Mast cells dysregulate apoptotic and cell cycle genes in mucosal squamous cell carcinoma

Abstract

Background: Mucosal squamous cell carcinoma of the head and neck is a disease of high mortality and morbidity. Interactions between the squamous cell carcinoma and the host's local immunity, and how the latter contributes to the biological behavior of the tumor are unclear. In vivo studies have demonstrated sequential mast cell infiltration and degranulation during squamous cell carcinogenesis. The degree of mast cell activation correlates closely with distinct phases of hyperkeratosis, dysplasia, carcinoma in-situ and invasive carcinoma. However, the role of mast cells in carcinogenesis is unclear.

Aim: This study explores the effects of mast cells on the proliferation and gene expression profile of mucosal squamous cell carcinoma using human mast cell line (HMC-1) and human glossal squamous cell carcinoma cell line (SCC25).

Methods: HMC-1 and SCC25 were co-cultured in a two-compartment chamber, separated by a polycarbonate membrane. HMC-1 was stimulated to degranulate with calcium ionophore A23187. The experiments were done in quadruplicate. Negative controls were established where SCC25 were cultured alone without HMC-1. At 12, 24, 48 and 72 hours, proliferation and viability of SCC25 were assessed with MTT colorimetric assay. cDNA microarray was employed to study differential gene expression between co-cultured and control SCC25.

Results: HMC-1/SCC25 co-culture resulted in suppression of growth rate for SCC-25 (34% compared with 110% for the control by 72 hours, p < 0.001), and dysregulation of genes TRAIL, BIRC4, CDK6, Cyclin G2 and CDC6 in SCC25.

Conclusion: We show that mast cells have a direct inhibitory effect on the proliferation of mucosal squamous cell carcinoma in vitro by dysregulating key genes in apoptosis and cell cycle control.

Figure 1

SCC25 co-cultured with (a) HMC-1 and (b) control SCC25 at 12 hours did not show discernible growth difference on microscopic examination. At 72 hours, (d) control SCC25 had outgrown (c) co-cultured SCC25, forming a confluent monolayer on the lower compartment of the culture plate.

Figure 2

Rate of proliferation of SCC25 as determined by MTT colorimetric assay. Co-culture of HMC-1 with SCC25 caused a decreased rate of proliferation evident by 12 hours, and the discrepancy in proliferation continued to increase at 24, 48 and 72 hours.

Figure 3

Schematic representation of dysregulation of apoptotic and cell cycle genes in SCC25 when co-cultured with HMC-1.

Figure 4

Optimal degranulation of HMC-1 with calcium ionophore A23187 was achieved with 1 μM concentration. Degranulation plateaued at 12 hours.