Lestaurtinib enhances the antitumor efficacy of chemotherapy in murine xenograft models of neuroblastoma

Abstract

Purpose: Neuroblastoma, a common pediatric tumor of the sympathetic nervous system, is characterized by clinical heterogeneity. The Trk family neurotrophin receptors play an important role in this behavior. Expression of TrkA is associated with favorable clinical features and outcome, whereas TrkB expression is associated with an unfavorable prognosis. We wanted to determine if the Trk-selective inhibitor lestaurtinib had therapeutic efficacy in a preclinical neuroblastoma model.

Experimental design: We performed intervention trials of lestaurtinib alone or in combination with other agents in TrkB-overexpressing neuroblastoma xenograft models.

Results: Lestaurtinib alone significantly inhibited tumor growth compared to vehicle-treated animals [P = 0.0004 for tumor size and P = 0.011 for event-free survival (EFS)]. Lestaurtinib also enhanced the antitumor efficacy of the combinations of topotecan plus cyclophosphamide (P < 0.0001 for size and P < 0.0001 for EFS) or irinotecan plus temozolomide (P = 0.011 for size and P = 0.012 for EFS). There was no additive benefit of combining either 13-cis-retinoic acid or fenretinide with lestaurtinib compared to lestaurtinib alone. There was dramatic growth inhibition combining lestaurtinib with bevacizumab (P < 0.0001), but this combination had substantial systemic toxicity.

Conclusions: We show that lestaurtinib can inhibit the growth of neuroblastoma both in vitro and in vivo and can substantially enhance the efficacy of conventional chemotherapy, presumably by inhibition of the Trk/brain-derived neurotrophic factor autocrine survival pathway. It may also enhance the efficacy of selected biological agents, but further testing is required to rule out unanticipated toxicities. Our data support the incorporation of Trk inhibitors, such as lestaurtinib, in clinical trials of neuroblastoma or other tumors relying on Trk signaling pathways for survival.

Figure 1. Effect of Lestaurtinib on TrkB autophosphorylation induced by BDNF

A. The SY5Y-TrkB neuroblastoma line was exposed to BDNF in the absence and presence of increasing concentrations of Lestaurtinib. Maximal inhibition of ligand-induced autophosphorylation was seen by 100-200 nM. B. Densitometry of phospho-Trk relative to total Trk for each of the conditions in Fig. 1A.

Figure 2. Effect of Lestaurtinib (± cyclo) on inhibiting growth of SY5Y-TrkB xenografts

Lestaurtinib significantly slowed the growth of SY5Y-TrkB cells growing as xenografts in athymic nu/nu mice compared to vehicle alone (p= 0.0004, Fig. 2A). Lestaurtinib plus cyclo significantly slowed the growth of SY5Y-TrkB cells growing as xenografts in nude mice compared to Cyclo alone (p= 0.0001, Fig. 2B).

Figure 3. Effect of Lestaurtinib in combination with Topo-Cyclo on SY5Y-TrkB xenografts

Lestaurtinib significantly slowed the growth of SY5Y-TrkB cells growing as xenografts in nude mice compared to vehicle alone, and it significantly enhanced the efficacy of Topo-Cyclo (p< 0.0001, Fig. 3A). Lestaurtinib also significantly improved the EFS of animals treated with either vehicle or Topo-Cyclo alone (p<0.0001, Fig. 3B).

Figure 4. Effect of Lestaurtinib in combination with Irino-Temo on SY5Y-TrkB xenografts

Lestaurtinib significantly slowed the growth of SY5Y-TrkB cells growing as xenografts in nude mice compared to vehicle alone, and it significantly enhanced the efficacy of Irino-Temo (p=0.011, Fig. 4A). Lestaurtinib also significantly improved the EFS of animals treated with either vehicle or Irino-Temo alone (p=0.012, Fig. 4B).

Figure 5. Effect of Lestaurtinib in combination with 4-HPR on SY5Y-TrkB xenografts

Lestaurtinib significantly slowed the growth of SY5Y-TrkB cells growing as xenografts in nude mice compared to either vehicle or 4HPR alone, and the addition of 4-HPR did not significantly improve this efficacy (p< 0.0001, Fig. 5A). Lestaurtinib also significantly improved the EFS of animals treated with either vehicle or 4HPR alone (p=0.0007, Fig. 5B).