Dipeptidyl Peptidase IV as a Prognostic Marker and Therapeutic Target in Papillary Thyroid Carcinoma

Ferroptosis in thyroid cancer: Potential mechanisms, effective therapeutic targets and predictive biomarker

Thyroid cancer is a prevalent endocrine malignancy whose global incidence has risen over the past several decades. Ferroptosis, a regulated form of cell death distinguished by the excessive buildup of iron-dependent lipid peroxidates, stands out from other programmed cell death pathways in terms of morphological and molecular characteristics. Increasing evidence suggests a close association between thyroid cancer and ferroptosis, that is, inducing ferroptosis effectively suppresses the proliferation of thyroid cancer cells and impede tumor advancement. Therefore, ferroptosis represents a promising therapeutic target for the clinical management of thyroid cancer in clinical settings. Alterations in ferroptosis-related genes hold potential for prognostic prediction in thyroid cancer. This review summarizes current studies on the role of ferroptosis in thyroid cancer, elucidating its mechanisms, therapeutic targets, and predictive biomarkers. The findings underscore the significance of ferroptosis in thyroid cancer and offer valuable insights into the development of innovative treatment strategies and accurate predictors for the thyroid cancer.

Estrogen-mediated DNMT1 and DNMT3A recruitment by EZH2 silences miR-570-3p that contributes to papillary thyroid malignancy through DPP4

BACKGROUND

Papillary thyroid carcinoma (PTC) is a common endocrine malignancy. Studies have indicated that estrogen can regulate the expression of miRNAs in numerous malignancies. MiR-570-3p has been shown to have a regulatory function in various cancers. However, studies of the regulatory function of miR-570-3p and a direct link between estrogen (especially estradiol E2) and miR-570-3p in PTC have not been done.

METHODS

Expression of miR-570-3p and its downstream target DPP4 in PTC tissues and cells was predicted using bioinformatics and validated by qRT-PCR and western blot assays. We then performed a series of gain-and-loss experiments to assess the functional significance of miR-570-3p/DPP4 axis in PTC progression in vitro and in vivo. Additionally, the methylation of the miR-570-3p promoter region was examined via bioinformatics analysis and MSP. Finally, the effects of E2 on PTC progression and the correlation between DNMT1/DNMT3A and EZH2 were predicted by bioinformatic tools and proved by luciferase reporter, ChIP, and co-IP assays.

RESULTS

In PTC tumor tissues and cell lines, there was a lower expression level and a higher methylation level of miR-570-3p compared to normal tissues and cell lines. DPP4 was identified as the downstream target of miR-570-3p. Overexpression of miR-570-3p reduced the proliferative, migratory, and invasive capabilities, and promoted apoptosis, while overexpression of DPP4 reversed these effects in PTC cells. It was also discovered that DNMT1 and DNMT3A increased the CpG methylation level of the miR-570-3p promoter in an EZH2-dependent manner, which led to decreased expression of miR-570-3p. Furthermore, we observed that estrogen (E2) enhanced the methylation of miR-570-3p and suppressed its expression levels, resulting in augmented tumor growth in vivo in PTC.

CONCLUSION

Estrogen regulates the EZH2/DNMTs/miR-570-3p/DPP4 signaling pathway to promote PTC progression.

Role of SGLT2 Inhibitors, DPP-4 Inhibitors, and Metformin in Pancreatic Cancer Prevention

Pancreatic carcinoma is a highly aggressive tumor that usually presents when it has already metastasized. Therapeutic options for cure remain scarce and rely on combination chemotherapy with limited sustainability. Diabetes is considered an important risk factor for the development of pancreatic cancer due to the production of proinflammatory cytokines, which result in increased cell proliferation. More than half of patients diagnosed with pancreatic cancer eventually develop diabetes due to the destruction of insulin-producing cells. The interlinkage of both diseases might identify a possible preventative strategy for reducing the incidence of pancreatic carcinoma. This study reviewed the recent literature on the association between pancreatic cancer risk and SGLT2 inhibitors, GLP-1 RA, DPP-4 inhibitors, and biguanides. There are mixed data regarding the relationship between GLP-1 RA and DPP-4 inhibitors and pancreatic cancer, with some trials suggesting that they might increase the risk. In contrast, studies have mostly revealed that SGLT2 inhibitors have an antiproliferative effect on various tumors, such as liver, pancreatic, prostate, bowel, lung, and breast carcinoma, which might be due to their mechanism of blockage of reabsorption of glucose by cells, lowering the amount of available glucose for the growth of tumor cells. Metformin, the first-line agent for diabetes, has also been shown to be associated with decreasing pancreatic cancer risk and improving prognosis in those who already have the disease. Dedicated trials are needed to further delineate the association of antidiabetic drugs with the risk of pancreatic cancer in the general population, as previous studies have mostly focused on diabetic patients.

m6A reader IGF2BP2 promotes lymphatic metastasis by stabilizing DPP4 in papillary thyroid carcinoma

Lymph node metastasis (LNM) is a major cause of locoregional recurrence of papillary thyroid carcinoma (PTC). However, the mechanisms responsible for LNM are unclear. Aberrant N6-methyladenosine (m6A) RNA modification plays a vital role in cancer progression and metastasis, and whether m6A modification regulates LNM in PTC remains to be determined. This study showed that IGF2BP2 was upregulated in PTC and positively associated with LNM. Functionally, IGF2BP2 knockdown significantly inhibited PTC cell proliferation and invasion in vitro, and vice versa. Moreover, IGF2BP2 knockdown significantly inhibited lymphatic metastasis in vivo. Mechanistically, Human m6A epitranscriptomic microarray, MeRIP, and RIP assays demonstrated that IGF2BP2 activated the NF-KB pathway by enhancing DPP4 stability in an m6A-dependent manner. Furthermore, IGF2BP2 knockdown increased the sensitivity of PTC cells to cisplatin therapy to a certain extent, while its overexpression produced the opposite effects. Overall, this study uncovers that IGF2BP2 promotes lymphatic metastasis via stabilizing DPP4 in an m6A-dependent manner, and provides new insights for understanding the mechanism of lymphatic metastasis in PTC.

Exploring the clinical utility of DPP-IV and SGLT2 inhibitors in papillary thyroid cancer: a literature review

In the realm of clinical management, Papillary Thyroid Cancer (PTC) stands out as a prevalent thyroid malignancy, characterized by significant metabolic challenges, particularly in the context of carbohydrate metabolism. Recent studies have unveiled promising applications of Dipeptidyl Peptidase-IV (DPP-IV) and Sodium-Glucose Cotransporter 2 (SGLT2) inhibitors, which are conventionally employed in the treatment of type 2 diabetes mellitus (T2DM), as potential adjuncts in anticancer therapy. DPP-IV and SGLT2 inhibitors can be imply to counteract the Warburg effect in cancer, with a specific focus on PTC, owing to their potential metabolic advantages and their influence on the tumor microenvironment, achieved by imposing restrictions on glucose accessibility. Consequently, a comprehensive review has been undertaken, involving meticulous examination of the existing body of evidence pertaining to the utilization of DPP-IV and SGLT2 inhibitors in the context of PTC. The mechanisms of action inherent to these inhibitors have been thoroughly explored, drawing upon insights derived from preclinical investigations. Furthermore, this review initiates discussions concerning the implications for future research directions and the formulation of innovative therapeutic strategies for PTC. As the intricate interplay between carbohydrate metabolism, the Warburg effect, and cancer progression garners increasing attention, attaining a comprehensive understanding of the roles played by DPP-IV and SGLT2 inhibitors in PTC management may serve as the cornerstone for novel approaches aimed at enhancing patient care and broadening the spectrum of available therapeutic modalities.

Drug repositioning in thyroid cancer treatment: the intriguing case of anti-diabetic drugs

Cancer represents the main cause of death worldwide. Thyroid cancer (TC) shows an overall good rate of survival, however there is a percentage of patients that do not respond or are refractory to common therapies. Thus new therapeutics strategies are required. In the past decade, drug repositioning become very important in the field of cancer therapy. This approach shows several advantages including the saving of: i) time, ii) costs, iii) de novo studies regarding the safety (just characterized) of a drug. Regarding TC, few studies considered the potential repositioning of drugs. On the other hand, certain anti-diabetic drugs, were the focus of interesting studies on TC therapy, in view of the fact that they exhibited potential anti-tumor effects. Among these anti-diabetic compounds, not all were judjed as appropriate for repositioning, in view of well documented side effects. However, just to give few examples biguanides, DPP-4-inhibitors and Thiazolidinediones were found to exert strong anti-cancer effects in TC. Indeed, their effects spaced from induction of citotoxicity and inhibition of metastatic spread, to induction of de-differentiation of TC cells and modulation of TC microenvironment. Thus, the multifacial anti-cancer effect of these compounds would make the basis also for combinatory strategies. The present review is aimed at discuss data from studies regarding the anti-cancer effects of several anti-diabetic drugs recently showed in TC in view of their potential repositioning. Specific examples of anti-diabetic repositionable drugs for TC treatment will also be provided.

