Mechanisms Contributing to Tyrosin Kinase Inhibitor Resistance in GISTs: Toward a Personalized Therapy

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors in the gastrointestinal tract. This work considers the pharmacological response in GIST patients treated with imatinib by two different angles: the genetic and somatic point of view. We analyzed polymorphisms influence on treatment outcome, keeping in consideration SNPs in genes involved in drug transport and folate pathway. Naturally, all these intriguing results cannot be considered as the only main mechanism in imatinib response. GIST mainly depends by oncogenic gain of function mutations in tyrosin kinase receptor genes, KIT or PDGFRA, and the mutational status of these two genes or acquisition of secondary mutation is considered the main player in GIST development and progression. To this purpose we analyzed the secondary mutations to better understand how these are involved in imatinib resistance. In our analysis we considered both imatinib and the second line treatment, sunitinib, in a subset of progressive patients. KIT/PDGFRA mutation analysis is an important tool for physicians, as specific mutations may guide therapeutic choices. Currently, the only adaptations in treatment strategy include imatinib starting dose of 800 mg/daily in KIT exon-9-mutated GISTs. In the attempt to individualize treatment, genetic polymorphisms represent a novelty in the definition of biomarkers of imatinib response in addition to the use of tumor genotype. Accumulating data indicate a contributing role of pharmacokinetics in imatinib efficacy, as well as initial response, time to progression and acquired resistance. At the same time it is becoming evident that genetic host factors may contribute to the observed pharmacokinetic inter-patient variability. Genetic polymorphisms in transporters and metabolism may affect the activity or stability of the encoded enzymes. Thus, integrating pharmacogenetic data of imatinib transporters and metabolizing genes, whose interplay has yet to be fully unraveled, has the potential to provide further insight into imatinib response/resistance mechanisms.

Role of bioactive compounds in the gastrointestinal host-pathogen interaction of poultry and swine

The better understanding of mechanisms at the basis of host-pathogen interaction can represent a valid tool to increase productivity and contain economic losses in animal production through the maintenance of intestinal homeostasis. With this project, three preliminary in vitro studies were conducted with the aim of investigating how bioactive compounds could influence mechanisms of host-pathogen interaction in poultry and swine. Different panels of nature identical compounds, medium chain fatty acids, and plant extracts were employed against strains of Salmonella Typhimurium, Brachyspira hyodysenteriae, and Salmonella Enteritidis, respectively. When bacterial field strains were tested, the comparison between natural compounds and antibiotics was examined, with the aim of evaluating the role of the substances in the antibiotic-resistance context. Results demonstrate that bioactive compounds have positive effects on the host, the pathogen, or both in different experimental conditions. Additionally, when compared to antibiotics, bioactive compounds have proven to be valid alternatives to address the phenomenon of antibiotic resistance.

Gastrointestinal stromal tumors: Arbutus unedo L. as a source of novel chemotherapeutics & mechanisms behind metastasis

Gastrointestinal stromal tumors (GIST) are mesenchymal neoplasms frequently caused by a gain of function mutation in KIT or PDGFRα, two tyrosine kinase receptors (TKR). For this reason, they are successfully treated with imatinib, a tyrosine kinase inhibitor (TKI). However, the therapy is typically long-term ineffective due to imatinib resistance, which represents the main issue in the clinic of GISTs. Although numerous efforts have been made in the last two decades to develop novel therapies for imatinib-resistant GISTs, the approvals of multi-target TKIs have only improved the clinical outcomes modestly. Emblematic is the recent failure of ripretinib in the phase III INTRIGUE trial, decisively marking the end of the paradigm only based on the central role of KIT secondary mutations in imatinib resistance, and the consequent seeking of multi-target TKIs as the solution. Consistent with this clinical result, preclinical studies have revealed numerous mechanisms of resistance that are not targetable with multi-target TKIs, indicating that imatinib resistance is more multifaceted than initially hypothesized and explaining the modest efficacy of these latter. In this scenario, the absence of drugs capable of long-term counteracting the rise of imatinib-resistant subclones unavoidably leads to progressive disease and metastasis. In particular, the onset of metastases remarkably impacts the median overall survival and determines the most GIST-related deaths. Therefore, new therapy proposals are needed. Here, we present two project lines investigating novel strategies to counteract imatinib-resistant GISTs.