Elemental Zn and its Binding Protein Zinc-α2-Glycoprotein are Elevated in HPV-Positive Oropharyngeal Squamous Cell Carcinoma

Abstract

Human papillomavirus (HPV)-positive head and neck squamous cell carcinoma (HNSCC) is biologically distinct from HPV-negative HNSCC. Outside of HPV-status, few tumor-intrinsic variables have been identified that correlate to improved survival. As part of exploratory analysis into the trace elemental composition of oropharyngeal squamous cell carcinoma (OPSCC), we performed elemental quanitification by X-ray fluorescence microscopy (XFM) on a small cohort (n = 32) of patients with HPV-positive and -negative OPSCC and identified in HPV-positive cases increased zinc (Zn) concentrations in tumor tissue relative to normal tissue. Subsequent immunohistochemistry of six Zn-binding proteins—zinc-α2-glycoprotein (AZGP1), Lipocalin-1, Albumin, S100A7, S100A8 and S100A9—revealed that only AZGP1 expression significantly correlated to HPV-status (p < 0.001) and was also increased in tumor relative to normal tissue from HPV-positive OPSCC tumor samples. AZGP1 protein expression in our cohort significantly correlated to a prolonged recurrence-free survival (p = 0.029), similar to HNSCC cases from the TCGA (n = 499), where highest AZGP1 mRNA levels correlated to improved overall survival (p = 0.023). By showing for the first time that HPV-positive OPSCC patients have increased intratumoral Zn levels and AZGP1 expression, we identify possible positive prognostic biomarkers in HNSCC as well as possible mechanisms of increased sensitivity to chemoradiation in HPV-positive OPSCC.

Expression of Zinc Alpha-2 Glycoprotein in Oral Squamous Cell Carcinoma and Oral Dysplasia

“…In this study, the oral squamous cell carcinoma samples that showed positive staining for Zinc Alpha-2 Glycoprotein (ZAG) belonged to the early stages (I and II) and of a moderately differentiated variant. This is in accordance with Poropatich et al study; they have also found high expression of ZAG in the early stages and moderately differentiated oropharyngeal squamous cell carcinoma 17 . Similarly, other studies have also reported higher expression of ZAG in well-differentiated oral squamous cell carcinoma and reduced in poorly differentiated tumors [18][19][20] .…”

Effects of low dose and low dose rate low linear energy transfer radiation on animals – review of recent studies relevant for carcinogenesis

“…Irradiated tissues showed decreased concentrations of S, K, Ca, Fe, and Zn regardless of the dose used. Considering that elemental concentration perturbations correlate with differences in radiation sensitivity, this study may be opening a new area of investigation for radiation studies (Poropatich et al 2019).…”

Use of X-Ray Fluorescence Microscopy for Studies on Research Models of Hepatocellular Carcinoma

“…Silicon drift energy dispersive detector positioned was used to collect the fluorescence signal from samples, at 90 • to the incident beam. Per pixel elemental concentration was obtained by comparison with the thin-film standards NBS-1832 and NBS-1833 from the National Bureau of Standards (Gaithersburg, MD), and the analysis was done using MAPS software (38) as detailed in other studies (20,(34)(35)(36).…”

“…We have used this animal model for different types of studies for more than 15 years (14,20,23,(26)(27)(28)(29)(30)(31). Over the same period, we have also worked on introducing a unique imaging technique, x-ray fluorescence microscopy (XFM), into pathology (20,(32)(33)(34)(35)(36). Although we have previously used XFM to image liver VX2 samples (20), this is the very first study where we have developed and implemented necessary sample preparation techniques to process radioactive tissue samples and make them suitable for XFM imaging.…”