Inhibition of PLK‐1 by using a Small Molecule Inhibitor HMN‐214 is a Novel Therapeutic Approach for High‐risk Neuroblastoma

Abstract

Polo‐like kinase1 (PLK‐1), a member of the polo‐like kinase family of serine/threonine protein kinases, plays an essential role in regulating the cell cycle. PLK‐1 has a strong relationship with numerous regulatory events progressing during G2/M transition, chromosomal segregation, spindle assembly maturation, and mitotic exit. In addition, PLK‐1 also regulates DNA damage response, DNA replication, transcription, translation, chromosomes dynamics, and checkpoint adoption. Elevated levels of PLK‐1 have been observed in a plethora of cancers, including neuroblastoma (NB). NB is the most prevalent solid tumor that develops during the early embryonic stage and accounts for 15% of pediatric cancer‐related deaths. Current cytotoxic treatment strategies for NB are limiting and failed to prevent relapse and metastasis. In the present study, we hypothesized that inhibition of cell cycle regulator PLK‐1 by a small molecule inhibitor HMN‐214 will inhibit NB growth. To determine the role of PLK‐1 in NB, we analyzed multiple NB patient datasets and observed that PLK‐1 expression is inversely correlated with overall patient survival. PLK‐1 also strongly correlates with MYCN amplification and overall NB disease progression in our patient dataset analysis. Further, we used six NB cell lines, including MYCN‐ amplified and ‐non‐amplified cell lines, to evaluate the anti‐proliferative effects of HMN‐214 in NB. Results showed that HMN‐214 significantly and in a dose‐dependent manner inhibits NB proliferation and colony formation capacity. Additionally, we found that HMN‐214 significantly induces apoptosis and blocks cell cycle progression at the G2‐M phase in treatment groups compared to controls. Our molecular analysis further revealed that HMN‐214 significantly inhibits the mRNA and protein levels of PLK‐1 and CDK1 in contrast to control treatments. Further, we developed a 3D spheroid tumor model for NB to mimic in vivo tumor growth and utilized it to determine the effects of HMN‐214 on NB tumor growth. Results showed that HMN‐214 significantly and in a dose‐dependent manner inhibits NB 3D spheroidal tumor growth by specifically inducing tumor cell death. Overall, our data highlights the role of PLK‐1 in the oncogenic progression of NB and showed the efficacy of HMN‐214 in inhibiting NB growth. Our future efforts will be directed towards elucidating the role of PLK‐1 in NB and developing effective therapeutic strategies incorporating PLK‐1 inhibitor.