Expression of platelet-derived growth factor (PDGF)-B and PDGF-receptor β is associated with lymphatic metastasis in human gastric carcinoma

Review of treatment strategies after lymphadenectomy: From molecular therapeutics to immediate microsurgical lymphatic reconstruction

OBJECTIVE

Lymphedema is a common complication of cancer treatment, such as lymphadenectomy and radiation therapy. It is a debilitating condition with pathologic tissue changes that hinder effective curative treatment and jeopardize patients' quality of life. Various attempts to prevent the development of lymphedema have been made, with improvements in the incidence of the pathology. However, it is still prevalent among survivors of cancer. In this paper, we review both molecular therapeutics and immediate surgical lymphatic reconstruction as treatment strategies after lymphadenectomy. Specifically, we discuss pro-lymphangiogenic molecules that have proved efficient in animal models of lymphedema and clinical trials, and review currently available microsurgical techniques of immediate lymphatic reconstruction.

METHODS

A literature search was conducted in PubMed, Embase, Cochrane Library, and Google Scholar through May 2022. Searches were done separately for molecular therapeutics and microsurgical techniques for immediate lymphatic reconstruction. Search terms used for (1) non-surgical methods include 'lymphangiogenesis,' 'lymphedema,' 'growth factor,' and 'gene therapy.' Search terms used for (2) surgical methods include 'lymphedema,' 'lymph node excision,' 'lymphatic vessels,' 'primary prevention,' and 'microsurgery.'

RESULTS

Various pro-lymphangiogenic factors with therapeutic potential include VEGF-C, VEGF-D, HGF, bFGF, PDGF, IGF, Retinoic acid, Ang-1, S1P, TLR4, and IL-8. Microsurgical lymphatic reconstruction for prevention of secondary lymphedema includes lymphovenous anastomosis, vascularized lymph node flap transfer, and lymph-interpositional flap transfer, with promising clinical outcomes.

CONCLUSIONS

With growing knowledge of the lymphangiogenic pathway and lymphedema pathology and advances in microsurgical techniques to restore lymphatic channels, molecular and surgical approaches may represent a promising method for primary prevention of lymphedema.

Identification of angiogenesis-related subtypes and risk models for predicting the prognosis of gastric cancer patients

Gastric cancer (GC) is a leading cause of cancer-related mortality and is characterized by significant heterogeneity, highlighting the need for further studies aimed at personalized treatment strategies. Tumor angiogenesis is critical for tumor development and metastasis, yet its role in molecular subtyping and prognosis prediction remains underexplored. This study aims to identify angiogenesis-related subtypes and develop a prognostic model for GC patients. Using data from The Cancer Genome Atlas (TCGA), we performed consensus cluster analysis on differentially expressed angiogenesis-related genes (ARGs), identifying two patient subtypes with distinct survival outcomes. Differentially expressed genes between the subtypes were analyzed via Cox and LASSO regression, leading to the establishment of a subtype-based prognostic model using a machine learning algorithm. Patients were classified into high- and low-risk groups based on the risk score. Validation was performed using independent datasets (ICGC and GSE15459). We utilized a deconvolution algorithm to investigate the tumor immune microenvironment in different risk groups and conducted analyses on genetic profiling, sensitivity and combination of anti-tumor drug. Our study identified ten prognostic signature genes, enabling the calculation of a risk score to predict prognosis and overall survival. This provides critical data for stratified diagnosis and treatment upon patient admission, monitoring disease progression throughout the entire course, evaluating immunotherapy efficacy, and selecting personalized medications for GC patients.

Functional and clinical roles of stromal PDGF receptors in tumor biology

PDGF receptors play pivotal roles in both developmental and physiological processes through the regulation of mesenchymal cells involved in paracrine instructive interactions with epithelial or endothelial cells. Tumor biology studies, alongside analyses of patient tissue samples, provide strong indications that the PDGF signaling pathways are also critical in various types of human cancer. This review summarizes experimental findings and correlative studies, which have explored the biological mechanisms and clinical relevance of PDGFRs in mesenchymal cells of the tumor microenvironment. Collectively, these studies support the overall concept that the PDGF system is a critical regulator of tumor growth, metastasis, and drug efficacy, suggesting yet unexploited targeting opportunities. The inter-patient variability in stromal PDGFR expression, as being linked to prognosis and treatment responses, not only indicates the need for stratified approaches in upcoming therapeutic investigations but also implies the potential for the development of PDGFRs as biomarkers of clinical utility, interestingly also in settings outside PDGFR-directed treatments.

Cell-cell communication network-based interpretable machine learning predicts cancer patient response to immune checkpoint inhibitors

Immune checkpoint inhibitors (ICIs) have revolutionized cancer treatment. However, only some patients respond to ICIs, and current biomarkers for ICI efficacy have limited performance. Here, we devised an interpretable machine learning (ML) model trained using patient-specific cell-cell communication networks (CCNs) decoded from the patient's bulk tumor transcriptome. The model could (i) predict ICI efficacy for patients across four cancer types (median AUROC: 0.79) and (ii) identify key communication pathways with crucial players responsible for patient response or resistance to ICIs by analyzing more than 700 ICI-treated patient samples from 11 cohorts. The model prioritized chemotaxis communication of immune-related cells and growth factor communication of structural cells as the key biological processes underlying response and resistance to ICIs, respectively. We confirmed the key communication pathways and players at the single-cell level in patients with melanoma. Our network-based ML approach can be used to expand ICIs' clinical benefits in cancer patients.

Cancer Cell-Derived PDGFB Stimulates mTORC1 Activation in Renal Carcinoma

Clear cell renal cell carcinoma (ccRCC) is a hypervascular tumor that is characterized by bi-allelic inactivation of the VHL tumor suppressor gene and mTOR signalling pathway hyperactivation. The pro-angiogenic factor PDGFB, a transcriptional target of super enhancer-driven KLF6, can activate the mTORC1 signalling pathway in ccRCC. However, the detailed mechanisms of PDGFB-mediated mTORC1 activation in ccRCC have remained elusive. Here, we investigated whether ccRCC cells are able to secrete PDGFB into the extracellular milieu and stimulate mTORC1 signalling activity. We found that ccRCC cells secreted PDGFB extracellularly, and by utilizing KLF6- and PDGFB-engineered ccRCC cells, we showed that the level of PDGFB secretion was positively correlated with the expression of intracellular KLF6 and PDGFB. Moreover, the reintroduction of either KLF6 or PDGFB was able to sustain mTORC1 signalling activity in KLF6-targeted ccRCC cells. We further demonstrated that conditioned media of PDGFB-overexpressing ccRCC cells was able to re-activate mTORC1 activity in KLF6-targeted cells. In conclusion, cancer cell-derived PDGFB can mediate mTORC1 signalling pathway activation in ccRCC, further consolidating the link between the KLF6-PDGFB axis and the mTORC1 signalling pathway activity in ccRCC.

Nintedanib Induces the Autophagy-Dependent Death of Gastric Cancer Cells by Inhibiting the STAT3/Beclin1 Pathway

BACKGROUND

Tyrosine kinase inhibitors are currently the most widely studied targeted therapies for gastric cancer. As a triple tyrosine inhibitor, nintedanib can alleviate the progression of a variety of cancers, but it is poorly studied in gastric cancer.

