DIGNA BIOTECH

APO A1 OXIDATED APOLIPOPROTEIN A1 DETECTION AS EARLY HEPATOCELLULAR CARCINOMA (HCC) MARKER

The cell hepatocellular carcinoma (HCC) accounts for 80-90% of primary malignant liver tumors, is the fifth highest incidence in malignant disease and the third leading cause of cancer deaths with an average of 450,000 new cases diagnosed annually. Although risk factors such as hepatitis B or C, alcohol abuse or steatosis are known, that the population at risk is monitored regularly and the availability of new therapeutic strategies, the survival of patients (about 6 months) has not been able to improve substantially over the past two decades. The main reason is the advanced stage of disease at the time of diagnosis, which highlights the urgent need to develop new methods of early detection in the population at risk (hepatitis and cirrhosis) and to develop innovative therapeutic methods. The partial or total resection and hepatectomy followed by transplantation is the only curative therapy but is not always possible to apply and common recurrence of HCC. Therefore, it’s of great interest to identify biomarkers that allow us to detect early HCC and help us in prevention and/or treatment. To search for these markers is especially interesting the use of serum, since it is a sample that constantly perfused tissues and in which can be identified thousands of circulating proteins and peptides. In addition, serum determination techniques are non-painful and non-invasive for patients, with good availability of samples, easy to perform, fast and cheap.

One of the factors playing role in the HCC development is the Methionine adenosyltransferase (MAT1), responsible of the S-Adenosylmethionine (AdoMet) syntesis in liver. Patients with liver desease have impaired AdoMet biosynthesis, due to a impaired MAT1 activity, wich may contribute to the pathogenesis of liver disease and malignant development. In this study knockout mice MAT1-/-, which spontaneously develop HCC, were used. Serum samples were taken from normal (Wild Type-WT) and MAT1-/ - mice at 1, 3, 5, 8, 12 and 18 months of age were analyzed using two-dimensional electrophoresis (2DE) followed by mass spectrometry.

In the murine model higher oxidation level of Apo A-1 isoform 1 was detected in mice serum, much earlier than any histological manifestation of HCC.

Subsequently, levels and posttranslational stage of APO A1 in human serum samples of patients suffering from different liver diseases (nonalcoholic steatohepatitis, alcoholic cirrhosis, hepatitis A and B and HCC) were studied. Enrichment of an acidic isoform of apolipoprotein A-I was also assessed in the serum of HBV patients who developed hepatocarcinoma.

Specific oxidation of three amino acids, methionine 112 to methionine sulfoxide and tryptophan 50 and 108 to formylkinurenine, were identified selectively in the up-regulated isoform by means of mass spectrometry.

We think therefore that the development of systems to specifically recognize these APO A1 oxidized forms in serum samples will be useful to find an efficient system for early diagnosis of HCC using noninvasive techniques.