Raman spectroscopy in experimental oral carcinogenesis: investigation of abnormal changes in control tissues

Abstract

Oral cancer is a major cause of mortality in South Asian men owing to rampant tobacco abuse. Cancers are also reported in non‐tobacco habitués, especially women, attributed to chronic irritations from irregular/sharp teeth, improper fillings, and poorly fit dentures. Conventional screening approaches are shown to be effective for high‐risk groups (tobacco/alcohol habitués). Raman spectroscopy (RS) is being extensively explored as an alternate/adjunct tool for diagnosis and management of oral cancers. In a previous Raman study on sequential oral carcinogenesis using hamster buccal pouch model, misclassifications between spectra from control and carcinogen [7,12‐dimethylbenz(a)anthracene (DMBA)]‐treated tissues were observed. Histopathology of some control tissues suggested pathological changes, attributable to repeated forceps‐induced irritations/trauma during animal handling. To explore these changes, in the present study, we recorded spectra from three different types of controls – vehicle control (n = 45), vehicle contralateral (n = 45), and DMBA contralateral (n = 70) – exposed to varying degree of forceps handling, along with DMBA‐treated pouches (n = 70) using a 14‐week carcinogenesis protocol. Spectra certified on the basis of histopathology and abnormal cell proliferation (cyclin D1 expression) were used to build models that were evaluated by independent test spectra from an exclusive set of DMBA‐treated and control animals. Many DMBA‐contralateral, vehicle‐control, and vehicle‐contralateral spectra were identified as higher pathologies, which subsequently corroborated with histopathology/cyclin D1 expression. Repeated forceps‐mediated injuries/irritations, during painting and animal handling, may elicit inflammatory responses, leading to neoplasm. The findings of the study suggest that RS could identify micro‐changes. Further, RS‐based in vivo imaging can serve as a promising label‐free tool for screening even in the non‐habitué population where conventional screening is shown to be not effective. Copyright © 2016 John Wiley & Sons, Ltd.

In vivo Raman spectroscopy–assisted early identification of potential second primary/recurrences in oral cancers: An exploratory study

“…These misclassifications were putatively attributed to either the inherent heterogeneity of tumors, especially islands of normal cells within tumors, or could be possibly attributed to probing of advancing front of tumors (at the tumor periphery). On the other hand, experimental carcinogenesis studies on hamster buccal pouch (a well‐known animal model that mimics human buccal mucosa and oral carcinogenesis) could detect microsized tumors in controls, which were attributable to mechanical irritation . In these studies, repeated misclassifications were reported between control and treated conditions.…”

“…On the other hand, experimental carcinogenesis studies on hamster buccal pouch (a wellknown animal model that mimics human buccal mucosa and oral carcinogenesis) could detect microsized tumors in controls, which were attributable to mechanical irritation. 34,35 In these studies, repeated misclassifications were reported between control and treated conditions. In this case, unlike in human healthy volunteer studies, in depth histopathology and immunohistochemistry analysis were carried out.…”

“…Studies on this model have shown significant incidence of misclassifications between spectra from 7,12‐Dimethylbenz(a)anthracene (DMBA)‐treated and control buccal pouches suggesting a role of either heterogeneity in treated pouches or presence of some changes in the control pouches . Definitive histopathological and biochemical changes, including severe dysplasia, were detected in these control sections, thus, all such misclassifications should be given due consideration . In view of this, the present Raman spectroscopy study was carried out in patients diagnosed with oral squamous cell carcinoma (SCC) to screen the mucosa adjacent to the cancer lesion (contralateral normal) for detecting such misclassifications, as these misclassifications may be indicative of underlying carcinogenic events.…”

“…34 Definitive histopathological and biochemical changes, including severe dysplasia, were detected in these control sections, thus, all such misclassifications should be given due consideration. 35 In view of this, the present Raman spectroscopy study was carried out in patients diagnosed with oral squamous cell carcinoma (SCC) to screen the mucosa adjacent to the cancer lesion (contralateral normal) for detecting such misclassifications, as these misclassifications may be indicative of underlying carcinogenic events. These patients were then followed up clinically for appearance of any clinically apparent cancerous lesion in the oral cavity.…”

Recent advances in linear and non‐linear Raman spectroscopy. Part XI

“…Kumar and co‐workers used Raman spectroscopy in an experimental oral carcinogenesis study to determine abnormal changes in control tissues. They concluded that Raman‐based in vivo imaging can serve as a promising label‐free tool for screening even in the nonhabitue population where conventional screening is shown to be not effective . Nosenko et al reported the nature of some features in the Raman spectra of hydroxyapatite‐containing materials.…”