Gemcitabine is a cytotoxic
nucleoside analog with activity in relapsing/refractory
Hodgkin's disease (HD). Because
gemcitabine is hydrophilic, it requires plasma membrane
nucleoside transporter proteins to access intracellular targets. The most abundant and widely distributed transporter in human cells is human
equilibrative nucleoside transporter 1 (hENT1). Because our prior studies showed that a deficiency in hENT1 confers high-level resistance to
gemcitabine toxicity in vitro, we developed an immunohistochemical method to assess the hENT1 abundance of cells in
tumor tissue. We now report the application of this method for visualizing the hENT1
protein abundance in the plasma membranes of Reed-Sternberg cells in lymph nodes of HD patients. Frozen sections of 30 lymph nodes were stained with
monoclonal antibodies (mAb 10D7G2) raised against a synthetic
peptide comprised of residues 254-271 from the large intracellular loop of hENT1 and staining intensity was scored on a 0-4 + scale. hENT1-staining intensity varied among HD lymph node samples (score/n; 0/8; 1/10; 2/9; 3/3; 4/0) and suggested that at least 60% of the
tumors appeared hENT1 deficient. Because Epstein-Barr virus (EBV) is often associated with HD, staining for Epstein-Barr early
RNA was also examined. Although 9/30 patients tested positive for EBV, there was no correlation with hENT1 staining. hENT1-staining intensities were positively correlated with age of the patient but were independent of other clinical, laboratory or pathology features (
tumor stage, histologic subtype, presence of B symptoms, staining for CD15 or CD30, serum biochemistry, disease free survival, and overall survival). We conclude that, because hENT1 deficiency has been previously related to
nucleoside-drug resistance, immunohistochemical staining for hENT1 warrants evaluation as a predictive tool for guiding the appropriate use of
gemcitabine in the treatment of HD.