Differential kinase activity of ACVR1 G328V and R206H mutations with implications to possible T\u03b2RI cross-talk in diffuse intrinsic pontine glioma

Hongnan Cao,Miao Jin,Yizhi Jane Tao,Jeffrey Skolnick,Hongyi Zhou,Mu Gao

doi:10.1038/s41598-020-63061-0

Hongnan Cao, Miao Jin + Show 4 more

Open Access

https://doi.org/10.1038/s41598-020-63061-0

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Abstract

Diffuse intrinsic pontine glioma (DIPG) is a lethal pediatric brain cancer whose median survival time is under one year. The possible roles of the two most common DIPG associated cytoplasmic ACVR1 receptor kinase domain mutants, G328V and R206H, are reexamined in the context of new biochemical results regarding their intrinsic relative ATPase activities. At 37 °C, the G328V mutant displays a 1.8-fold increase in intrinsic kinase activity over wild-type, whereas the R206H mutant shows similar activity. The higher G328V mutant intrinsic kinase activity is consistent with the statistically significant longer overall survival times of DIPG patients harboring ACVR1 G328V tumors. Based on the potential cross-talk between ACVR1 and TβRI pathways and known and predicted off-targets of ACVR1 inhibitors, we further validated the inhibition effects of several TβRI inhibitors on ACVR1 wild-type and G328V mutant patient tumor derived DIPG cell lines at 20–50 µM doses. SU-DIPG-IV cells harboring the histone H3.1K27M and activating ACVR1 G328V mutations appeared to be less susceptible to TβRI inhibition than SF8628 cells harboring the H3.3K27M mutation and wild-type ACVR1. Thus, inhibition of hidden oncogenic signaling pathways in DIPG such as TβRI that are not limited to ACVR1 itself may provide alternative entry points for DIPG therapeutics.

Highlights

Diffuse intrinsic pontine glioma (DIPG) is an aggressive brainstem pediatric cancer with no effective treatment and a median survival of less than a year according to the International DIPG Registry[1]
There clearly exists a high frequency of ACVR1 somatic mutations in DIPG patients[5,14,15] and the demonstrated preclinical potency of ACVR1 inhibitors at a μM level to inhibit DIPG cells with different biological backgounds[2,12], we suggest that additional target validation and mechanistic studies of ACVR1 and associated pathways for DIPG therapeutics are required for the following reasons: First, the G328E/V/W mutations correlate with longer patient survival[2,15]
We further showed that an investigational TβRI blocker SB525334, with a previously reported ~1000-fold selectivity for TβRI over ACVR140, demonstrated statistically significant inhibition in both SF8628 (ACVR1 wild-type, histone H3.3K27M) and SU-DIPG-IV (ACVR1 G328V, histone H3.1K27M) DIPG cells at a relatively high 50 μM dose (Fig. 6)

Summary

Introduction

Diffuse intrinsic pontine glioma (DIPG) is an aggressive brainstem pediatric cancer with no effective treatment and a median survival of less than a year according to the International DIPG Registry[1]. The understanding of the genetic and epigenetics context of DIPG led to therapeutic efforts that targeted chromatin modifiers such as histone deacetylase (HDAC), demethylase or methyltransferase complexes[6,8,9,10,11] as well as kinases such as ACVR1 ( called ALK2)[2,12]. These studies yielded promising preclinical efficacy of single agent or combinations in different DIPG cell and mice xenograft models. While ACVR1 might be an attractive target for kinase inhibitors, is this a viable strategy for DIPG? As detailed below, our results suggest that further target validation is needed and may lead to the discovery of alternative therapeutic strategies

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