Digitoxin Affects Metabolism, ROS Production and Proliferation in Pancreatic Cancer Cells Differently Depending on the Cell Phenotype

Exosomal SOX21-AS1 Regulates EREG by Sponging miR-451a and Promotes the Malignancy of Pancreatic Ductal Adenocarcinoma

The incidence and mortality of pancreatic ductal adenocarcinoma (PDAC) have increased. Exosomes, as a regulatory mode of intercellular communication, contain lncRNAs. SOX21-AS1 has been studied in other cancers, and its expression is elevated in PDAC, but its role in PDAC remains unclear. First, we analyzed the expression of lncRNAs in PDAC tissues and nontumor tissues through the TCGA database. Next, the results of the RT-qPCR experiment confirmed the prediction that the expression of SOX21-AS1 was elevated in PDAC tissues. In vivo and in vitro cell function assays confirmed that the degree of malignancy of PDAC was proportional to the expression of SOX21-AS1. In addition, through exosome isolation and uptake experiments, we first found that PDAC could secrete exosomal SOX21-AS1 and play an angiogenic role in HUVECs. Subsequently, the relationship between SOX21-AS1, miR-451a and epiregulin (EREG) was verified through database prediction and analysis and RIP assays. Finally, functional recovery assays in vivo and in vitro verified that SOX21-AS1 regulates the expression of EREG through combination with miR-451a and thus promotes the malignancy of PDAC. SOX21-AS1 was upregulated in PDAC. The upregulation of SOX21-AS1 can stimulate the proliferation, migration, invasion, stemness and epithelial-mesenchymal transition (EMT) progression of PDAC cells. Furthermore, PDAC cells secrete exosomal SOX21-AS1, which is absorbed by HUVECs and promotes angiogenesis. Our study first identified that SOX21-AS1 promotes the malignancy of PDAC through the SOX21-AS1/miR-451a/EREG axis, and also that exosomal SOX21-AS1 promotes angiogenesis in PDAC.

Incorporating Network Pharmacology and Experimental Validation to Identify Bioactive Compounds and Potential Mechanisms of Digitalis in Treating Anaplastic Thyroid Cancer

Anaplastic thyroid cancer (ATC) is one of the most lethal malignant tumors for which there is no effective treatment. There are an increasing number of studies on herbal medicine for treating malignant tumors, and the classic botanical medicine Digitalis and its active ingredients for treating heart failure and arrhythmias have been revealed to have significant antitumor efficacy against a wide range of malignant tumors. However, the main components of Digitalis and the molecular mechanisms of its anti-ATC effects have not been extensively studied. Here, we screened the main components and core targets of Digitalis and verified the relationship between the active components and targets through network pharmacology, molecular docking, and experimental validation. These experiments showed that the active ingredients of Digitalis inhibit ATC cell activity and lead to ATC cell death through the apoptotic pathway.

The mechanistic role of cardiac glycosides in DNA damage response and repair signaling

Cardiac glycosides (CGs) are a class of bioactive organic compounds well-known for their application in treating heart disease despite a narrow therapeutic window. Considerable evidence has demonstrated the potential to repurpose CGs for cancer treatment. Chemical modification of these CGs has been utilized in attempts to increase their anti-cancer properties; however, this has met limited success as their mechanism of action is still speculative. Recent studies have identified the DNA damage response (DDR) pathway as a target of CGs. DDR serves to coordinate numerous cellular pathways to initiate cell cycle arrest, promote DNA repair, regulate replication fork firing and protection, or induce apoptosis to avoid the survival of cells with DNA damage or cells carrying mutations. Understanding the modus operandi of cardiac glycosides will provide critical information to better address improvements in potency, reduced toxicity, and the potential to overcome drug resistance. This review summarizes recent scientific findings of the molecular mechanisms of cardiac glycosides affecting the DDR signaling pathway in cancer therapeutics from 2010 to 2022. We focus on the structural and functional differences of CGs toward identifying the critical features for DDR targeting of these agents.