AIMS

To investigate the effect of nintedanib on gastric cancer.

METHODS

This study investigated nintedanib's effect on gastric cancer autophagy in vivo and in vitro, and the activity and morphological changes of gastric cancer cells were detected by MTT and HE staining. Proliferation, migration, invasion, and EMT-related marker proteins of AGS and MKN-28 cells were detected. The effects of nintedanib on autophagy in gastric cancer cells were detected by acridine orange, immunofluorescence, and Western blotting assays. The regulation of nintedanib on STAT3 and Beclin1 was detected by qPCR and Western blotting assays. Subsequently, the effects of nintedanib on the tumor STAT3/Beclin1 pathway were verified by stably overexpressing STAT3 in gastric cancer cell lines and tumor-bearing experiments in nude mice.

RESULTS

The results showed that nintedanib could inhibit gastric cancer cells' proliferation and EMT process. Meanwhile, autophagy was induced in AGS and MKN-28 cells, and the expression of autophagy-related protein Beclin1 was upregulated, and the phosphorylation level of STAT3 was downregulated. Nintedanib inhibited STAT3 phosphorylation and upregulated Beclin1 to inhibit tumor growth in gastric cancer cell lines with stable STAT3 overexpression and tumor-bearing experiments in nude mice.

CONCLUSIONS

By inhibiting STAT3, nintedanib upregulated Beclin1 and caused autophagic death in gastric cancer cells.

Intratumoral PDGFB gene predominantly expressed in endothelial cells is associated with angiogenesis and lymphangiogenesis, but not with metastasis in breast cancer

PURPOSE

Platelet-derived growth factor B (PDGFB) is known to play essential roles in angiogenesis and lymphangiogenesis during development, and tumor growth and vessel stabilization in experimental models. However, whether these findings could be translated to breast cancer patients remains unclear. We hypothesized that PDGFB gene expression is associated with angiogenesis, cell proliferation, and clinical outcomes in breast cancer patients.

METHODS

A total of 7635 primary breast cancer patients with full transcriptome and clinical data available from 13 independent cohorts were analyzed using in silico approach. The median value was used to divide each cohort into high and low PDGFB expression groups.

RESULTS

High PDGFB gene expression was associated with increased expression of angiogenesis-related genes, higher amount of vascular cell infiltrations, and with enrichment of angiogenesis gene set, lymphangiogenesis-related gene expressions, lymphangiogenesis-related cell infiltrations, and enrichmentof lymphangiogenesis gene set in GSE96058 and validated by TCGA cohorts; however, not with lymphatic metastasis. PDGFB expression was neither associated with cell proliferation as assessed by Ki67 expression nor with Nottingham histological grade, or response to neoadjuvant chemotherapy. We found that PDGFB was most extensively expressed by endothelial and perivascular-like cells in the tumor microenvironment, and minimally by cancer cells consistently in two single-cell sequence cohorts. High PDGFB expression enriched TGFβ, epithelial-mesenchymal transition, hypoxia, and cancer stem cell-associated pathways. However, no association with distant metastasis was observed. Disease-specific and disease-free survival were worse in the high PDGFB expression group consistently in TCGA and METABRIC cohorts.

CONCLUSION

PDGFB is predominantly expressed in endothelial cells and is associated with angiogenesis and lymphangiogenesis, but not with cellular proliferation or metastasis in breast cancer.

PDGFB targeting biodegradable FePt alloy assembly for MRI guided starvation-enhancing chemodynamic therapy of cancer

The application of chemodynamic therapy (CDT) for cancer is a serious challenge owing to the low efficiency of the Fenton catalyst and insufficient H₂O₂ expression in cells. Herein, we fabricated a PDGFB targeting, biodegradable FePt alloy assembly for magnetic resonance imaging (MRI)-guided chemotherapy and starving-enhanced chemodynamic therapy for cancer using PDGFB targeting, pH-sensitive liposome-coated FePt alloys, and GOx (pLFePt-GOx). We found that the Fenton-catalytic activity of FePt alloys was far stronger than that of traditional ultrasmall iron oxide nanoparticle (UION). Upon entry into cancer cells, pLFePt-GOx nanoliposomes degraded into many tiny FePt alloys and released GOx owing to the weakly acidic nature of the tumor microenvironment (TME). The released GOx-mediated glucose consumption not only caused a starvation status but also increased the level of cellular H₂O₂ and acidity, promoting Fenton reaction by FePt alloys and resulting in an increase in reactive oxygen species (ROS) accumulation in cells, which ultimately realized starving-enhanced chemodynamic process for killing tumor cells. The anticancer mechanism of pLFePt-GOx involved ROS-mediated apoptosis and ferroptosis, and glucose depletion-mediated starvation death. In the in vivo assay, the systemic delivery of pLFePt-GOx showed excellent antitumor activity with low biological toxicity and significantly enhanced T₂-weighted magnetic resonance imaging (MRI) signal of the tumor, indicating that pLFePt-GOx can serve as a highly efficient theranostic tool for cancer. This work thus describes an effective, novel multi-modal cancer theranostic system.

Proteins and polysaccharides from vegetative mycelium of medicinal basidiomycete Lentinus edodes display cytotoxicity towards human and animal cancer cell lines

Detection and study of biologically active compounds seems a promising area of research in cancer diagnostics and therapies. The glycoprotein and polysaccharide fractions showing high cytotoxicity towards several human and animal cancer cell lines: A549, Hep-2, HeLa, С6 and SPEV-2 were isolated from basidiomycete Lentinus edodes vegetative mycelium and fruiting body and further characterized. It was found that water-soluble glycoprotein fractions caused the most significant, 70-100% inhibition of metabolic activity of SPЕV-2, А549 and С6 cell lines. The effective concentrations of glycoprotein fractions reducing the viability of cancer cell lines were determined. The protein and subunit composition of fractions was studied; the highly active galactose-specific lectins were found to be present in these fractions. Comparative analysis of transcriptomes of L. edodes vegetative mycelium, fruiting body and primordium revealed the presence of carbohydrate-binding glycoproteins (lectins) specific for each stage of basidiomycete morphogenesis. Histological examination revealed some morphological indicators of immune system activation and the absence of toxic effect on gastro-intestinal mucosa of animals at peroral administration of fungal glycoprotein fractions. Fungal protein and, in particular, lectin preparations derived from L. еdodes vegetative mycelium might be considered as novel prospective tools in cancer diagnostics and therapies.

