Differential effects of thiopurine methyltransferase (TPMT) and multidrug resistance-associated protein gene 4 (MRP4) on mercaptopurine toxicity

GALNT6, GALNT14, and Gal-3 in association with GDF-15 promotes drug resistance and stemness of breast cancer via β-catenin axis

N-acetylgalactosaminyltransferases (GALNTs) are a polypeptide responsible for aberrant glycosylation in breast cancer (BC), but the mechanism is unclear. In this study, expression levels of GALNT6, GALNT14, and Gal-3 were assessed in BC, and their association with GDF-15, β-catenin, stemness (SOX2 and OCT4), and drug resistance marker (ABCC5) was evaluated. Gene expression of GALNT6, GALNT14, Gal-3, GDF-15, OCT4, SOX2, ABCC5, and β-catenin in tumor and adjacent non-tumor tissues (n = 30) was determined. The same was compared with GEO-microarray datasets. A significant increase in the expression of candidate genes was observed in BC tumor compared to adjacent non-tumor tissue; and in pre-therapeutic patients compared to post-therapeutic. GALNT6, GALNT14, Gal-3, and GDF-15 showed positive association with β-catenin, SOX2, OCT4, and ABCC5 and were significantly associated with poor Overall Survival. Our findings were also validated via in silico analysis. Our study suggests that GALNT6, GALNT14, and Gal-3 in association with GDF-15 promote stemness and intrinsic drug resistance in BC, possibly by β-catenin signaling pathway.

Circular Sponge against miR-21 Enhances the Antitumor Activity of Doxorubicin against Breast Cancer Cells

Breast cancer is the most common type of cancer in women, with chemotherapy being the main strategy. However, its effectiveness is reduced by drug resistance mechanisms. miR-21 is upregulated in breast cancer that has been linked to drug resistance and carcinogenic processes. Our aim was to capture miR-21 with a circular sponge (Circ-21) and thus inhibit the carcinogenic processes and drug resistance mechanisms in which it participates. Proliferation, migration, colony formation, cell cycle, and poly [ADP-ribose] polymerase 1 (PARP-1) and vascular endothelial growth factor (VEGF) detection assays were performed with MCF7 breast cancer cells and MCF10A non-tumor cells. In addition, doxorubicin resistance tests and detection of drug resistance gene expression were performed in MCF7 cells. Reduction in proliferation, as well as migration and colony formation, increased PARP-1 expression, inhibition of VEGF expression and cell cycle arrest in G2/M phase were displayed in the Circ-21 MCF7, which were not observed in the MCF10A cells. Furthermore, in the MCF7 cells, the Circ-21 enhanced the antitumor activity of doxorubicin and decreased the expression of resistance genes: ABCA1, ABCC4, and ABCC5. Based on these results, the use of Circ-21 can be considered a first step for the establishment of an effective gene therapy in the treatment of breast cancer.

Impact of SLC43A3/ENBT1 Expression and Function on 6-Mercaptopurine Transport and Cytotoxicity in Human Acute Lymphoblastic Leukemia Cells

