Background: Cancer pain is a complex medical syndrome. Understanding its underlying mechanisms
relies on the use of animal models which can mimic the human condition. A crucial component of this
model is the quantity of tumor cells; however, the exact relationship between the doses of tumor cells
on bone cancer pain is yet unknown.
Objective: We explored the relationship of different doses of Walker 256 carcinoma cells using a
bone cancer pain model in rats, and evaluated its success and stability.
Study Design: Experimental animal study using a comparative design.
Setting: Experimental Animal Center and Tumor Institute of Traditional Chinese Medicine.
Methods: We constructed the bone cancer pain model by implanting Walker 256 carcinoma
cells into the right tibia of Sprague-Dawley (SD) rats (150 – 170 g). Spontaneous pain, mechanical
threshold, and paw withdrawal latency (PWL) were measured and x-ray, bone mineral density (BMD),
histological, interleukin-1 beta (IL-1β) mRNA, carboxyterminal telopeptide of type I collagen (ICTP),
and bone alkaline phosphatase (BAP) were analyzed for bone pain model evaluation.
Results: The results showed that: (1) the 3 doses (3×105
, 3.5×105
, 4×105
) of Walker 256 carcinoma
cells can induce bone cancer pain from day 7 to day 21 after implantation into the right tibia of SD rats;
(2) compared to the control group, 3×105
, 3.5×105
, and 4×105
Walker 256 carcinoma cells produced
different pain manifestations, where the 3.5×105
dose of Walker 256 carcinoma cells resulted in the
greatest bone cancer pain response; (3) the 3.5×105
dose induced the lowest mortality rate in rats;
(4) Walker 256 carcinoma cells (3×105
, 3.5×105
, and 4×105
) resulted in a significant decrease in the
general condition and body weight of rats, where the 3.5×105
and 4×105
doses of carcinoma cells
produced a greater effect than 3×105
dose of carcinoma cells; (5) progressive spontaneous pain,
PWL, and mechanical threshold were exacerbated by 3.5×105
and 4×105
doses of carcinoma cells; (6)
implantation of 3.5×105
and 4×105
doses of carcinoma cells induced progressive bone destruction
and decrease in BMD; (7) ICTP and BAP were significantly increased following the implantation of
3.5×105
and 4×105
doses of carcinoma cells; (8) IL-1βmRNA was significantly up-regulated in the
spinal cord of rats implanted with 3.5×105
and 4×105
doses of carcinoma cells.
Limitations: One limitation of this study was the small sample size; therefore, additional research
is needed to provide better validation. Another limitation is the unavailability of small animal Micro
computed tomography (CT), which is a more advanced and precise technique in determining bone
marrow density than the x-ray imaging system we used. In addition, ethology experiments during
late-stage tumor progression can be more objective.
Conclusion: This study provides evidence that implantation of 3.5×105
and 4×105
dose of Walker
256 carcinoma cells produced the greatest effects in relation to the bone cancer pain model in SD
rats, and 3.5×105
dose induced the lowest mortality rate.
Key words: Bone cancer pain model, Walker 256 carcinoma cells, different doses
Enhanced
GABA
ergic synaptic transmission at
VLPAG
neurons and potent modulation by oxycodone in a bone cancer pain model