Effects of Lidocaine and Morphine on canine mammary tumor cells proliferation: preliminary results

Anesthesia for cancer surgery might influence recurrence via multiple mechanisms (Snyder and Greenberg 2010). The effects of analgesics on canine tumor cell proliferation are unknown. Primary (CypP) and metastatic (CypM) canine mammary tumor cells were incubated with cell culture media (control), lidocaine (1, 5 and 10 μg ml-1; Valverde et al. 2004) or morphine (0.005, 0.05 and 0.5 μg ml-1; Kukanich et al. 2005). A 3-(4,5-Dimethylthiazol-2-Yl)-2,5-Diphenyltetrazolium Bromide (MTT) assay was performed after 6 and 12 hours of incubation. Cell concentrations (i.e. absorbance) were obtained with a spectrophotometer. Values were compared using a 3-way ANOVA (n = 6). Significance was set at p < 0.05. After 6 hours, no statistically significant effects were observed in CypM, while in CypP the middle concentration of lidocaine increased absorbance. At 12 hours both treatments showed a statistically significant decrease in cells number in CypM at all concentrations (table 1). Conversely, all concentrations of lidocaine and the lower concentration of morphine significantly increased cell number in CypP compared to controls. Both treatments influenced cell proliferation with divergent effects depending on exposure time and cellular line. Concentrations seemed to have a minor role. Further studies are warranted to better understand this phenomenon and potential clinical implications.