6-Mercaptopurine (6-MP) is used extensively in the treatment of acute lymphoblastic leukemia (ALL) and inflammatory bowel diseases. Our laboratory determined previously, using a recombinant HEK293 cell model, that the SLC43A3-encoded equilibrative nucleobase transporter 1 (ENBT1) transports 6-MP into cells and significantly impacts the cytotoxicity of 6-MP in that model. To further investigate the clinical relevance of this finding, we now extend this work to an analysis of the impact of SLC43A3/ENBT1 expression and function on 6-MP uptake and cytotoxicity in leukemic lymphoblasts, the therapeutic target of 6-MP in ALL. A panel of ALL cell lines was assessed for SLC43A3/ENBT1 expression, ENBT1 function, and sensitivity to 6-MP. There was a significant difference in SLC43A3 expression among the cell lines that positively correlated with the rate of ENBT1-mediated 6-MP uptake. Cells with the lowest expression of SLC43A3 (SUP-B15: Vmax = 22± 5 pmol/µl per second) were also significantly less sensitive to 6-MP-induced cytotoxicity than were the highest expressing cells (ALL-1: Vmax = 69 ± 10 pmol/µl per second). Furthermore, knockdown of ENBT1 using short hairpin RNA interference (shRNAi) in RS4;11 cells caused a significant decrease in ENBT1-mediated 6-MP uptake (Vmax: RS4;11 = 40 ± 4 pmol/µl per second; RS4;11 shRNAi = 26 ± 3 pmol/µl per Second) and 6-MP cytotoxicity (EC50: RS4;11 = 0.58 ± 0.05 µM; RS4;11 shRNAi =1.44 ± 0.59 µM). This study showed that ENBT1 is a major contributor to 6-MP uptake in leukemia cell lines and may prove to be a biomarker for the therapeutic efficacy of 6-MP in patients with ALL. SIGNIFICANCE STATEMENT: This study shows that SLC43A3-encoded equilibrative nucleobase transporter 1 is responsible for the transport of 6-mercaptopurine (6-MP) into leukemia cells and that its level of expression can impact the cytotoxicity of 6-MP. Further studies are warranted to investigate the therapeutic implications in patient populations.

Human drug efflux transporter ABCC5 confers acquired resistance to pemetrexed in breast cancer

Aim

Pemetrexed, a new generation antifolate drug, has been approved for the treatment of locally advanced or metastatic breast cancer. However, factors affecting its efficacy and resistance have not been fully elucidated yet. ATP-binding cassette (ABC) transporters are predictors of prognosis as well as of adverse effects of several xenobiotics. This study was designed to explore whether ABC transporters affect pemetrexed resistance and can contribute to the optimization of breast cancer treatment regimen.

Methods

First, we measured the expression levels of ABC transporter family members in cell lines. Subsequently, we assessed the potential role of ABC transporters in conferring resistance to pemetrexed in primary breast cancer cells isolated from 34 breast cancer patients and the role of ABCC5 in mediating pemetrexed transport and apoptotic pathways in MCF-7 cells. Finally, the influence of ABCC5 expression on the therapeutic effect of pemetrexed was evaluated in an in vivo xenograft mouse model of breast cancer.

Results

The expression levels of ABCC2, ABCC4, ABCC5, and ABCG2 significantly increased in the pan-resistant cell line, and the ABCC5 level in the MCF-7-ADR cell line was 5.21 times higher than that in the control group. ABCC5 expression was inversely correlated with pemetrexed sensitivity (IC₅₀, r = 0.741; p < 0.001) in breast cancer cells derived from 34 patients. Furthermore, we found that the expression level of ABCC5 influenced the efflux and cytotoxicity of pemetrexed in MCF-7 cells, with IC₅₀ values of 0.06 and 0.20 μg/mL in ABCC5 knockout and over-expression cells, respectively. In the in vivo study, we observed that ABCC5 affected the sensitivity of pemetrexed in breast tumor-bearing mice, and the tumor volume was much larger in the ABCC5-overexpressing group than in the control group when compared with their own initial volumes (2.7-fold vs. 1.3-fold).

Conclusions

Our results indicated that ABCC5 expression was associated with pemetrexed resistance in vitro and in vivo, and it may serve as a target or biomarker for the optimization of pemetrexed regimen in breast cancer treatment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-021-01842-x.

Childhood acute lymphoblastic leukemia mercaptopurine intolerance is associated with NUDT15 variants

BACKGROUND

Mercaptopurine-induced neutropenia can interrupt chemotherapy and expose patients to infection during childhood acute lymphoblastic leukemia (ALL) treatment. Previously, six candidate gene variants associated with mercaptopurine intolerance were reported. Herein, we investigated the association between the mean tolerable dose of mercaptopurine and these genetic variants in Taiwanese patients.

METHODS

In total, 294 children with ALL were treated at the National Taiwan University Hospital from April 1997 to December 2017. Germline variants were analyzed for NUDT15, SUCLA2, TPMT, ITPA, PACSIN2, and MRP4. Mean daily tolerable doses of mercaptopurine in the continuation phase of treatment were correlated with these genetic variants.

