Immunohistochemical quantification of partial-EMT in oral cavity squamous cell carcinoma primary tumors is associated with nodal metastasis

Objectives: Quantify by immunohistochemistry (IHC) a partial epithelial-to-mesenchymal transition (p-EMT) population in oral cavity squamous cell carcinoma (OCSCC) and determine its predictive value for lymph node metastasis. Methods: Tissue microarrays (TMA) were created using 2 mm cores from 99 OCSCC patients (47 with low volume T2 disease, 52 with high volume T4 disease, and - 50% in each group with nodal metastasis). IHC staining was performed for three validated p-EMT markers (PDPN, LAMB3, LAMC2) and one marker of well-differentiated epithelial cells (SPRR1B). Staining was quantified in a blinded manner by two reviewers. Tumors were classified as malignant basal subtype based on staining for the four markers. In this subset, the p-EMT score was computed as the average of p-EMT markers. Results: 84 tumors were classified as malignant basal. There was 87% inter-rater consistency in marker quantification. There were associations of p-EMT scores with higher grade (2.15 vs. 1.92, p = 0.04), PNI (2.13 vs. 1.83, p = 0.003), and node positivity (2.09 vs. 1.87, p = 0.02), including occult node positivity (56% vs. 19%, p = 0.005). P-EMT was independently associated with nodal metastasis in a multivariate analysis (OR 3.12, p = 0.039). Overall and disease free survival showed trends towards being diminished in the p-EMT high group. Conclusions: IHC quantification of p-EMT in OCSCC primary tumors is reliably associated with nodal metastasis, PNI, and high grade. With prospective validation, p-EMT biomarkers may aid in decision-making over whether to perform a neck dissection in the NO neck and/or for adjuvant therapy planning.