SEROLOGICAL IMMUNE RESPONSE AGAINST ADAM10 IN COLORECTAL CANCER PATIENTS IS A FAVORABLE SIGNATURE

In cancer the immune system is activated in response to qualitative and quantitative aberrant expression by tumor cells of certain proteins named tumor-associated antigens (TAAs). In a previous study in the laboratory, has been investigated the presence of TAAs inducing auto-antibodies (auto-Abs) in the Colorectal cancer (Crc) by exploiting the patients serological reactivity against the surface membrane proteoma. Among several candidates, a specific immunoreactivity against A Disintegrin And Metalloprotease 10 (ADAM10) protein has been identify.ADAM10 is a disintegrin metalloprotease with a potential role in tumor progression and invasion due to its sheddase activity. ADAM10 is able to promote ERK1/2 signaling activation promoting cell proliferation by the cleavage of the extracellular domain (ECD) of the HER2 tyrosine kinase receptor, which is released in serum. Moreover, ADAM10 plays a critical physiological function in the epithelial morphogenesis since its sheddase activity is crucial for the cell migration and extracellular matrix (ECM) remodelling, a phenomenon that also drives tumor metastasis. Thus, an aberrant expression of the ADAM10 in epithelial tissues might elicit a specific serological immune response. The serological screening performed on purified ADAM10, showed a significant presence of immunoreactivity against ADAM10 in the sera from patients affected by tumors of epithelial origin like Crc, Pancreatic cancer (Pc) and Breast cancer (Brc) if compared with serological reactivity of healthy subjects. On the contrary, sera from patients affected by hematological malignancies such as chronic lymphocytic leukemia (B-CLL) and Multiple Myeloma (MM), did not showed significant immunoreactivity against ADAM10. These results suggested that the presence of auto-Abs against ADAM10 in patients sera might be a candidate biomarker for carcinomas of epithelial origin. Since it is known that ADAM10 is overexpressed in advanced stages of the Crc disease, when the lymph nodes are infiltrated by the tumor, we evaluated the disease course of this patients after surgical resection in order to define whether the presence of auto-Abs anti-ADAM10 is a favourable or detrimental signature, correlating the immunoreactivity with the patients follow-up. The results showed that the presence of auto-Abs anti-ADAM10 prolonged significantly the disease-free condition if compared with Crc patients without serological immunoreactivity against ADAM10. Thus, in order to investigate the effects of these auto-Abs, in vitro experiments of both HER2 ECD release and cell migration were performed using the Colon carcinoma cell line LoVo. Results showed that commercial anti-ADAM10 antibodies resulted to be effective in inhibiting cell migration and HER2 ECD release in LoVo cell line while IgG fraction purified from representative Crc patients did not. This lack of inhibition might be the consequence of the fact that LoVo cell line did not express the specific epitope that elicited the serological reactivity in Crc patients. In fact, Crc patients showed different expression of ADAM10 in tumoral tissues. Patients with a positive immunoreactivity against ADAM10 (Ser-ADAM10 +) showed an overexpression of the inactive form of ADAM10 and, accordingly, an high expression of the inactive HER2 (p195) isoform and a decreased expression of phosphorilated-ERK1/2. These results suggest a reduced activity of ADAM10 on the HER2 ECD cleaveage which is supported by the observation that Ser-ADAM10 + patients showed lower HER2 ECD concentrations in serum compared to Ser-ADAM10 - patients. In conclusion, the presence of auto-antibodies anti-ADAM10 may be considered a biomarker of favourable prognosis for Crc patients at advanced stages of the disease that reflects an overexpression of inactive ADAM10 during the cell transformation and accordingly the lower protein maturation leads to a decrease of its sheddase activity which in turnt declines the proliferative and invasive capacity of tumor cells.