Targeted FGFR/VEGFR/PDGFR inhibition with dovitinib enhances the effects of nab-paclitaxel in preclinical gastric cancer models

Standard chemotherapy regimens for gastric adenocarcinoma (GAC) have limited efficacy and considerable toxicity profiles. Nab-paclitaxel has shown promising antitumor benefits in previous GAC preclinical studies. Dovitinib inhibits members of the receptor tyrosine kinase family including FGFR, VEGFR and PDGFR, and has exhibited antitumor effects in many solid tumors including GAC. Based on the antimitotic, antistromal and EPR effects of nab-paclitaxel, we investigated augmentation of nab-paclitaxel response by dovitinib in multiple GAC preclinical models. In MKN-45 subcutaneous xenografts, inhibition in tumor growth by nab-paclitaxel and dovitinib was 75% and 76%, respectively. Dovitinib plus nab-paclitaxel had an additive effect on tumor growth inhibition and resulted in tumor regression (85% of its original value). Dovitinib monotherapy resulted in minimal improvement in animal survival (25 days) compared to control (23 days), while nab-paclitaxel monotherapy or dovitinib plus nab-paclitaxel combination therapy led to a clinically significant lifespan extension of 83% (42 days) and 187% (66 days), respectively. IHC analysis of subcutaneous tumors exhibited reduced tumor cell proliferation and tumor vasculature by dovitinib. In vitro studies demonstrated that dovitinib and nab-paclitaxel individually reduced tumor cell proliferation, with an additive effect from combination therapy. Immunoblot analyses of MKN-45 and KATO-III cells revealed that dovitinib decreased phospho-FGFR, phospho-AKT, phospho-ERK, phospho-p70S6K, phospho-4EBP1, Bcl-2 and increased cleaved PARP-1, cleaved-caspase-3, p27, Bax, Bim, with an additive effect from combination therapy. These results demonstrate that the FGFR/VEGFR/PDGFR inhibitor, dovitinib, has the potential to augment the antitumor effects of nab-paclitaxel, with implications for use in the advancement of clinical GAC therapy.

Corneal Lymphangiogenesis: Current Pathophysiological Understandings and Its Functional Role in Ocular Surface Disease

The cornea is a transparent and avascular tissue that plays a central role in light refraction and provides a physical barrier to the external environment. Corneal avascularity is a unique histological feature that distinguishes it from the other parts of the body. Functionally, corneal immune privilege critically relies on corneal avascularity. Corneal lymphangiogenesis is now recognized as a general pathological feature in many pathologies, including dry eye disease (DED), corneal allograft rejection, ocular allergy, bacterial and viral keratitis, and transient corneal edema. Currently, sizable data from clinical and basic research have accumulated on the pathogenesis and functional role of ocular lymphangiogenesis. However, because of the invisibility of lymphatic vessels, ocular lymphangiogenesis has not been studied as much as hemangiogenesis. We reviewed the basic mechanisms of lymphangiogenesis and summarized recent advances in the pathogenesis of ocular lymphangiogenesis, focusing on corneal allograft rejection and DED. In addition, we discuss future directions for lymphangiogenesis research.

A signature of 24 aging‑related gene pairs predict overall survival in gastric cancer

BACKGROUND

Aging is the major risk factor for most human cancers. We aim to develop and validate a reliable aging-related gene pair signature (ARGPs) to predict the prognosis of gastric cancer (GC) patients.

METHODS

The mRNA expression data and clinical information were obtained from two public databases, The Cancer Genome Atlas (TCGA) dataset, and Gene Expression Omnibus (GEO) dataset, respectively. The best prognostic signature was established using Cox regression analysis (univariate and least absolute shrinkage and selection operator). The optimal cut-off value to distinguish between high- and low-risk patients was found by time-dependent receiver operating characteristic (ROC). The prognostic ability of the ARGPS was evaluated by a log-rank test and a Cox proportional hazards regression model.

RESULTS

The 24 ARGPs were constructed for GC prognosis. Using the optimal cut-off value - 0.270, all patients were stratified into high risk and low risk. In both TCGA and GEO cohorts, the results of Kaplan-Meier analysis showed that the high-risk group has a poor prognosis (P < 0.001, P = 0.002, respectively). Then, we conducted a subgroup analysis of age, gender, grade and stage, and reached the same conclusion. After adjusting for a variety of clinical and pathological factors, the results of multivariate COX regression analysis showed that the ARGPs is still an independent prognostic factor of OS (HR, 4.919; 95% CI 3.345-7.235; P < 0.001). In comparing with previous signature, the novel signature was superior, with an area under the receiver operating characteristic curve (AUC) value of 0.845 vs. 0.684 vs. 0.695. The results of immune infiltration analysis showed that the abundance of T cells follicular helper was significantly higher in the low-risk group, while the abundance of monocytes was the opposite. Finally, we identified and incorporated independent prognostic factors and developed a superior nomogram to predict the prognosis of GC patients.

CONCLUSION

Our study has developed a robust prognostic signature that can accurately predict the prognostic outcome of GC patients.

Platelet-derived growth factor-B signalling might promote epithelial-mesenchymal transition in gastric carcinoma cells through activation of the MAPK/ERK pathway

Introduction

Epithelial-mesenchymal transition (EMT) is important in the metastasis of tumours and is triggered by several key growth factors, including platelet-derived growth factor-B (PDGF-B). But, whether PDGF-B signalling promotes EMT in gastric carcinoma cells is still unknown.

Material and methods

We established 2 gastric carcinoma cell lines (MKN28 and MKN45) to stably overexpress PDGF-B by lentiviral vectors, and expression of E-cadherin, N-cadherin, and ERK-1 were detected by western blot assay. Then, PDGF-B overexpression and normal MKN28 and MKN45 cells were cocultured with PDGFR-b positive fibroblast (hs738) and MAPK inhibitors were added; also, the expressions of ERK-1, E-cadherin, and N-cadherin were detected by western blot assay.

Results

After being cocultured with hs738 cells, expressions of ERK-1 and N-cadherin protein in PDGF-B overexpression MKN28 and MKN45 cells were much higher than normal MKN28 and MKN45 cells (p < 0.05), and those could be decreased by MAPK inhibitor. Also, expressions of E-cadherin protein in PDGF-B overexpression MKN28 and MKN45 cells were much lower than normal MKN28 and MKN45 cells (p < 0.05), and they could be increased by MAPK inhibitor.

Conclusions

Our data indicate that PDGF-B signalling can induce EMT in gastric carcinoma cells. Thr tumour microenvironment is imperative in the process of PDGF-B signalling inducing EMT in gastric carcinoma cells. Also, activation of MAPK/ERK pathway, which is a downstream pathway of PDGF-B signalling, might participate in this process.

Engineering the Lymphatic Network: A Solution to Lymphedema

Secondary lymphedema is a life-long disorder characterized by chronic tissue swelling and inflammation that obstruct interstitial fluid circulation and immune cell trafficking. Regenerating lymphatic vasculatures using various strategies represents a promising treatment for lymphedema. Growth factor injection and gene delivery have been developed to stimulate lymphangiogenesis and augment interstitial fluid resorption. Using bioengineered materials as growth factor delivery vehicles allows for a more precisely targeted lymphangiogenic activation within the injured site. The implantation of prevascularized lymphatic tissue also promotes in situ lymphatic capillary network formation. The engineering of larger scale lymphatic tissues, including lymphatic collecting vessels and lymph nodes constructed by bioengineered scaffolds or decellularized animal tissues, offers alternatives to reconnecting damaged lymphatic vessels and restoring lymph circulation. These approaches provide lymphatic vascular grafting materials to reimpose lymphatic continuity across the site of injury, without creating secondary injuries at donor sites. The present work reviews molecular mechanisms mediating lymphatic system development, approaches to promoting lymphatic network regeneration, and strategies for engineering lymphatic tissues, including lymphatic capillaries, collecting vessels, and nodes. Challenges of advanced translational applications are also discussed.

