Implementation of upfront DPYD genotyping with a low-cost and high-throughput assay to guide fluoropyrimidine treatment in cancer patients.

OBJECTIVES: Genetic variants in the dihydropyrimidine dehydrogenase (DPYD ) gene are associated with reduced dihydropyrimidine dehydrogenase enzyme activity and can cause severe fluoropyrimidine-related toxicity. We assessed the frequency of the four most common and well-established DPYD variants associated with fluoropyrimidine toxicity and implemented a relatively low-cost and high-throughput genotyping assay for their detection. METHODS: This study includes 457 patients that were genotyped for the DPYD c.1129-5923C>G, c.1679T>G, c.1905 + 1G>A and c.2846A>T variants, either by Sanger sequencing or kompetitive allele specific PCR (KASP) technology. Of these, 172 patients presented toxicity during treatment with fluoropyrimidines (post-treatment group), and 285 were tested before treatment (pretreatment group). RESULTS: Heterozygous DPYD variants were identified in 7.4% of the entire series of 457 patients, being the c.2846A>T the most frequent variant. In the post-treatment group, 15.7% of the patients presented DPYD variants, whereas only 2.5% of the patients in the pretreatment group presented a variant. The KASP assays designed in this study presented 100% genotype concordance with the results obtained by Sanger sequencing. CONCLUSIONS: The combined assessment of the four DPYD variants in our population increases the identification of patients at high risk for developing fluoropyrimidine toxicity, supporting the upfront routine implementation of DPYD variant genotyping. Furthermore, the KASP genotyping assay described in this study presents a rapid turnaround time and relatively low cost, making upfront DPYD screening feasible in clinical practice.

Promoter Demethylation Upregulates STEAP1 Gene Expression in Human Prostate Cancer: In Vitro and In Silico Analysis.

The Six Transmembrane Epithelial Antigen of the Prostate (STEAP1) is an oncogene overexpressed in several human tumors, particularly in prostate cancer (PCa). However, the mechanisms involved in its overexpression remain unknown. It is well known that epigenetic modifications may result in abnormal gene expression patterns, contributing to tumor initiation and progression. Therefore, this study aimed to analyze the methylation pattern of the STEAP1 gene in PCa versus non-neoplastic cells. Bisulfite amplicon sequencing of the CpG island at the STEAP1 gene promoter showed a higher methylation level in non-neoplastic PNT1A prostate cells than in human PCa samples. Bioinformatic analysis of the GEO datasets also showed the STEAP1 gene promoter as being demethylated in human PCa, and a negative association with STEAP1 mRNA expression was observed. These results are supported by the treatment of non-neoplastic PNT1A cells with DNMT and HDAC inhibitors, which induced a significant increase in STEAP1 mRNA expression. In addition, the involvement of HDAC in the regulation of STEAP1 mRNA expression was corroborated by a negative association between STEAP1 mRNA expression and HDAC4,5,7 and 9 in human PCa. In conclusion, our work indicates that STEAP1 overexpression in PCa can be driven by the hypomethylation of STEAP1 gene promoter.

STEAP1 is overexpressed in prostate cancer and prostatic intraepithelial neoplasia lesions, and it is positively associated with Gleason score.

BACKGROUND: Six transmembrane epithelial antigen of the prostate 1 (STEAP1) is a transmembrane protein of epithelial cells, mostly located at cell-cell junctions, and is overexpressed in several types of tumors, particularly prostate cancer. Several studies have pointed STEAP1 as a biomarker, but the clinical significance of its overexpression is not fully understood. Therefore, we aimed to establish the association of STEAP1 immunoreactivity with histologic diagnosis and clinical data of patients. MATERIALS AND METHODS: Human tissue microarrays were constructed from tissue biopsies of prostate adenocarcinoma (n = 63), including nonneoplastic adjacent tissue (n = 41), prostatic intraepithelial neoplasia (PIN) lesions (n = 7), and 41 prostate samples from patients diagnosed with benign prostatic hyperplasia (BPH). The histologic features of tumor specimens were classified and clinical and pathologic data were retrieved. STEAP1 expression was evaluated by immunohistochemical analysis, and a semiquantitative quantification was performed using a grade score system based on the intensity and percentage of stained cells. RESULTS: Overexpression of STEAP1 protein was found in both plasma membrane and cytoplasm of prostate cancer and PIN lesions when compared with nonneoplastic adjacent tissue and BPH samples. Furthermore, its expression associates positively with higher Gleason scores, but not with other clinical data, such as age, prostate-specific antigen levels, pathologic stage, and metastasis. Regarding its role as a biomarker, STEAP1 is highly liable for distinguishing malignant prostate stages from BPH. On the contrary, it lacks specificity in distinguishing PIN lesions from prostate cancer. CONCLUSIONS: STEAP1 is consistently overexpressed in malignant prostate tissue, namely adenocarcinoma and PIN lesions. Its overexpression in PIN lesions and positive association with higher Gleason scores suggest that STEAP1 could be involved in tumor initiation and progression. The high sensitivity and specificity for detection of malignant lesions suggests that STEAP1 may be of clinical usefulness in early disease diagnosis.