CYP2D6 genotyping and the clinical impact on outcomes in breast cancer tamoxifen-treated patients

Aims: To report the distribution of allele frequencies of CYP2D6 gene and to evaluate their influence on the clinical outcomes of a group of breast cancer patients receiving adjuvant tamoxifen treatment from Uruguay. Patients & methods: 199 samples were genotyped through real-time polymerase chain reaction assays. Metabolization profiles were inferred from the genotypes. Correlations were evaluated using Pearson's χ2 test. Results: Phenotype frequencies were 0.65 normal (NM), 0.30 intermediate (IM) and 0.05 poor metabolizers (PM). Similar clinical outcomes between NM and (PM + IM) patient groups (odds ratio = 1.011, 95% CI = 0.2703-3.7826; p = 0.987) were found. Conclusion: CYP2D6 allele frequencies were analyzed for the first time in a cohort from Uruguay. Results did not support any impact of CYP2D6 gene polymorphisms on clinical outcomes.

An updated examination of the perception of barriers for pharmacogenomics implementation and the usefulness of drug/gene pairs in Latin America and the Caribbean

Pharmacogenomics (PGx) is considered an emergent field in developing countries. Research on PGx in the Latin American and the Caribbean (LAC) region remains scarce, with limited information in some populations. Thus, extrapolations are complicated, especially in mixed populations. In this paper, we reviewed and analyzed pharmacogenomic knowledge among the LAC scientific and clinical community and examined barriers to clinical application. We performed a search for publications and clinical trials in the field worldwide and evaluated the contribution of LAC. Next, we conducted a regional structured survey that evaluated a list of 14 potential barriers to the clinical implementation of biomarkers based on their importance. In addition, a paired list of 54 genes/drugs was analyzed to determine an association between biomarkers and response to genomic medicine. This survey was compared to a previous survey performed in 2014 to assess progress in the region. The search results indicated that Latin American and Caribbean countries have contributed 3.44% of the total publications and 2.45% of the PGx-related clinical trials worldwide thus far. A total of 106 professionals from 17 countries answered the survey. Six major groups of barriers were identified. Despite the region's continuous efforts in the last decade, the primary barrier to PGx implementation in LAC remains the same, the "need for guidelines, processes, and protocols for the clinical application of pharmacogenetics/pharmacogenomics". Cost-effectiveness issues are considered critical factors in the region. Items related to the reluctance of clinicians are currently less relevant. Based on the survey results, the highest ranked (96%-99%) gene/drug pairs perceived as important were CYP2D6/tamoxifen, CYP3A5/tacrolimus, CYP2D6/opioids, DPYD/fluoropyrimidines, TMPT/thiopurines, CYP2D6/tricyclic antidepressants, CYP2C19/tricyclic antidepressants, NUDT15/thiopurines, CYP2B6/efavirenz, and CYP2C19/clopidogrel. In conclusion, although the global contribution of LAC countries remains low in the PGx field, a relevant improvement has been observed in the region. The perception of the usefulness of PGx tests in biomedical community has drastically changed, raising awareness among physicians, which suggests a promising future in the clinical applications of PGx in LAC.

Genetic and epigenetic characteristics of patients with colorectal cancer from Uruguay

Colorectal cancer (CRC), the 3rd most frequent cancer worldwide, affects both men and women. This pathology arises from the progressive accumulation of genetic and epigenetic alterations. In this study, KRAS, NRAS, PIK3CA, and BRAF gene mutations, mismatch repair (MMR) genes methylation profile, microsatellite instability (MSI) and CpG Island Methylator Phenotype (CIMP) status were assessed. The associations of these molecular features with clinicopathological data were also investigated. A hundred and eight unselected CRC samples and their histological and clinical data, were gathered between 2017 and 2020. The prevalence of KRAS, NRAS and BRAF gene mutations was similar to that described in other populations. 28.7% of tumors were KRAS-mutated, mostly in men, distal location, with a CIMP-negative status. BRAFV600E frequency was 6.5% and associated with MSI (p = 0.048), MLH1-methylated (p < 0.001) and CIMP-High (p < 0.001) status. We also confirmed that BRAFV600E tumors were more prevalent in older women and proximal location. A striking different result was the lack of most common variants in the PIK3CA gene. A complete absence of PIK3CA-mutated tumors in a population has not been previously reported. Among MMR genes, the only with an aberrant methylation pattern was MLH1 gene. Its frequency was 9.25%, lower than previously reported. Methylated tumors were most frequent in patients older than 70 years old and proximal tumor location. Finally, CIMP-High status was mainly observed in moderately differentiated tumors with a rate of 15.7%. Our findings were consistent with previous reports in other populations, but also showed some features unique to our cohort. This study is the first to report the analysis of a large number molecular biomarkers of CRC in Uruguay and one of the few performed in Latin-America.