Identification of the subtypes of gastric cancer based on DNA methylation and the prediction of prognosis

BACKGROUND

Gastric cancer (GC) is a digestive system cancer with a high mortality rate globally. Previous experiences and studies have provided clinicians with ample evidence to diagnose and treat patients with reasonable therapeutic options. However, there remains a need for sensitive biomarkers that can provide clues for early diagnosis and prognosis assessment.

RESULTS

We found 610 independent prognosis-related 5'-cytosine-phosphate-guanine-3' (CpG) sites (P < 0.05) among 21,121 sites in the training samples. We divided the GC samples into seven clusters based on the selected 610 sites. Cluster 6 had relatively higher methylation levels and high survival rates than the other six clusters. A prognostic risk model was constructed using the significantly altered CpG sites in cluster 6 (P < 0.05). This model could distinguish high-risk GC patients from low-risk groups efficiently with the area under the receiver operating characteristic curve of 0.92. Risk assessment showed that the high-risk patients had poorer prognosis than the low-risk patients. The methylation levels of the selected sites in the established model decreased as the risk scores increased. This model had been validated in testing group and its effectiveness was confirmed. Corresponding genes of the independent prognosis-associated CpGs were identified, they were enriched in several pathways such as pathways in cancer and gastric cancer. Among all of the genes, the transcript level of transforming growth factor β2 (TGFβ2) was changed in different tumor stages, T categories, grades, and patients' survival states, and up-regulated in patients with GC compared with the normal. It was included in the pathways as pathways in cancer, hepatocellular carcinoma or gastric cancer. The methylation site located on the promoter of TGFβ2 was cg11976166.

CONCLUSIONS

This is the first study to separate GC into different molecular subtypes based on the CpG sites using a large number of samples. We constructed an effective prognosis risk model that can identify high-risk GC patients. The key CpGs sites or their corresponding genes such as TGFβ2 identified in this research can provide new clues that will enable gastroenterologists to make diagnosis or personalized prognosis assessments and better understand this disease.

Long noncoding RNA PART1 restrains aggressive gastric cancer through the epigenetic silencing of PDGFB via the PLZF-mediated recruitment of EZH2

Current reports refer to the role of long noncoding RNA (lncRNA) prostate androgen-regulated transcript 1 (PART1) as a tumor suppressor in some types of cancer but as an oncogene in other kinds of cancer. In gastric cancer, it had been reported to be downregulated. However, the clinical significance and underlying mechanism of PART1 function in gastric cancer remains undefined. Here, seven differential expression levels of noncoding RNAs (DE-lncRNAs) were screened from gastric cancer through a probe reannotation of a human exon array. PART1 was selected for further study because of its high fold change number. In our cohort, PART1 was identified as a significant downregulated lncRNA in gastric cancer tissues by qPCR and in situ hybridization (ISH), and its low expression was significantly correlated with postoperative metastasis and short overall survival time after surgery. Through the results of gain-of-function experiments, PART1 was confirmed as a tumor suppressor that can decrease not only cell viability, migration, and invasion in vitro but also tumorigenesis and tumor metastasis in vivo. Mechanistically, RNA pull-down and RNA-binding protein immunoprecipitation (RIP) showed that PART1 interacts with androgen receptor (AR), and then, promyelocytic leukemia zinc finger (PLZF) is upregulated in an androgen-independent manner. In a chain reaction, chromatin immunoprecipitation (ChIP) assay additionally illustrated that PLZF upregulation increased the enrichment of EZH2 and H3K27 trimethylation in the platelet-derived growth factor (PDGFB) promotor, thereby inhibition of PDGFB and the subsequent PDGFRβ/PI3K/Akt signaling pathway. Based on these findings, we showed PART1 plays a tumor suppressor role by promoting PLZF expression followed by recruitment of EZH2 to mediate epigenetic PDGFB silencing and downstream PI3K/Akt inhibition, suggesting that PART1 has a key role in restraining the aggressive ability of GC cells and providing a novel perspective on lncRNAs in GC progression.

Fibroblast Reprogramming in Gastrointestinal Cancer

Gastrointestinal cancers are a significant cause of cancer mortality worldwide and have been strongly linked with chronic inflammation. Current therapies focus on epithelial/cancer cells; however, the importance of the tumor microenvironment in the development and treatment of the disease is also now well established. Cancer-associated fibroblasts (CAFs) are a major component of the tumor microenvironment, and are actively participating in tumor initiation, promotion and metastasis. They structurally and functionally affect cancer cell proliferation, tumor immunity, angiogenesis, extracellular matrix remodeling and metastasis through a variety of signaling pathways. CAFs originate predominantly from resident mesenchymal cells, which are activated and reprogrammed in response to cues from cancer cells. In recent years, chronic inflammation of the gastrointestinal tract has also proven an important driver of mesenchymal cell activation and subsequent CAF development, which in turn are capable of regulating the transition from acute to chronic inflammation and cancer. In this review, we will provide a concise overview of the mechanisms that drive fibroblast reprogramming in cancer and the recent advances on the downstream signaling pathways that regulate the functional properties of the activated mesenchyme. This new mechanistic insight could pave the way for new therapeutic strategies and better prognosis for cancer patients.

Expression of Angiogenic Proteins in Tumor and Stroma Affects Survival in Patients With Gastric Cancer

BACKGROUND

Gastric cancer is one of the most frequent malignancies worldwide. Angiogenic growth factors play a crucial role in mediating the crosstalk between cancer cells and the surrounding microenvironment. In this exploratory study, we investigate the impact of angiogenic proteins within the tumor cell or stroma compartment on survival of patients with gastric cancer.

MATERIALS AND METHODS

In 29 patients, tumor and stromal compartments were separated using laser capture microdissection. Angiogenic protein expression was measured using a bead-based immunoassay and correlated with tumor stage and overall survival.

RESULTS

Overall survival was significantly shorter in patients with a high stroma concentration of vascular endothelial growth factor (VEGF)-A (23.5 (±17.6) versus 33.6 (±21.0) mo; P = 0.009) and stem cell factor (22.2 (±18.5) versus 33.6 (±21.8) mo; P = 0.01) compared with patients with a low stroma concentration. High stromal VEGF-D showed a trend toward worse survival (26.8 (±22.0) versus 37.2 (±19.0) mo; P = 0.09). We did not observe any significant correlation between tumor-specific expression of angiogenic cytokines and survival.

CONCLUSIONS

This translational study highlights the difference in clinical impact between tumor and stromal expression of angiogenic proteins. Compartment-specific concentrations of VEGF-A and stem cell factor affect the clinical prognosis and help to identify the best therapy for patients with gastric cancer.