Sitagliptin inhibits the survival, stemness and autophagy of glioma cells, and enhances temozolomide cytotoxicity

The standard regimen treatment has improved GBM outcomes, but the survival rate of patients is still unsatisfactory. Temozolomide (TMZ) resistance is one of main reasons limiting the therapeutic efficacy of GBM. However, there are currently no TMZ-sensitizing drugs available in the clinic. Here we aimed to study whether the antidiabetic drug Sitagliptin can inhibit the survival, stemness and autophagy of GBM cells, and thus enhance TMZ cytotoxicity. We used CCK-8, EdU, colony formation, TUNEL and flow cytometry assays to assess cell proliferation and apoptosis; sphere formation and limiting dilution assays to measure self-renewal and stemness of glioma stem cells (GSCs); Western blot, qRT-PCR or immunohistochemical analysis to measure the expression of proliferation or stem cell markers; Western blot/fluorescent analysis of LC3 and other molecules to evaluate autophagy formation and degradation in glioma cells. We found that Sitagliptin inhibited proliferation and induced apoptosis in GBM cells and suppressed self-renewal and stemness of GSCs. The in vitro findings were further confirmed in glioma intracranial xenograft models. Sitagliptin administration prolonged the survival time of tumor-bearing mice. Sitagliptin could inhibit TMZ-induced protective autophagy and enhance the cytotoxicity of TMZ in glioma cells. In addition, Sitagliptin acted as a dipeptidyl peptidase 4 inhibitor in glioma as well as in diabetes, but it did not affect the blood glucose level and body weight of mice. These findings suggest that Sitagliptin with established pharmacologic and safety profiles could be repurposed as an antiglioma drug to overcome TMZ resistance, providing a new option for GBM therapy.

Integrative Analysis of Potential Biomarkers Involved in the Progression of Papillary Thyroid Cancer

This study aims to explore key prognostic and diagnostic biomarkers involved in the pathogenesis of papillary thyroid cancer (PTC) which is one of the most common endocrine cancers and whose occurrence is rapidly increasing. Papillary thyroid cancer datasets containing normal and tumor samples were collected from Gene Expression Omnibus. Protein-protein interaction (PPI) network for common upregulated differentially expressed genes (DEGs) was constructed, and hub genes were studied. Gene ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis were performed to identify the vital biological behaviors and pathways involved in PTC. PPI network analysis demonstrated the interaction between 134 common upregulated DEGs, and top 15 pivotal genes with highest degree of connectivity were retrieved. Three of the hub genes (DPP4, ITGA2, FN1) were linked to the prognosis of PTC patients and considered clinically relevant core genes via survival analysis. We suggest that the identification of key genes associated with PTC development help us in understanding molecular mechanisms related to disease. These genes could also be considered the diagnostic biomarkers or as therapeutic targets in the future treatment for PTC.

Dipeptidyl Peptidase-4 Stabilizes Integrin α4β1 Complex to Promote Thyroid Cancer Cell Metastasis by Activating Transforming Growth Factor-Beta Signaling Pathway

Background: Metastatic disease is a major cause of thyroid cancer-related death. However, the mechanisms responsible for thyroid cancer metastasis are unclear. Dipeptidyl peptidase-4 (DPP4) is a multifunctional cell surface glycoprotein that has been reported to be a negative prognostic factor in thyroid cancer. We explored the molecular mechanism of the role of DPP4 in thyroid cancer cell metastasis. Methods: The effects of DPP4 on thyroid cancer cell migration/invasion in vitro were assessed by transwell assays. A lung metastatic mouse model was also established to determine the effect of DPP4 on tumor metastasis in vivo. DPP4 inhibitor sitagliptin was used to test its effect on thyroid cancer cell metastasis. The mechanism of which DPP4 promotes thyroid cancer cell metastasis was explored by a series of molecular and biochemical experiments. Results: We observed that DPP4 was significantly upregulated in papillary thyroid cancers compared with control subjects, and its expression was positively associated with lymph node metastasis and BRAF^V600E mutation. Functional studies showed that DPP4 knockdown significantly inhibited metastatic potential of thyroid cancer cells, and vice versa. However, DPP4 inhibitor sitagliptin did not affect the metastatic ability of thyroid cancer cells, indicating that the promoting effect of DPP4 on tumor metastasis was independent of its enzymatic activity. Mechanistically, DPP4 interacted with the α4 and β1 integrin subunits, and stabilized the formation of integrin α4β1 complex. DPP4-mediated integrin signal activation promoted the nuclear localization of c-Jun through the FAK/AKT pathway, thereby inducing the transcription of transforming growth factor-beta 1 (TGFB1 coding for protein TGF-β1). TGF-β1 then facilitated tumor metastasis by inducing the epithelial-mesenchymal transition. Conclusions: DPP4 promotes thyroid cancer cell metastasis through the integrins/FAK/AKT/c-Jun/TGF-β1 signaling axis. These findings may have implications for an alternative therapeutic strategy for thyroid cancer.

CRABP2 Is Associated With Thyroid Cancer Recurrence and Promotes Invasion via the Integrin/FAK/AKT Pathway

Cellular retinoic acid-binding protein 2 (CRABP2) participates in retinoid partitioning between different nuclear receptors. Recently, we identified that CRABP2 is one of the progression-associated genes in thyroid cancer. To explore the prognostic and functional significance of CRABP2, immunohistochemical analysis was performed in thyroid tissues and neoplasms. Overexpression of CRABP2 was observed in malignant thyroid neoplasms but not in benign thyroid lesions. CRABP2 expression was an independent predictive factor for recurrence-free survival in patients with differentiated thyroid cancer. Knockdown of CRABP2 reduced the sensitivity of thyroid cancer cells to retinoic acid. Importantly, CRABP2 expression in thyroid cancer cells was associated with epithelial-mesenchymal transition properties, including anoikis resistance, migration, and invasion capacity. Furthermore, invasion promoted by CRABP2 was mediated at least partly by the integrin/focal adhesion kinase/AKT pathway. In summary, CRABP2 expression is upregulated in thyroid cancer with adverse prognostic implications. The invasion-stimulating effects appear independent of canonical retinoic acid signaling and may serve as a potential therapeutic target.

The Role of Serum CD26 in the Diagnosis of Gastric Cancer

Purpose

The value of serum cluster of differentiation 26 (CD26) in gastric cancer remains unknown. We investigated serum CD26 as a non-invasive serological marker for the diagnosis of gastric cancer and its relationship with serum human epidermal growth factor receptor-2 (HER2) levels.

Patients and Methods

We enrolled 393 gastric cancer patients treated with endoscopic resection or surgery, and 90 healthy controls. HER2 positivity in tissue was evaluated by immunohistochemistry staining, and the serum CD26 and HER2 levels were measured using an enzyme-linked immunosorbent assay.

Results

Serum CD26 levels were significantly lower in gastric cancer patients than in healthy controls (582.2 ± 254.3 vs 862.7 ± 410.6 ng/mL, P<0.001). Serum CD26 levels were significantly lower in advanced gastric cancer compared to early gastric cancer (642.2 ± 333.9 vs 503.4 ± 332.7 ng/mL, P<0.001), and tended to decrease with gastric cancer progression. To diagnose gastric cancer, the optimal cut-off value of serum CD26 was 762.7 ng/mL with 75.6% sensitivity and 64.4% specificity. Serum CD26 levels were weakly correlated with serum HER2 levels (rs=0.363, P<0.001). However, no difference in serum CD26 levels was observed between tissue HER2-negative and HER2-positive gastric cancer groups (586.2 ± 362.1 vs 579.6 ± 264.8 ng/mL, P=0.898).

Conclusion

CD26 is a useful non-invasive serological marker for gastric cancer diagnosis; however, its levels do not correlate with HER2 status.

Assessment of serum dipeptidyl peptidase-IV levels in autoimmune thyroid disease

OBJECTIVE

Decreased serum dipeptidyl peptidase-IV (sDPPIV) levels have been reported in patients with autoimmune diseases. However, few studies have analyzed the association between sDPPIV levels and autoimmune thyroid disease (AITD). This study aimed to evaluate the association between sDPPIV levels and three types of AITD: Graves' disease (GD), Graves' ophthalmopathy (GO), and Hashimoto's thyroiditis (HT).

METHODS

Patients newly diagnosed with GD (n = 65), GO (n = 22), and HT (n = 27) and healthy individuals (n = 30) were recruited. Clinical characteristics and thyroid function data were collected. sDPPIV was measured using enzyme-linked immunosorbent assays.

RESULTS

Compared with controls (786.3 ± 46.95), patients with GD and GO had significantly lower sDPPIV levels (662.2 ± 38.81 and 438.4 ± 31.78). Additionally, sDPPIV levels were negatively associated with antithyroid peroxidase antibody (r = -0.20) and antithyroglobulin antibody (r = -0.19), but there was no significant relationship between thyroid hormone and sDPPIV levels. GO cases were divided by proptosis with and without muscle thickening; sDPPIV levels were lower in the muscle thickening group than those in the without muscle thickening group. Logistic regression analysis showed that sDPPIV was negatively correlated with GO and GD.

CONCLUSIONS

sDPPIV concentrations were abnormal in patients with GD and GO, and reduced sDPPIV expression may be involved in the progression of GO and GD.

PINTology: A short history of the lncRNA LINC-PINT in different diseases

LINC-PINT is a p53-induced long intergenic noncoding transcript that plays a crucial role in many diseases, especially cancer. This long noncoding RNA (lncRNA) gene produces in total 102 (LNCipedia) alternatively spliced variants (LINC-PINT:1 to LINC-PINT:102). The functions of known variants include RNA transcripts, host transcripts for circular RNA (circRNA) generation and as sources for the translation of short peptides. In most human tumors, LINC-PINT is down-regulated where it serves as a tumor suppressor. However, the diversity of its functions in other maladies signifies its general clinical importance. Current LINC-PINT molecular functions include RNA-protein interactions, miRNA sponging and epigenetic modulation with these mechanisms operating in different cellular contexts to exert effects on biological processes ranging from DNA damage responses, cell cycle and growth arrest, senescence, cell migration and invasion, and apoptosis. Genetic polymorphisms in LINC-PINT have also been functionally associated with cancer and other pathologies including the autoimmune diseases pemphigus foliaceus and arthritis. Hence, LINC-PINT shows great potential as a clinical biomarker, especially for the diagnosis and prognosis of cancer. In this review, we explore the current knowledge highlighting the distinctive molecular functions of LINC-PINT in specific cancers and other disease states. This article is categorized under: RNA in Disease and Development > RNA in Disease.

