Peroxiporins Are Induced upon Oxidative Stress Insult and Are Associated with Oxidative Stress Resistance in Colon Cancer Cell Lines

Aquaporins in colorectal cancer: exploring their role in tumorigenesis, metastasis, and drug response

Aquaporins (AQPs) are small, integral proteins facilitating water transport across plasma cell membranes in response to osmotic gradients. This family has 13 unique members (AQP0-12), which can also transport glycerol, urea, gases, and other salute small molecules. AQPs play a crucial role in the regulation of different cellular processes, including metabolism, migration, immunity, barrier function, and angiogenesis. These proteins are found to aberrantly overexpress in various cancers, including colorectal cancer (CRC). Growing evidence has explored AQPs as a potential diagnostic biomarker and therapeutic target in different cancers. However, there is no comprehensive review compiling the available information on the crucial role of AQPs in the context of colorectal cancer. This review highlights the significance of AQPs as the biomarker and regulator of tumor cells metabolism. In addition, the proliferation, angiogenesis, and metastasis of tumor cells related to AQPs expression as well as function are discussed. Understanding the AQPs prominent role in chemotherapy resistance is of great importance clinically.

Peroxiporins in Triple-Negative Breast Cancer: Biomarker Potential and Therapeutic Perspectives

Triple-negative breast cancer (TNBC) remains one of the most challenging subtypes since it is initially characterized by the absence of specific biomarkers and corresponding targeted therapies. Advances in methodology, translational informatics, genomics, and proteomics have significantly contributed to the identification of therapeutic targets. The development of innovative treatments, such as antibody-drug conjugates and immune checkpoint inhibitors, alongside chemotherapy, has now become the standard of care. However, the quest for biomarkers defining therapy outcomes is still ongoing. Peroxiporins, which comprise a subgroup of aquaporins, which are membrane pores facilitating the transport of water, glycerol, and hydrogen peroxide, have emerged as potential biomarkers for therapy response. Research on peroxiporins reveals their involvement beyond traditional channeling activities, which is also reflected in their cellular localization and roles in cellular signaling pathways. This research on peroxiporins provides fresh insights into the mechanisms of therapy resistance in tumors, offering potential avenues for predicting treatment outcomes and tailoring successful TNBC therapies.

Protective roles of peroxiporins AQP0 and AQP11 in human astrocyte and neuronal cell lines in response to oxidative and inflammatory stressors

In addition to aquaporin (AQP) classes AQP1, AQP4 and AQP9 known to be expressed in mammalian brain, our recent transcriptomic analyses identified AQP0 and AQP11 in human cortex and hippocampus at levels correlated with age and Alzheimer's disease (AD) status; however, protein localization remained unknown. Roles of AQP0 and AQP11 in transporting hydrogen peroxide (H2O2) in lens and kidney prompted our hypothesis that up-regulation in brain might similarly be protective. Established cell lines for astroglia (1321N1) and neurons (SHSY5Y, differentiated with retinoic acid) were used to monitor changes in transcript levels for human AQPs (AQP0 to AQP12) in response to inflammation (simulated with 10-100 ng/ml lipopolysaccharide [LPS], 24 h), and hypoxia (5 min N2, followed by 0 to 24 h normoxia). AQP transcripts up-regulated in both 1321N1 and SHSY5Y included AQP0, AQP1 and AQP11. Immunocytochemistry in 1321N1 cells confirmed protein expression for AQP0 and AQP11 in plasma membrane and endoplasmic reticulum; AQP11 increased 10-fold after LPS and AQP0 increased 0.3-fold. In SHSY5Y cells, AQP0 expression increased 0.2-fold after 24 h LPS; AQP11 showed no appreciable change. Proposed peroxiporin roles were tested using melondialdehyde (MDA) assays to quantify lipid peroxidation levels after brief H2O2. Boosting peroxiporin expression by LPS pretreatment lowered subsequent H2O2-induced MDA responses (∼50%) compared with controls; conversely small interfering RNA knockdown of AQP0 in 1321N1 increased lipid peroxidation (∼17%) after H2O2, with a similar trend for AQP11 siRNA. Interventions that increase native brain peroxiporin activity are promising as new approaches to mitigate damage caused by aging and neurodegeneration.

AQP3-Dependent PI3K/Akt Modulation in Breast Cancer Cells

Aquaporin 3 (AQP3) is a peroxiporin, a membrane protein that channels hydrogen peroxide in addition to water and glycerol. AQP3 expression also correlates with tumor progression and malignancy and is, therefore, a potential target in breast cancer therapy. In addition, epithelial growth factor receptor (EGFR) plays an important role in breast cancer. Therefore, we investigated whether disruption of the lipid raft harboring EGFR could affect AQP3 expression, and conversely, whether AQP3 silencing would affect the EGFR/phosphoinositide-3-kinase (PI3K)/Protein kinase B (PKB or Akt) signaling pathway in breast cancer cell lines with different malignant capacities. We evaluated H₂O₂ uptake, cell migratory capacity, and expression of PI3K, pAkt/Akt in three breast cancer cell lines, MCF7, SkBr3, and SUM159PT, and in the nontumorigenic breast epithelial cell line MCF10A. Our results show different responses between the tested cell lines, especially when compared to the nontumorigenic cell line. Neither lipid raft disruption nor EGF stimuli had an effect on PI3K/Akt pathway in MCF10A cell line. AQP3-silencing in SkBr3 and SUM159PT showed that AQP3 can modulate PI3K/Akt activation in these cells. Interestingly, SUM159PT cells increase nuclear factor-E2-related factor 2 (NRF2) in response to lipid raft disruption and EGF stimuli, suggesting an oxidative-dependent response to these treatments. These results suggest that in breast cancer cell lines, AQP3 is not directly related to PI3K/Akt pathway but rather in a cell-line-dependent manner.

