The Differentiation-Inducing Effect of a Retinoic Acid Derivative on a Pulmonary Carcinoma Cell Line

Abstract

Pulmonary carcinoma is a main cause of cancer death internationally. Chemotherapeutic regimens in most solid tumors have limited effect. And in the targeted inhibition of carcinogenic driver mutations with molecular therapies, in a large number of cases, patients acquire resistance to drugs. Therefore, the development of new therapeutic approaches is highly desirable. In the present study, we evaluated the applicability of 4[(5,6,7,8-tetrahydro-5,5,8,8- tetramethyl- 2-naphthalenyl)carbamoyl]benzoic acid (Am80), a synthetic retinoid, as a differentiation inducer in pulmonary carcinoma and examined its effect on the viability and differentiation of Calu-6 cells (a human nonsmall cell lung cancer cell line), with the final goal of establishing a new approach to pulmonary carcinoma therapy. The cell viability of Calu-6 cells after Am80 treatment was assessed by the CellTiter-Glo Luminescent Cell Viability Assay. The early apoptosis of cells was detected by Terminal deoxynucleotidyl Transferase-mediated deoxyuridine triphosphate Nick End Labeling (TUNEL) staining. The differentiation-inducing effect of Am80 on Calu-6 cells was investigated by immunostaining. Am80 induced the differentiation of Calu-6 to alveolar type I and II cells. However, Am80 reduced the viability of Calu-6 cells without inducing apoptosis. In addition, in order to investigate whether Am80 inhibits tumor growth in vivo, we conducted an in vivo experiment to determine he effect of the intratumoral administration of Am80 in mice harboring sc tumors composed of Calu-6 cells. Am80 significantly influenced the suppression of tumor growth.