Molecular Imaging of Oral Premalignant and Malignant Lesions Using Fluorescently Labeled Lectins

Abstract

Aberrant glycosylation during carcinogenesis results in altered glycan expression on oral cancer cells. The objective of this study was to detect this atypical glycosylation via imaging of fluorophore-conjugated lectins. Paired normal and tumor tissue from seven patients with oral squamous cell carcinoma were investigated for sialic acid expression via the legume protein wheat germ agglutinin (WGA). Fluorophore (Alexa Fluor 350 and Alexa Fluor 647) conjugated WGA was topically applied to the tissue samples and imaged using a custom wide-field fluorescence imaging system. All seven patients had histologically confirmed disease with 6/7 exhibiting squamous cell carcinoma and 1/7 exhibiting dysplasia. Fluorescent data collected from all patients demonstrated that fluorophore conjugated WGA could distinguish between pathologically normal and diseased tissue with the average signal-to-noise ratio (SNR) among all patients being 5.88 (P = .00046). This SNR was statistically significantly higher than the SNR from differences in tissue autofluorescence (P = .0049). A lectin inhibitory experiment confirmed that lectin binding is molecularly specific to overexpressed tumor glycans and that fluorescence is not due to tissue optical properties or tissue diffusion differences. These results illustrate that changes in tumor glycan content of oral neoplasms can be detected with optical imaging using topically applied fluorescently labeled WGA. Lectin targeting of oral lesions using optical imaging may provide a new avenue for the early detection of oral cancers.

Management update of potentially premalignant oral epithelial lesions

“…1,6 A new method based on the change in expression of certain glycan residues on the surface of cancerous and dysplastic cells shows promising initial results. 16,17 A chairside in vivo study by Baeten et al tested a specific fluorescent conjugated lectin to target this aberrant glycosylation on cancerous and dysplastic cells in the oral cavity. The study yielded a sensitivity of 89% and a specificity of 82% in vivo.…”

Chairside molecular imaging of aberrant glycosylation in subjects with suspicious oral lesions using fluorescently labeled wheat germ agglutinin

“…Previous researchers have shown that sialic acid levels can distinguish between normal subjects and subjects with OPMDs and cancerous lesions . Additionally, we previously showed the ability of WGA‐FITC to differentially stain malignant biopsies compared with normal biopsies . However, the ability of WGA‐FITC to differentially stain malignant tissue in vivo in a clinically relevant timeframe (ie, seconds compared to 30‐60 minutes in previous testing) is profound as WGA‐FITC is a semi‐large protein (36 kDa) and requires time to diffuse and bind sialic acid.…”

“…10,12,24 Additionally, we previously showed the ability of WGA-FITC to differentially stain malignant biopsies compared with normal biopsies. 6 However, the ability of WGA-FITC to differentially stain malignant tissue in vivo in a clinically relevant timeframe (ie, seconds compared to 30-60 minutes in previous testing) is profound as WGA-FITC is a semi-large protein (36 kDa) and requires time to diffuse and bind sialic acid. The data presented in this article agrees well with prior research as WGA-FITC LOD scores directly correlate with greater malignancy progression regardless of the cancer type (LOD scores: cancerous lesions > dysplastic lesions > benign lesions).…”

“…Utilizing an effect size of 0.5 (assumed based on our previous ex vivo testing), a standard significance level of 0.05, and a standard power of 0.8, a sample size of 64 was recommended for this study. Accounting for potential patient fallout of 15%, a sample size of 75 was determined.…”

Protein Post-translational Modifications in Head and Neck Cancer

“…Glycosylation is also expected to be used in the early diagnosis of HNC. Inspired by the aberrant glycan expression in oral cancer tissues, a study (42) applied legume protein wheat germ agglutinin (WGA) to selectively recognize sialic acid and N-acetylglucosamine residues, and detected atypical glycosylation via imaging of fluorophore-conjugated lectins. The results demonstrated that WGA fluorophore probes can successfully yielding statistically higher fluorescence in OSCC tissues, which exhibited its promising ability to distinguish cancerous tissues from pathologically normal tissues.…”