Does DPP-IV Inhibition Offer New Avenues for Therapeutic Intervention in Malignant Disease?

Simple Summary

There is growing interest in identifying the effects of antidiabetic agents on cancer risk, progression, and anti-cancer treatment due to the long-term use of these medications and the inherently increased risk of malignancies in diabetic patients. Tumor development and progression are affected by multiple mediators in the tumor microenvironment, several of which may be proteolytically modified by the multifunctional protease dipeptidyl peptidase-IV (DPP-IV, CD26). Currently, low-molecular-weight DPP-IV inhibitors (gliptins) are used in patients with type 2 diabetes based on the observation that DPP-IV inhibition enhances insulin secretion by increasing the bioavailability of incretins. However, the DPP-IV-mediated cleavage of other biopeptides and chemokines is also prevented by gliptins. The potential utility of gliptins in other areas of medicine, including cancer, is therefore being evaluated. Here, we critically review the existing evidence on the role of DPP-IV inhibitors in cancer pathogenesis, their potential to be used in anti-cancer treatment, and the possible perils associated with this approach.

Abstract

Dipeptidyl peptidase IV (DPP-IV, CD26) is frequently dysregulated in cancer and plays an important role in regulating multiple bioactive peptides with the potential to influence cancer progression and the recruitment of immune cells. Therefore, it represents a potential contributing factor to cancer pathogenesis and an attractive therapeutic target. Specific DPP-IV inhibitors (gliptins) are currently used in patients with type 2 diabetes mellitus to promote insulin secretion by prolonging the activity of the incretins glucagon-like peptide 1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP). Nevertheless, the modulation of the bioavailability and function of other DPP-IV substrates, including chemokines, raises the possibility that the use of these orally administered drugs with favorable side-effect profiles might be extended beyond the treatment of hyperglycemia. In this review, we critically examine the possible utilization of DPP-IV inhibition in cancer prevention and various aspects of cancer treatment and discuss the potential perils associated with the inhibition of DPP-IV in cancer. The current literature is summarized regarding the possible chemopreventive and cytotoxic effects of gliptins and their potential utility in modulating the anti-tumor immune response, enhancing hematopoietic stem cell transplantation, preventing acute graft-versus-host disease, and alleviating the side-effects of conventional anti-tumor treatments.

Identification of DPP4/CTNNB1/MET as a Theranostic Signature of Thyroid Cancer and Evaluation of the Therapeutic Potential of Sitagliptin

Simple Summary

In recent years, the incidence of thyroid cancer has been increasing globally, with papillary thyroid cancer (PTCa) being the most prevalent pathological type. Although PTCa has been regarded to be slow growing and has a good prognosis, in some cases, PTCa can be aggressive and progress despite surgery and radioactive iodine treatment. Therefore, searching for new targets and therapies is required. We utilized bioinformatics analyses to identify critical theranostic markers for PTCa. We found that DPP4/CTNNB1/MET is an oncogenic signature that is overexpressed in PTCa and associated with disease progression, distant metastasis, treatment resistance, immuno-evasive phenotypes, and poor clinical outcomes. Interestingly, our in silico molecular docking results revealed that sitagliptin, an antidiabetic drug, has strong affinities and potential for targeting DPP4/CTNNB1/MET signatures, even higher than standard inhibitors of these genes. Collectively, our findings suggest that sitagliptin could be repurposed for treating PTCa.

Abstract

In recent years, the incidence of thyroid cancer has been increasing globally, with papillary thyroid cancer (PTCa) being the most prevalent pathological type, accounting for approximately 80% of all cases. Although PTCa has been regarded to be slow growing and has a good prognosis, in some cases, PTCa can be aggressive and progress despite surgery and radioactive iodine treatment. In addition, most cancer treatment drugs have been shown to be cytotoxic and nonspecific to cancer cells, as they also affect normal cells and consequently cause harm to the body. Therefore, searching for new targets and therapies is required. Herein, we explored a bioinformatics analysis to identify important theranostic markers for THCA. Interestingly, we identified that the DPP4/CTNNB1/MET gene signature was overexpressed in PTCa, which, according to our analysis, is associated with immuno-invasive phenotypes, cancer progression, metastasis, resistance, and unfavorable clinical outcomes of thyroid cancer cohorts. Since most cancer drugs were shown to exhibit cytotoxicity and to be nonspecific, herein, we evaluated the anticancer effects of the antidiabetic drug sitagliptin, which was recently shown to possess anticancer activities, and is well tolerated and effective. Interestingly, our in silico molecular docking results exhibited putative binding affinities of sitagliptin with DPP4/CTNNB1/MET signatures, even higher than standard inhibitors of these genes. This suggests that sitagliptin is a potential THCA therapeutic, worthy of further investigation both in vitro and in vivo and in clinical settings.

Impaired Glucose Metabolism, Anti-Diabetes Medications, and Risk of Thyroid Cancer

Simple Summary

An epidemiologic link exists between obesity, insulin resistance, diabetes, and some cancers, such as breast cancer and colon cancer. The prevalence of obesity and diabetes is increasing, and additional epidemiologic data suggest that there may be a link between obesity and risk of thyroid abnormalities. Factors that may link obesity and diabetes with thyroid proliferative disorders include elevated circulating levels of insulin, increased body fat, high blood sugars, and exogenous insulin use. However, mechanisms underlying associations of obesity, diabetes, and thyroid proliferative disorders are not yet fully understood. The present manuscript reviews and summarizes current evidence of mechanisms and epidemiologic associations of obesity, insulin resistance, and use of anti-diabetes medications with benign and malignant proliferative disorders of the thyroid.

Abstract

The prevalence of obesity is progressively increasing along with the potential high risk for insulin resistance and development of type 2 diabetes mellitus. Obesity is associated with increased risk of many malignancies, and hyperinsulinemia has been proposed to be a link between obesity and cancer development. The incidence of thyroid cancer is also increasing, making this cancer the most common endocrine malignancy. There is some evidence of associations between obesity, insulin resistance and/or diabetes with thyroid proliferative disorders, including thyroid cancer. However, the etiology of such an association has not been fully elucidated. The goal of the present work is to review the current knowledge on crosstalk between thyroid and glucose metabolic pathways and the effects of obesity, insulin resistance, diabetes, and anti-hyperglycemic medications on the risk of thyroid cancer development.

DPP4 Is a Potential Prognostic Marker of Thyroid Carcinoma and a Target for Immunotherapy

DPP4 (dipeptidyl peptidase 4) is expressed in many cancers, but the relationship between DPP4 and thyroid carcinoma (THCA) is incompletely understood. We aim to explore the expression of DPP4 in THCA and the correlation between DPP4 expression with the prognosis of THCA and antitumor immunity. We systematically analyzed data from The Cancer Genome Atlas (TCGA), Genotype-Tissue Expression (GTEx), and Gene Expression Omnibus (GEO) databases and explored DPP4 expression, its impact on prognosis, and its relationship with antitumor immunity in THCA. Next, we collected 18 pairs of fresh THCA and adjacent paracancerous tissues and performed RT-qPCR to validate the DPP4 mRNA level. Concurrently, immunohistochemistry (IHC) analysis was performed on 12 pairs of paraffin-embedded tissues of medullary thyroid carcinoma (MTC) and paracancerous tissues to validate the DPP4 protein level. Bioinformatics analysis showed that DPP4 mRNA expression in THCA was significantly higher than that in paracancerous tissues (p < 0.01). DPP4 was expressed at the highest levels in MTC than in other pathological types. The DPP4 expression level was different between groups with different clinical characteristics. The higher the DPP4 expressed in THCA, the lower the disease-free survival (DFS) was (HR = 1.8, p=0.048). DPP4 was significantly correlated with immune cell infiltration and immune response and was positively associated with 21 immune checkpoint genes (ICGs) in THCA (p < 0.05). The results of RT-qPCR showed that the relative mRNA expression of DPP4 was significantly upregulated in 18 THCA tissues compared to that in paracancerous tissues (p=0.011). IHC results showed that the DPP4 protein level was higher in 12 MTC tissues than in paracancerous tissues (p=0.011). In conclusion, DPP4 is a potential prognostic marker of THCA and may become an effective target for immunotherapy.

Ferroptosis-related gene signature predicts the prognosis of papillary thyroid carcinoma

BACKGROUND

Papillary thyroid carcinoma (PTC) is the most common type of thyroid cancer (TC), accounting for more than 80% of all cases. Ferroptosis is a novel iron-dependent and Reactive oxygen species (ROS) reliant type of cell death which is distinct from the apoptosis, necroptosis and pyroptosis. Considerable studies have demonstrated that ferroptosis is involved in the biological process of various cancers. However, the role of ferroptosis in PTC remains unclear. This study aims at exploring the expression of ferroptosis-related genes (FRG) and their prognostic values in PTC.

METHODS

A ferroptosis-related gene signature was constructed using lasso regression analysis through the PTC datasets of the Cancer Genome Atlas (TCGA). Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were performed to investigate the bioinformatics functions of significantly different genes (SDG) of ferroptosis. Additionally, the correlations of ferroptosis and immune cells were assessed through the single-sample gene set enrichment analysis (ssGSEA) and CIBERSORT database. Finally, SDG were test in clinical PTC specimens and normal thyroid tissues.

