Lactate dehydrogenase (LDH) is a key enzyme in the last step of glycolysis, playing a role in the pyruvate-to-lactate reaction. It is associated with the prognosis and metastasis of many cancers, including breast cancer. In this study, we investigated the changes in LDH gene expression and lactate concentrations in the culture media during tamoxifen resistance development in the MCF-7 cell line, and examined LDHB promoter methylation levels. An upregulation of 2.9 times of LDHB gene expression was observed around the IC50 concentration of tamoxifen in treated cells, while fluctuation in LDHA gene expression levels was found. Furthermore, morphological changes in the cell shape accompanied the changes in gene expression. Bisulfate treatment followed by sequencing of the LDHB promoter was performed to track any change in methylation levels; hypomethylation of CpG areas was found, suggesting that gene expression upregulation could be due to methylation level changes. Changes in LDHA and LDHB gene expression were correlated with the increase in lactate concentration in the culture media of treated MCF-7 cells.

Breast cancer is the second leading cause of cancer death in women after lung cancer. The first-line treatment of metastatic breast cancer in premenopausal women relies on tamoxifen. The development of tamoxifen resistance is not fully understood. In this study, capillary electrophoresis with capacitively coupled contactless conductivity detector was developed to monitor the changes in lactate and pyruvate levels in supernatant media of three models of developed MCF-7 tamoxifen-resistant cells and correlate these metabolites changes with lactate dehydrogenase genes expression and glucose consumption. The electrophoretic separation was achieved under reversed electroosmotic flow conditions. The linear ranges were 0.15-5 and 0.01-1 mM with a correlation coefficient of 0.9966 and 0.9971 and the limits of detection were 0.01 and 0.02 μM for lactate and pyruvate, respectively. Inter-and intrarun accuracy were in the range of 96.88-105.94% with precision (CV, %) of ≤7.35%. The method was completely validated and the results were in agreement with those obtained using the lactate and glucose assay kits. The results revealed a significant increase in both lactate and pyruvate production in the three tamoxifenresistant MCF-7 cells models compared to control cells. This increase was correlated with the increase of lactate dehydrogenase genes expression and the increase of glucose consumption.

Breast cancer is one of the most prevalent cancers worldwide usually treated with Tamoxifen. Tamoxifen resistance development is the most challenging issue in an initially responsive breast tumor, and mechanisms of resistance are still under investigation. The objective of this study is to develop and validate a selective, sensitive, and simultaneous high performance liquid chromatography–tandem mass spectrometry method to explore the changes in substrates and metabolites in supernatant media of developed Tamoxifen resistance MCF-7 cells. We focus on the determination of lactate, pyruvate, and L-glutamine which enables the tracking of changes in metabolic pathways as a result of the resistance process. Chromatographic separation was achieved within 3.5 min. using a HILIC column (4.6 × 100 mm, 3.5 µm particle size) and mobile phase of 0.05 M acetic acid–ammonium acetate buffer solution pH 3.0: Acetonitrile (40:60 v/v). The linear range was 0.11–2.25, 0.012–0.227, and 0.02–0.20 mM for lactate, pyruvate, and L-glutamine, respectively. Within- and between-run accuracy was in the range 98.94-105.50% with precision (CV, %) of ≤0.86%. The results revealed a significant increase in both lactate and pyruvate production after acquiring the resistant. An increase in L-glutamine levels was also observed and could be attributed to its over production or decline in its consumption. Therefore, further tracking of genes responsible of lactate, pyruvate, and glutamine metabolic pathways should be performed in parallel to provide in-depth explanation of resistance mechanism.

The rate of smokers in Jordan has been among the highest globally. Electronic Nicotine Delivery systems (ENDs) are considered helpful in smoking cessation but also have the potential for metals exposure resulting from their transfer from the metallic coils to the e-liquid upon use. Metal exposure is associated with severe health outcomes. We sought to assess the levels of toxic metals (Cr, Cd, Pb, Ni and Al) transfer from two of the most popular coils used in ENDs among users in Jordan. The validated inductively coupled plasma-optical emission spectroscopy (ICP-OES) with limit of detections (LODs) of 0.10, 0.90, 0.15, 0.13 and 1.00 mg.kg−1 was employed to measure the levels of toxic metals in the e-liquid samples. Following a repetitive usage of coils in both tank and pod systems for five continuous days, the cumulative amount of toxic metals; Ni, Cr, Al and Pb levels were significantly increased in all e-liquids used (p < 0.0001) compared to the fresh unheated samples. The obtained results showed a time-dependent increase of metals transfer from coils to e-liquids, thus highlighting the need for additional studies to re-assess the safety claims of using ENDs for smoking cessation.