High resolution melting analysis (HRM) for the assessment of clonality in feline B-cell lymphomas.

Analysis of clonality is gaining importance in diagnosing lymphomas in veterinary medicine. Usually, PCR for the analysis of antigen receptor rearrangement (PARR) is followed by electrophoretic separation of the PCR products. Aim of this study was to test the feasibility of HRM for the assessment of clonality in B-cell lymphomas of cats. High resolution melting analysis differentiates PCR products by their different melting point using the decrease in fluorescence of an intercalating dye during melting of the PCR product. Additionally, the method is easy to use with no post-PCR manipulation of the samples. Forty-seven feline B-cell lymphomas and 31 reactive lymphatic proliferations of cats were investigated by PARR followed either by capillary electrophoresis or an HRM assay. To objectify the interpretation of the HRM results a recently published mathematical approach was applied to the melting curve. To overcome discrepancies between the visual interpretation and the mathematical approach, the latter was modified to include testing of reproducibility and recognition of pseudoclonality. In 11 of 47 lymphoma cases clonal populations were detectable by HRM assay compared to 14 of 47 lymphomas in which clonal populations were detected by capillary electrophoresis assay. Neither of the methods showed a clonal pattern in any of the reactive samples. However, the HRM assay showed a unique pattern in cases of follicular lymphatic hyperplasia that had no corresponding pattern in capillary electrophoresis. CONCLUSION: The capillary electrophoresis assay could identify 3 lymphomas that were not detected by the HRM assay and is therefore regarded superior to the HRM assay. The comparison however, was hampered by the overall bad performance of the PARR, that might be the consequence of insufficient primer binding due to somatic hypermutation of the binding sites during antigen stimulated proliferation of the B lymphocytes.

Applicability of 3T body MRI in assessment of nonfocal bone marrow involvement of hematopoietic neoplasia in dogs.

BACKGROUND: The utility of whole body magnetic resonance imaging (MRI) in detecting bone marrow infiltration in dogs with cancer has not been investigated. OBJECTIVES: To assess the feasibility of 3T body MRI for bone marrow assessment in dogs with hematopoietic neoplasia. ANIMALS: Seven dogs with B-cell lymphoma, 3 dogs with myelodysplastic syndrome (MDS), and 2 clinically normal dogs. METHODS: A prospective study of dogs with hematopoetic cancer was conducted using T1W, T2W, In-Phase, Out-of-Phase and STIR pulse sequences of the body excluding the head prior to bone marrow sampling. The relative signal intensity of a midlumbar vertebral body and a midshaft femoral bone marrow was compared by visual and point region of interest analysis to regional skeletal muscle. RESULTS: Similarity of femoral diaphyseal and vertebral body marrow signal intensity to that of skeletal muscle on the Out-of-Phase sequence was useful in distinguishing the 3 dogs with hypercellular marrow because of MDS from the 7 dogs with B-cell lymphoma and from the 2 clinically normal dogs. 1/7 dogs with lymphoma had proven bone marrow involvement but normal cellularity and less than 5% abnormal cells. Unaffected midfemoral marrow had greater signal intensity than skeletal muscle and unaffected vertebral marrow had less signal intensity than skeletal muscle on the Out-of-Phase sequence. CONCLUSIONS AND CLINICAL IMPORTANCE: 3T, Out-of-Phase MR pulse sequence was useful in distinguishing diffuse bone marrow infiltrate (MDS) from minimally or unaffected marrow using skeletal muscle for signal intensity comparison on whole body MRI.

Assessment of bone marrow infiltration diagnosed by flow cytometry in canine large B cell lymphoma: prognostic significance and proposal of a cut-off value.