RESULTS

Mercaptopurine intolerance was significantly associated with polymorphisms in NUDT15 (P value < 0.0001). Patients with SUCLA2 variants received lower mercaptopurine doses (P value = 0.0119). The mean mercaptopurine doses did not differ among patients with TPMT, ITPA, MRP4, and PACSIN2 polymorphisms (P value = 0.9461, 0.5818, and 0.7951, respectively). After multivariable linear regression analysis, only NUDT15 variants retained their clinically significant correlation with mercaptopurine intolerance (P value < 0.0001).

CONCLUSION

In this cohort, the major genetic determinant of mercaptopurine intolerance was NUDT15 in Taiwanese patients.

IMPACT

NUDT15 causes mercaptopurine intolerance in children with ALL. The NUDT15 variant is a stronger predictor of mercaptopurine intolerance than TPMT in a Taiwanese cohort. This finding is similar with studies performed on Asian populations rather than Caucasians. Pre-emptive genotyping of the patients' NUDT15 before administering mercaptopurine may be more helpful than genotyping TPMT in Asians.

Genetic polymorphisms of pharmacogenomic VIP variants in the Dai population from Yunnan province

Background

Pharmacogenomics plays a crucial role in individualized therapy, but the variant information of pharmacogenomics in the Dai population is limited. We therefore aimed to screen very important pharmacogenetic (VIP) in the Dai population and compared differences between Dai and other 25 populations.

Methods

In this study, we genotyped 73 VIP variants from the PharmGKB and compared genotype distribution of variants in Dai with other 25 populations by χ2 test. To assess the genetic relationship among 26 populations, we performed the structure analysis. In addition, pair‐wise F‐statistics (Fst) was calculated to measure the population differentiation.

Results

We found 12, 10, 13, 17, 11, 39, 46, 46, 45, 43, 49, 46, 46, 46, 49, 45, 41, 42, 48, 53, 45, 50, 50, 51, 47, and 50 significantly different variants in Dai compared with other 25 populations. Genetic structure analysis showed Dai had close relationships with CDX (Chinese Dai in Xishuangbanna), CHB (Han Chinese in Beijing), JPT (Japanese in Tokyo), and KHV (Kinh in Ho Chi Minh City, Vietnam). Moreover, Dai is the most similar to KHV according to Fst analysis.

Conclusions

Our study complement the pharmacogenomics information of Dai population from Yunnan province and provide a theoretical basis for personalized medicine.

Identification of MRP4/ABCC4 as a Target for Reducing the Proliferation of Pancreatic Ductal Adenocarcinoma Cells by Modulating the cAMP Efflux

Pancreatic cancer is one of the most lethal types of tumors with no effective therapy available; is currently the third leading cause of cancer in developed countries; and is predicted to become the second deadliest cancer in the United States by 2030. Due to the marginal benefits of current standard chemotherapy, the identification of new therapeutic targets is greatly required. Considering that cAMP pathway is commonly activated in pancreatic ductal adenocarcinoma (PDAC) and its premalignant lesions, we aim to investigate the multidrug resistance-associated protein 4 (MRP4)-dependent cAMP extrusion process as a cause of increased cell proliferation in human PDAC cell lines. Our results from in silico analysis indicate that MRP4 expression may influence PDAC patient outcome; thus, high MRP4 levels could be indicators of poor survival. In addition, we performed in vitro experiments and identified an association between higher MRP4 expression levels and more undifferentiated and malignant models of PDAC and cAMP extrusion capacity. We studied the antiproliferative effect and the overall cAMP response of three MRP4 inhibitors, probenecid, MK571, and ceefourin-1 in PDAC in vitro models. Moreover, MRP4-specific silencing in PANC-1 cells reduced cell proliferation (P < 0.05), whereas MRP4 overexpression in BxPC-3 cells significantly incremented their growth rate in culture (P < 0.05). MRP4 pharmacological inhibition or silencing abrogated cell proliferation through the activation of the cAMP/Epac/Rap1 signaling pathway. Also, extracellular cAMP reverted the antiproliferative effect of MRP4 blockade. Our data highlight the MRP4-dependent cAMP extrusion process as a key participant in cell proliferation, indicating that MRP4 could be an exploitable therapeutic target for PDAC. SIGNIFICANCE STATEMENT: ABCC4/MRP4 is the main transporter responsible for cAMP efflux. In this work, we show that MRP4 expression may influence PDAC patient outcome and identify an association between higher MRP4 expression levels and more undifferentiated and malignant in vitro models of PDAC. Findings prove the involvement of MRP4 in PDAC cell proliferation through a novel extracellular cAMP mitogenic pathway and further support MRP4 inhibition as a promising therapeutic strategy for PDAC treatment.

