# Nuclear factor-κB activation by transforming growth factor-β1 drives tumour microenvironment-mediated drug resistance in neuroblastoma

## TL;DR

This study shows that TGF-β1 in the tumor environment causes drug resistance in neuroblastoma by activating NF-κB, and blocking this pathway can reverse resistance.

## Contribution

The study identifies a novel TGF-β1/NF-κB signaling mechanism in the tumor microenvironment that drives drug resistance in neuroblastoma.

## Key findings

- TGF-β1 from the tumor microenvironment increases drug resistance in neuroblastoma cells.
- NF-κB activation via TAK1 and SMAD2 is essential for this resistance, which can be reversed by inhibiting these pathways.
- Interleukin-6 and other cytokines contribute to resistance through a STAT3-activating autocrine loop.

## Abstract

Intrinsic and extrinsic factors in the tumour microenvironment (TME) contribute to therapeutic resistance. Here we demonstrate that transforming growth factor (TGF)-β1 produced in the TME increased drug resistance of neuroblastoma (NB) cells.

Human NB cell lines were tested in vitro for their sensitivity to Doxorubicin (DOX) and Etoposide (ETOP) in the presence of tumour-associated macrophages (TAM) and mesenchymal stromal cells/cancer-associated fibroblasts (MSC/CAF). These experiments were validated in xenotransplanted and primary tumour samples.

Drug resistance was associated with an increased expression of efflux transporter and anti-apoptotic proteins. Upregulation was dependent on activation of nuclear factor (NF)-κB by TGF-β-activated kinase (TAK1) and SMAD2. Resistance was reversed upon pharmacologic and genetic inhibitions of NF-κB, and TAK1/SMAD2. Interleukin-6, leukaemia inhibitory factor and oncostatin M were upregulated by this TGF-β/TAK1/NF-κB/SMAD2 signalling pathway contributing to drug resistance via an autocrine loop activating STAT3. An analysis of xenotransplanted NB tumours revealed an increased presence of phospho (p)-NF-κB in tumours co-injected with MSC/CAF and TAM, and these tumours failed to respond to Etoposide but responded if treated with a TGF-βR1/ALK5 inhibitor. Nuclear p-NF-κB was increased in patient-derived tumours rich in TME cells.

The data provides a novel insight into a targetable mechanism of environment-mediated drug resistance.