Activity of the Calcineurin Pathway in Patients on the Liver Transplantation Waiting List: Factors of Variability and Response to Tacrolimus Inhibition

BACKGROUND

We sought to evaluate, in patients on a liver transplantation waiting list, potential biomarkers of the base calcineurin pathway activity with use of a new model of nonstimulated peripheral blood mononuclear cells (PBMC) and ex vivo response to tacrolimus (TAC).

METHODS

The calcineurin pathway activity was explored ex vivo in stimulated and nonstimulated PBMC from 19 patients. The inhibition of NFAT1 translocation to PBMC nuclei, expression of intracellular IL-2, and membrane CD25 in different T-cell subsets were measured by multiparametric flow cytometry before and after exposure to TAC. We also studied the influence on the individual response of polymorphisms in 3 key genes of the calcineurin pathway: PPIA, PPP3CA, and IL2RA.

RESULTS

All pharmacodynamics profiles closely fitted an I/Imax sigmoid model. Interindividual variability was higher in nonstimulated than in stimulated conditions, as well as in the presence of TAC. IL-2+CD8+ cells at TAC Imax showed the highest interindividual variability, suggesting its usefulness as a biomarker of individual TAC effects integrating many different sources of regulation and variability. Moreover, in the absence of TAC, patients with end-stage liver disease exhibited lower NFAT1 translocation and T-cell activation than healthy volunteers from a previous study under similar conditions. Multivariate statistical analysis showed strong and significant associations between TAC pharmacodynamic parameters and 2 polymorphisms in the gene-coding cyclophilin A (rs8177826 and rs6850).

CONCLUSIONS

We show the feasibility of using nonstimulated PBMCs to explore the calcineurin pathway under more physiologic conditions and point toward potential biomarkers for TAC pharmacodynamic monitoring. ClinicalTrials.gov Identifier: NCT01760356

Evaluation of a Labelled Bacteriophage with 99mTc as a Potential Agent for Infection Diagnosis

BACKGROUND AND OBJECTIVE

The design of target-specific molecular imaging probes to determine infection sites are mainly based on the biochemistry of the inflammatory response that may lead to an ideal agent for infection imaging. Infectious diseases timely and specifically diagnosed can be clinically challenging but essential for the patient's recovery. Laboratory tests can detect the responsible microorganism but cannot discriminate between sterile inflammatory disease and truly infectious disease. On the other hand, scintigraphic images, can pinpoint the infection in the body.

METHODS

Bacteriophages (phages) are viruses that infect specific bacterial strains. Given the composition of the protein capsid, they could be used as radiopharmaceuticals to diagnose bacterial infection. In this case, PP7 phage was labelled and evaluated as a specific tracer for Pseudomonas aeruginosa infections. 99mTc-Phage synthesis used HYNIC as a bifunctional agent. Physicochemical evaluation included studies such as stability in time, ligand exchange, lipophilicity and bacterial binding assay. Three groups of animals namely; healthy, infected with Pseudomonas aeruginosa and induced sterile inflammation were used to conduct biological evaluation Results: The radiolabelling process required size exclusion purification of the 99mTc-Phage, which was obtained with a radiochemical purity higher than 90%, during 18 hours post labelling. The collective accumulation in the stomach, small intestine and large intestine and thyroid of 99mTc-Phage was negligible, indicating no in vivo reoxidation. The complex presented urinary elimination. Target/ non-target ratio (T/NT) was determined both for sterile inflammation and for infection. Values were 2.5 ± 0.4 and 4.2 ± 0.3 respectively. These values indicate significant differences between sterile inflammation and infection by Pseudomonas aeruginosa (p<0.05 unpaired two sided t-test).