The genetic vulnerability to cisplatin ototoxicity: a systematic review

Ototoxicity is one of the major side-effects of platinum-based chemotherapy, in particular cisplatin (cis-diammine dichloroplatinum II). To our knowledge, no systematic review has previously provided a quantitative summary estimate of the impact of genetics upon the risk of developing hearing loss. We searched Embase, Medline, ASSIA, Pubmed, Scopus, and Web of Science, for studies documenting the genetic risk of ototoxicity in patients with cancer treated with cisplatin. Titles/abstracts and full texts were reviewed for inclusion. Meta-analytic estimates of risk (Odds Ratio) from the pooled data were calculated for studies that have been repeated twice or more. The search identified 3891 papers, of which 30 were included. The majority were retrospective (44%), ranging from n = 39 to n = 317, some including only patients younger than 25 years of age (33%), and some on both genders (80%). The most common cancers involved were osteosarcoma (53%), neuroblastoma (37%), prostate (17%) and reproductive (10%). Most studies performed genotyping, though only 5 studies performed genome-wide association studies. Nineteen single-nucleotide polymorphisms (SNPs) from 15 genes were repeated more than twice. Meta-analysis of group data indicated that rs1872328 on ACYP2, which plays a role in calcium homeostasis, increases the risk of ototoxicity by 4.61 (95% CI: 3.04-7.02; N = 696, p < 0.0001) as well as LRP2 rs4668123 shows a cumulated Odds Ratio of 3.53 (95% CI: 1.48-8.45; N = 118, p = 0.0059), which could not be evidenced in individual studies. Despite the evidence of heterogeneity across studies, these meta-analytic results from 30 studies are consistent with a view of a genetic predisposition to platinum-based chemotherapy mediated ototoxicity. These new findings are informative and encourage the genetic screening of cancer patients in order to identify patients with greater vulnerability of developing hearing loss, a condition having a potentially large impact on quality of life. More studies are needed, with larger sample size, in order to identify additional markers of ototoxic risk associated with platinum-based chemotherapy and investigate polygenic risks, where multiple markers may exacerbate the side-effects.

Pharmacogenomic and Pharmacotranscriptomic Profiling of Childhood Acute Lymphoblastic Leukemia: Paving the Way to Personalized Treatment

Personalized medicine is focused on research disciplines which contribute to the individualization of therapy, like pharmacogenomics and pharmacotranscriptomics. Acute lymphoblastic leukemia (ALL) is the most common malignancy of childhood. It is one of the pediatric malignancies with the highest cure rate, but still a lethal outcome due to therapy accounts for 1%⁻3% of deaths. Further improvement of treatment protocols is needed through the implementation of pharmacogenomics and pharmacotranscriptomics. Emerging high-throughput technologies, including microarrays and next-generation sequencing, have provided an enormous amount of molecular data with the potential to be implemented in childhood ALL treatment protocols. In the current review, we summarized the contribution of these novel technologies to the pharmacogenomics and pharmacotranscriptomics of childhood ALL. We have presented data on molecular markers responsible for the efficacy, side effects, and toxicity of the drugs commonly used for childhood ALL treatment, i.e., glucocorticoids, vincristine, asparaginase, anthracyclines, thiopurines, and methotrexate. Big data was generated using high-throughput technologies, but their implementation in clinical practice is poor. Research efforts should be focused on data analysis and designing prediction models using machine learning algorithms. Bioinformatics tools and the implementation of artificial i Lack of association of the CEP72 rs924607 TT genotype with intelligence are expected to open the door wide for personalized medicine in the clinical practice of childhood ALL.