Cytotoxic and Pro-Apoptotic Effects of Leaves Extract of Antiaris africana Engler (Moraceae)

Antiaris africana Engler leaves have been used in Senegalese folk medicine to treat breast cancer. The present study aimed to investigate the anticancer potential of Antiaris africana Engler leaves using several human cancer cell lines. The leaves of Antiaris africana Engler were extracted in parallel with water or 70% ethanol and each extract divided into three parts by successive liquid-liquid extraction with ethyl acetate and butanol. The phytochemical components of the active extract were investigated using ultra-performance liquid chromatography-diode array detector-quadrupole time-of-flight tandem mass spectrometry (UPLC-DAD-QTOF-MS/MS). The cytotoxic and cytostatic effects of each extract, as well as their fractions, were evaluated in vitro via flow and image cytometry on different human cancer phenotypes, such as breast (MCF-7), pancreas (AsPC-1), colon (SW-620) and acute monocytic leukemia (THP-1). Both hydro-alcoholic and aqueous extracts induced strong apoptosis in MCF-7 cells. The water fraction of the hydro-alcoholic extract was found to be the most active, suppressing the cell growth of MCF-7 in a dose-dependent manner. The half maximum effective concentration (EC₅₀) of this fraction was 64.6 ± 13.7 μg/mL for MCF-7, with equivalent values for all tested phenotypes. In parallel, the apoptotic induction by this fraction resulted in a EC₅₀ of 63.5 ± 1.8 μg/mL for MCF-7, with again equivalent values for all other cellular tested phenotypes. Analysis of this fraction by UPLC-DAD-QTOF-MS/MS led to the identification of hydroxycinnamates as major components, one rutin isomer, and three cardiac glycosides previously isolated from seeds and bark of Antiaris africana Engler and described as cytotoxic in human cancer models. These results provide supportive data for the use of Antiaris africana Engler leaves in Senegal.

Na/K‑ATPase subunit α3 expression is associated with the efficacy of digitoxin treatment in pancreatic cancer cells

The alpha subunits (ATP1A1-3) of Na⁺/K⁺-ATPase binds digitoxin with varying affinity. The expression levels of these subunits dictate the anticancer effects of digitoxin. In the present study, three pancreatic cancer cell lines, AsPC-1, Panc-1 and CFPAC-1, were used to investigate the effects of digitoxin in relation to the expression of the subunits ATP1A1 and ATP1A3. Cell viability and intracellular calcium concentrations was measured in relation to the gene and protein expression of ATP1A1 and ATP1A3. Digitoxin was used to treat the cells at concentrations of 1-100 nM, and the intracellular calcium concentrations increased in a concentration-dependent manner in the Panc-1 and in the CFPAC-1 cells with treatment at 100 nM. In the AsPC-1 cells only the supraphysiological concentration of digitoxin (100 nM) resulted in a decrease in the number of viable cells (unviable cells increased to 22%), whereas it had no effect on intracellular calcium levels. The number of viable Panc-1 and CFPAC-1 cells decreased after digitoxin treatment at 25-100 nM (unviable Panc-1 cells increased to 33-59%; unviable CFPAC-1 cells increased to 22-56%). Digitoxin treatment also affected the transcriptional expression of the ATP1A1 and ATP1A3 subunits. In Panc-1 cells, ATP1A3 gene expression was negatively associated with the digitoxin concentration (25-100 nM). In the AsPC-1 and CFPAC-1 cells, the expression of the ATP1A1 gene increased in the cells treated with the 100 nM digitoxin concentration. The protein expression of ATP1A1 and ATP1A3 was not altered with digitoxin treatment. The basal protein expression of ATP1A1 was high in the AsPC-1 and CFPAC-1 cells, compared to the Panc-1 cells, in contrast to the basal expression of ATP1A3, which was higher in the Panc-1 cells, compared to the other pancreatic cancer cells used. On the whole, the present study demonstrates that the high expression of ATP1A3 renders pancreatic cancer cells more susceptible to digitoxin-induced cell death. The findings suggest that the expression of ATP1A3 may be used as a marker for tumor sensitivity to digitoxin treatment, where a high expression of ATP1A3 is favorable for the anticancer effects of digitoxin.