hENT1 expression in human urothelium; Evaluating hENT1 prognostic potential for intravesical Gemcitabine treatment outcome in patients with superficial urothelial carcinoma. Introduction Gemcitabine (2’, 2’ -difluorodeoxycytidine), a cytidine analogue, requires plasma membrane nucleoside transporter proteins to enter cells and exert its cytotoxicity. Studies of other epithelial cancers such as Non-Small-Cell Lung Cancer (NSCLC) 1 and pancreatic adenocarcinoma 2, have identified the nucleoside transporter protein hENT1 (human Equilibrative Nucleoside Transporter 1; also SLC29A1), as responsible for the majority of Gemcitabine uptake. Further, they have demonstrated that hENT1 expression is prognostic for patients’ Gemcitabine response 3. Conclusions The presence and expression patterns of hENT1 in human normal urothelia and superficial TCC were determined for the first time. Our results appear to indicate that hENT1 expression is not prognostic for Gemcitabine response in superficial TCC however, a larger sample size and longer follow-up would clarify the relationship. Results SLC29A1 antibody was found to uniformly stain the epithelial cells of all ‘normal’ urothelial samples with > 75% of patient samples achieving a score of 3+ hENT1 stain intensity (Fig 1). hENT1 expression in TCC samples was found to differ markedly from normal urothelium with heterogeneous staining across the sample, including regions of 0 staining (Fig 2). Univariate analysis found no clear relationship between Gemcitabine response and hENT1 expression in TCC (Table). Methods A novel immunohistochemistry stain was developed for formalin fixed paraffin embedded human urothelium using SLC29A1 monoclonal antibody. A histological review was undertaken of 30 normal urothelial samples (no history of TCC or > 2 years TCC free; age range 58 to 89, median 68; 2:1 male: female ratio), and 33 recurrent superficial bladder transitional cell carcinomas (naïve, T0-Ta; age range 61 to 83, median 66; 2:1 male to female ratio), obtained as part of the biomarker study for a Phase II trial of intravesical gemcitabine in patients with superficial urothelial carcinoma. Scoring for hENT1 was based on relative staining intensity and pattern. Two pathologists, blinded to clinical characteristics and outcomes, assessed and scored patient samples. Univariate analysis was used to assess relationships between patient outcome at 3 months post Gemcitabine treatment and pre-Gemcitabine hENT1 score. Aim In this report we describe hENT1 expression in normal urothelia, recurrent superficial Transitional Cell Carcinoma (TCC) prior to Gemcitabine treatment, and assess the relationship between hENT1 expression and patient Gemcitabine response. References 1) Oguri, T., H. Achiwa, et al. Cancer Letters. 2007;256(1): ; 2) Spratlin, J., R. Sangha, et al. Clinical Cancer Research. 2004; 10(20): ; 3) Gazzaniga P, Silvestri I et al. Anticcancer Res. 2007; 18(2): ; Wei Melbourne 1, Kim Tran 1, Loreena Johnson 2, Paul de Souza 3, William J. Lynch 2 1 SEALS, Dpt Anatomical Pathology, St George Hospital, Kogarah, Australia; 2 St George Urology, St George hospital, Kogarah, Australia; 3 Dpt Medical Oncology, St George Hospital, Kogarah, Australia Poster presentation sponsor No. 078 Score/outcome Clear Response0771 Partial Response0311 Stable Disease1451 Disease Progression 1100 Summary of hENT1 score vs 3mth clinical outcome; Fig 1. Normal urothelia with hENT1; Top left; : Small bowel, ctl Top Right: : 1+ Bottom left: : 2+ Bottom Right: : 3+ Fig 2. TCC Ta with hENT1; Top left : 0+ Top Right: : 1+ Bottom left: : 2+ Bottom Right: : 3+ Acknowledgements We would like to acknowledge the ongoing support of SEALS, St George Hospital Anatomical Pathology department.