Between EGFR/ErbB and GPCR signaling pathways, we found KIT:GNAQ (in Reactome), MDM2:GNAQ (in Reactome and WikiPathway), CBL:GNAQ (in Reactome), FGFR2:GNAQ (in Reactome), PDGFRA:GNAQ (in Reactome), KIT:TSHR (in Reactome), MDM2:TSHR (in Reactome), CBL:TSHR (in Reactome), PDGFRA:TSHR (in Reactome), KIT:GNAS (in Reactome), MDM2:GNAS (in Reactome and WikiPathway), KIT:SMO (in Reactome), MDM2:SMO (in Reactome), TP53:GNAQ (in WikiPathway), and MYC:GNAQ (in WikiPathway). GPCR-like signaling contributes to acquired drug resistance after being mediated by Smoothened (SMO) via activating Gli, a canonical hedgehog (Hh) transcription factor [57]. GPCR and EGFR/ErbB over-expression often contributes to cancer growth. Cross-talk between the two at the receptor level contributes to HNSCC (head and neck squamous cell carcinoma) via triggering EGFR/ErbB signaling by a GPCR ligand [58]. For the MDM2:SMO cross-talk, found between the EGFR/ErbB and GPCR signaling pathways, a SMO-mutant from Hh signal transducer activates PI3K/Akt/Gli pathway that eventually increases MDM2 phosphorylation [59]. This in turn increases MDM2-mediated p53 degradation and thus reduces p53-induced apoptosis [59]. Furthermore, recently it has been reported that SMO (Hh signal transducer) functions like a G-protein coupled receptor due to its structural resemblance to GPCRs [60,61] which may be further evidence for a drug-resistant cross-talk between hedgehog signaling and EGFR/ErbB signaling [1].