The Current State of Clinical Application of Serum Biomarkers for Canine Lymphoma

The acute-phase protein C-reactive protein (CRP) is used as a diagnostic and prognostic marker in humans with various neoplasias, including non-Hodgkin's lymphoma. To evaluate if CRP could be used to detect different remission states in dogs with lymphoma. Twenty-two dogs with untreated multicentric lymphoma. Prospective observational study. Blood samples were collected at the time of diagnosis, before each chemotherapy session, and at follow-up visits, resulting in 287 serum samples. Before therapy, a statistically significant majority of the dogs (P = .0019) had CRP concentrations above the reference range (68%, 15/22). After achieving complete remission 90% (18/20) of the dogs had CRP concentrations within the reference range, and the difference in values before and after treatment was statistically significant (P < .001). CRP concentrations of dogs in complete remission (median, 1.91; range, 0.2-103) were significantly different (P = .031) from those of dogs with partial remission (median, 2.48; range, 0-89), stable disease (median, 1.77; range, 1.03-42.65), or progressive disease (median, 8.7; range, 0-82.5). There was profound variation of CRP measurements within each dog. CRP is useful in determining complete remission status after treatment with cytotoxic drugs. However, the individual variation between dogs means CRP concentration is not sufficiently different in other remission states to permit its use in monitoring progression of the disease. Greater reliability in determining remission status might be achieved by combining CRP concentration with other serum markers.

Acute phase proteins (APP) are regarded as a useful diagnostic tool in humans with lymphomas, leukaemias and multiple myeloma. C-reactive protein (CRP) and haptoglobin concentrations were measured in dogs with malignant multicentric (high grade) lymphoma (n=16), acute lymphoblastic leukaemia (ALL) (n=11), chronic lymphocytic leukaemia (CLL) (n=7) and multiple myeloma (n=8). Twenty-five healthy dogs served as controls. Measurements of the CRP plasma concentration were performed using a commercial ELISA and haptoglobin was measured with an assay based on its haemoglobin binding capacity. Global group comparisons using Kruskal-Wallis-test revealed significant group differences for both APPs (P<0.0001). Median CRP concentrations were increased in all groups with neoplastic lymphatic disorders (lymphoma: 37.2mg/L, ALL: 47.8mg/L, CLL: 35.5mg/L, myeloma: 17.6mg/L) compared to controls (1.67mg/L; P<0.001). Compared to the healthy controls (median=0.59g/L), haptoglobin was especially increased in dogs with ALL (6.8g/L, P<0.0001) followed by dogs with malignant lymphoma (3.8g/L, P<0.0001), CLL (3.2g/L, P=0.0008), and multiple myeloma (3.0g/L, P=0.0163). For both APPs, a wide range of values was found in all patient groups. The results indicate that particularly severe and acute lymphatic neoplasia, such as high grade lymphoma and ALL, cause significant acute phase reactions in dogs and must be included in the differential diagnoses of increased blood levels of these APPs.

Thymidine kinase 1 (TK1) is a cell cycle regulated enzyme with maximum expression during the S phase. Serum TK1 (S-TK1) is a unique biomarker for cell proliferation. Here, an optimized [(3)H]-thymidine (dThd) phosphorylation assay is described, which is as sensitive as the commercially available TK-REA and TK-Liaison assays for measurement of S-TK1 activity in dogs and humans. Serum samples from dogs (35 healthy, 32 with lymphoma, 2 with leukemia, and 35 with solid tumors) and humans (18 healthy, 9 with chronic lymphocytic leukemia, 10 with myelodysplastic syndrome) were analyzed using the [(3)H]-dThd assay. Mean S-TK1 activities were 1.11 ± 0.46 pmol/min/mL in healthy dogs and 1.15 ± 0.32 pmol/min/mL in healthy humans. S-TK1 activities in dogs with hematological malignancies were 24.2 ± 47.9 pmol/min/mL, and the receiver operating characteristic curve showed an area under the curve of 0.88. With a cut-off value of 1.9 pmol/min/mL (mean value ± 2 SD), the sensitivity was 0.94 and the specificity was 0.68. Very similar results were obtained with human samples (healthy and lymphoma cases). S-TK1 activities measured during chemotherapy of six dogs with lymphoma were drastically reduced. In one case, S-TK1 activity increased prior to relapse. S-TK1 levels in dogs with solid tumors did not differ from the healthy group. S-TK1 activities correlated with those determined with the TK-REA and TK-Liaison assays (r=0.92 and r=0.96, respectively). In conclusion, this optimized [(3)H]-dThd assay is fast, sensitive and economical for measuring S-TK1 activity and should increase its clinical use as biomarker. Copyright © 2012 Elsevier Ltd. All rights reserved.