RESULTS

LASSO regression model was utilized to establish a novel FRG signature with 10 genes (ANGPTL7, CDKN2A, DPP4, DRD4, ISCU, PGD, SRXN1, TF, TFRC, TXNRD1) to predicts the prognosis of PTC, and the patients were separated into high-risk and low-risk groups by the risk score. The high-risk group had poorer survival than the low-risk group (p < 0.001). Receiver operating characteristic (ROC) curve analysis confirmed the signature's predictive capacity. Multivariate regression analysis identified the prognostic signature-based risk score was an independent prognostic indicator for PTC. The functional roles of the DEGs in the TGCA PTC cohort were explored using GO enrichment and KEGG pathway analyses. Immune related analysis demonstrated that the most types of immune cells and immunological function in the high-risk group were significant different with those in the low-risk group. Quantitative Real-Time Polymerase Chain Reaction (qRT-PCR) verified the SDG have differences in expression between tumor tissue and normal thyroid tissue. In addition, cell experiments were conducted to observe the changes in cell morphology and expression of signature's genes with the influence of ferroptosis induced by sorafenib.

CONCLUSIONS

We identified differently expressed FRG that may involve in PTC. A ferroptosis-related gene signature has significant values in predicting the patients' prognoses and targeting ferroptosis may be an alternative for PTC's therapy.

The Role of Post-Translational Modifications of Chemokines by CD26 in Cancer

Chemokines are a large family of small chemotactic cytokines that fulfill a central function in cancer. Both tumor-promoting and -impeding roles have been ascribed to chemokines, which they exert in a direct or indirect manner. An important post-translational modification that regulates chemokine activity is the NH₂-terminal truncation by peptidases. CD26 is a dipeptidyl peptidase (DPPIV), which typically clips a NH₂-terminal dipeptide from the chemokine. With a certain degree of selectivity in terms of chemokine substrate, CD26 only recognizes chemokines with a penultimate proline or alanine. Chemokines can be protected against CD26 recognition by specific amino acid residues within the chemokine structure, by oligomerization or by binding to cellular glycosaminoglycans (GAGs). Upon truncation, the binding affinity for receptors and GAGs is altered, which influences chemokine function. The consequences of CD26-mediated clipping vary, as unchanged, enhanced, and reduced activities are reported. In tumors, CD26 most likely has the most profound effect on CXCL12 and the interferon (IFN)-inducible CXCR3 ligands, which are converted into receptor antagonists upon truncation. Depending on the tumor type, expression of CD26 is upregulated or downregulated and often results in the preferential generation of the chemokine isoform most favorable for tumor progression. Considering the tight relationship between chemokine sequence and chemokine binding specificity, molecules with the appropriate characteristics can be chemically engineered to provide innovative therapeutic strategies in a cancer setting.

The Involvement of the Mammalian Target of Rapamycin, Protein Tyrosine Phosphatase 1b and Dipeptidase 4 Signaling Pathways in Cancer and Diabetes: A Narrative Review

BACKGROUND

The mammalian target of rapamycin (mTOR), protein tyrosine phosphatase 1b (PTP1B) and dipeptidase 4 (DPP4) signaling pathways regulate eukaryotic cell proliferation and metabolism. Previous researches described different transduction mechanisms in the progression of cancer and diabetes.

METHODOLOGY

We reviewed recent advances in the signal transduction pathways of mTOR, PTP1B and DPP4 regulation and determined the crosstalk and common pathway in diabetes and cancer.

RESULTS

We showed that according to numerous past studies, the proteins participate in the signaling networks for both diseases.

CONCLUSION

There are common pathways and specific proteins involved in diabetes and cancer. This article demonstrates and explains the potential mechanisms of association and future prospects for targeting these proteins in pharmacological studies.

DPP4 gene silencing inhibits proliferation and epithelial-mesenchymal transition of papillary thyroid carcinoma cells through suppression of the MAPK pathway

PURPOSE

Papillary thyroid carcinoma (PTC) is characterized by epithelial malignancy and is the most prevalent thyroid neoplasm with the best overall prognosis. Notably, recently published studies have indicated remarkably high expression of dipeptidyl peptidase 4 (DPP4) in PTC. However, the underlying molecular mechanism and regulatory factors of PTC progression remain unknown. Therefore, the current study aimed to elucidate the effects of DPP4 gene silencing on PTC and further investigated whether the mechanism of PTC progression is related to the mitogen-activated protein kinase (MAPK) pathway.

METHODS

Herein, microarray-based gene expression profiling of PTC was conducted to identify the differentially expressed genes between tumor thyroid tissue and normal thyroid tissue as well as the underlying signaling pathway involved in PTC pathogenesis. Moreover, protein quantification was performed to assess the protein expression of DPP4 in PTC tissues collected from 65 patients. In addition, DPP4 was silenced in PTC cell lines (GLAG-66 and TPC-1) through siRNA-mediated DPP4 knockdown or sitagliptin (inhibitor of DPP4)-mediated inhibition to assess the effects of DPP4 on the MAPK pathway and cellular processes, including proliferation, apoptosis, and epithelial-to-mesenchymal transition (EMT).

RESULTS

Intriguingly, our data revealed markedly high expression of DPP4 in PTC tissues. However, in GLAG-66 and TPC-1 cells, the silencing of DPP4 resulted in significantly reduced expression of ERK1/2, JNK1, P38 MAPK, VEGF, FGFR-1, TGF-β1, Snail, HIF-1α, N-cadherin, and Bcl-2 along with reduced phosphorylation of ERK1/2, JNK1, and P38 MAPK, whereas the expression of E-cadherin and Bax was increased. Furthermore, DPP4 silencing was found to hinder cell proliferation and potentiate cell apoptosis.

CONCLUSION

Collectively, the present study demonstrated that DPP4 gene silencing inhibits PTC cell proliferation and EMT and promotes cell apoptosis via suppression of the MAPK pathway, thus highlighting a possible regulatory pathway in PTC progression.

Gene expression profile of epithelial-mesenchymal transition mediators in papillary thyroid cancer

PURPOSE

Platelet derived growth receptor alpha (PDGFRA) promotes the epithelial-mesenchymal transition (EMT) in thyroid follicular cells and is linked to lymphatic metastases in papillary thyroid cancer (PTC). We probed the regulatory network of genes linked to PDGFRA and EMT, comparing matched patient primary tumor and metastatic specimens, as well as engineered cell lines and ex vivo primary cultures with and without PDGFRA.

METHODS

Freshly isolated thyroid tumors with or without metastases, with matching neighboring benign or normal tissue, was isolated for comparative transcriptional analysis using a TaqMan Low Density array (TLDA) assay with genes representing important markers of EMT, cellular adhesion, apoptosis, differentiation, senescence, and signal transduction pathways in thyroid cancer. Transfected primary cultures and immortalized cell lines were also analyzed with respect to PDGFRA expression and cell phenotype.

RESULTS

We reveal the consistent upregulation of serine protease DPP4 and structural protein SPP1 with the progression of PTC to metastatic disease, as well as with PDGFRA expression. Conversely, epithelial integrity gene TFF3 and transcription factor SOX10 were strongly down-regulated. This gene network also includes important mediators of EMT including DSG1, MMP3, MMP9, and BECN. We observed similar genomic changes in ex vivo normal thyroid cells transfected with PDGFRA that also exhibited a partially dedifferentiated phenotype. In particular, we observed lamellopodia with induction of PDGFRA and illustrate that DPP4 and SPP1 were upregulated in this process, with decreased TFF3 and SOX10 as seen in tissue specimens. PDGFRA did decrease nuclear protein levels of differentiation factor TTF1, but not the transcription of TTF1 and PAX8.

CONCLUSIONS

We demonstrate that PDGFRA activates EMT pathways and decreases expression of genes favoring epithelial integrity, pushing follicular cells toward a dedifferentiated phenotype. SPP1 and DPP4, previously linked with adverse outcomes in thyroid cancer, appear to be regulated by PDGFRA. PDGFRA expression promotes metastatic disease through multiple EMT levers that favor formation of an invasive phenotype and increased metalloproteinase expression.

DPP4 Inhibitor Sitagliptin Enhances Lymphocyte Recruitment and Prolongs Survival in a Syngeneic Ovarian Cancer Mouse Model

Immunity plays a key role in epithelial ovarian cancer (EOC) progression with a well-documented correlation between patient survival and high intratumoral CD8+ to T regulatory cell (Treg) ratios. We previously identified dysregulated DPP4 activity in EOCs as a potentially immune-disruptive influence contributing to a reduction in CXCR3-mediated T-cell infiltration in solid tumours. We therefore hypothesized that inhibition of DPP4 activity by sitagliptin, an FDA-approved inhibitor, would improve T-cell infiltration and function in a syngeneic ID8 mouse model of EOC. Daily oral sitagliptin at 50 mg/kg was provided to mice with established primary EOCs. Sitagliptin treatment decreased metastatic tumour burden and significantly increased overall survival and was associated with significant changes to the immune landscape. Sitagliptin increased overall CXCR3-mediated CD8+ T-cell trafficking to the tumour and enhanced the activation and proliferation of CD8+ T-cells in tumour tissue and the peritoneal cavity. Substantial reductions in suppressive cytokines, including CCL2, CCL17, CCL22 and IL-10, were also noted and were associated with reduced CD4+ CD25+ Foxp3+ Treg recruitment in the tumour. Combination therapy with paclitaxel, however, typical of standard-of-care for patients in palliative care, abolished CXCR3-specific T-cell recruitment stimulated by sitagliptin. Our data suggest that sitagliptin may be suitable as an adjunct therapy for patients between chemotherapy cycles as a novel approach to enhance immunity, optimise T-cell-mediated function and improve overall survival.

