Schwann cell lines derived from malignant peripheral nerve sheath tumors respond abnormally to platelet‐derived growth factor‐BB

Abstract

Neurofibromatosis type 1 (NF1) is a genetic disease caused by the loss of neurofibromin, which can lead to formation of highly invasive malignant peripheral nerve sheath tumors (MPNST). We characterized platelet-derived growth factor-beta (PDGF-beta) receptor expression levels and signal transduction pathways in NF1 MPNST cell lines and compared them with the expression of PDGF-beta receptors in normal human Schwann cells (nhSC). As examined by Western blotting, PDGF-beta receptor expression levels were similar in nhSC and NF1 MPNST cell lines. MAPK and Akt also were phosphorylated in both cell types to a similar degree in response to PDGF B chains (PDGF-BB). However, increased intracellular calcium (Ca2+) levels in response to PDGF-BB were observed only in the NF1 MPNST cell lines; nhSC did not show any increase in intracellular calcium when stimulated with PDGF-BB. The calcium response in NF1 MPNST cell lines was blocked with thapsigargin, suggesting that the PDGF-BB-stimulated increases in intracellular calcium originated in the internal compartment of the cell rather than reflecting influx of calcium from the extracellular compartment. Calmodulin kinase II (CAMKII) is phosphorylated in response to PDGF-BB in the NF1 MPNST cell lines, whereas no phosphorylation of CAMKII was observed in nhSCs. The decreased growth of NF1 MPNST cell lines after treatment with a CAMKII inhibitor is consistent with the view that aberrant activation of the calcium-signaling pathway by PDGF-BB contributes to the formation of MPNST in NF1 patients.

Expression of CD1d Molecules by Human Schwann Cells and Potential Interactions with Immunoregulatory Invariant NK T Cells

“…The ST88-14 and T265-2C were established from a malignant peripheral nerve sheath tumor (MPNST), and STS-26T was derived from a benign schwannoma (15,16). As previously described and confirmed in our hands, all three of these cell lines expressed the Schwann cell marker S100␤ confirming their lineage of origin (data not shown).…”

“…Transformed human Schwann cell lines, ST88-14, T265-2C, and STS-26T and HeLa/CD1d transfectants were grown in DMEM supplemented with 10% FBS (HyClone Laboratories) (15)(16)(17). Human iNKT cell clones, DN2.D5, DN2.D6, and DN2.B10, and control CD4 ϩ T cell clone T1.5B2 have been previously described (18), and murine iNKT hybridoma DN3A4.1-2 was a generous gift from Dr. M. Kronenberg, La Jolla Institute for Allergy and Immunology (San Diego, CA).…”

Imatinib mesylate inhibits cell invasion of malignant peripheral nerve sheath tumor induced by platelet-derived growth factor-BB

“…Therefore, PDGF-BB induced higher levels of proliferation in MPNST cell lines than in normal human adult Schwann cells. 15 The above studies were concerned with the mitogenic activity of growth factors, and few papers have investigated motogenic or invasion-enhancing activity of growth factors in MPNSTs; for example, HGF-promoted MPNST cell invasion through an HGF/c-Met autocrine loop. 16 Acquisition of invasive properties also plays an important role in tumor progression.…”

Experimental therapeutic approaches to peripheral nerve tumors

“…Although a clinical trial for treatment of MPNST through PDGF receptor inhibition has not been reported, this receptor has been identified as a potential contributor to tumor progression and so represents a potential therapeutic target. 24 Directed Therapeutics for Intracellular Signaling Pathways. The Ras protein undergoes posttranslational modification with the ultimate result of achieving membrane attachment.…”