The aims of this study were to assess the prognostic significance of bone marrow (BM) infiltration in canine large B cell lymphoma (LBCL) and to establish cut-off values for designating the BM as infiltrated by lymphoid blasts. The degree of BM infiltration by large CD21 positive cells in dogs with LBCL was assessed by flow cytometry (FC) and related to time to progression (TTP) and lymphoma-specific survival (LSS). Forty-six dogs were prospectively enrolled, staged and treated with a dose-intense chemotherapeutic protocol. BM infiltration was directly correlated with peripheral blood infiltration (P=0.001), high lactate dehydrogenase activity (P=0.0024) and substage b disease (P<0.001). In the univariate analysis, there was a significant association between BM infiltration diagnosed by FC and both TTP (P=0.001) and LSS (P<0.001). Substage was the only factor associated with TTP in the multivariate analysis (P=0.002), whereas substage (P<0.001) and anaemia (P=0.008) were associated with LSS. A cut-off of 3% BM infiltration had the strongest prognostic value, since it discriminated between dogs with a poorer prognosis (median TTP 69 days; median LSS 155 days) and dogs with a better prognosis (median TTP 149 days; median LSS 322 days). BM analysis is an essential step in the staging of LBCL. The presence of BM infiltration by FC at diagnosis is a negative prognostic indicator in canine LBCL.

Discovery and canine preclinical assessment of a nontoxic procaspase-3-activating compound.

A critical event in the apoptotic cascade is the proteolytic activation of procaspases to active caspases. The caspase autoactivating compound PAC-1 induces cancer cell apoptosis and exhibits antitumor activity in murine xenograft models when administered orally as a lipid-based formulation or implanted s.c. as a cholesterol pellet. However, high doses of PAC-1 were found to induce neurotoxicity, prompting us to design and assess a novel PAC-1 derivative called S-PAC-1. Similar to PAC-1, S-PAC-1 activated procaspase-3 and induced cancer cell apoptosis. However, S-PAC-1 did not induce neurotoxicity in mice or dogs. Continuous i.v. infusion of S-PAC-1 in dogs led to a steady-state plasma concentration of ∼10 µmol/L for 24 to 72 hours. In a small efficacy trial of S-PAC-1, evaluation of six pet dogs with lymphoma revealed that S-PAC-1 was well tolerated and that the treatments induced partial tumor regression or stable disease in four of six subjects. Our results support this canine setting for further evaluation of small-molecule procaspase-3 activators, including S-PAC-1, a compound that is an excellent candidate for further clinical evaluation as a novel cancer chemotherapeutic.

A new subgroup of immunoglobulin heavy chain variable region genes for the assessment of clonality in feline B-cell lymphomas.

In human medicine, PCR-amplification of the complementarity determining region 3 of the immunoglobulin heavy chain genes followed by polyacrylamide gel electrophoresis (PAGE) is an accepted method to assess clonality in B-cell lymphomas and thereby facilitates the differentiation of neoplasias from benign hyperplasias or reactive infiltrates. To generate a basis for the development of a PCR-based assay for the assessment of clonality in feline B-cell lymphomas we analyzed 28 transcripts (cDNA) of the feline immunoglobulin heavy chain variable region genes (IGHV). Transcripts were generated using techniques for the amplification of unknown sequences (i.e. the SMART RACE and the CapFishing technique) as well as primers derived from sequences of the NCBI Trace archive of the cat. Analysis of this archive revealed traces similar to the human IGHV-1 and IGHV-3 subgroups of genes. By identification of the subgroup-specific leader sequence within the traces, two subgroup-specific primers for this region were designed and used to amplify the heavy chain variable region genes. Using all amplification techniques, transcripts of both subgroups were created and the subgroups were denominated according to their human counterparts as feline IGHV-1 and feline IGHV-3. By aligning previously described transcripts of the feline IGHV genes to our transcripts we were able to assign these to the IGHV-3 subgroup; therefore, this study provides the first description of the feline IGHV-1 subgroup of genes. On the basis of the IGHV-1 and IGHV-3 transcripts we developed a PCR-based assay. For each of the two subgroups we used one sense primer derived from the first and one sense primer derived from the third framework region each in combination with a mixture of three antisense primers derived from the fourth framework region. With these four sets of primers, the assay was able to detect monoclonality in 7/10 (70%) cats with histologically and immunohistochemically diagnosed B-cell lymphomas. In two of these cases, monoclonal rearrangement of the IGHV genes was only detectable with IGHV-1 subgroup-specific primers. Amplification of feline hyperplastic lymphatic tissue only gave results indicative of polyclonal populations. The use of a PCR-based assay in combination with standard techniques for the diagnosis of feline lymphoma is helpful and the characterization of the additional subgroup of feline variable regions genes puts this assay on a broader basis.