CONCLUSION

Targeted biodistribution profile and good T/NT ratios, indicate that this complex presents enough specificity to discriminate between infection caused by Pseudomonas aeruginosa and sterile inflammation.

Tacrolimus Pharmacodynamics and Pharmacogenetics along the Calcineurin Pathway in Human Lymphocytes

BACKGROUND

Although therapeutic drug monitoring has improved the clinical use of immunosuppressive drugs, there is still interpatient variability in efficacy and toxicity that pharmacodynamic monitoring may help to reduce. To select the best biomarkers of tacrolimus pharmacodynamics, we explored the strength and variability of signal transduction and the influence of polymorphisms along the calcineurin pathway.

METHODS

Peripheral blood mononuclear cells from 35 healthy volunteers were incubated with tacrolimus (0.1–50 ng/mL) and stimulated ex vivo. Inhibition of NFAT1 (nuclear factor of activated T cells 1) translocation to the nucleus and intracellular expression of interleukin-2 in CD4+ and CD8+ T cells and the surface activation marker CD25 in CD3+ cells were measured by flow cytometry. We sequenced the promoter regions of immunophilins and calcineurin subunits and characterized selected single nucleotide polymorphisms in the genes of the calcineurin pathway with allelic discrimination assays.

RESULTS

All responses closely fitted an I/Imax sigmoid model. Large interindividual variability (n = 30) in I0 and IC50 was found for all biomarkers. Moreover, strong and statistically significant associations were found between tacrolimus pharmacodynamic parameters and polymorphisms in the genes coding cyclophilin A, the calcineurin catalytic subunit α isoenzyme, and CD25.

CONCLUSIONS

This study demonstrates the consistency and large interindividual variability of signal transduction along the calcineurin pathway, as well as the strong influence of pharmacogenetic polymorphisms in the calcineurin cascade on both the physiological activity of this route and tacrolimus pharmacodynamics.

Characterisation of the proximal regulatory domain of the Echinococcus granulosus homeodomain-containing gene EgHbx1

In an attempt to understand the molecular basis of the development of Echinococcus granulosus, we have previously isolated several homeobox-containing genes (EgHbx1-5). Here we report the characterisation of the EgHbx1 proximal regulatory domain. EgHbx1 codes for an amino acid sequence presenting 90% identity at the homeodomain level with the Drosophila melanogaster NK1-S59 transcription factor. The proximal regulatory domain sequence and the transcription start site were determined. Electrophoretic mobility shift assays using nuclear extracts from protoscoleces revealed the presence of specific DNA-protein complexes. These results constitute a hint and provide new tools to decipher regulatory cascades during E. granulosus development.

Echinococcus granulosus: preparation of protein extracts from protoscolex nuclei for mobility-shift assays

Nuclei from Echinococcus granulosus protoscolices were isolated from infected sheep. Protein extracts were prepared for analysis of DNA-protein interactions involving specific transcriptional regulatory factors. Gel mobility-shift assays were done using a heterologous probe containing binding sites for widespread transcription factors. A fragment of the promoter of GATA-1 transcription factor from the chicken was selected. When nuclear extracts from E. granulosus protoscolices were assayed a specific band shift was observed. The methodologies developed in this study could provide an important contribution for the characterization of the DNA-protein interactions involved in transcriptional regulation within the context of recent developments in the molecular biology of this parasite.

Presence of a conserved domain of GATA transcription factors in Echinococcus granulosus

In order to characterize GATA transcription factors in Echinococcus granulosus, a PCR-based cloning strategy was developed. Degenerate oligonucleotides were designed for the most conserved sequence in GATA proteins that include 20 amino acids of the zinc domain. A 60 bp fragment was isolated that had high homology among this sequence and those reported in other species. An analogous sequence was obtained by performing the same procedure with DNA from the free living platyhelminth Dugesia tigrina. High stringency Southern blotting experiments confirmed the presence of this sequence in the parasite genome.