cells responds similarly to inhibition by cycloheximide and actinomycin D, and to steroid concentration. The enzymes from induced and noninduced hepatoma cells and from induced hybrid cells are similar in heat sensitivity and intracellular distribution; those from noninduced hybrid and diploid rat epithelial cells are different.