Characteristics of extracellular cyclic AMP-dependent protein kinase as a biomarker of cancer in dogs

Protein Kinase A Detection in Human Urine Samples

Actively involved in tumor maintenance, cAMP-dependent protein kinase A (PKA) has been proposed as a putative biomarker in cancer. Recently, an active PKA form has been identified in human sera and PKA autoantibodies have been detected in cancer patients. However, their serum functions, as well as diagnostic significance, remain largely unknown. Although several PKA detection assays have been developed, none refer to a laboratory diagnostic procedure. Among these, ELISA and Western blotting (WB) assays have been employed in PKA detection. Since, to the best of our knowledge, there are no data showing its presence in human urine samples, herein, we explore the possibility of PKA's existence in this biological specimen. Interestingly, among the 30 screened urines by quantitative sandwich ELISA, we recognized detectable PKA levels in 5 different samples, and of those two exhibited a considerable high concentration. To corroborate these results, we also evaluated PKA's presence in both positive and negative ELISA urines by WB. Remarkably, immunoblotting analysis confirmed PKA's existence in certain, but not in all, human urine specimens. Despite being quite preliminary, these findings firstly identify PKA in urine samples and provide evidence for its potential clinic usage as a diagnostic analyte in laboratory medicine.

AniScan Using Extracellular Cyclic AMP-Dependent Protein Kinase A as a Serum Biomarker Assay for the Diagnosis of Malignant Tumors in Dogs

The early detection of tumors improves chances of decreased morbidity and prolonged survival. Serum biomarkers are convenient to use and have several advantages over other approaches, such as accuracy and straightforward protocols. Reliable biomarkers from easily accessible sources are warranted for the development of cost-effective assays for routine screening, particularly in veterinary medicine. Extracellular c-AMP-dependent protein kinase A (ECPKA) is a cytosolic leakage enzyme. The diagnostic accuracy of detecting autoantibodies against ECPKA was found to be higher than that of ECPKA activity from enzymatic assays, which use a complicated method. Here, we investigated the diagnostic significance of measuring serum ECPKA autoantibody levels using an in-house kit (AniScan cancer detection kit; Biattic, Anyang, Korea). We used sera from 550 dogs, including healthy dogs and those with malignant and benign tumors. Serum ECPKA and immunoglobulin G were determined using the AniScan cancer detection kit. ECPKA autoantibody levels were significantly higher (p < 0.01) in malignant tumors than in benign tumors, non-tumor diseases, and healthy controls. On the basis of sensitivity and specificity values, AniScan ECPKA is a rapid and easy-to-use assay that can be applied to screen malignant tumors from benign tumors or other diseases in dogs.

Drug repurposing for targeting cyclic nucleotide transporters in acute leukemias - A missed opportunity

While current treatment regimens for acute leukemia can dramatically improve patient survival, there remains room for improvement. Due to its roles in cell differentiation, cell survival, and apoptotic signaling, modulation of the cyclic AMP (cAMP) pathway has provided a meaningful target in hematological malignancies. Several studies have demonstrated that gene expression profiles associated with increased pro-survival cAMP activity or downregulation of various pro-apoptotic factors associated with the cAMP pathway are apparent in acute leukemia patients. Previous work to increase leukemia cell intracellular cAMP focused on the use of cAMP analogs, stimulating cAMP production via transmembrane-associated adenylyl cyclases, or decreasing cAMP degradation by inhibiting phosphodiesterase activity. However, targeting cyclic nucleotide efflux by ATP-binding cassette (ABC) transporters represents an unexplored approach for modulation of intracellular cyclic nucleotide levels. Preliminary studies have shown that inhibition of cAMP efflux can stimulate leukemia cell differentiation, cell growth arrest, and apoptosis, indicating that targeting cAMP efflux may show promise for future therapeutic development. Furthermore, inhibition of cyclic nucleotide transporter activity may also contribute multiple anticancer benefits by reducing extracellular pro-survival signaling in malignant cells. Hence, several opportunities for drug repurposing may exist for targeting cyclic nucleotide transporters.

Extracellular cyclic adenosine monophosphate-dependent protein kinase A autoantibody and C-reactive protein as serum biomarkers for diagnosis of cancer in dogs

Protein kinase A, a cyclic adenosine monophosphate (AMP)‐dependent enzyme, normally exists within mammalian cells; however, in cancer cells, it can leak out and be found in the serum. Extracellular cyclic AMP‐dependent protein kinase A (ECPKA) has been determined to increase in the serum of cancer‐bearing dogs. However, there have been no reports in the veterinary literature on serum ECPKA autoantibody (ECPKA‐Ab) expression in dogs with cancer. The aim of this study was to evaluate ECPKA‐Ab and C‐reactive protein (CRP) as serum biomarkers for cancer in dogs. ECPKA‐Ab and CRP levels were detected by an enzyme‐linked immunosorbent assay in serum samples from dogs with malignant tumours (n = 167), benign tumours (n = 42), or non‐tumour disease (n = 155) and from healthy control dogs (n = 123). ECPKA‐Ab and CRP levels were significantly higher in the dogs with malignant tumours than in those with benign tumours or non‐tumour diseases, as well as in the healthy controls (P < 0.001, Kruskal‐Wallis test). There was a significant positive correlation between the neoplastic index, which was developed using ECPKA‐Ab and CRP levels, and the presence of cancer in dogs (P < 0.001); the area under the receiver‐operating characteristic curve was estimated to be >0.85 (P < 0.001). In conclusion, ECPKA‐Ab is a potential serum biomarker for a broad spectrum of cancers. Combined measurement of CRP and ECPKA‐Ab levels in serum improves the sensitivity and accuracy of a diagnosis of cancer in dogs.