DOK6 promoter methylation serves as a potential biomarker affecting prognosis in de novo acute myeloid leukemia

BACKGROUND

Downstream of tyrosine kinase 6 (DOK6), which is specifically expressed in the nervous system, was previously recognized as an adapter only in neurite outgrowth. Recent studies also demonstrated the potential role of DOK6 in solid tumors such as gastric cancer and breast cancer. However, previous studies of DOK6 have not dealt with its roles in myeloid malignancies. Herein, we verified the promoter methylation status of DOK6 and further explored its clinical implication in de novo acute myeloid leukemia (AML).

METHODS

A total of 100 newly diagnosed adult AML patients were involved in the current study. DOK6 expression and methylation were detected by real-time qPCR and methylation-specific PCR (MSP), respectively. Bisulfite sequencing PCR (BSP) was performed to assess the methylation density of the DOK6 promoter.

RESULTS

Downstream of tyrosine kinase 6 promoter methylation was significantly increased in AML patients compared to controls (P = .037), whereas DOK6 expression significantly decreased in AML patients (P < .001). The expression of DOK6 was markedly up-regulated after treated by 5-aza-2'-deoxycytidine (5-aza-dC) in THP-1 cell lines. The methylation status of the DOK6 promoter was associated with French-American-British classifications (P = .037). There was no significant correlation existed between DOK6 expression and its promoter methylation (R = .077, P = .635). Interestingly, of whole-AML and non-APL AML patients, both have a tendency pertaining to the DOK6 methylation group and a significantly longer overall survival (OS) than the DOK6 unmethylation group (P = .042 and .036, respectively).

CONCLUSION

Our study suggested that DOK6 promoter hypermethylation was a common molecular event in de novo AML patients. Remarkably, DOK6 promoter methylation could serve as an independent and integrated prognostic biomarker not only in non-APL AML patients but also in AML patients who are less than 60 years old.

Platelet-derived growth factor-D enables liver myofibroblasts to promote tumor lymphangiogenesis in cholangiocarcinoma

BACKGROUND & AIMS

In cholangiocarcinoma, early metastatic spread via lymphatic vessels often precludes curative therapies. Cholangiocarcinoma invasiveness is fostered by an extensive stromal reaction, enriched in cancer-associated fibroblasts (CAFs) and lymphatic endothelial cells (LECs). Cholangiocarcinoma cells recruit and activate CAFs by secreting PDGF-D. Herein, we investigated the role of PDGF-D and liver myofibroblasts in promoting lymphangiogenesis in cholangiocarcinoma.

METHODS

Human cholangiocarcinoma specimens were immunostained for podoplanin (LEC marker), α-SMA (CAF marker), VEGF-A, VEGF-C, and their cognate receptors (VEGFR2, VEGFR3). VEGF-A and VEGF-C secretion was evaluated in human fibroblasts obtained from primary sclerosing cholangitis explants. Using human LECs incubated with conditioned medium from PDGF-D-stimulated fibroblasts we assessed migration, 3D vascular assembly, transendothelial electric resistance and transendothelial migration of cholangiocarcinoma cells (EGI-1). We then studied the effects of selective CAF depletion induced by the BH3 mimetic navitoclax on LEC density and lymph node metastases in vivo.

RESULTS

In cholangiocarcinoma specimens, CAFs and LECs were closely adjacent. CAFs expressed VEGF-A and VEGF-C, while LECs expressed VEGFR2 and VEGFR3. Upon PDGF-D stimulation, fibroblasts secreted increased levels of VEGF-C and VEGF-A. Fibroblasts, stimulated by PDGF-D induced LEC recruitment and 3D assembly, increased LEC monolayer permeability, and promoted transendothelial EGI-1 migration. These effects were all suppressed by the PDGFRβ inhibitor, imatinib. In the rat model of cholangiocarcinoma, navitoclax-induced CAF depletion, markedly reduced lymphatic vascularization and reduced lymph node metastases.

CONCLUSION

PDGF-D stimulates VEGF-C and VEGF-A production by fibroblasts, resulting in expansion of the lymphatic vasculature and tumor cell intravasation. This critical process in the early metastasis of cholangiocarcinoma may be blocked by inducing CAF apoptosis or by inhibiting the PDGF-D-induced axis.

LAY SUMMARY

Cholangiocarcinoma is a highly malignant cancer affecting the biliary tree, which is characterized by a rich stromal reaction involving a dense population of cancer-associated fibroblasts that promote early metastatic spread. Herein, we show that cholangiocarcinoma-derived PDGF-D stimulates fibroblasts to secrete vascular growth factors. Thus, targeting fibroblasts or PDGF-D-induced signals may represent an effective tool to block tumor-associated lymphangiogenesis and reduce the invasiveness of cholangiocarcinoma.

Hypomethylated gene NRP1 is co-expressed with PDGFRB and associated with poor overall survival in gastric cancer patients

Gastric cancer (GC) has been an increasingly serious problem in public health. However, there is still a lack of efficient approach to diagnosis and treatment in time, especially in the field of targeted therapy. Increasing evidences demonstrated that DNA methylation plays an essential role in tumorigenesis and progression of GC. Thus the present study aims to identify DNA methylation-based prognostic biomarkers in GC. Two methylation array datasets (GSE25869 and GSE30601) and RNA-seq based gene profiling dataset (TCGA-STAD) were employed for exploring candidate DNA methylation-based biomarkers. Univariate Cox regression analysis was used to select the most efficient prognostic genes in GC patients. Weighted gene correlation network analysis (WGCNA) was performed to screen the cluster of co-expressed genes. As a result, our data proved that NRP1 was a hypomethylated / upregulated gene in GC tissues, and PDGFRB was strongly co-expressed with it. Both of them were significantly associated with the overall survival of patients. More importantly, high expression levels of NRP1 and PDGFRB were associated with malignant phenotypes in GC patients, including Laurén histological diffuse type and higher histological grade. Patients carrying high expression level of NRP1 and PDGFRB had a nearly two-fold increased death risk than others. In summary, the hypomethylated gene, NRP1, and its co-expressed gene, PDGFRB, were significantly correlated with tumor malignant phenotypes, which might serve as potential prognostic biomarkers for GC patients.

Hypoxia-Dependent Angiogenesis and Lymphangiogenesis in Cancer

Hypoxia (low O₂) is a ubiquitous feature of solid cancers, arising as a mismatch between cellular O₂ supply and consumption. Hypoxia is associated to metastatic disease and mortality owing to its ability to stimulate the formation of blood (angiogenesis) and lymphatic vessels (lymphangiogenesis), thereby allowing cancer cells to escape the unfavorable tumor microenvironment and disseminate into secondary sites. This review outlines molecular mechanisms by which intratumoral hypoxia regulates the expression of motogenic and mitogenic factors that induce angiogenesis and lymphangiogenesis, whilst discussing their implications for metastatic cancers.

