Suppression of PTP1B in gastric cancer cells in vitro induces a change in the genome-wide expression profile and inhibits gastric cancer cell growth

Can Allostery Be a Key Strategy for Targeting PTP1B in Drug Discovery? A Lesson from Trodusquemine

Protein tyrosine phosphatase 1B (PTP1B) is an enzyme crucially implicated in aberrations of various signaling pathways that underlie the development of different human pathologies, such as obesity, diabetes, cancer, and neurodegenerative disorders. Its inhibition can prevent these pathogenetic events, thus providing a useful tool for the discovery of novel therapeutic agents. The search for allosteric PTP1B inhibitors can represent a successful strategy to identify drug-like candidates by offering the opportunity to overcome some issues related to catalytic site-directed inhibitors, which have so far hampered the development of drugs targeting this enzyme. In this context, trodusquemine (MSI-1436), a natural aminosterol that acts as a non-competitive PTP1B inhibitor, appears to be a milestone. Initially discovered as a broad-spectrum antimicrobial agent, trodusquemine exhibited a variety of unexpected properties, ranging from antidiabetic and anti-obesity activities to effects useful to counteract cancer and neurodegeneration, which prompted its evaluation in several preclinical and clinical studies. In this review article, we provide an overview of the main findings regarding the activities and therapeutic potential of trodusquemine and their correlation with PTP1B inhibition. We also included some aminosterol analogues and related structure-activity relationships that could be useful for further studies aimed at the discovery of new allosteric PTP1B inhibitors.

Critical roles of PTPN family members regulated by non-coding RNAs in tumorigenesis and immunotherapy

Since tyrosine phosphorylation is reversible and dynamic in vivo, the phosphorylation state of proteins is controlled by the opposing roles of protein tyrosine kinases (PTKs) and protein tyrosine phosphatase (PTPs), both of which perform critical roles in signal transduction. Of these, intracellular non-receptor PTPs (PTPNs), which belong to the largest class I cysteine PTP family, are essential for the regulation of a variety of biological processes, including but not limited to hematopoiesis, inflammatory response, immune system, and glucose homeostasis. Additionally, a substantial amount of PTPNs have been identified to hold crucial roles in tumorigenesis, progression, metastasis, and drug resistance, and inhibitors of PTPNs have promising applications due to striking efficacy in antitumor therapy. Hence, the aim of this review is to summarize the role played by PTPNs, including PTPN1/PTP1B, PTPN2/TC-PTP, PTPN3/PTP-H1, PTPN4/PTPMEG, PTPN6/SHP-1, PTPN9/PTPMEG2, PTPN11/SHP-2, PTPN12/PTP-PEST, PTPN13/PTPL1, PTPN14/PEZ, PTPN18/PTP-HSCF, PTPN22/LYP, and PTPN23/HD-PTP, in human cancer and immunotherapy and to comprehensively describe the molecular pathways in which they are implicated. Given the specific roles of PTPNs, identifying potential regulators of PTPNs is significant for understanding the mechanisms of antitumor therapy. Consequently, this work also provides a review on the role of non-coding RNAs (ncRNAs) in regulating PTPNs in tumorigenesis and progression, which may help us to find effective therapeutic agents for tumor therapy.

Protein Tyrosine Phosphatase 1B (PTP1B): Insights into Its New Implications in Tumorigenesis

In vivo, tyrosine phosphorylation is a reversible and dynamic process governed by the opposing activities of protein tyrosine kinases and phosphatases. Defective or inappropriate operation of these proteins leads to aberrant tyrosine phosphorylation, which contributes to the development of many human diseases, including cancers. PTP1B, a non-transmembrane phosphatase, is generally considered a negative regulator of the metabolic signaling pathways and a promising drug target for type Ⅱ diabetes and obesity. Recently, PTP1B is also attracting considerable interest due to its important function and therapeutic potential in other diseases. An increasing number of studies have indicated that PTP1B plays a vital role in the initiation and progression of cancers and could be a target for new cancer therapies. Following recent advances in the aspects mentioned above, this review is focused on the major functions of PTP1B in different types of cancer and the underlying mechanisms behind these functions, as well as the potential pharmacological effects of PTP1B inhibitors in cancer therapy.

