Liquid Biopsy in Gastrointestinal Stromal Tumors: Ready for Prime Time?

OPINION STATEMENT

Gastrointestinal stromal tumor (GIST) constitutes a paradigm for clinically effective targeted inhibition of oncogenic driver mutations. Therefore, GIST has emerged as a compelling clinical and biological model to study oncogene addiction and to validate preclinical concepts for drug response and drug resistance. Oncogenic activation of KIT or PDGFRA receptor tyrosine kinases is the essential drivers of GIST progression throughout all stages of the disease. Interestingly, KIT/PDGFRA genotype predicts the response to first-line imatinib and to all tyrosine kinase inhibitors (TKIs) approved or in investigation after imatinib failure. Considering that TKIs are effective only against a subset of KIT or PDGFRA resistance mutations, close monitoring of tumor dynamics with non-invasive methods such as liquid biopsy emerges as a necessary step forward in the field. Liquid biopsy, in contrast to solid tumor biopsy, aims to characterize tumors irrespective of heterogeneity. Although there are several components in the peripheral blood, most recent studies have been focused on circulating tumor (ct)DNA, due to the technological feasibility, the stability of DNA itself and DNA alterations, and the therapeutic development in precision oncology largely based on the identification of genetic driver mutations. In the present review, we systematically dissect the current wealth of data of ctDNA in GIST. To do so, a critical understanding of the promises and limitations of the current technologies will be followed by an exposition of the knowledge gathered with such studies in GIST. Collectively, our goal is to establish clear premises that can be used as the foundations to build future studies towards the clinical implementation of ctDNA evaluation in GIST patients.

Aberrant expression of N-glycolyl GM3 ganglioside is associated with the aggressive biological behavior of human sarcomas

BACKGROUND

The aberrant expression of N-glycolyl GM3 ganglioside (NeuGcGM3) in patients with sarcomas was reevaluated by assessing the relation of this molecule with some clinicopathological features and overall survival (OS) of patients.

METHODS

Fifty formalin-fixed and paraffin-embedded specimens from patients diagnosed with sarcomas were included. For the evaluation of NeuGcGM3, the 14F7 monoclonal antibody followed by a peroxidase avidin-biotin system was used. Clinicopathological features were obtained from patient records. Survival rates were estimated by the Kaplan-Meier method and compared with the log-rank test. For multivariate analyses, the Cox regression model was used to identify independent prognostic factors for OS.

RESULTS

The majority of samples had high levels of NeuGcGM3 expression (66.0%) that showed statistical correlation with age (p = 0.014), TNM stage (p = 0.022), histological grade (p = 0.013) and proliferation rates (p = 0.012). In addition, a tendency for association with tumor depth (p = 0.070) was evidenced. In univariate survival analysis, TNM stage (p = 0.000), occurrence of metastasis (p = 0.000) and expression of NeuGcGM3 (p = 0.034) were significant prognostic factors for OS, while a tendency for association was evidenced for histological grade (p = 0.091). Among these variables, only the presence of metastasis (p = 0.001) was an independent prognostic factor on multivariate analysis.

CONCLUSIONS

The present research suggests the evaluation of NeuGcGM3 expression as a complementary prognostic factor in sarcoma, although our results need to be validated in a larger series and prospective studies. Moreover, our results could support the use of this molecule as a target for immunotherapy.