Using HSV-thymidine kinase for safety in an allogeneic salivary graft cellline

Extreme salivary hypofunction is a result of tissue damage caused by irradi ation therapy for cancer in the head and neck region. Unfortunately, there is no currently satisfactory treatment for this condition that affects up t o 40,000 people in the United States every year. As a novel approach to man aging this problem, we are attempting to develop an orally implantable, flu id-secreting device (an artificial salivary gland). We are using the well-s tudied HSG salivary cell line as a potential allogeneic graft cell for this device. One drawback of using a cell line is the potential for malignant t ransformation. If such an untoward response occurred, the device could be r emoved. However, in the event that any HSG cells escaped, we wished to prov ide additional patient protection. Accordingly, we have engineered HSG cell s with a hybrid adeno-retroviral vector, AdLTR. CMV-tk, to express the herp es simplex virus thymidine kinase (HSV-tk) suicide gene as a novel safety f actor. Cells were grown on plastic plates or on poly-L-lactic acid disks an d then transduced with different multiplicities of infection (MOIs) of the hybrid vector. Thereafter, various concentrations of ganciclovir (GCV) were added, and cell viability was tested. Transduced HSG cells expressed HSV-t k and were sensitive to GCV treatment. Maximal effects were seen at a MOI o f 10 with 50 muM of GCV, achieving 95% cell killing on the poly-L-lactic ac id substrate. These results suggest that engineering the expression of a su icide gene in an allogeneic graft cell may provide additional safety for us e in an artificial salivary gland device.