One hypothesis for the difficulty in curing tumors is the differential sensitivity to various therapies of dividing or proliferating (P) and nondividing or quiescent (Q) cells. The overall objective of this grant is to determine the differential response of tumor P and Q cells to heat treatment both in vitro and in vivo. The experiments will be performed on a heterogeneous tumor system composed of two mouse mammary tumor cell lines, 66 and 67, that can be grown both in vitro and in vivo (as solid tumors). Pure populations of both P and Q cells can be easily obtained in vitro with either 66 or 67 cells, thus allowing clear delineation of the role of a cell's proliferative status in determining its response to heat. Relatively homogeneous populations of P and Q cells from 66 or 67 tumors isolated by centrifugal elutriation will also be evaluated for their response to heat in vivo where factors (e.g. pH and glucose concentration) other than proliferative status influence a cells' sensitivity. The sensitivity of these cells to heat treated either in vitro or in vivo will be measured with a clonogenic cell assay (for cell survival) or with flow cytometric techniques (for recruitment of Q cells into the P compartment). The in vivo response of the tumor cells will also be evaluated using assays of tumor cure and growth delay. The work proposed in this grant will include: 1) the determination of the relative heat sensitivity (cell kill, expression of thermotolerance, and recruitment) of P and Q cells. 2) the identification of factors (e.g. pH, glucose, and the addition of proteins to the nucleus) which may effect this sensitivity. 3) the measurement of the in vivo tumor response, and 4) the correlation of the in vivo and in vitro data on P and Q cells. These experiments will identify under what conditions Q cells may be a determinant of tumor response after heat treatment. Futhermore, they will elucidate under what conditions heat may be successfully combined with other therapies to eradicate tumors. Studying the responses of Q cells to hyperthermia both in vitro and in vivo should provide a valuable correlation between biological responses under controlled conditions and the simulated clinical responses of tumors.
