PDPN and head and neck squamous cell carcinoma: One marker widely used to identify p‐EMT in multiple tumor types is PDPN [23, 35] and our data demonstrated that PDPN expression increased with invasion in all HNSCC keratinocyte populations tested here (Figures 2D, 3D, and 4D), and this increase was independent of overall p‐EMT score or TGF‐β response, although PDPN expression was increased by the addition of TGF‐β in TGF‐β‐responsive keratinocytes (Figure 2G).