The Role of Extracellular Factors in Human Metastatic Chordoma Cell Growth In Vitro

Abstract

Human metastatic chordoma cells were isolated, and initial in vitro characterization was performed. Biochemical and physiologic changes were observed in response to pH, oxygen, and glucose. The extracellular microenvironment directly affects metastatic chordoma cell phenotype in vitro. Chordomas are primary bone tumors that usually occur in the spine or skull. Chordomas arise from embryonic notochordal remnants along the axial skeleton, most commonly the sacrum, followed by the base of the skull and the mobile spine. Due to a high degree of resistance to radiation and chemotherapy, chordomas eventually cause death by direct growth or by metastasizing to other organs. Extracellular pH, oxygen, and glucose levels in the culture medium were controlled, and cell response was assessed using MTT staining, SDS-PAGE, Western blotting, tandem mass spectrometry, TUNEL, immunofluorescence, and flow cytometry. In this study, we present a new chordoma cell line established from metastatic tissue and novel data characterizing some aspects of chordoma cell phenotype in different conditions in vitro. Chordoma biologic markers were expressed in the new cell line. Alkaline pH dramatically increased intracellular protein tyrosine phosphorylation, metabolic activity, and albumin accumulation in the cells, while acidic pH caused apoptosis. The level of proliferation, apoptosis, and tyrosine phosphorylation, as well as the overall protein expression profile, strongly depended on extracellular media pH and oxygen/glucose levels. Chordoma's preferred extracellular microenvironment in vitro was rather alkaline, with an optimum at pH 8.5, and apoptotic changes were induced at acidic pH. We found that bovine serum albumin was accumulated by chordoma cells from the incubation media, and this accumulation depended on extracellular pH, with the highest accumulation at alkaline pH.