Endothelial cell activation on 3D-matrices derived from PDGF-BB-stimulated fibroblasts is mediated by Snail1

Carcinomas, such as colon cancer, initiate their invasion by rescuing the innate plasticity of both epithelial cells and stromal cells. Although Snail is a transcriptional factor involved in the Epithelial-Mesenchymal Transition, in recent years, many studies have also identified the major role of Snail in the activation of Cancer-Associated Fibroblast (CAF) cells and the remodeling of the extracellular matrix. In CAFs, Platelet-derived growth factor (PDGF) receptor signaling is a major functional determinant. High expression of both SNAI1 and PDGF receptors is associated with poor prognosis in cancer patients, but the mechanism(s) that underlie these connections are not understood. In this study, we demonstrate that PDGF-activated fibroblasts stimulate extracellular matrix (ECM) fiber remodeling and deposition. Furthermore, we describe how SNAI1, through the FAK pathway, is a necessary factor for ECM fiber organization. The parallel-oriented fibers are used by endothelial cells as “tracks”, facilitating their activation and the creation of tubular structures mimicking in vivo capillary formation. Accordingly, Snail1 expression in fibroblasts was required for the co-adjuvant effect of these cells on matrix remodeling and neoangiogenesis when co-xenografted in nude mice. Finally, in tumor samples from colorectal cancer patients a direct association between stromal SNAI1 expression and the endothelial marker CD34 was observed. In summary, our results advance the understanding of PDGF/SNAI1-activated CAFs in matrix remodeling and angiogenesis stimulation.

The role of PDGF-B/PDGFR-BETA axis in the normal development and carcinogenesis of the breast

PDGFs/PDGFRs axis is documented as an important tumor-promoting agent and potential therapeutic target for several human carcinomas, including breast cancer. However, little is known about the role played by the PDGF family members in the normal development of the breast tissue, breast carcinogenesis and tumor-microenvironment dynamics Despite its potent pro-lymphangiogenic effects, PDGF-B/PDGFR-beta axis remains controversial and incompletely elucidated in the field of breast cancer, with emphasis to its differential implications in breast cancer molecular subtypes. Although some data are available concerning this aspect, little or no information is found regarding the role of the PDGF-B/PDGFR-beta axis in rare and aggressive types of breast cancers, such as triple negative breast cancers (TNBCs) and its associated subtypes This review attempted to gather as many data as possible concerning PDGFs family members in the normal breast tissue and in breast carcinogenesis with special focus on their role in diagnosis and therapeutic approach.

Generation of sphingosine-1-phosphate is enhanced in biliary tract cancer patients and is associated with lymphatic metastasis

Lymphatic metastasis is known to contribute to worse prognosis of biliary tract cancer (BTC). Recently, sphingosine-1-phosphate (S1P), a bioactive lipid mediator generated by sphingosine kinase 1 (SPHK1), has been shown to play an important role in lymphangiogenesis and lymph node metastasis in several types of cancer. However, the role of the lipid mediator in BTC has never been examined. Here we found that S1P is elevated in BTC with the activation of ceramide-synthetic pathways, suggesting that BTC utilizes SPHK1 to promote lymphatic metastasis. We found that S1P, sphingosine and ceramide precursors such as monohexosyl-ceramide and sphingomyelin, but not ceramide, were significantly increased in BTC compared to normal biliary tract tissue using LC-ESI-MS/MS. Utilizing The Cancer Genome Atlas cohort, we demonstrated that S1P in BTC is generated via de novo pathway and exported via ABCC1. Further, we found that SPHK1 expression positively correlated with factors related to lymphatic metastasis in BTC. Finally, immunohistochemical examination revealed that gallbladder cancer with lymph node metastasis had significantly higher expression of phospho-SPHK1 than that without. Taken together, our data suggest that S1P generated in BTC contributes to lymphatic metastasis.

Dapper homolog 1 alpha suppresses metastasis ability of gastric cancer through inhibiting planar cell polarity pathway

Dapper homolog 1 alpha (DACT1α) is a member of DACT family and an important regulator in the planar cell polarity pathway. We aim to clarify its functional role in metastasis ability of gastric cancer. DACT1α was silenced in all gastric cancer cell lines (8/8), but expressed in normal gastric tissue. Ectopic expression of DACT1α in silenced gastric cancer cell lines (AGS, BGC823 and MGC803) by stable transfection significantly suppressed cancer cell spreading (P < 0.05), migration (P < 0.01) and invasion (P < 0.01). These effects were associated with downregulation of planar cell polarity pathway related genes involved in cell proliferation (PDGFB, VEGFA), adhesion (ITGA1, ITGA2, ITGA3, ITGB3) and migration/invasion (PLAU, MMP9, MCAM, Dvl-2 and JNK). DACT1α promoter methylation was detected in 205 gastric cancers and 20 normal controls by direct bisulfite genomic sequencing. DACT1α methylation was detected in 29.3% (60/205) of gastric cancer patients, but not in normal tissues. DACT1α methylation was associated with poor survival of gastric cancer patients. In conclusion, DACT1α plays a pivotal role as a potential tumor suppressor in migration and invasion of gastric cancer. DACT1α methylation may serve as a biomarker for the prognosis of gastric cancer.

Common Deregulation of Seven Biological Processes by MicroRNAs in Gastrointestinal Cancers

MicroRNAs are frequently dysregulated in human neoplasms, including gastrointestinal cancers. Nevertheless, the global influence of microRNA dysregulation on cellular signaling is still unknown. Here we sought to elucidate cellular signaling dysregulation by microRNAs in gastrointestinal cancers at the systems biology level followed by experimental validation. Signature dysregulated microRNAs in gastric, colorectal and liver cancers were defined based on our previous studies. Targets of signature dysregulated miRNAs were predicted using multiple computer algorithms followed by gene enrichment analysis to identify biological processes perturbed by dysregulated microRNAs. Effects of microRNAs on endocytosis were measured by epidermal growth factor (EGF) internalization assay. Our analysis revealed that, aside from well-established cancer-related signaling pathways, several novel pathways, including axon guidance, neurotrophin/nerve growth factor signaling, and endocytosis, were found to be involved in the pathogenesis of gastrointestinal cancers. The regulation of EGF receptor (EGFR) endocytosis by two predicted miRNAs, namely miR-17 and miR-145, was confirmed experimentally. Functionally, miR-145, which blocked EGFR endocytosis, prolonged EGFR membrane signaling and altered responsiveness of colon cancer cells to EGFR-targeting drugs. In conclusion, our analysis depicts a comprehensive picture of cellular signaling dysregulation, including endocytosis, by microRNAs in gastrointestinal cancers.

Involvement of platelet-derived growth factor ligands and receptors in tumorigenesis

Platelet-derived growth factor (PDGF) isoforms and their receptors have important roles during embryogenesis, particularly in the development of various mesenchymal cell types in different organs. In the adult, PDGF stimulates wound healing and regulates tissue homeostasis. However, overactivity of PDGF signalling is associated with malignancies and other diseases characterized by excessive cell proliferation, such as fibrotic conditions and atherosclerosis. In certain tumours, genetic or epigenetic alterations of the genes for PDGF ligands and receptors drive tumour cell proliferation and survival. Examples include the rare skin tumour dermatofibrosarcoma protuberance, which is driven by autocrine PDGF stimulation due to translocation of a PDGF gene, and certain gastrointestinal stromal tumours and leukaemias, which are driven by constitute activation of PDGF receptors due to point mutations and formation of fusion proteins of the receptors, respectively. Moreover, PDGF stimulates cells in tumour stroma and promotes angiogenesis as well as the development of cancer-associated fibroblasts, both of which promote tumour progression. Inhibitors of PDGF signalling may thus be of clinical usefulness in the treatment of certain tumours.

