Background
Cell lines are often used to assess the resistance of anticancer drugs when in vivo analysis is not possible. However, the process for establishing anti-cancer drug resistance in cell cultures in vitro and the subsequent method of then evaluating resistance are not clearly established. Traditionally, the IC50 is the most commonly used indicator of resistance evaluation but it cannot represent the effectiveness of anti-cancer drugs in a clinical setting and lacks reliability because it is heavily affected by the cell doubling time. Hence, new indicators that can evaluate anti-cancer drug resistance are needed.
Conclusion
Since the GR100 has properties that indicate the efficiency of anti-cancer drugs, both the efficacy and GR100 of a particular anti-cancer drug can be used to effectively assess the resistance.
Methods
A novel resistance evaluation methodology was validated in this present study by establishing sunitinib resistance in renal cell carcinoma cells and assessing the cross-resistance of five different anti-cancer drugs.
Results
It was confirmed in this present study that the IC50 does not reflect the cell proliferation rates in a way that represents anti-cancer drug resistance. An alternative indicator that can also be clinically meaningful when using in vitro cell line systems is GI100. Additionally, the GR100 allows different cell populations to be calibrated on the same basis when multiple experimental results are compared.