ErbB3 upregulation by the HNSCC 3D microenvironment modulates cell survival and growth

Abstract

Head and neck squamous carcinomas (HNSCC) present as dense epithelioid three-dimensional (3D) tumor nests that can mediate signals via the human epidermal growth factor receptor (ErbB) tyrosine kinase family to promote intratumoral survival and growth. We examined the role of the tumor microenvironment on ErbB receptor family expression and found that the status of intercellular organization altered the receptor profile. We showed that HNSCC cells forced into tumor island-like 3D aggregates strongly upregulated ErbB3 at the level of transcription. Not only was the elevated ErbB3 responsive to HRG-β1-induced enhanced signaling mechanism, but also analysis by siRNA-knockdown and kinase inhibitor strategies revealed that the ErbB3/AKT signaling pathway was sufficient to enhance tumor cell survival and growth potential. Elevated ErbB3 expression in the high-density 3D culture system was strongly associated with hypoxia-induced HIF-1α. Hypoxia-regulated ErbB3 expression was mediated by the HIF-1α-binding consensus sequence in the ErbB3 proximal promoter. The findings show that the local 3D tumor microenvironment can trigger reprograming and switching of ErbB family members and thereby influence ErbB3-driven tumor growth.

Organotypic three-dimensional cancer cell cultures mirror drug responsesin vivo: lessons learned from the inhibition of EGFR signaling

“…In addition, upon stimulation with ligands the extent of phosphorylation of EGFR and c-MET was lower in the 3D cultures [ 112 ]. Similarly, alterations in ErbB3 expression and phosphorylation were previously shown to modulate cell survival and growth in a 3D microenvironment [ 63 ].…”

Mechanisms of Receptor Tyrosine-Protein Kinase ErbB-3 (ERBB3) Action in Human Neoplasia

“…Relative to two-dimensional monolayer cultures, ERBB3 protein expression is much higher in multicellular aggregate three-dimensional cultures of head and neck squamous carcinomas; furthermore, ERBB3 signaling pathways operate continuously in multicellular aggregate cultures despite low levels of ERBB2 and EGFR expression. 87 Responses to drugs targeting ERBB receptors also differ between two-dimensional monolayer and multicellular aggregate cultures. 88 Although relatively few such comparisons have been performed to date, it will be important to bear in mind the impact of culture methods as we continue to dissect the role that ERBB3 plays in human cancer and assess new therapeutic agents targeting this receptor tyrosine kinase.…”

Anti-Trop2 blockade enhances the therapeutic efficacy of ErbB3 inhibition in head and neck squamous cell carcinoma

“…This suggested that ErbB3 signaling is particularly important for aspects of tumor growth related to the in vivo tumor microenvironment that are not required for in vitro growth. In three-dimensional in vitro culture systems, ErbB3 has been shown to be upregulated by HIF1α 46 , which is particularly important as tumors grow beyond their blood supply and encounter a hypoxic environment. In addition, in some contexts, EGFR promotes HIF1α stabilization primarily through its ability to activate the PI3 kinase-AKT pathway (Heeg et al and references therein 47 ).…”

“…EGFR itself has been reported to drive HIF1α expression in some systems 53 , but we did not observe any effect of Cetuximab on HIF1α levels in controlled CoCl 2 experiments. Interestingly, 3D tissue culture assays of HNSCC cells have shown that linked HIF1α upregulates ErbB3 46 . Our data suggest that regulation may occur in both directions, as suppression of ErbB3 significantly reduced the ability of CoCl 2 -induced hypoxia signaling to upregulate HIF1α.…”