hENT1 Predicts Benefit from Gemcitabine in Pancreatic Cancer but Only with Low CDA mRNA

Abstract

Gemcitabine or 5-fluorouracil (5-FU) based treatments can be selected for pancreatic cancer. Equilibrative nucleoside transporter 1 (hENT1) predicts adjuvant gemcitabine treatment benefit over 5-FU. Cytidine deaminase (CDA), inside or outside of the cancer cell, will deaminate gemcitabine, altering transporter affinity. ESPAC-3(v2) was a pancreatic cancer trial comparing adjuvant gemcitabine and 5-FU. Tissue microarray sections underwent in situ hybridization and immunohistochemistry. Analysis of both CDA and hENT1 was possible with 277 patients. The transcript did not correlate with protein levels for either marker. High hENT1 protein was prognostic with gemcitabine; median overall survival was 26.0 v 16.8 months (p = 0.006). Low CDA transcript was prognostic regardless of arm; 24.8 v 21.2 months with gemcitabine (p = 0.02) and 26.4 v 14.6 months with 5-FU (p = 0.02). Patients with low hENT1 protein did better with 5-FU, but only if the CDA transcript was low (median survival of 5-FU v gemcitabine; 29.3 v 18.3 months, compared with 14.2 v 14.6 with high CDA). CDA mRNA is an independent prognostic biomarker. When added to hENT1 protein status, it may also provide treatment-specific predictive information and, within the frame of a personalized treatment strategy, guide to either gemcitabine or 5FU for the individual patient.

Keywords: 5-fluorouracil; biomarker; chemotherapy; gemcitabine; predictive marker; prognostic marker; pyrimidine.

Figure 1

Representative images of tissue cores showing CDA mRNA expression before and after SpotStudio^® analysis. (A) Raw and digitized images of tissue expressing low CDA mRNA. (B) Raw and digitized images of tissue expressing high CDA, with inset example of cells with high CDA expression. Thick red line surrounds areas with tumor cells. Blue lines = Cells without any spots. Green lines = Cells with one single spot. Orange lines = Cells with between two and five spots. Thin red lines = Cells with six or more spots. Scale bar = 20 µm.

Figure 2

Kaplan-Meier survival curves separated by both treatment arms (5-FU and gemcitabine) and biomarker expression levels. (A,B): Survival curves for patients with low and high CDA mRNA levels (low ≤ 0.61, high > 0.61 MSPC), for patients randomized to adjuvant treatment with 5-FU (A) and gemcitabine (B). (C,D): Survival curves for low and high hENT1 expressing patients (low ≤48, high >48 H-Score), for patients randomized to adjuvant treatment with 5-FU (C) and gemcitabine (D). All groups and the number of at-risk individuals are shown in each graph. All p-values were determined by log-rank analyses using two-sided χ² tests.

Figure 3

Kaplan-Meier survival curves for analyses of combined CDA mRNA and hENT1 protein biomarker interaction looking at all expression level combinations (CDA low, hENT1 low; CDA high, hENT1 low; CDA low, hENT1 high; CDA high, hENT1 high). Graphs show response to treatment with 5-FU (A) and gemcitabine (B). In (C,D) the same data as above is presented showing the difference in survival for patients treated with 5-FU compared to gemcitabine in patients with low hENT1 protein and either low CDA (C) or high CDA (D), and patients with high hENT1 protein and either low CDA (E) or high CDA (F). All groups and the number of at-risk individuals are shown for each graph. All p-values were determined by log-rank analyses using two-sided χ² tests.