Therapeutic Implications of TGFβ in Cancer Treatment: A Systematic Review

Transforming growth factor β (TGFβ) is a pleiotropic cytokine that participates in a wide range of biological functions. The alterations in the expression levels of this factor, or the deregulation of its signaling cascade, can lead to different pathologies, including cancer. A great variety of therapeutic strategies targeting TGFβ, or the members included in its signaling pathway, are currently being researched in cancer treatment. However, the dual role of TGFβ, as a tumor suppressor or a tumor-promoter, together with its crosstalk with other signaling pathways, has hampered the development of safe and effective treatments aimed at halting the cancer progression. This systematic literature review aims to provide insight into the different approaches available to regulate TGFβ and/or the molecules involved in its synthesis, activation, or signaling, as a cancer treatment. The therapeutic strategies most commonly investigated include antisense oligonucleotides, which prevent TGFβ synthesis, to molecules that block the interaction between TGFβ and its signaling receptors, together with inhibitors of the TGFβ signaling cascade-effectors. The effectiveness and possible complications of the different potential therapies available are also discussed.

Galectin-3 Inhibitors Suppress Anoikis Resistance and Invasive Capacity in Thyroid Cancer Cells

Accumulating evidence suggests that galectin-3 is a histologic marker of thyroid cancer. However, the pharmacological lectin-based approach has not been well studied. In the present study, we aimed to investigate the therapeutic potential of novel galectin-3 inhibitors by treating thyroid cancer cells with different concentrations of GB1107 or TD139. At high doses, TD139, but not GB1107, reduced cell viability and clonogenicity of thyroid cancer cells. TD139 induced apoptosis of thyroid cancer cells, as evident by an increase in the percentage of sub-G1 cells on cell cycle analysis, caspase-3 activation, and PARP1 cleavage. Either GB1107 or TD139 significantly inhibited cell coherence and counteracted anoikis resistance. Both inhibitors decreased migratory and invasive abilities in a dose-dependent manner. Furthermore, GB1107 and TD139 treatment attenuated AKT phosphorylation and decreased the expression of β-catenin and MMP2. In conclusion, these novel galectin-3 inhibitors suppressed the anoikis resistance, motility, and invasive capacity of thyroid cancer cells at least partly through the AKT/β-catenin pathway. Galectin-3 inhibitors are potentially suitable for preclinical evaluation of treatment and/or prevention of metastatic spread in thyroid cancer.

Diagnostic significance of apical membranous and cytoplasmic dot-like CD26 expression in encapsulated follicular variant of papillary thyroid carcinoma: a useful marker for capsular invasion

Non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) and invasive encapsulated follicular variant of papillary thyroid carcinoma (EFV-PTC) are indistinguishable preoperatively. CD26 expression in follicular tumor-uncertain malignant potential (FT-UMP) is reported to be clearly higher than in that without capsular invasion. To verify the diagnostic significance of CD26 immunostaining in EFV-PTC, we examined the expression pattern of CD26 in non-invasive EFV-PTC (NIFTP) and invasive EFV-PTC. We performed immunohistochemical analysis using CD26 antibody for 37 NIFTPs and 54 EFV-PTCs (34 minimally invasive EFV-PTCs and 20 widely invasive EFV-PTCs). Most NIFTP samples showed an apical membranous pattern or a cytoplasmic diffuse pattern of expression. Invasive EFV-PTCs more frequently showed a cytoplasmic dot-like pattern, and the labeling indices of tumor cells with cytoplasmic dot-like patterns were significantly higher than those in NIFTPs. The sizes of dots seen in NIFTPs (mean: 1.12 μm) were significantly smaller than in invasive EFV-PTCs (1.33 μm), minimally invasive EFV-PTC (1.27 μm), and widely invasive EFV-PTC (1.38 μm). We, therefore, conclude that cytoplasmic diffuse and/or cytoplasmic dot-like CD26 expression, particularly the larger CD26-positive dots, could be useful markers for capsular invasion in EFV-PTC. CD26 immunostaining, using cell blocks or cytological specimens, may preoperatively distinguish between NIFTP and invasive EFV-PTC.

CD26 as a Promising Biomarker for Predicting Prognosis in Patients with Pancreatic Tumors

Purpose

Pancreatic cancer is associated with a high mortality rate owing to insufficient approaches for early diagnosis and the invasive biological behavior of the cancer. CD26 is a membrane-anchored protein involved in multiple physiological and pathological processes. Here, we investigated correlations between CD26 expression and clinicopathological features in patients with pancreatic tumors.

Methods

We collected 170 tumor tissue specimens and 138 paired paratumoral tissues from patients with pancreatic tumors and evaluated CD26 expression using immunohistochemistry.

Results

CD26 was expressed in 79.4% of pancreatic tumors, which was significantly (P < 0.001) higher than that in paratumoral pancreatic tissues (23.2%). High expression of CD26 was correlated with ABO blood type (P = 0.035), malignancy degree (P = 0.001), CA199 (P = 0.01), and CA242 (P = 0.027). In pancreatic malignancies, CD26 expression was observed in 80.7% (130/161) of cases. Lower CD26 expression was correlated with longer disease-free survival (P = 0.048) and overall survival (P = 0.024) and was an independent predictor of overall survival (hazard ratio [HR]: 1.713; P = 0.042). Similar results were observed in pancreatic ductal adenocarcinoma (PDAC) tissues, and CD26 expression level (HR: 2.117; P = 0.008) was an independent predictor of overall survival in patients with PDAC. CD26 expression was significantly increased in pancreatic tumors and gradually increased with increasing malignancy degree, suggesting that CD26 may be involved in the tumorigenic proliferation of pancreatic tumors.

Conclusion

Therefore, CD26 is a potential marker for early diagnosis and a promising therapeutic target in pancreatic tumors.

Mesenchymal stem cells-originated exosomal microRNA-152 impairs proliferation, invasion and migration of thyroid carcinoma cells by interacting with DPP4

BACKGROUND

Thyroid carcinoma (THCA) is the most prevalent tumor in the endocrine system with an increasing incidence. Recent studies have underscored the function of microRNAs (miRNAs) in THCA. Nevertheless, knowledge regarding the effects of exosomal miRNAs in THCA is still limited. This report intended to probe the regulatory effects of exosomal miR-152 on THCA and the underlying mechanism.

METHODS

The expression profile of miR-152 was studied in clinical samples as well as B-CPAP and TPC-1 cells. Transwell, CCK-8, and flow cytometric assays were performed to investigate the roles of miR-152 on invasion, migration, proliferation, and apoptosis in B-CPAP and TPC-1 cells. The putative target of miR-152 was predicted using the bioinformatic analysis, and the targeting relationship was confirmed verified subsequently. Afterward, exosomes were isolated from bone marrow mesenchymal stem cells (BM-MSCs) and co-cultured with B-CPAP and TPC-1 cells to explore the function of exosomal miR-152 on THCA cells.

RESULTS

miR-152 was reduced in THCA tissues and cells. Restoration of miR-152 inhibited proliferation, invasion and migration of B-CPAP and TPC-1 cells, but promoted cell apoptosis. Dipeptidyl dipeptidase 4 (DPP4), a target of miR-152, was found to promote THCA cell invasion and migration. miR-152 ferried by BM-MSCs-derived exosomes repressed THCA cell invasion and migration, and pcDNA-DPP4 weakened the repression effect.

CONCLUSION

Exosomal miR-152 inhibited proliferation, migration and invasion of THCA cells by binding with DPP4, which may represent a novel target for the treatment of THCA.

Upregulation of miR-421 predicts poor prognosis and promotes proliferation, migration, and invasion of papillary thyroid cancer cells

BACKGROUND

Papillary thyroid carcinoma (PTC) represents the most frequent subtype of thyroid cancer (TC) with poor prognosis mainly due to the severe invasion and metastasis. As an oncogene, microRNA-421 (miR-421) is involved in the development of various cancers. This study was to investigate the clinical significance of miR-421 in PTC and its effects on the biological function of PTC cells.

METHODS

The expression level of miR-421 in all tissues and PTC cell lines was measured by quantitative real-time polymerase chain reaction (qRT-PCR). Subsequently, the relationship between miR-421 expression and the clinicopathological feature was detected by chi-square analysis in 106 patients with PTC. In addition, Kaplan-Meier and multivariate Cox regression analysis were used to detect the survival time and the prognostic value of miR-421. Finally, the regulatory effect of miR-421 on the proliferation, migration, and invasion ability of PTC cells was detected by Cell Counting Kit (CCK-8) and Transwell assay.

RESULTS

Compared with all control groups, the expression of miR-421 was significantly increased in 106 patients tissues and PTC cell lines (p < 0.001). In addition, patients with miR-421 upregulated in PTC showed more positive lymph node metastasis (p = 0.011), positive tumor infiltration (p = 0.031), and TNM stage III/IV (p = 0.019), and when miR-421 expression level was elevated, the survival rate of PTC patients was poor (log-rank test, p = 0.023). Furthermore, miR-421 might be an independent prognostic biomarker for PTC (hazard ratio [HR] = 3.172, 95% CI = 1.071-9.393, p = 0.037). Finally, increased levels of miR-421 can significantly promote cell proliferation, migration, and invasion (p < 0.01).

