Monocytes secrete interleukin-6 when co-cultured in vitro with benign or malignant autologous fragment spheroids from squamous cell carcinoma patients.

Biopsies from tumour and benign mucosa were removed from patients with head and neck squamous-cell carcinoma (HNSCC), chopped into cubes and transferred to a nonadhesive culture system where in vitro fragment (F)-spheroids were established. The F-spheroids stabilized within 14 days of culture in vitro with epithelial cells and fibroblasts on the surface. F-spheroids were co-cultured with freshly isolated autologous monocytes. The monocytes of 10 of 11 patients secreted interleukin (IL)-6 at a level similar to that of the average monocyte endotoxin-stimulated response. Secreted IL-1beta or tumour necrosis factor-alpha (TNF-alpha) levels greater than 0.1 times the endotoxin-stimulated secretion were determined in one and two of the 11 co-culture experiments, respectively. This different monocyte response to F-spheroids compared with endotoxin stimulation was also present at the mRNA expression level. HNSCC monocytes secreted no IL-6 after co-culture with autologous fibroblasts. When monocytes and F-spheroids were cultured separated by a semipermeable membrane, the IL-6 supernatant level was only approximately 25% of that observed during co-culture with direct contact. F-spheroids secreted only trace amounts of IL-6. In conclusion, monocytes of HNSCC patients generally secrete IL-6, but not IL-1beta or TNF-alpha, after stimulation with epithelial-associated components of F-spheroids upon direct contact and in part by a soluble substance.