Page 183 - Haematologica - Vol. 105 n. 6 - June 2020

Plasma Cell Disorders
Identification of PIKfyve kinase as a target in multiple myeloma
Cecilia Bonolo de Campos,1 Yuan Xiao Zhu,1 Nikolai Sepetov,2 Sergei Romanov,2 Laura Ann Bruins,1 Chang-Xin Shi,1 Caleb K. Stein,1 Joachim L. Petit,1 Alysia N. Polito,1 Meaghen E. Sharik,1 Erin W. Meermeier,1 Gregory J. Ahmann,1 Ilsel D. Lopez Armenta,1 Jonas Kruse,1 P. Leif Bergsagel,1 Marta Chesi,1 Nathalie Meurice,1 Esteban Braggio1 and A. Keith Stewart1
1Division of Hematology/Oncology, Mayo Clinic Arizona, Scottsdale, AZ and 2Nanosyn Inc., Santa Clara, CA, USA
ABSTRACT
The cellular cytotoxicity of APY0201, a PIKfyve inhibitor, against mul- tiple myeloma was initially identified in an unbiased in vitro chemical library screen. The activity of APY0201 was confirmed in all 25 cell lines tested and in 40% of 100 ex vivo patient-derived primary samples, with increased activity in primary samples harboring trisomies and lacking t(11;14). The broad anti-multiple myeloma activity of PIKfyve inhibitors was further demonstrated in confirmatory screens and showed the superior potency of APY0201 when compared to the PIKfyve inhibitors YM201636 and apilimod, with a mid-point half maximal effective concentration (EC50) at nanomolar concentrations in, respectively, 65%, 40%, and 5% of the test- ed cell lines. Upregulation of genes in the lysosomal pathway and increased cellular vacuolization were observed in vitro following APY0201 treatment, although these cellular effects did not correlate well with responsiveness. We confirm that PIKfyve inhibition is associated with activation of the transcrip- tion factor EB, a master regulator of lysosomal biogenesis and autophagy. Furthermore, we established an assay measuring autophagy as a predictive marker of APY0201 sensitivity. Overall, these findings indicate promising activity of PIKfyve inhibitors secondary to disruption of autophagy in mul- tiple myeloma and suggest a strategy to enrich for likely responders.
Introduction
Although the survival outcomes of patients with multiple myeloma (MM) have improved significantly, in the majority of patients the disease remains character- ized by recurrent episodes of relapse. Identification of vulnerable targets, particu- larly those targeting plasma cell biology, is thus an attractive approach aiming towards advances of therapeutic strategies. Consequently, we utilized an ex vivo chemo-genomics screening approach to identify potentially unrecognized targets in this disease. As part of this study, and somewhat unexpectedly, PIKfyve was identified as a vulnerable target in MM.
PIKfyve, first described in 1999,1 is a mammalian protein and lipid kinase that controls complex and distinct cellular functions (reviewed by Shisheva et al.2). PIKfyve phosphorylation of protein substrates includes autophosphorylation3 while lipid kinase activity generates two phosphorylated species of phos- phatidylinositol (PtdIns):-5-P and -3,5-P2.4 PtdIns-5-P plays crucial roles in remod- eling the actin cytoskeleton, endocytosis, and nuclear signaling, and is suggested to be a critical signal in innate immune responses. PtdIns-3,5-P2 is involved mainly in intracellular trafficking and lysosomal acidification and is thus crucial for the regulation of macroautophagy (herein denominated autophagy).5 Apilimod, ini- tially identified in functional screens as negatively interfering with the production of interleukin (IL-)12 and IL-236 and used in clinical trials of the treatment of inflammatory diseases,7-10 was subsequently characterized as a PIKfyve inhibitor.11 Interestingly, apilimod inhibition has recently been described as a potentially use- ful therapeutic approach for the treatment of non-Hodgkin lymphoma (NHL).12
Ferrata Storti Foundation
Haematologica 2020 Volume 105(6):1641-1649
Correspondence:
A. KEITH STEWART
stewart.keith@mayo.edu
Received: March 21, 2019. Accepted: September 26, 2019. Pre-published: October 3, 2019.
doi:10.3324/haematol.2019.222729
Check the online version for the most updated information on this article, online supplements, and information on authorship & disclosures: www.haematologica.org/content/105/6/1641
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