Lysosomal Sequestration of Sunitinib: A Novel Mechanism of Drug Resistance

Abstract

Purpose Resistance to antiangiogenic tyrosine kinase inhibitors such as sunitinib is an important clinical problem, but its underlying mechanisms are largely unknown. We analyzed tumor sunitinib levels in mice and patients and studied sensitivity and resistance mechanisms to sunitinib. Experimental Design Intratumoral and plasma sunitinib concentrations in mice and patients were determined. Sunitinib exposure on tumor cell proliferation was examined. Resistant tumor cells were derived by continuous exposure and studied for alterations in intracellular sunitinib accumulation and activity. Results Intratumoral concentrations of sunitinib in mice and patients were 10.9 ± 0.5 and 9.5 ± 2.4 μmol/L, respectively, whereas plasma concentrations were 10-fold lower, 1.0 ± 0.1 and 0.3 ± 0.1 μmol/L, respectively. Sunitinib inhibited tumor cell growth at clinically relevant concentrations in vitro, with IC50 values of 1.4 to 2.3 μmol/L. Continuous exposure to sunitinib resulted in resistance of 786-O renal and HT-29 colon cancer cells. Fluorescent microscopy revealed intracellular sunitinib distribution to acidic lysosomes, which were significantly higher expressed in resistant cells. A 1.7- to 2.5-fold higher sunitinib concentration in resistant cells was measured because of increased lysosomal sequestration. Despite the higher intracellular sunitinib accumulation, levels of the key signaling p-Akt and p-ERK 1/2 were unaffected and comparable with untreated parental cells, indicating reduced effectiveness of sunitinib. Conclusion We report that sunitinib inhibits tumor cell proliferation at clinically relevant concentrations and found lysosomal sequestration to be a novel mechanism of sunitinib resistance. This finding warrants clinical evaluation whether targeting lysosomal function will overcome sunitinib resistance.

Transport of six tyrosine kinase inhibitors: active or passive?

“…In addition, cimetidine had a similar effect as desipramine on crizotinib mass transport. The higher sunitinib and crizotinib accumulation in the Caco-2 intestinal monolayer after the incubation of verapamil and cimetidine is probably masked by lysosomal accumulation [22,39]. Just like sunitinib, sorafenib does not seem to be dependent on hOCT transport from apical to basolateral side.…”

“…These drugs are also not a highaffinity substrate for the ABC-family transporters, which is in agreement with the data reported by this study. However, passive transport can be masked by the lysosomal uptake leading to more accumulation in the cell at 37 °C as seen with sunitinib [22,39].…”

“…At later time-points the pattern changes, erlotinib accumulation at 4 °C continued to increase, but at 37 °C the accumulation decreased (Figure 2A), indicating an active efflux process. Sunitinib accumulation at 37 °C continued to increase, possibly due to a lysosomal accumulation ( Figure 2C) [22,39]. For crizotinib, the accumulation continued to increase under both conditions ( Figure 2E), but for sorafenib no change was observed ( Figure 2D).…”

La résistance aux traitements antiangiogéniques

“…L'autophagie permet ainsi aux cellules de survivre avant l'induction de l'angiogenèse, en dégradant les protéines et les organites qui ne leur sont pas essentiels. La séquestration dans des lysosomes de cellules tumorales, de l'inhibiteur sunitinib, constitue ainsi un mécanisme de résistance au traitement [33]. Les cellules inflammatoires, nerveuses et endothé- SYNTHÈSE REVUES concentration plasmatique des facteurs de l'angiogenèse comme le VEGF, le PlGF, le FGF-2 ou l'IL-8, qui est le reflet d'une résistance ayant pour origine une néoangiogenèse, est considérée comme un marqueur de mauvais pronostic.…”

974 Modulation of Akt/Mtor Signaling Overcomes Sunitinib Resistance in Renal and Prostate Cancer Cells

“…In Phase II trials, a heterogeneous response to sunitinib was noted in both docetaxel-resistant and chemotherapy naïve patients with a significant proportion of tumors demonstrating at least a partial radiographic response. In the most recent study of subjects with docetaxel-resistant CRPC, 11.1% of patients demonstrated 30% tumor reduction by Response Evaluation Criteria In Solid Tumors (RECIST) criteria. Another 44.4% of patients had quantifiable but less significant tumor response (5).…”