Berberine Inhibited Growth and Migration of Human Colon Cancer Cell Lines by Increasing Phosphatase and Tensin and Inhibiting Aquaporins 1, 3 and 5 Expressions

Introduction: Berberine is a natural isoquinoline alkaloid with anti-cancer properties. Nevertheless, the underlying mechanism of its action in human colorectal cancer (CRC) has not been thoroughly elucidated. We investigated the anti-cancer effect of berberine on HT-29, SW-480 and HCT-116 human CRC cell lines. Methods: Cell proliferation, migration and invasion were studied by MTT assay, wound healing, transwell chambers and flow cytometry. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and immunostaining were used to evaluate the expression of aquaporins (AQPs) 1, 3 and 5 in colon cancer cell lines before and after treatment with berberine (10, 30 and 100 µM). RT-qPCR and Western blotting were used to further explore the PI3K/AKT signaling pathway and the molecular mechanisms underlying berberine-induced inhibition of cell proliferation. Results: We demonstrated that treatment of these CRC cell lines with berberine inhibited cell proliferation, migration and invasion through induction of apoptosis and necrosis. HT-29, SW-480 and HCT-116 stained positively for AQP 1, 3 and 5, and berberine treatment down-regulated the expression of all three types of AQPs. Berberine also modulated PI3K/AKT pathway activity through up-regulating PTEN and down-regulating PI3K, AKT and p-AKT expression as well as suppressing its downstream targets, mTOR and p-mTOR at the protein level. Discussion/Conclusions: These findings indicate that berberine inhibited growth, migration and invasion of these colon cancer cell lines via down-regulation of AQP 1, 3 and 5 expressions, up-regulating PTEN which inhibited the PI3K/AKT pathway at the gene and protein levels, and that AQP 1, 3 and 5 expression level can be used as prognostic biomarkers for colon cancer metastasis.

Relevant Membrane Transport Proteins as Possible Gatekeepers for Effective Pharmacological Ascorbate Treatment in Cancer

Despite the increasing number of newly diagnosed malignancies worldwide, therapeutic options for some tumor diseases are unfortunately still limited. Interestingly, preclinical but also some clinical data suggest that the administration of pharmacological ascorbate seems to respond well, especially in some aggressively growing tumor entities. The membrane transport and channel proteins are highly relevant for the use of pharmacological ascorbate in cancer therapy and are involved in the transfer of active substances such as ascorbate, hydrogen peroxide, and iron that predominantly must enter malignant cells to induce antiproliferative effects and especially ferroptosis. In this review, the relevant conveying proteins from cellular surfaces are presented as an integral part of the efficacy of pharmacological ascorbate, considering the already known genetic and functional features in tumor tissues. Accordingly, candidates for diagnostic markers and therapeutic targets are mentioned.

Establishment and external verification of an oxidative stress-related gene signature to predict clinical outcomes and therapeutic responses of colorectal cancer

Objective: Accumulated evidence highlights the biological significance of oxidative stress in tumorigenicity and progression of colorectal cancer (CRC). Our study aimed to establish a reliable oxidative stress-related signature to predict patients' clinical outcomes and therapeutic responses. Methods: Transcriptome profiles and clinical features of CRC patients were retrospectively analyzed from public datasets. LASSO analysis was used to construct an oxidative stress-related signature to predict overall survival, disease-free survival, disease-specific survival, and progression-free survival. Additionally, antitumor immunity, drug sensitivity, signaling pathways, and molecular subtypes were analyzed between different risk subsets through TIP, CIBERSORT, oncoPredict, etc. approaches. The genes in the signature were experimentally verified in the human colorectal mucosal cell line (FHC) along with CRC cell lines (SW-480 and HCT-116) through RT-qPCR or Western blot. Results: An oxidative stress-related signature was established, composed of ACOX1, CPT2, NAT2, NRG1, PPARGC1A, CDKN2A, CRYAB, NGFR, and UCN. The signature displayed an excellent capacity for survival prediction and was linked to worse clinicopathological features. Moreover, the signature correlated with antitumor immunity, drug sensitivity, and CRC-related pathways. Among molecular subtypes, the CSC subtype had the highest risk score. Experiments demonstrated that CDKN2A and UCN were up-regulated and ACOX1, CPT2, NAT2, NRG1, PPARGC1A, CRYAB, and NGFR were down-regulated in CRC than normal cells. In H₂O₂-induced CRC cells, their expression was notably altered. Conclusion: Altogether, our findings constructed an oxidative stress-related signature that can predict survival outcomes and therapeutic response in CRC patients, thus potentially assisting prognosis prediction and adjuvant therapy decisions.

