Chordomas are rare bone
tumors, developed from the notochord and largely resistant to
chemotherapy. A special feature of this
tumor is the heterogeneity of its cells. By combining high pressure freezing (HPF) with electron tomography we were able to illustrate the connections within the cells, the cell-cell interface, and the mitochondria-associated endoplasmic reticulum membrane complex that appears to play a special role among the characteristics of
chordoma. These
lipid raft-like regions are responsible for
lipid syntheses and for calcium signaling. Compared to other
tumor cells,
chordoma cells show a close connection of rough endoplasmic reticulum and mitochondria, which may influence the
sphingolipid metabolism and
calcium release. We quantified levels of
ceramide and glycosylceramide species by the
methyl tert-butyl ether extraction method and we assessed the intracellular
calcium concentration with the ratiometric
fluorescent dye Fura-2AM. Measurements of the changes in the intracellular
calcium concentration revealed an increase in
calcium due to the application of
acetylcholine. With regard to
lipid synthesis,
glucosylceramide levels in the
chordoma cell line were significantly higher than those in normal healthy cells. The accumulation of glycosylceramide in drug resistant
cancer cells has been confirmed in many types of
cancer and may also account for drug resistance in
chordoma. This study aimed to provide a deep morphological description of
chordoma cells, it demonstrated that HPF analysis is useful in elucidating detailed structural information. Furthermore we demonstrate how an accumulation of glycosylceramide in
chordoma provides links to drug resistance and opens up the field for new research options.