CONCLUSION

miR-421 is a novel oncogene of PTC and is a valuable prognostic biomarker. Moreover, the upregulation of miR-421 enhances the proliferation, migration, and invasion of PTC cells.

Hypoxia Regulates DPP4 Expression, Proteolytic Inactivation, and Shedding from Ovarian Cancer Cells

The treatment of ovarian cancer has not significantly changed in decades and it remains one of the most lethal malignancies in women. The serine protease dipeptidyl peptidase 4 (DPP4) plays key roles in metabolism and immunity, and its expression has been associated with either pro- or anti-tumour effects in multiple tumour types. In this study, we provide the first evidence that DPP4 expression and enzyme activity are uncoupled under hypoxic conditions in ovarian cancer cells. Whilst we identified strong up-regulation of DPP4 mRNA expression under hypoxic growth, the specific activity of secreted DPP4 was paradoxically decreased. Further investigation revealed matrix metalloproteinases (MMP)-dependent inactivation and proteolytic shedding of DPP4 from the cell surface, mediated by at least MMP10 and MMP13. This is the first report of uncoupled DPP4 expression and activity in ovarian cancer cells, and suggests a previously unrecognized, cell- and tissue-type-dependent mechanism for the regulation of DPP4 in solid tumours. Further studies are necessary to identify the functional consequences of DPP4 processing and its potential prognostic or therapeutic value.

Angiogenesis is promoted by exosomal DPP4 derived from 5-fluorouracil-resistant colon cancer cells

Cancer cells can communicate with the tumor microenvironment and contribute to tumor progression. However, the effects of drug-resistant tumor cells on angiogenesis are unclear. Current anti-angiogenic strategies also have limitations and it would be useful to develop novel targets and treatment strategies. Here, our study showed that the conditioned medium and exosomes from 5-FU-resistant colon cancer cells promoted angiogenesis, and we observed that exosomal dipeptidyl peptidase IV (DPP4) was a potent inducer of this angiogenesis. DPP4-enriched exosomes increased periostin (POSTN) expression in human umbilical vein endothelial cells via Twist1 nuclear translocation or activating Smad signaling pathway, while silencing or inhibition of DPP4 neutralized those effects. The in vivo and clinical data indicated that high DPP4 expression was related to tumor progression. These findings indicate that DPP4 may be a target for inhibiting angiogenesis in 5-FU-resistant colon cancer. Furthermore, exosomal DPP4 concentrations may be a useful prognostic marker for colon cancer.

The DPP-IV inhibitor saxagliptin promotes the migration and invasion of papillary thyroid carcinoma cells via the NRF2/HO1 pathway

Dipeptidyl peptidase-IV (DPP-IV) inhibitors are used to control blood glucose levels in patients with type 2 diabetes. However, the influence of DPP-IV inhibitors on malignant tumors remains unknown. The present study aimed to investigate the effect of the DPP-IV inhibitor saxagliptin on thyroid carcinoma cells. Transwell assays and a nude mouse lung metastasis model were used to evaluate the invasion and metastasis of thyroid carcinoma cells. Western blotting was used to determine the protein levels of migration and invasion-related molecules. We tested the expression and distribution of nuclear factor, erythroid 2 like 2 (NRF2) in thyroid carcinoma cells with and without saxagliptin. Furthermore, we silenced NRF2 and observed saxagliptin's effect on migration and invasion. Quantitative real-time reverse transcription PCR (qRT-PCR) and western blotting were then used to measure the expression of NFR2's downstream molecules (heme oxygenase 1 (HO1), matrix metalloproteinase 2 (MMP2), and vascular endothelial growth factor (VEGF)). A luciferase reporter assay was used to validate whether NRF2 could regulate the transcriptional activity of the HO1 promoter. Saxagliptin enhanced the migratory and invasive ability of thyroid carcinoma cells. MMP2 and VEGF levels were also elevated by saxagliptin treatment. We found that saxagliptin treatment increases the nuclear and cytoplasmic accumulation NRF2. Silencing NRF2 abolished the effect of saxagliptin on migration and invasion. Accordingly, NRF2 silencing downregulated HO1, MMP2, and VEGF levels. The luciferase assay showed that NRF2 activated transcription from the HO1 promoter. Saxagliptin could promote this transcriptional activity by upregulating NRF2. Saxagliptin enhanced the migratory and invasive ability of human thyroid carcinoma cells, as well as the expression of MMP2 and VEGF, by activating the NRF2/HO1 pathway.

FosB recruits KAT5 to potentiate the growth and metastasis of papillary thyroid cancer in a DPP4-dependent manner

OBJECTIVE

Dipeptidyl peptidase IV (DPP4) has been indicated as a possible prognostic biomarker in papillary thyroid cancer (PTC). However, the mechanism of DPP4 during metastasis of PTC remains unclear. In this study, we investigated whether lysine acetyltransferase 5 (KAT5) and FBJ murine osteosarcoma viral oncogene homolog B (FosB) synergistically regulate high DPP4 expression in PTC.

METHODS

PTC tissues and matched paracancerous tissues were harvested, followed by the establishment of IHH-4 and TPC-1 cells with downregulation of DPP4. The relevance of DPP4 on the metastasis of PTC cells was assessed. Subsequently, the effect of KAT5 on the transcription of DPP4 was verified. The binding relationship between FosB and DPP4 was predicted by a bioinformatics website. Functional rescue experiments were performed to evaluate cell activities after overexpression of KAT5 or FosB in cells with DPP4 knockdown.

RESULTS

DPP4 was overexpressed in PTC tissues and cell lines, which was correlated with higher risks for metastases and poorer survival. DPP4 downregulation curtailed cell growth and metastasis. Moreover, KAT5 acetylated DPP4 promoter histone, which promoted transcription activation of DPP4. Subsequently, FosB recruited KAT5 at the DPP4 promoter, thereby enhancing DPP4 transcriptional activation. Further overexpression of KAT5 or FosB in cells with low expression of DPP4 promoted cell activity. Finally, DPP4 expedited p62 nuclear translocation to elevate Keap1/Nrf2 expression, thus facilitating the growth and metastasis of PTC cells.

CONCLUSION

FosB enhanced the growth and metastasis of PTC cells by recruiting histone acetyltransferases KAT5 to increase DPP4 transcription and activate the p62/Keap1/Nrf2 signaling.

Preoperative Factors Associated with Extrathyroidal Extension in Papillary Thyroid Cancer

OBJECTIVE

Extrathyroidal extension may not be accurately recognized during thyroidectomy and can increase the risk of positive margins and even recurrence. This study aimed to investigate the preoperative factors associated with extrathyroidal extension.

METHODS

We analyzed 887 patients with papillary thyroid cancer (PTC) who underwent surgery in the period of 2005-2017. Binary logistic regression analyses and generalized additive models were used to identify associations.

RESULTS

Minimal extrathyroidal extension was present in 233 (26%) patients and advanced extrathyroidal extension was found in 60 (7%) patients. Age, BMI, and tumor size were independent predictors of all or advanced extrathyroidal extension. Among the 493 patients whose BRAF mutation status was available, age (OR = 1.025), BMI (OR = 1.091), tumor size (OR = 1.544), and BRAF V600E mutation (OR = 2.311) were independently associated with extrathyroidal extension.

CONCLUSIONS

Older age, a greater BMI, a larger tumor size, and presence of the BRAF mutation were predictive of extrathyroidal extension. These factors should be taken into consideration in decision-making before surgery is performed.

Overexpression of chitinase-3-like protein 1 is associated with structural recurrence in patients with differentiated thyroid cancer

We previously identified that the expression of chitinase-3-like protein 1 (CHI3L1) was upregulated during thyroid cancer progression. Here, we investigated the prognostic significance of CHI3L1 expression in thyroid neoplasms and examined the potential oncogenic roles. CHI3L1 immunochemical staining was performed on tissue microarrays of benign and malignant thyroid tumours. Compared with normal thyroid tissue and benign thyroid lesions that had low or no detectable CHI3L1 expression, CHI3L1 was overexpressed in both differentiated and undifferentiated thyroid cancer. High CHI3L1 expression was associated with extrathyroidal extension, lymph node metastasis, and shorter recurrence-free survival in differentiated thyroid cancer. The biological roles of CHI3L1 were further investigated by gain- and loss-of-function assays. CHI3L1 silencing suppressed clonogenicity, migration, invasion, anoikis resistance, and angiogenesis in thyroid cancer cells, although exogenous CHI3L1 treatment promoted these malignant phenotypes. Cysteine-rich angiogenic inducer 61 (CYR61) was identified as a downstream target of CHI3L1 by RNA-seq analysis. CYR61 silencing or treatment reversed the alterations induced by CHI3L1 modulation. Our results demonstrate that CHI3L1 is overexpressed in thyroid cancer and is associated with an increased risk of disease recurrence. Additionally, CYR61 may participate in CHI3L1-mediated tumour progression. © 2020 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Lymphovascular invasion of papillary thyroid carcinoma revisited in the era of active surveillance

INTRODUCTION

Lymphovascular invasion (LVI) is associated with disease recurrence and compromised survival in patients with thyroid cancer. Nonetheless, LVI is not identifiable on preoperative ultrasound or cytologic assessment. We aimed to explore the clinicopathological features associated with LVI.

PATIENTS AND METHODS

We conducted a retrospective review of our prospectively maintained database from 2009 to 2018. Multivariate analyses were performed to determine the associations between clinicopathological parameters and LVI. Generalized additive models were used to examine the nonlinear relationship between continuous variables and LVI.