Gastric poorly cohesive carcinoma: a correlative study of mutational signatures and prognostic significance based on histopathological subtypes

AIMS

Genome-wide next-generation sequencing has revealed several driver mutations and has allowed the establishment of a molecular taxonomy of gastric cancer. However, there are few detailed studies on the mutational spectrum of poorly cohesive gastric carcinoma. Thus, this study aim to investigate its mutation profile based on clinicopathological characteristics.

METHODS AND RESULTS

Herein, we analysed the mutational pattern of 77 genes in a cohort of 91 patients with poorly cohesive carcinoma by using targeted sequencing, and evaluated the clinicopathological significance of the various mutations based on histological pattern, either signet ring cell (SRC) or other types of poorly cohesive carcinoma (not otherwise specified) (PCC-NOS). Panels of seven (PIK3CA, CDH1, PTEN, RHOA, HDCA9, KRAS, and ATM), three (PIK3CA, CTNNB1, and KRAS) and two (HDCA9 and IGF1R) genes were associated with a diffuse infiltrative growth pattern, lymphovascular invasion, and perineural invasion, respectively. Furthermore, PDGFRB mutations were associated with a favourable prognosis, whereas MET mutations were associated with a poor prognosis. The PCC-NOS-predominant type was associated with a greater depth of invasion, lymph node metastasis and poorer prognosis than the SRC-predominant type. Mutations in TP53, BRAF, PI3CA, SMAD4 and RHOA were associated with PCC-NOS. Interestingly, RHOA-mutated gastric cancers showed a distinct morphology, as they were characterised by a superficial SRC or tubular component and a deep invasive PCC-NOS component with desmoplasia.

CONCLUSIONS

Taken together, our findings demonstrate that gastric poorly cohesive carcinomas show several mutational patterns associated with specific clinicopathological characteristics, and particularly show distinct morphological findings when associated with RHOA mutation.

PDGF receptors in tumor stroma: Biological effects and associations with prognosis and response to treatment

Platelet-derived growth factor (PDGF) ligands and their receptors (PDGFRα and PDGFRβ) regulate mesenchymal cells, such as fibroblasts and pericytes. These cells are important constituents of tumor stroma where they impact on tumor growth, metastasis and drug response. Studies in model systems have demonstrated ability of the PDGF system to regulate the tumor-stimulatory effects of fibroblasts, as well as their ability to promote cancer cell migration and invasion. Animal studies imply PDGFR-signaling as a regulator of tumor drug uptake. Emerging correlative analyses of different tumor collections are identifying clinically relevant variations in stromal PDGFR status, and associations between PDGFR status in tumor stroma and survival. These associations could either relate to effects of stromal PDGFR signaling on the natural course of the disease or response to treatment. The availability of clinically approved PDGFR-inhibitory drugs suggest interesting possibilities for novel clinical studies, performed on selected patient sub-groups, which further exploits tumor stroma-derived PDGFR signaling.

Quantitative proteomic analysis of gastric cancer tissue reveals novel proteins in platelet-derived growth factor b signaling pathway

Gastric cancer is one of the most common cancers in Asian countries. Searching for reliable biomarkers involving the development of gastric cancer is important for clinical practice. Quantitative proteomics has become an important method contributed to the discovery of novel diagnostic or therapeutic targets for the management of cancer. Here, we identified differently expressed proteins in gastric cancer and normal gastric tissues by using the high resolution mass spectrometer. Among the total of 2280 identified proteins, 87 were differentially expressed between gastric cancer and normal gastric tissues. Notably, several significant proteins are in the PDGF-B signaling pathway, including peroxiredoxin5 (PRDX5), S100A6, calreticulin (CALR) and cathepsin D (CTSD), which were validated by western blot. Furthermore, upstream regulators including PDGF-B, PDGFR-β, Akt, eIF4E and p70s6K were found significantly increased in the gastric cancer tissues. In addition, silencing of PRDX5 and PDGF-B suppressed the proliferation of gastric cancer cells in vitro. The administration of exogenous PDGF-BB recovered the reduced expression of PDGF-B signaling pathway in PDGF-B knockdown cells. Taken together, our findings suggested that PDGF-B signaling pathway plays an important role in the regulation of gastric cancer proliferation and the inhibition of this pathway may be a potential approach for treatment of gastric cancer.

Chromosomal breaks at FRA18C: association with reduced DOK6 expression, altered oncogenic signaling and increased gastric cancer survival

Chromosomal rearrangements are common in cancer. More than 50% occur in common fragile sites and disrupt tumor suppressors. However, such rearrangements are not known in gastric cancer. Here we report recurrent 18q2 breakpoints in 6 of 17 gastric cancer cell lines. The rearranged chromosome 18, t(9;18), in MKN7 cells was flow sorted and identified by reverse chromosome painting. High-resolution tiling array hybridization mapped breakpoints to DOK6 (docking protein 6) intron 4 in FRA18C (18q22.2) and an intergenic region in 9q22.2. The same rearrangement was detected by FISH in 22% of 99 primary gastric cancers. Intron 4 truncation was associated with reduced DOK6 transcription. Analysis of The Cancer Genome Atlas stomach adenocarcinoma cohort showed significant correlation of DOK6 expression with histological and molecular phenotypes. Multiple oncogenic signaling pathways (gastrin-CREB, NGF-neurotrophin, PDGF, EGFR, ERK, ERBB4, FGFR1, RAS, VEGFR2 and RAF/MAP kinase) known to be active in aggressive gastric cancers were strikingly diminished in gastric cancers with low DOK6 expression. Median survival of patients with low DOK6-expressing tumors was 2100 days compared with 533 days in patients with high DOK6-expressing tumors (log-rank P = 0.0027). The level of DOK6 expression in tumors predicted patient survival independent of TNM stage. These findings point to new functions of human DOK6 as an adaptor that interacts with diverse molecular components of signaling pathways. Our data suggest that DOK6 expression is an integrated biomarker of multiple oncogenic signals in gastric cancer and identify FRA18C as a new cancer-associated fragile site.