Differential Sensitivity of Two Leukemia Cell Lines towards Two Major Gas Plasma Products Hydrogen Peroxide and Hypochlorous Acid

Oxidative stress has major implications for health and disease. At the same time, the term collectively describes the reactions to different types of reactive oxygen species (ROS) and oxidants, including hydrogen peroxide (H2O2) and hypochlorous acid (HOCl). However, how both compare in terms of cytotoxicity and mechanism of action is less known. Using two leukemia cell lines, Jurkat and THP-1, as model systems at similar cell concentrations, we found an 8-fold greater sensitivity of the former over the latter for H2O2 exposure. Unexpectantly, this was not the case with HOCl exposure. Jurkat cells were 2-fold more resistant to HOCl-induced cytotoxicity than THP-1 cells. In each cell type, the relatively more toxic oxidant also induced activation of caspases 3 and 7 at earlier time points, as time-lapse fluorescence microscopy revealed. The effects observed did not markedly correlate with changes in intracellular GSH and GSSG levels. In addition, siRNA-mediated knockdown of the Nrf2 target HMOX-1 encoding for HO-1 protein and the growth and survival factor IL-8 revealed Jurkat cells to become more sensitive to HOCl, while HO-1 and IL-8 siRNA-mediated knockdown in THP-1 cells produced greater sensitivity towards H2O2. siRNA-mediated knockdown of catalase increased oxidant sensitivity only negligibly. Collectively, the data suggest striking HOCl-resistance of Jurkat and H2O2 resistance of THP-1 cells, showing similar protective roles of HO-1 and IL-8, while caspase activation kinetics differ.

The Effect of Nutritional Ketosis on Aquaporin Expression in Apolipoprotein E-Deficient Mice: Potential Implications for Energy Homeostasis

Ketogenic diets (KDs) are very low-carbohydrate, very high-fat diets which promote nutritional ketosis and impact energetic metabolism. Aquaporins (AQPs) are transmembrane channels that facilitate water and glycerol transport across cell membranes and are critical players in energy homeostasis. Altered AQP expression or function impacts fat accumulation and related comorbidities, such as the metabolic syndrome. Here, we sought to determine whether nutritional ketosis impacts AQPs expression in the context of an atherogenic model. To do this, we fed ApoE^−/− (apolipoprotein E-deficient) mice, a model of human atherosclerosis, a KD (Kcal%: 1/81/18, carbohydrate/fat/protein) or a control diet (Kcal%: 70/11/18, carbohydrate/fat/protein) for 12 weeks. Plasma was collected for biochemical analysis. Upon euthanasia, livers, white adipose tissue (WAT), and brown adipose tissue (BAT) were used for gene expression studies. Mice fed the KD and control diets exhibited similar body weights, despite the profoundly different fat contents in the two diets. Moreover, KD-fed mice developed nutritional ketosis and showed increased expression of thermogenic genes in BAT. Additionally, these mice presented an increase in Aqp9 transcripts in BAT, but not in WAT, which suggests the participation of Aqp9 in the influx of excess plasma glycerol to fuel thermogenesis, while the up-regulation of Aqp7 in the liver suggests the involvement of this aquaporin in glycerol influx into hepatocytes. The relationship between nutritional ketosis, energy homeostasis, and the AQP network demands further investigation.

Metformin Promotes Differentiation and Attenuates H2O2-Induced Oxidative Damage of Osteoblasts via the PI3K/AKT/Nrf2/HO-1 Pathway

At present, the drug treatment of osteoporosis is mostly focused on inhibiting osteoclastogenesis, which has relatively poor effects. Metformin is a drug that can potentially promote osteogenic differentiation and improve bone mass in postmenopausal women. We aimed to detect the molecular mechanism underlying the osteogenic effect of metformin. Our study indicated that metformin obviously increased the Alkaline phosphatase activity and expression of osteogenic marker genes at the mRNA and protein levels. The PI3K/AKT signaling pathway was revealed to play an essential role in the metformin-induced osteogenic process, as shown by RNA sequencing. We added LY294002 to inhibit the PI3K/AKT pathway, and the results indicated that the osteogenic effect of metformin was also blocked. Additionally, the sequencing data also indicated oxidation-reduction reaction was involved in the osteogenic process of osteoblasts. We used H₂O₂ to mimic the oxidative damage of osteoblasts, but metformin could attenuate it. Antioxidative Nrf2/HO-1 pathway, regarded as the downstream of PI3K/AKT pathway, was modulated by metformin in the protective process. We also revealed that metformin could improve bone mass and oxidative level of OVX mice. In conclusion, our study revealed that metformin promoted osteogenic differentiation and H₂O₂-induced oxidative damage of osteoblasts via the PI3K/AKT/Nrf2/HO-1 pathway.