SLC26A6 and NADC‑1: Future direction of nephrolithiasis and calculus‑related hypertension research (Review)

Nephrolithiasis is the most common type of urinary system disease in developed countries, with high morbidity and recurrence rates. Nephrolithiasis is a serious health problem, which eventually leads to the loss of renal function and is closely related to hypertension. Modern medicine has adopted minimally invasive surgery for the management of kidney stones, but this does not resolve the root of the problem. Thus, nephrolithiasis remains a major public health issue, the causes of which remain largely unknown. Researchers have attempted to determine the causes and therapeutic targets of kidney stones and calculus‑related hypertension. Solute carrier family 26 member 6 (SLC26A6), a member of the well‑conserved solute carrier family 26, is highly expressed in the kidney and intestines, and it primarily mediates the transport of various anions, including OXa^2‑, HCO₃^‑, Cl^‑ and SO₄^2‑, amongst others. Na⁺‑dependent dicarboxylate‑1 (NADC‑1) is the Na⁺‑carboxylate co‑transporter of the SLC13 gene family, which primarily mediates the co‑transport of Na⁺ and tricarboxylic acid cycle intermediates, such as citrate and succinate, amongst others. Studies have shown that Ca²⁺ oxalate kidney stones are the most prevalent type of kidney stones. Hyperoxaluria and hypocitraturia notably increase the risk of forming Ca²⁺ oxalate kidney stones, and the increase in succinate in the juxtaglomerular device can stimulate renin secretion and lead to hypertension. Whilst it is known that it is important to maintain the dynamic equilibrium of oxalate and citrate in the kidney, the synergistic molecular mechanisms underlying the transport of oxalate and citrate across kidney epithelial cells have undergone limited investigations. The present review examines the results from early reports studying oxalate transport and citrate transport in the kidney, describing the synergistic molecular mechanisms of SLC26A6 and NADC‑1 in the process of nephrolithiasis formation. A growing body of research has shown that nephrolithiasis is intricately associated with hypertension. Additionally, the recent investigations into the mediation of succinate via regulation of the synergistic molecular mechanism between the SLC26A6 and NADC‑1 transporters is summarized, revealing their functional role and their close association with the inositol triphosphate receptor‑binding protein to regulate blood pressure.

miR-146b Regulates Cell Proliferation and Apoptosis in Gastric Cancer by Targeting PTP1B

BACKGROUND/AIMS

The purpose of this study is to explore the inhibition or activation effects of microRNA-146 B on the expression of PTP1B in gastric cancer cells.

METHODS

The expressions of PTP1B and miR-146b in gastric cancer were detected by RT-qPCR. The effects of miR-146b on cell apoptosis and proliferation of gastric cancer were detected. The methods used in the detection process included Annexin V/PI dying method, colony formation assay, and MTT assay. The downstream target gene miR-146b was predicted and screened by bioinformatics and luciferase reporter assay. The mRNA and protein expressions of the target gene PTP1B miR-146b were determined using RT-qPCR and western blot. The expression of miR-146 B in mice was detected by the cells transfected with microRNA-146 B in vivo.

RESULTS

Compared with normal tissues, PTP1B was higher and miR-146b was lower in cancer cells. Over-expression of miR-146b can inhibit cell viability and increase the apoptosis rate. According to the luciferase reporter assay, PTP1B was the downstream target gene of miR-146b. The re-introduction of PTP1B reversed the growth inhibition and apoptosis of gastric cancer cells induced by miR-146b. From the mouse xenograft model, the over-expression of miR-146b inhibited the tumor growth and reduced the expression level of PTP1B.

CONCLUSION

miR-146b directly inhibits the expression of PTP1B and suppressed the growth and development of gastric cancer.

PTP1B up-regulates EGFR expression by dephosphorylating MYH9 at Y1408 to promote cell migration and invasion in esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is one of the most common cancers worldwide. Protein tyrosine phosphatase 1B (PTP1B) is a member of protein tyrosine phosphatases (PTPs) family. In our previous work, PTP1B was found to be overexpressed in ESCC tissues and made contributions to the the cell migration and invasion as well as lung metastasis of ESCC. In this study, we explored the underlying molecular mechanisms. PTP1B enhanced cell migration and invasion by promoting epidermal growth factor receptor (EGFR) expression in ESCC, which was relied on phosphatase activity of PTP1B. Using GST-pulldown combined with LC/MS/MS, we found that nonmuscle myosin IIA (MYH9) was a novel substrate of PTP1B in ESCC cells. PTP1B dephosphorylated MYH9 at Y1408, by which PTP1B up-regulated EGFR expression and enhanced cell migration and invasion in ESCC. In conclusion, our study first reported that PTP1B was the positive regulator of EGFR by dephosphorylating MYH9 at Y1408 to promote cell migration and invasion, which revealed the regulatory mechanism of PTP1B-MYH9-EGFR axis in ESCC.

