Immortalized rat mesencephalic cells (1RB3AN27) produced dopamine (DA) at a level that was higher than produced by undifferentiated or differentiated murine neuroblastoma cells (NBP2) in culture. Treatment of 1RB3AN27 and NBP2 cells with a cAMP stimulating agent increased tyrosine hydroxylase (TH) activity and the intensity of immunostaining for the DA transporter protein (DAT). 1RB3AN27 cells were labelled with primary antibodies to neuron specific enolase (NSE) and nestin and exhibited very little or no labeling with anti-glial fibrillary acidic protein (GFAP). 1RB3AN27 cells exhibited beta- and alpha-adrenoreceptors, and prostaglandin E1 receptors, all of which were linked to adenylate cyclase (AC). Dopamine receptor (D1) and cholinergic muscarinic receptors linked to AC were not detectable. The levels of PKC alpha and PKC beta isoforms were higher than those of PKC gamma and PKC delta in 1RB3AN27 cells. The 1RB3AN27 cells were more effective in reducing the rate of methamphetamine-induced turning in rats with unilateral 6-OHDA lesion of the nigrostriatal system than differentiated NBP2 cells. The grafted 1RB3AN27 were viable as determined by DiI labelling, but they did not divide and did not produce T-antigen protein; however, when these grafted cells were cultured in vitro, they resumed production of T-antigen and proliferated after the primary glia cells and neurons of host brain died due to maturation and subsequent degeneration. Examination of H&E stained sections of the grafted sites revealed no evidence of infiltration of inflammatory cells in the grafted area suggesting that these cells were not immunogenic. They also did not form tumors.
The effect of a mixture of vitamins in modifying the efficacy of commonly used drugs in the treatment of human melanoma has not been studied. Vitamin C and d-alpha-tocopheryl succinate (alpha-TS) alone reduced the growth of human melanoma (SK-30) cells in culture, whereas beta-carotene (BC), 13-cis-retinoic acid (RA), or sodium selenite alone was ineffective. RA caused morphological changes, as evidenced by flattening of cells and formation of short cytoplasmic processes. A mixture of four vitamins (vitamin C, BC, alpha-TS, and RA) was more effective in reducing growth of human melanoma cells than a mixture of three vitamins. The growth-inhibitory effect of cis-platin, decarbazine, tamoxifen, and recombinant interferon-alpha 2b was enhanced by vitamin C alone, a mixture of three vitamins (BC, alpha-TS, and RA), and a mixture of four vitamins (vitamin C, BC, alpha-TS, and RA) that contained 50 micrograms/ml of vitamin C. These data show that a mixture of three or four vitamins can enhance the growth-inhibitory effect of currently used chemotherapeutic agents on human melanoma cells.
This investigation reports for the first time the establishment of immortalized clones of dopamine-producing nerve cells in culture. Freshly prepared single-cell suspensions from fetal (12-day-old) rat mesencephalic tissue were transfected with plasmid vectors, pSV3neo and pSV5neo, using an electroporation technique. Cells were plated in tissue culture dishes which were precoated with a special substrate and contained modified MCDB-153 growth medium with 10% heat inactivated fetal bovine serum. The immortalized cells were selected by placing the transfected cells in a selection medium (modified MCDB-153 containing 400 micrograms/ml geneticin). The survivors showed the presence of T-antigens and were non-tumorigenic. Two cell lines, 1RB3 derived from cells transfected with pSV3neo, and 2RB5 derived from cells transfected with pSV5neo revealed only 1 to 2% tyrosine hydroxylase (TH)-positive cells. Repeated single-cell cloning of these cell lines by a standard technique failed to increase the number of TH-positive cells in any clones. Using three cycles of growth, alternating between hormone-supplemented, serum-free medium and serum-containing medium produced a cell line (1RB3A) that was very rich in TH-positive cells. The recloning of 1RB3A yielded clones some of which contained over 95% TH-positive cells. These cells produced homovanillic acid, a metabolite of dopamine, and may be useful not only for neural transplant but also for basic neurobiological studies.
The replacement of dopamine (DA) by DA neuron transplants in the treatment of advanced Parkinson disease (PD) is a rational approach. Because of limitations associated with fetal tissue transplants, a clone (1RB 3 AN 27 ) of simian virus 40 large tumor antigen (LTa) gene-induced immortalized DA neurons were used in this study. These allogeneic immortalized dopamine neurons, when grafted into striata of normal rats, did not divide, did not form tumors, did not produce LTa, did not extend neurites to host neurons, and were not rejected, for as long as 13 months after transplantation. Grafted cells when recultured in vitro resumed cell proliferation and LTa production, suggesting the presence of a LTa gene-inhibiting factor in the brain. The grafting of undifferentiated and differentiated 1RB 3 AN 27 cells or differentiated murine neuroblastoma (NBP 2 ) cells into striata of 6-hydroxydopamine-lesioned rats (an animal model of PD) caused a time-dependent improvement in neurological deficits (reduction in the methamphetamine-induced turning rate). At 3 months after transplantation, 100% of the animals receiving differentiated 1RB 3 AN 27 cells, 63% of the animals receiving undifferentiated 1RB 3 AN 27 cells, 56% of the animals receiving differentiated NBP 2 cells, and 0% of the sham-transplanted animals showed improvements in neurological deficits. At 6 months after transplantation, there was a progressive increase in spontaneous recovery in sham-transplanted animals. These results suggest that immortalized DA neurons should be further studied for their potential use in transplant therapy in advanced PD patients.
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