A critical review on modulators of Multidrug Resistance Protein 1 in cancer cells

Multidrug resistance protein 1 (MRP1/ABCC1) is an ATP-dependent efflux transporter, and responsible for the transport of a broad spectrum of xenobiotics, toxins, and physiological substrates across the plasma membrane. As an efflux pump, it plays a significant role in the absorption and disposition of drugs including anticancer drugs, antivirals, antimalarials, and antibiotics and their metabolites across physiological barriers in cells. MRP1 is also known to aid in the regulation of several physiological processes such as redox homeostasis, steroid metabolism, and tissue defense. However, its overexpression has been reported to be a key clinical marker associated with multidrug resistance (MDR) of several types of cancers including lung cancer, childhood neuroblastoma, breast and prostate carcinomas, often resulting in a higher risk of treatment failure and shortened survival rates in cancer patients. Aside MDR, overexpression of MRP1 is also implicated in the development of neurodegenerative and cardiovascular diseases. Due to the cellular importance of MRP1, the identification and biochemical/molecular characterization of modulators of MRP1 activity and expression levels are of key interest to cancer research and beyond. This review primarily aims at highlighting the physiological and pharmacological importance of MRP1, known MRP1 modulators, current challenges encountered, and the potential benefits of conducting further research on the MRP1 transporter.

Prostate-specific membrane antigen is a biomarker for residual disease following neoadjuvant intense androgen deprivation therapy in prostate cancer

Neoadjuvant intense androgen deprivation therapy can exert a wide range of histologic responses, which in turn are reflected in the final prostatectomy specimen. Accurate identification and measurement of residual tumor volumes are critical for tracking and stratifying patient outcomes. The goal of this current study was to evaluate the ability of antibodies against prostate-specific membrane antigen (PSMA) to detect residual tumor in a cohort of 35 patients treated with androgen deprivation therapy plus enzalutamide for six months prior to radical prostatectomy. Residual carcinoma was detected in 31 patients, and PSMA reacted positively with tumor in all cases. PSMA staining was 95.5% sensitive for tumor, with approximately 81.6% of benign regions showing no reactivity. By contrast, PSMA positively reacted with 72.2% of benign regions in a control cohort of 37 untreated cases, resulting in 27.8% specificity for tumor. PSMA further identified highly dedifferentiated prostate carcinomas including tumors with evidence of neuroendocrine differentiation. We propose that anti-PSMA immunostaining be a standardized marker for identifying residual cancer in the setting of neoadjuvant intense androgen deprivation therapy.

Real-World Performance of a Comprehensive Genomic Profiling Test Optimized for Small Tumor Samples

PURPOSE Tissue-based comprehensive genomic profiling (CGP) is increasingly used for treatment selection in patients with advanced cancer; however, tissue availability may limit widespread implementation. Here, we established real-world CGP tissue availability and assessed CGP performance on consecutively received samples. MATERIALS AND METHODS We conducted a post hoc, nonprespecified analysis of 32,048 consecutive tumor tissue samples received for StrataNGS, a multiplex polymerase chain reaction (PCR)–based comprehensive genomic profiling (PCR-CGP) test, as part of an ongoing observational trial ( NCT03061305 ). Sample characteristics and PCR-CGP performance were assessed across all tested samples, including exception samples not meeting minimum input quality control (QC) requirements (< 20% tumor content [TC], < 2 mm2 tumor surface area [TSA], DNA or RNA yield < 1 ng/µL, or specimen age > 5 years). Tests reporting ≥ 1 prioritized alteration or meeting TC and sequencing QC were considered successful. For prostate carcinoma and lung adenocarcinoma, tests reporting ≥ 1 actionable or informative alteration or meeting TC and sequencing QC were considered actionable. RESULTS Among 31,165 (97.2%) samples where PCR-CGP was attempted, 10.7% had < 20% TC and 59.2% were small (< 25 mm2 tumor surface area). Of 31,101 samples evaluable for input requirements, 8,089 (26.0%) were exceptions not meeting requirements. However, 94.2% of the 31,101 tested samples were successfully reported, including 80.5% of exception samples. Positive predictive value of PCR-CGP for ERBB2 amplification in exceptions and/or sequencing QC-failure breast cancer samples was 96.7%. Importantly, 84.0% of tested prostate carcinomas and 87.9% of lung adenocarcinomas yielded results informing treatment selection. CONCLUSION Most real-world tissue samples from patients with advanced cancer desiring CGP are limited, requiring optimized CGP approaches to produce meaningful results. An optimized PCR-CGP test, coupled with an inclusive exception testing policy, delivered reportable results for > 94% of samples, potentially expanding the proportion of CGP-testable patients and impact of biomarker-guided therapies.

Comprehensive genomic profiling of 30,000 consecutive solid tumors

PurposeTissue-based comprehensive genomic profiling (CGP) is increasingly utilized for treatment selection in patients with advanced solid tumors, however real-world tissue availability may limit widespread implementation. Here we established real-world CGP tissue availability and assessed CGP performance on consecutively received samples.Patients and MethodPost-hoc, non-prespecified analysis of 32,048 consecutive tumor tissue samples received for StrataNGS, a multiplex PCR based-CGP (PCR-CGP) test, as part of an ongoing observational trial (NCT03061305). Tumor tissue sample characteristics and PCR-CGP performance were assessed across all tested tumor samples, including exception samples not meeting minimum input requirements (<20% tumor content [TC], <2mm2 tumor surface area [TSA], DNA or RNA yield <1ng/ul, or specimen age >5yrs). Tests reporting at least one prioritized alteration or meeting all sequencing QC metrics (and ≥20% TC) were considered successful. For prostate carcinoma and lung adenocarcinoma, tests reporting at least one actionable/informative alteration or those meeting all sequencing QC metrics (and ≥20% TC) were considered actionable.ResultsPCR-CGP was attempted in 31,165 of 32,048 (97.2%) consecutively received solid tumor tissue samples. Among the 31,165 tested samples, 10.7% had low (<20%) tumor content (TC) and 58.4% were small (<25mm2 TSA), highlighting the challenging nature of samples received for CGP. Of the 31,101 samples evaluable for input requirements, 8,079 (26.0%) were exceptions not meeting requirements. However, 94.2% of the 31,101 tested samples were successfully reported, including 80.6% of exception samples. Importantly, 80.6% of 1,344 tested prostate carcinomas and 87.8% of 1,144 tested lung adenocarcinomas yielded results informing treatment selection.ConclusionMost real-world tumor tissue samples from patients with advanced cancer desiring CGP are limited, requiring optimized CGP approaches to produce meaningful results. An optimized PCR-CGP test, coupled with an inclusive exception testing policy, delivered reportable results for >94% of samples, potentially expanding the proportion of CGP-testable patients, and thus the impact of biomarker-guided targeted and immunotherapies.