A head and neck cancer protein interaction map reveals PIK3CA mutant drug sensitivity

Despite extensive DNA sequencing of patient tumors, it remains challenging to translate the immense landscape of heterogeneous genetic alterations into function and clinical outcomes due to a limited understanding of cancer specific molecular network architectures. To bridge this gap, we have used affinity purification-mass spectrometry to generate protein interaction networks for 31 proteins with significant alterations in head and neck squamous cell carcinoma. This network includes 771 interactions covering both cancer and non-tumorigenic cell states, as well as wild-type and mutant proteins. Differential analysis across these dimensions reveals a strong interaction between PIK3CA and ERBB3 (HER3), dependent upon mutations in PIK3CA. We show that this interaction correlates with ERBB3 activity in vitro and can be targeted in vivo using a clinical ERBB3 inhibitor, CDX3379, to prohibit growth of tumors with common PIK3CA mutations. This study provides a roadmap for elucidating genetic complexity through multidimensional maps of cancer cell biology.