RESULTS

A total of 795 patients were included in the analysis, and 174 (22%) had LVI. Patients' age (odds ratio [OR] = 0.982), tumor size (OR = 1.466), clinical lymphadenopathy (OR = 6.975), and advanced extrathyroidal extension (OR = 2.938) were independently associated with LVI. In the subset analysis of 198 patients with available genetic information, tumor size (OR = 1.599), clinical lymph node metastasis (OR = 3.657), and TERT promoter mutation (OR = 4.726) were predictive of LVI. Among 573 patients who had no clinical lymphadenopathy or advanced extrathyroidal extension, tumor size was the only predictor of LVI. Tumor size >1.5 cm had an increased risk of LVI based on the generalized additive model plot and receiver operating characteristic curve analysis.

CONCLUSION

Tumor size is positively associated with the risk of LVI in papillary thyroid cancer. To avoid delayed treatment in patients with LVI, a tumor size of 1.5 cm may be considered as the safe upper limit for active surveillance.

LINC-PINT Suppresses the Aggressiveness of Thyroid Cancer by Downregulating miR-767-5p to Induce TET2 Expression

Long noncoding RNA (lncRNA) long intergenic nonprotein-coding RNA, p53-induced transcript (LINC-PINT) has shown anti-invasive activity in lung and colon cancer cells. However, the role of LINC-PINT in thyroid cancer is unclear. In the present work, we explored the expression of LINC-PINT in 60 paired thyroid cancer and adjacent normal tissues. The clinical significance and biological function of LINC-PINT in thyroid cancer were determined. LINC-PINT expression was downregulated in thyroid cancer relative to adjacent normal tissues (p = 0.0002). Low expression of LINC-PINT was significantly associated with advanced tumor node metastasis (TNM) stage (p = 0.0306) and lymph node metastasis (p = 0.0359). Ectopic expression of LINC-PINT suppressed the proliferation, invasion, and tumorigenesis of thyroid cancer cells. Mechanistically, LINC-PINT associated with and downregulated microRNA (miR)-767-5p. Moreover, LINC-PINT overexpression relieved miR-767-5p-mediated repression of ten-eleven translocation 2 (TET2). miR-767-5p promoted aggressiveness of thyroid cancer, which was reversed by overexpression of TET2. Coexpression of miR-767-5p or depletion of TET2 rescued the inhibitory effect of LINC-PINT on thyroid cancer cell proliferation and invasion. In addition, there was a negative correlation between miR-767-5p and LINC-PINT in thyroid cancer (r = -0.34772, p = 0.01789). Taken together, LINC-PINT functions as a tumor suppressor in thyroid cancer via the miR-767-5p/TET2 axis, representing a potential therapeutic target for thyroid cancer.

Loss of Integrase Interactor 1 (INI1) Expression in a Subset of Differentiated Thyroid Cancer

Alterations in the switching defective/sucrose non-fermenting (SWI/SNF) chromatin-remodeling complex are enriched in advanced thyroid cancer. Integrase interactor 1 (INI1), encoded by the SMARCB1 gene on the long arm of chromosome 22, is one of the core subunits of the SWI/SNF complex. INI1 immunohistochemistry is frequently used for the diagnosis of malignant rhabdoid neoplasms. In the present study, we found normal and benign thyroid tissues generally had diffusely intense nuclear immunostaining. Loss of INI1 immunohistochemical expression was observed in 8% of papillary thyroid cancer and 30% of follicular thyroid cancer. Furthermore, loss of INI1 expression was associated with extrathyroidal extension (p < 0.001) and lymph node metastasis (p = 0.038). Analysis of The Cancer Genome Atlas database revealed that SMARCB1 underexpression was associated with the follicular variant subtype and aneuploidy in papillary thyroid cancer. We speculate that SMARCB1 is an important effector in addition to NF2 and CHEK2 inactivation among thyroid cancers with chromosome 22q loss.

A poor prognosis in human hepatocellular carcinoma is associated with low expression of DPP4

This study aimed to explore the prognostic role of dipeptidyl peptidase 4 (DPP4) expression in hepatocellular carcinoma (HCC). DPP4 expression was measured in formalin-fixed paraffin-embedded specimens that were gathered from 327 HCC patients. Immunohistochemistry analyses were utilized to examine DPP4 expression characteristics and prognostic values (overall survival (OS) and time to recurrence) of DDP4 in HCC tissues. In addition, a patient-derived xenograft (PDX) model was used to assess the correlation between DPP4 expression and tumor growth in vivo. DPP4 was expressed in low levels in HCC tissues in contrast to paired peritumoral tissues (38 cases were down-regulated in a total of 59 cases, 64.4%. P=0.0202). DPP4 expression was significantly correlated with TNM stage (P=0.038), tumor number (P=0.035), and vascular invasion (P=0.024), and significantly reduced in patients who were in TNM stages II and III-V, with multiple tumors, and with microvascular invasion compared to patients with TNM stage I, single tumor, and no microvascular invasion. Notably, HCC tissues with low expression of DPP4 had poor OS (P=0.016) compared with HCC tissues with high expression of DPP4, and results from PDX model showed that tumor growth was significantly faster in HCC patients that lowly expressed DPP4 compared to those with highly expressed DPP4. Our findings suggested that low levels of DPP4 could impact the aggressiveness of HCC and contribute to a poor prognosis.

Association between subjective symptoms and obesity and postoperative recurrence in differentiated thyroid cancer: a matched-pair analysis

Several patients with thyroid cancer experience symptom distress after diagnosis and surgery. Data on the association between symptomatology and disease recurrence are limited. A retrospective review of a prospectively maintained database was performed, and 57 patients who had recurrence after operation of differentiated thyroid cancer were identified. Controlling for age, sex, surgery, and tumour stage, 114 patients without recurrent disease were selected by case-control matching. Subjective symptoms at follow-up visits were extracted from medical records and classified into three symptom clusters: pharyngolaryngeal, psychoneurological, and gastrointestinal. Compared to the control group, patients with recurrence had higher symptom totals in the pharyngolaryngeal (P < 0.001) and psychoneurological clusters (P = 0.005). Symptom score >3 yielded a sensitivity of 61.4% and a specificity of 80.7% to predict recurrence. Multivariate Cox regression analysis revealed that high symptom score (hazard ratio [HR] = 4.184), family history of thyroid cancer (HR = 2.463), and obesity (HR = 1.981) were independently associated with disease recurrence. Taken together, the likelihood of postoperative recurrence seemed to increase with high self-perceived symptom burden, family history, and obesity in patients with thyroid cancer. The results could be applied to the recurrence surveillance and symptomatic management of thyroid cancer post-operation.

Targeting the pentose phosphate pathway increases reactive oxygen species and induces apoptosis in thyroid cancer cells

The pentose phosphate pathway (PPP) plays an important role in the biosynthesis of ribonucleotide precursor and NADPH. Cancer cells frequently increase the flux of glucose into the PPP to support the anabolic demands and regulate oxidative stress. Consistently, metabolomic analyses indicate an upregulation of the PPP in thyroid cancer. In the present study, we found that the combination of glucose-6-phosphate dehydrogenase (G6PD) and transketolase inhibitors (6-aminonicotinamide and oxythiamine) exerted an additive or synergistic effect on cell growth inhibition in thyroid cancer cells. Targeting PPP significantly increased cellular reactive oxygen species (ROS) and induced endoplasmic reticulum (ER) stress and apoptosis. Suppressed cell viability could be partially rescued with treatment with the ROS scavenger or apoptosis inhibitor but not ER-stress inhibitor. Taken together, dual PPP blockade leads to pharmacologic additivity or synergism and causes ROS-mediated apoptosis in thyroid cancer cells.

Overexpression of Histone H3 Lysine 27 Trimethylation Is Associated with Aggressiveness and Dedifferentiation of Thyroid Cancer

A variety of epigenetic dysregulations are observed in thyroid malignancies. EZH2, the catalytic subunit of polycomb repressive complex 2, is upregulated in advanced thyroid cancers. EZH2 can catalyze trimethylation of histone H3 at lysine 27 (H3K27me3) and contribute to transcriptional silencing of target genes. Here, we investigated the immunohistochemical expression of H3K27me3 in neoplastic and normal thyroid tissues. Normal thyroid epithelial cells typically exhibited nuclear staining of moderate intensity. A similar expression pattern was observed in nodular goiters and follicular adenomas. By contrast, strong H3K27me3 expression was evident in 80% (8/10) lymphocytic thyroiditis, 63% (80/127) papillary thyroid cancer, 41% (7/17) follicular thyroid cancer, and 73% (8/11) poorly differentiated and anaplastic thyroid cancer. In differentiated thyroid cancer, strong H3K27me3 expression was associated with extrathyroidal extension (p < 0.001), lymphovascular invasion (p = 0.029), lymph node metastasis (p = 0.006), and higher risk of recurrence (p = 0.003). Our results indicate that H3K27me3 overexpression may be implicated in aggressiveness and dedifferentiation of thyroid cancer. In addition to prognostication, the predictive value of H3K27me3 expression deserves further investigation given the recent development of epigenetic targeting agents.

Is papillary thyroid microcarcinoma a biologically different disease? A propensity score-matched analysis

BACKGROUND

Papillary thyroid microcarcinoma exhibits an indolent clinical course and could be a candidate for active surveillance in the appropriate setting. It remains unknown whether papillary microcarcinoma is biologically different from larger papillary carcinoma >1 cm.

METHODS

We analyzed clinicopathological information and transcriptome data of papillary thyroid cancer samples from The Cancer Genome Atlas. Propensity-score matching was used to construct a matched cohort consisting of 29 microcarcinomas and 58 carcinomas. Principal component analysis and unsupervised hierarchical cluster analysis were carried out to investigate the similarity of gene expression profiles.