Increased PTPRA expression leads to poor prognosis through c-Src activation and G1 phase progression in squamous cell lung cancer

PTPRA is reported to be involved in cancer development and progression through activating the Src family kinase (SFK) signaling pathways, however, the roles of PTPRA in the squamous cell lung cancer (SCC) development are unclear. The purpose of this study was to clarify the clinical relevance and biological roles of PTPRA in SCC. We found that PTPRA was upregulated in squamous cell lung cancer compared to matched normal tissues at the mRNA (N=20, P=0.004) and protein expression levels (N=75, P<0.001). Notably, high mRNA level of PTPRA was significantly correlated with poorer prognosis in 675 SCC patients from the Kaplan-Meier plotter database. With 75 cases, we found that PTPRA protein expression was significantly correlated with tumor size (P=0.002), lymph node metastasis (P=0.008), depth of tumor invasion (P<0.001) and clinical stage (P<0.001). The Kaplan-Meier plot suggested that high expression of PTPRA had poorer overall survival in SCC patients (P=0.009). Multivariate Cox regression analysis suggested that PTPRA expression was an independent prognostic factor in SCC patients. In the cellular models, PTPRA promotes SCC cell proliferation through modulating Src activation as well as cell cycle progression. In conclusion, higher PTPRA level was associated with worse prognosis of SCC patients and PTPRA could promote the cell cycle progression through stimulating the c-Src signaling pathways.

Increased PTP1B expression and phosphatase activity in colorectal cancer results in a more invasive phenotype and worse patient outcome

Cell signaling is dependent on the balance between phosphorylation of proteins by kinases and dephosphorylation by phosphatases. This balance if often disrupted in colorectal cancer (CRC), leading to increased cell proliferation and invasion. For many years research has focused on the role of kinases as potential oncogenes in cancer, while phosphatases were commonly assumed to be tumor suppressive. However, this dogma is currently changing as phosphatases have also been shown to induce cancer growth. One of these phosphatases is protein tyrosine phosphatase 1B (PTP1B). Here we report that the expression of PTP1B is increased in colorectal cancer as compared to normal tissue, and that the intrinsic enzymatic activity of the protein is also enhanced. This suggests a role for PTP1B phosphatase activity in CRC formation and progression. Furthermore, we found that increased PTP1B expression is correlated to a worse patient survival and is an independent prognostic marker for overall survival and disease free survival. Knocking down PTP1B in CRC cell lines results in a less invasive phenotype with lower adhesion, migration and proliferation capabilities. Together, these results suggest that inhibition of PTP1B activity is a promising new target in the treatment of colorectal cancer and the prevention of metastasis.

Phosphatases: Their Roles in Cancer and Their Chemical Modulators

Phosphatases are involved in basically all cellular processes by dephosphorylating cellular components such as proteins, phospholipids and second messengers. They counteract kinases of which many are established oncogenes, and therefore kinases are one of the most important drug targets for targeted cancer therapy. Due to this relationship between kinases and phosphatases, phosphatases are traditionally assumed to be tumour suppressors. However, research findings over the last years prove that this simplification is incorrect, as bona-fide and putative phosphatase oncogenes have been identified. We describe here the role of phosphatases in cancer, tumour suppressors and oncogenes, and their chemical modulators, and discuss new approaches and opportunities for phosphatases as drug targets.

PTP1B promotes cell proliferation and metastasis through activating src and ERK1/2 in non-small cell lung cancer

Previous studies have demonstrated that protein tyrosine phosphatase 1B (PTP1B) can promote tumor progression in breast cancer, colon cancer and prostate cancer. Additionally, PTP1B acts as a tumor suppressor in other cancers, such as esophageal cancer and lymphoma. These findings suggest that PTP1B functions as a double-facet molecule in tumors, and the role of PTP1B in non-small cell lung cancer (NSCLC) is unknown. The present study demonstrates that the expression of PTP1B in NSCLC tissue is significantly higher than its expression in benign lung disease and is associated with the stage and overall survival (OS) of NSCLC patients. In vitro studies have demonstrated that PTP1B promotes the proliferation and metastasis of NSCLC cells by reducing the expression of p-src (Tyr527), which activates src and ERK1/2. This study provides the first exploration of the role of PTP1B in the proliferation and metastasis of NSCLC and subsequently elucidates the role of PTP1B in cancer. Our study uncovered that PTP1B can promote NSCLC proliferation and metastasis by activating src and subsequently ERK1/2 and provides a theoretical basis for future applications of PTP1B inhibitors in the treatment of NSCLC.

Targeting the disordered C terminus of PTP1B with an allosteric inhibitor

PTP1B, a validated therapeutic target for diabetes and obesity, has a critical positive role in HER2 signaling in breast tumorigenesis. Efforts to develop therapeutic inhibitors of PTP1B have been frustrated by the chemical properties of the active site. We define a new mechanism of allosteric inhibition that targets the C-terminal, noncatalytic segment of PTP1B. We present what is to our knowledge the first ensemble structure of PTP1B containing this intrinsically disordered segment, within which we identified a binding site for the small-molecule inhibitor MSI-1436. We demonstrate binding to a second site close to the catalytic domain, with cooperative effects between the two sites locking PTP1B in an inactive state. MSI-1436 antagonized HER2 signaling, inhibited tumorigenesis in xenografts and abrogated metastasis in the NDL2 mouse model of breast cancer, validating inhibition of PTP1B as a therapeutic strategy in breast cancer. This new approach to inhibition of PTP1B emphasizes the potential of disordered segments of proteins as specific binding sites for therapeutic small molecules.

