In-transit melanoma: the role of alkylating-agent resistance in regional therapy.
BACKGROUND
Regional perfusion treatments for melanoma, using the alkylating agent melphalan, show variable responses in magnitude and duration. Surprisingly, the potential contribution of alkylating-agent resistance mechanisms to diminish tumor responses, especially the crucial cellular detoxifying system formed by glutathione (GSH) and its associated enzyme glutathione-S-transferase (GST), has remained unexplored. Objectives of this study were to characterize GSH levels and GST activity in melanoma of patients undergoing regional perfusion and examine the effect of melphalan concentration in both an in vitro human melanoma cell line and in the extremity melanoma of an in vivo rodent limb infusion model.


METHODS
Human in-transit melanoma, muscle, subcutaneous tissue, and skin (n = 9) and metastatic regional lymph nodes (n = 7) were evaluated for GSH level and GST activity. Effects of increasing melphalan exposure on GSH and GST were studied in an in vitro human melanoma cell line. A survival human melanoma xenograft model of isolated limb infusion using increasing dosages of melphalan was used, with evaluation of GSH and GST in the recurrent tumor.


RESULTS
GSH levels in human in-transit lesions and muscle were significantly higher than that of skin and subcutaneous tissue. Four of 9 patients had tumor-to-muscle GSH ratio > 1. A strong correlation was seen between in vitro melphalan dose and resultant GSH level and GST activity. In vivo recurrent tumor GSH levels correlated with increasing melphalan infusion dose.


CONCLUSIONS
A GSH-based resistance pathway may play a role in effecting response and toxicity to regional melphalan perfusion.
Grubbs
Elizabeth G
EG
Department of General Surgery, Duke University Medical Center, Durham, NC 27710, USA.
Abdel-Wahab
Omar
O
Cheng
Tsung-Yen
TY
Abdel-Wahab
Zeinab
Z
Peterson
Bercedis
B
Pruitt
Scott K
SK
Colvin
O Michael
OM
Friedman
Henry S
HS
Tyler
Douglas S
DS
D000818:Animals; D018906:Antineoplastic Agents, Alkylating / Q000008:administration & dosage*; D010478:Chemotherapy, Cancer, Regional Perfusion; D019008:Drug Resistance, Neoplasm / Q000502:physiology*; D005260:Female; D005978:Glutathione / Q000378:metabolism*; D005982:Glutathione Transferase / Q000378:metabolism*; D006801:Humans; D008658:Inactivation, Metabolic; D008207:Lymphatic Metastasis; D008545:Melanoma / Q000188:drug therapy* / Q000378:metabolism; D008546:Melanoma, Experimental / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D008558:Melphalan / Q000008:administration & dosage*; D051381:Rats; D011923:Rats, Nude; D014183:Transplantation, Heterologous; D014407:Tumor Cells, Cultured
D018906:Antineoplastic Agents, Alkylating; D005982:Glutathione Transferase; D005978:Glutathione; D008558:Melphalan