Avaliação da técnica de biópsia líquida para pacientes com ameloblastoma

Abstract

Ameloblastoma is an epithelial benign odontogenic neoplasm subclassified into conventional, unicystic, and peripheral types, with the latter being rare. Conventional ameloblastoma exhibits aggressive clinical behavior, with the potential to infiltrate tissues, resorb teeth roots, perforate bone cortical, and reach considerable extensions that can sometimes lead to facial deformities. It also presents a high recurrence rate, and the recommended treatment is surgical removal with safety margins, often resulting in mutilation. Unicystic ameloblastoma tends to behave less aggressively, allowing for more conservative treatment. Approximately 64% of conventional ameloblastomas and 80% of unicystic ameloblastomas harbor the BRAF p.Val600Glu mutation. Given the tissue-invasive capacity of conventional ameloblastomas, the hypothesis was considered that ameloblastoma might release tumor-derived cell-free DNA (ctDNA) into the bloodstream and saliva, carrying the tumor’s signature mutation. To test this hypothesis, liquid biopsy was performed using blood plasma from 10 patients with BRAF p.Val600Glu-positive ameloblastoma, and saliva from 4 of these patients. The study included 7 conventional and 3 unicystic ameloblastomas. Tumor tissue samples, whole peripheral blood (collected preoperatively and during follow-ups of up to one year), and preoperative saliva samples were obtained. Genomic DNA (gDNA) was extracted from tissue samples and tested for the mutation using Sanger sequencing and allele-specific qPCR. Peripheral blood samples were processed to obtain blood plasma, and both plasma and saliva were used to isolate circulating cell-free DNA (cfDNA), followed by droplet digital PCR (ddPCR) to detect the mutation of interest. Among the 10 cases analyzed, 10 presented the BRAF p.Val600Glu mutation in tumor tissue. In 3 of them,the mutation was detected in the blood-based liquid biopsy samples before incisional or excisional biopsy. However, the mutation was not detected in any of the saliva-based liquid biopsy samples from the four patients evaluated. In postoperative controls, all samples were negative for the mutation. These results suggest that ameloblastoma is capable of releasing ctDNA into the bloodstream, but apparently not in the saliva, pending further confirmation.