Cancer Stem Cells in Moderately Differentiated Buccal Mucosal Squamous Cell Carcinoma Express Components of the Renin–Angiotensin System

Oral cancer is the sixth most common cancer worldwide, with a high prevalence in South Asia. Tobacco and alcohol consumption remain the most dominant etiologic factors, however HPV has been recently implicated in oral cancer. Surgery is the most well established mode of initial definitive treatment for a majority of oral cancers. The factors that affect choice of treatment are related to the tumor and the patient. Primary site, location, size, proximity to bone, and depth of infiltration are factors which influence a particular surgical approach. Tumors that approach or involve the mandible require specific understanding of the mechanism of bone involvement. This facilitates the employment of mandible sparing approaches such as marginal mandibulectomy and mandibulotomy. Reconstruction of major surgical defects in the oral cavity requires use of a free flap. The radial forearm free flap provides excellent soft tissue and lining for soft tissue defects in the oral cavity. The fibula free flap remains the choice for mandibular reconstruction. Over the course of the past thirty years there has been improvement in the overall survival of patients with oral carcinoma largely due to the improved understanding of the biology of local progression, early identification and treatment of metastatic lymph nodes in the neck, and employment of adjuvant post-operative radiotherapy or chemoradiotherapy. The role of surgery in primary squamous cell carcinomas in other sites in the head and neck has evolved with integration of multidisciplinary treatment approaches employing chemotherapy and radiotherapy either sequentially or concurrently. Thus, larynx preservation with concurrent chemoradiotherapy has become the standard of care for locally advanced carcinomas of the larynx or pharynx requiring total laryngectomy. On the other hand, for early staged tumors of the larynx and pharynx, transoral laser microsurgery has become an effective means of local control of these lesions. Advances in skull base surgery have significantly improved the survivorship of patients with malignant tumors of the paranasal sinuses approaching or involving the skull base. Surgery thus remains the mainstay of management of a majority of neoplasms arising in the head and neck area. Similarly, the role of the surgeon is essential throughout the life history of a patient with a malignant neoplasm in the head and neck area, from initial diagnosis through definitive treatment, post-treatment surveillance, management of complications, rehabilitation of the sequelae of treatment, and finally for palliation of symptoms.

Aldehyde dehydrogenase (ALDH) is a candidate marker for lung cancer cells with stem cell-like properties. Immunohistochemical staining of a large panel of primary non-small cell lung cancer (NSCLC) samples for ALDH1A1, ALDH3A1, and CD133 revealed a significant correlation between ALDH1A1 (but not ALDH3A1 or CD133) expression and poor prognosis in patients including those with stage I and N0 disease. Flow cytometric analysis of a panel of lung cancer cell lines and patient tumors revealed that most NSCLCs contain a subpopulation of cells with elevated ALDH activity, and that this activity is associated with ALDH1A1 expression. Isolated ALDH(+) lung cancer cells were observed to be highly tumorigenic and clonogenic as well as capable of self-renewal compared with their ALDH(-) counterparts. Expression analysis of sorted cells revealed elevated Notch pathway transcript expression in ALDH(+) cells. Suppression of the Notch pathway by treatment with either a γ-secretase inhibitor or stable expression of shRNA against NOTCH3 resulted in a significant decrease in ALDH(+) lung cancer cells, commensurate with a reduction in tumor cell proliferation and clonogenicity. Taken together, these findings indicate that ALDH selects for a subpopulation of self-renewing NSCLC stem-like cells with increased tumorigenic potential, that NSCLCs harboring tumor cells with ALDH1A1 expression have inferior prognosis, and that ALDH1A1 and CD133 identify different tumor subpopulations. Therapeutic targeting of the Notch pathway reduces this ALDH(+) component, implicating Notch signaling in lung cancer stem cell maintenance.