Human Parafollicular Cancer Cells: A Neuronal Model for Novel Drug Identification to Treat Neuropathic Pain

Abstract

Objectives: This study was conducted to identify the types of functional voltage-gated calcium channels expressed by the neuronal-like human parafollicular (CA77) cancer cell line. Methods: CA77 cells were grown in culture and the expression of functional calcium channels studied using Fura-2 am during live cell imaging to measure changes in intracellular calcium levels in response to stimulation with potassium chloride (KCl) alone and in combination with several voltage-gated calcium channel blockers. These included: nifedipine, funnel spider toxin (FTX), and ω-conotoxin, which inhibit L-type, P/Q-type, and N-type voltage-gated calcium channels, respectively. To investigate transcriptional expression, primers for L-, N-, and P/Q-type channels were used in reverse transcriptase polymerase chain reaction (RT-PCR). Results: Significant increases in intracellular calcium levels were measured in response to KCl ( P < .001, n = 45), which was not repressed by nifedipine or ω-conotoxin ( P = .893, n = 34, P = .957, n = 31). However, KCl-mediated intracellular calcium increase was repressed by FTX ( P < .001, n = 42). Using RT-PCR, mRNA for P/Q-type receptor was detectable but not the mRNA for the N- and L-type voltage-gated channels. Conclusions: Taken together, our results provide evidence that CA77 cells express functional P/Q (CaV2.1) calcium channels, which are known to promote increased neuronal excitability, inflammation, and nociception. Thus, CA77 cells can provide an efficient and cost-effective means to screen novel therapeutics to treat migraine and other neurological diseases of the head and neck that involve P/Q channel activation in the underlying pathology.