The regulatory roles of phosphatases in cancer

The relevance of potentially reversible post-translational modifications required for controlling cellular processes in cancer is one of the most thriving arenas of cellular and molecular biology. Any alteration in the balanced equilibrium between kinases and phosphatases may result in development and progression of various diseases, including different types of cancer, though phosphatases are relatively under-studied. Loss of phosphatases such as PTEN (phosphatase and tensin homologue deleted on chromosome 10), a known tumour suppressor, across tumour types lends credence to the development of phosphatidylinositol 3-kinase inhibitors alongside the use of phosphatase expression as a biomarker, though phase 3 trial data are lacking. In this review, we give an updated report on phosphatase dysregulation linked to organ-specific malignancies.

The SLC26 gene family of anion transporters and channels

The phylogenetically ancient SLC26 gene family encodes multifunctional anion exchangers and anion channels transporting a broad range of substrates, including Cl(-), HCO3(-), sulfate, oxalate, I(-), and formate. SLC26 polypeptides are characterized by N-terminal cytoplasmic domains, 10-14 hydrophobic transmembrane spans, and C-terminal cytoplasmic STAS domains, and appear to be homo-oligomeric. SLC26-related SulP proteins of marine bacteria likely transport HCO3(-) as part of oceanic carbon fixation. SulP genes present in antibiotic operons may provide sulfate for antibiotic biosynthetic pathways. SLC26-related Sultr proteins transport sulfate in unicellular eukaryotes and in plants. Mutations in three human SLC26 genes are associated with congenital or early onset Mendelian diseases: chondrodysplasias for SLC26A2, chloride diarrhea for SLC26A3, and deafness with enlargement of the vestibular aqueduct for SLC26A4. Additional disease phenotypes evident only in mouse knockout models include oxalate urolithiasis for Slc26a6 and Slc26a1, non-syndromic deafness for Slc26a5, gastric hypochlorhydria for Slc26a7 and Slc26a9, distal renal tubular acidosis for Slc26a7, and male infertility for Slc26a8. STAS domains are required for cell surface expression of SLC26 proteins, and contribute to regulation of the cystic fibrosis transmembrane regulator in complex, cell- and tissue-specific ways. The protein interactomes of SLC26 polypeptides are under active investigation.

Overexpression of PTP1B in human colorectal cancer and its association with tumor progression and prognosis

Protein tyrosine phosphatase 1B (PTP1B) is a non-transmembrane protein tyrosine phosphatase that has been implicated in cancer pathogenesis. However, the expression level and the role of PTP1B in the development and prognosis of colorectal cancer (CRC) remain unclear. In this study, the expression of PTP1B in CRC tissues and matched noncancerous tissues were detected by using immunohistochemistry, real-time PCR and Western blotting. The correlations between PTP1B expression level and clinicopathologic characteristics and patient survival were analyzed. We found that PTP1B expression was significantly higher in CRC tissues compared with matched non-tumour tissues. Statistical analysis showed that the PTP1B expression was correlated with tumor differentiation, tumor invasion, lymph node metastasis, and TNM stage. Patients with higher expressions of PTP1B had the lower survival (P = 0.012). Taken together, our results suggest that PTP1B expression might play a critical role in the progression of CRC and may serve as a valuable prognostic biomarker for CRC.

PTP1B expression contributes to gastric cancer progression

Protein tyrosine phosphatase 1B (PTP1B), a member of the superfamily of protein tyrosine phosphatases, has been implicated in cancer pathogenesis. However, the role of PTP1B in the development of gastric cancer is unclear. The purpose of this study was to clarify the expression pattern and role of PTP1B in the gastric cancer. The expression of PTP1B in gastric cancer tissues was determined by immunohistochemical staining. Cell growth assay, soft agar colony formation assay, and tumorigenicity assay were used for examining proliferation, colony formation, and in vivo tumorigenesis of gastric cancer cells. The total levels and phosphorylated levels of Akt, extracellular signal-regulated kinase (Erk1/2), focal adhesion kinase (FAK), and Src were examined by western blotting, respectively. PTP1B was overexpressed in gastric cancer tissues (65/80) and correlated with tumor metastasis and tumor-node-metastasis stage. Overexpression of PTP1B promoted the proliferation and in vivo tumorigenesis of MKN45 cells and also increased the phosphorylation levels of Akt, Erk1/2, and FAK and the activity of Src. These results were conformed by knockdown of PTP1B in MKN28 cells. Therefore, our study suggested that PTP1B expression might play an important role in the development of gastric cancer.