Abstract
Purpose :
Scarce information is available on pharmacological resistance in retinoblastoma with potential implications in the pharmacological treatment. Thus, we aimed to establish resistant-cells subtypes to topotecan, melphalan or carboplatin from primary cell cultures, and to study the degree of resistance and cross-resistance among compounds. We also evaluated the use of digoxin drug to circumvent acquired pharmacological resistance.
Methods :
Primary cell cultures were obtained after mechanical disaggregation of fresh tumor samples of two upfront enucleated patients with intraocular retinoblastoma, and named as HPG-RBT-12L and HSJD-RB-7. The parental cell lines (HPG-RBT-12L and HSJD-RB-7) were exposed to three weekly doses of topotecan, melphalan or caboplatin at the IC50 of each drug (concentration that inhibits 50% of cell proliferation) previously determined using the MTT assay. Then, the IC50s were determined in the topotecan-resistant (HPG-12L-RT and HSJD-7-RT), melpahlan-resistant (HPG-12L-RM and HSJD-7-RM), and carboplatin-resistant subtypes (HPG-12L-RC and HSJD-7-RC) to verify resistance and to test for possible cross-resistance. Digoxin IC50 was assessed in all parental and resistant-cell subtypes.
Results :
Mean topotecan IC50 in HPG-12L-RT and HSJD-7-RT was 7-fold and 5-fold higher than topotecan IC50 in HPG-RBT-12L and HSJD-RB-7, respectively (p<0.05). Mean melphalan IC50 in HPG-12L-RM and HSJD-7-RM was 4-fold higher than melphalan IC50 in HPG-RBT-12L and HSJD-RB-7 (p<0.05). Also, mean carboplatin IC50 in HPG-12L-RC and HSJD-7-RC was 2-fold higher than carboplatin IC50 determined in the corresponding parental cell lines (p<0.05). In all resistant-cell subtypes the IC50 of those drugs to which they had not been previously exposed e.g. were statistically higher than those in the parental cell lines confirming the pharmacological cross-resistance (p<0.05). In all cases, both parental and resistant cells showed similar digoxin IC50s (p>0.05).
Conclusions :
We were able to establish primary retinoblastoma cells cultures and the resistant subtypes to topotecan, melphalan or carboplatin. Acquisition of pharmacological resistance involved a 2-to-7 fold increase in the IC50 of each evaluated drug with potential implications in clinical response. Also, digoxin administration is suggested as a drug repositioning candidate to circumvent pharmacological resistance to commonly used chemotherapy in retinoblastoma.
This is a 2020 ARVO Annual Meeting abstract.