RESULTS

After adjustment for differences in baseline clinicopathological and genetic factors, transcriptome could be grouped mainly on the basis of tumor class (BRAF-like vs RAS-like) and tumor size (microcarcinoma vs carcinoma). The gene set enrichment analysis showed that extracellular matrix-associated pathways were enriched in the MSigDB database.

CONCLUSION

Papillary thyroid microcarcinomas display a distinct gene expression pattern different from the corresponding carcinomas. We hypothesize that tumor microenvironment may play a role in the microcarcinoma/carcinoma phenotypic divergence.

Effects of a DPP4 Inhibitor on Progression of NASH-related HCC and the p62/ Keap1/Nrf2-Pentose Phosphate Pathway in a Mouse Model

BACKGROUND AND AIMS

Diabetes mellitus is a risk factor for hepatocellular carcinoma (HCC) in patients with nonalcoholic steatohepatitis (NASH). Dipeptidyl peptidase-4 inhibitor (DPP4i), an antidiabetic agent, is reported to affect cell proliferation. We aimed to investigate the effects of DPP4i on the progression of NASH-related HCC and its metabolic pathway in a mouse model.

METHODS

A mouse model of NASH-related HCC was used in this study. Eight-week-old mice were administered either DPP4i (sitagliptin 30 mg/kg/day; DPP4i group; n = 8) or distilled water (control group; n = 8) for 10 weeks. Then, HCC progression was evaluated by computed tomography. Changes in metabolites of HCC tissue were analyzed by metabolomic analysis. The localization and expression of p62, Keap1, Nrf2, and MCM7 were evaluated by immunostaining and immunoblotting, respectively.

RESULTS

The number and volume of HCC were significantly lower in the DPP4i group than in the control group (1.8 ± 1.2 vs. 4.5 ± 1.7/liver, p < 0.01; 11.2 ± 20.8 vs. 37.5 ± 72.5 mm³/tumor, p < 0.05). Metabolome analysis revealed that DPP4i significantly increased 6-phosphogluconic acid and ribose 5-phosphate levels and decreased the AMP-to-adenine and GMP-to-guanine ratios (AMP-to-adenine ratio 0.7 ± 0.2 vs. 2.0 ± 1.2, p < 0.01; GMP-to-guanine ratio 0.6 ± 0.3 vs. 1.5 ± 0.7, p < 0.01). Immunostaining showed that p62 was localized in the cytoplasm of HCC in the DPP4i group, while p62 was localized in the nucleus of HCC in the control group. Keap1, Nrf2, and MCM7 expression decreased significantly in the DPP4i group compared to that in the control group.

CONCLUSIONS

We demonstrated that DDP4i prevented the progression of NASH-related HCC in a mouse model. Furthermore, metabolome analysis revealed that DDP4i downregulated the pentose phosphate pathway with suppression of the p62/Keap1/Nrf2 pathway. Thus, DDP4i may prevent tumor progression through inhibition of metabolic reprogramming in NASH-related HCC.

PGC1α downregulation and glycolytic phenotype in thyroid cancer

Increased aerobic glycolysis portends an unfavorable prognosis in thyroid cancer. The metabolic reprogramming likely results from altered mitochondrial activity and may promote cancer progression. Peroxisome proliferator-activated receptor γ coactivator 1α (PGC1α) plays a pivotal role in mitochondrial biogenesis and function. In the present study, we aimed to evaluate the clinicopathological significance of PGC1α expression and the potential effects of PGC1α modulation. Firstly, the expression of PGC1α in thyroid cancer samples was evaluated using western blot analysis and immunohistochemical staining. Compared with normal thyroid tissue, PGC1α expression was downregulated in thyroid cancer. PGC1α-negative papillary cancer was associated with BRAF V600E mutation, large tumor size, extrathyroidal or lymphovascular invasion, lymph node metastasis, and advanced stage. The results were consistent with the analysis of The Cancer Genome Atlas data. PGC1α expression correlated with oxygen consumption in thyroid cancer cells and was inversely related to AKT activity. The biologic relevance of PGC1α was further investigated by gain- and loss-of-function experimental studies. PGC1α overexpression led to augmented oxidative metabolism and accelerated tumor growth, whereas PGC1α knockdown induced a glycolytic phenotype but reduced tumor growth in vivo. In conclusion, PGC1α downregulation is associated with glycolytic metabolism and advanced disease in thyroid cancer. Nonetheless, manipulating PGC1α expression and metabolic phenotype does not necessarily translate into beneficial effects. It suggests that the metabolic phenotype is likely the consequence rather than the cause of disease progression in thyroid cancer.

Dipeptidyl peptidase 4 inhibitors as novel agents in improving survival in diabetic patients with colorectal cancer and lung cancer: A Surveillance Epidemiology and Endpoint Research Medicare study

Background

Dipeptidyl peptidase 4 (DPP4) is a cell surface protein that can act as a tumor suppressor or activator, depending upon the level of expression and interaction with the microenvironment and chemokines. DPP4 inhibitors are used to treat diabetes.

Methods

We conducted this Surveillance Epidemiology and Endpoint Research‐Medicare database study to evaluate the role of DPP4 inhibitors on the overall survival (OS) of diabetic patients diagnosed with colorectal (CRC) and lung cancers.

Results

Diabetic patients with CRC or lung cancer who were treated with DPP4 inhibitors exhibited a statistically significant survival advantage (hazard ratio [HR] of 0.89; CI: 0.82‐0.97, P = 0.007) that remained significant after controlling for all other confounders. When DPP4 inhibitors were used in combination of metformin which is known to suppress cancer, the survival advantage was even more pronounced (HR of 0.83; CI: 0.77‐0.90, P < 0.0001). Data were then analyzed separately for two cancer types. In the CRC‐only cohort, the use of DPP4 inhibitors alone had a positive trend but did not meet statistically significant threshold (HR of 0.87; CI: 0.75‐1.00, P = 0.055), while the combined use of DPP4 inhibitors and metformin was associated with statistically significant survival advantage (HR of 0.77; CI: 0.67‐0.89, P = 0.003). Similarly, for the lung cancer cohort, use of DPP4 alone was not found to be statistically significant (HR of 0.93; CI: 0.83‐1.03, P = 0.153), whereas lung cancer patients treated with the combination of DPP4 inhibitors and metformin showed statistically significant survival advantage (HR of 0.88; CI: 0.80‐0.97, P = 0.010).

Conclusions

DPP4 inhibition in CRC and lung cancer is associated with improved OS, which possibly may be due to the effect of DPP4 inhibition on immunoregulation of cancer.

Inhibition of 3β-Hydroxysteroid Dehydrogenase Type 1 Suppresses Interleukin-6 in Breast Cancer

BACKGROUND

Recently, we demonstrated that the expression of 3β-hydroxysteroid dehydrogenase type 1 (HSD3B1) in breast cancer is associated with shorter recurrence-free survival, and genetic or pharmacologic inhibition of HSD3B1 reduced colony formation and xenograft growth. However, the mechanisms are unclear.

METHODS

Triple-negative MDA-MB-231 and BT-20 breast cancer cells underwent HSD3B1 silencing. Microarray and bioinformatic analysis were performed. The interleukin-6 (IL-6) expression and secretion were evaluated using real-time quantitative polymerase chain reaction and enzyme-linked immunosorbent assay. Clonogenic ability and cell viability were determined in the absence or presence of recombinant IL-6.

RESULTS

Functional and pathway enrichment analyses showed that HSD3B1 silencing modulates the expression of several growth factors and cytokines. Cells transfected with HSD3B1-targeting small interfering RNA or treated with an HSD3B1 inhibitor (trilostane) had decreased IL-6 expression and secretion. HSD3B1 inhibition reduced colony formation, which was partially rescued by IL-6 supplementation. The HSD3B1 knockdown enhanced paclitaxel sensitivity, and IL-6 treatment partially reversed the augmented cytotoxicity.

CONCLUSIONS

Our findings suggest that the therapeutic potential of targeting HSD3B1 is in part mediated by IL-6 suppression.

CD26/DPP4 - a potential biomarker and target for cancer therapy

CD26/dipeptidyl peptidase (DPP)4 is a membrane-bound protein found in many cell types of the body, and a soluble form is present in body fluids. There is longstanding evidence that various primary tumors and also metastases express CD26/DPP4 to a variable extent. By cleaving dipeptides from peptides with a proline or alanine in the penultimate position at the N-terminus, it regulates the activity of incretin hormones, chemokines and many other peptides. Due to these effects and interactions with other molecules, a tumor promoting or suppressing role can be attributed to CD26/DPP4. In this review, we discuss the existing evidence on the expression of soluble or membrane-bound CD26/DPP4 in malignant diseases, along with the most recent findings on CD26/DPP4 as a therapeutic target in specific malignancies. The expression and possible involvement of the related DPP8 and DPP9 in cancer are also reviewed. A higher expression of CD26/DPP4 is found in a wide variety of tumor entities, however more research on CD26/DPP4 in the tumor microenvironment is needed to fully explore its use as a tumor biomarker. Circulating soluble CD26/DPP4 has also been studied as a cancer biomarker, however, the observed decrease in most cancer patients does not seem to be cancer specific. Encouraging results from experimental work and a recently reported first phase clinical trial targeting CD26/DPP4 in mesothelioma, renal and urological tumors pave the way for follow-up clinical studies, also in other tumor entities, possibly leading to the development of more effective complementary therapies against cancer.