In vitro sarcoma cells release a lipophilic substance that activates the pain transduction system via TRPV1.
BACKGROUND
Despite success in treating many forms of cancer, pain associated with malignancy remains a serious clinical issue with a poorly understood etiology. This study determined if certain sarcoma cell lines produced a soluble factor that activates the TRPV1 ion channel expressed on nociceptive sensory neurons, thereby activating a major pain transduction system.


METHODS
Trigeminal ganglia were harvested from rats and cultured. A rhabdomyosarcoma (CRL1598) and osteosarcoma (CRL 1543) cell line were grown to 75% confluency. Conditioned media (CM) was collected after 24 h of exposure and subjected to reverse phase chromatography. Neuronal activation in the presence of CM was measured using iCGRP RIA and calcium imaging after treatment with vehicle or I-RTX, a potent TRPV1 antagonist. Data were analyzed by ANOVA/Bonferroni or t test.


RESULTS
The rhabdomyosarcoma CM produced a 4-fold increase in iCGRP release compared with control media (P < 0.001). The osteosarcoma cell line CM produced a 7-fold increase in iCGRP release compared with control media (P < 0.001). This evoked iCGRP release was via TRPV1 activation since the effect was blocked by the antagonist I-RTX. The application of rhabdomyosarcoma CM produced about a 4-fold increase in [Ca(2+)]I levels (P < 0.001), and this effect was blocked by pretreatment with the TRPV1 antagonist, I-RTX.


CONCLUSIONS
We have shown that certain sarcoma cell lines produce a soluble, lipophilic factor that activates the peripheral nociceptor transduction system via TRPV1 activation, thereby contributing to cancer pain. Further investigations are needed to develop tumor-specific analgesics that do not produce unwanted or harmful side-effects.
Lautner
Meeghan A
MA
Department of Surgery, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA.
Ruparel
Shivani B
SB
Patil
Mayur J
MJ
Hargreaves
Kenneth M
KM
D000818:Animals; D001859:Bone Neoplasms / Q000378:metabolism*; D015740:Calcitonin Gene-Related Peptide / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D017077:Culture Media, Conditioned / Q000494:pharmacology; D004224:Diterpenes / Q000494:pharmacology; D006801:Humans; D008297:Male; D009619:Nociceptors / Q000378:metabolism*; D012516:Osteosarcoma / Q000378:metabolism*; D010146:Pain / Q000378:metabolism*; D011863:Radioimmunoassay; D051381:Rats; D017207:Rats, Sprague-Dawley; D012208:Rhabdomyosarcoma / Q000378:metabolism*; D050916:TRPV Cation Channels / Q000819:agonists / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D017077:Culture Media, Conditioned; D004224:Diterpenes; D050916:TRPV Cation Channels; C024353:resiniferatoxin; D015740:Calcitonin Gene-Related Peptide; D002118:Calcium