Lymphatic and vascular markers in an optic nerve crush model in rat

Only few tissues lack lymphatic supply, such as the CNS or the inner eye. However, if the scleral border is compromised due to trauma or tumor, lymphatics are detected in the eye. Since the situation in the optic nerve (ON), part of the CNS, is not clear, the aim of this study is to screen for the presence of lymphatic markers in the healthy and lesioned ON. Brown Norway rats received an unilateral optic nerve crush (ONC) with defined force, leaving the dura intact. Lesioned ONs and unlesioned contralateral controls were analyzed 7 days (n = 5) and 14 days (n = 5) after ONC, with the following markers: PDGFRb (pericyte), Iba1 (microglia), CD68 (macrophages), RECA (endothelial cell), GFAP (astrocyte) as well as LYVE-1 and podoplanin (PDPN; lymphatic markers). Rat skin sections served as positive controls and confocal microscopy in single optical section mode was used for documentation. In healthy ONs, PDGFRb is detected in vessel-like structures, which are associated to RECA positive structures. Some of these PDGFRb⁺/RECA⁺ structures are closely associated with LYVE-1⁺ cells. Homogenous PDPN-immunoreactivity (IR) was detected in healthy ON without vascular appearance, showing no co-localization with LYVE-1 or PDGFRb but co-localization with GFAP. However, in rat skin controls PDPN-IR was co-localized with LYVE-1 and further with RECA in vessel-like structures. In lesioned ONs, numerous PDGFRb⁺ cells were detected with network-like appearance in the lesion core. The majority of these PDGFRb⁺ cells were not associated with RECA-IR, but were immunopositive for Iba1 and CD68. Further, single LYVE-1⁺ cells were detected here. These LYVE-1⁺ cells were Iba1-positive but PDPN-negative. PDPN-IR was also clearly absent within the lesion site, while LYVE-1⁺ and PDPN⁺ structures were both unaltered outside the lesion. In the lesioned area, PDGFRb⁺/Iba1⁺/CD68⁺ network-like cells without vascular association might represent a subtype of microglia/macrophages, potentially involved in repair and phagocytosis. PDPN was detected in non-lymphatic structures in the healthy ON, co-localizing with GFAP but lacking LYVE-1, therefore most likely representing astrocytes. Both, PDPN and GFAP positive structures are absent in the lesion core. At both time points investigated, no lymphatic structures can be identified in the lesioned ON. However, single markers used to identify lymphatics, detected non-lymphatic structures, highlighting the importance of using a panel of markers to properly identify lymphatic structures.

The Role of PDGFs and PDGFRs in Colorectal Cancer

Introduction. Colorectal cancer (CRC) is an important cause of morbidity and mortality worldwide. Angiogenesis was reported as one important mechanism activated in colorectal carcinogenesis. Tumor microenvironment associated angiogenesis involves a large spectrum of signaling molecules and deciphering their role in colorectal carcinogenesis still represents a major challenge. The aim of our study is to point out the diagnosis and prediction role of PDGF family and their receptors in colorectal carcinogenesis. Material and Methods. A systematic search in Medline and PubMed for studies reporting the role of platelet-derived growth factors (PDGFs) and their receptors (PDGFRs) in tumor biology related to CRC was made. Results. PDGFs are important growth factors for normal tissue growth and division, with an important role in blood vessel formation. PDGFs/PDGFRs signaling pathway has been demonstrated to be involved in angiogenesis mainly by targeting pericytes and vascular smooth muscle cells. High levels of PDGF-BB were reported in CRC patients compared to those with adenomas, while elevated levels of PDGFR α/β in the stroma of CRC patients were correlated with invasion and metastasis. Moreover, PDGF-AB and PDGF-C were correlated with early diagnosis, cancer grading, and metastatic disease. Conclusions. Both PDGFs and PDGFRs families play an important role in colorectal carcinogenesis and could be considered to be investigated as useful biomarkers both for diagnosis and treatment of CRC.

Clinical significance of platelet-derived growth factor receptor-β gene expression in stage II/III gastric cancer with S-1 adjuvant chemotherapy

Overall survival remains unsatisfactory in stage II/III gastric cancer, even after curative surgery and adjuvant chemotherapy. Platelet-derived growth factor receptor-β (PDGFR-β) is associated with the proliferation of cancer cells. The present study therefore investigated the association of PDGFR-β gene expression with patient outcome in 134 stage II/III gastric cancer patients who received adjuvant chemotherapy with S-1. Relative PDGFR-β gene expression was measured in surgical cancer tissue and adjacent normal mucosa specimens by reverse transcription-quantitative polymerase chain reaction. The PDGFR-β gene expression levels were found to be significantly higher in the cancer tissues compared with the adjacent normal mucosa. A high level of PDGFR-β gene expression was associated with a significantly poorer 5-year overall survival rate compared with a low level of PDGFR-β expression. Upon multivariate analysis, PDGFR-β gene expression was found to be an independent predictor of survival. Overall, the study indicates that PDGFR-β overexpression in gastric cancer tissues is a useful independent predictor of outcome in patients with stage II/III gastric cancer who receive adjuvant chemotherapy with S-1.

Expression of CAF-Related Proteins Is Associated with Histologic Grade of Breast Phyllodes Tumor

Purpose. The purpose of this study was to investigate the expression of cancer-associated fibroblast- (CAF-) related proteins and the implications in breast phyllodes tumor (PT). Methods. Tissue microarrays of 194 PT cases (151 benign PT, 27 borderline PT, and 16 malignant PT) were constructed. We performed immunohistochemical staining for CAF-related proteins (podoplanin, prolyl 4-hydroxylase, FAPα, S100A4, PDGFR α/β, and NG2) and analyzed the results according to clinicopathologic parameters. Results. Expression of PDGFRα and PDGFRβ in the stromal component increased with increasing histologic grade of PT (p = 0.003 and p = 0.034, resp.). Among clinicopathologic parameters, only expression of FAPα in stroma was associated with distant metastasis (p = 0.002). In univariate analysis, stromal expression of PDGFRα was associated with shorter overall survival (p = 0.002). In Cox multivariate analysis, stromal overgrowth and PDGFRα stromal positivity were associated with shorter overall survival (p = 0.006 and p = 0.050, resp.). Furthermore, expression of PDGFRβ in stroma was associated with shorter overall survival in patients with malignant PT (p = 0.041). Conclusion. Stromal expression of PDGFRα and PDGFRβ increased with increasing histologic grade of PT. In addition, PDGFR stromal positivity was associated with shorter overall survival. These results suggest that CAFs are associated with breast PT progression.

Kallikrein-related peptidases (KLKs) and the hallmarks of cancer

The kallikrein-related peptidases (KLKs) represent the largest family of serine proteases within the human genome and are expressed in various tissues. Although they regulate several important physiological functions, KLKs have also been implicated in numerous pathophysiological processes, including cancer. Growing evidence describing the deregulation of KLK expression and secretion, as well as activation in various malignancies, has uncovered their potential as mediators of cancer progression, biomarkers of disease and as candidate therapeutic targets. The diversity of signalling pathways and proteolytic cascades involving KLKs and their downstream targets appears to affect cancer biology through multiple mechanisms, including those related to the hallmarks of cancer. The aim of this review is to provide an update on the importance of KLK-driven molecular pathways in relation to cancer cell traits associated with the hallmarks of cancer and to highlight their potential in personalized therapeutics.

Targeting Angiogenesis in Cancer Therapy: Moving Beyond Vascular Endothelial Growth Factor

Angiogenesis, or the formation of new capillary blood vessels, occurs primarily during human development and reproduction; however, aberrant regulation of angiogenesis is also a fundamental process found in several pathologic conditions, including cancer. As a process required for invasion and metastasis, tumor angiogenesis constitutes an important point of control of cancer progression. Although not yet completely understood, the complex process of tumor angiogenesis involves highly regulated orchestration of multiple signaling pathways. The proangiogenic signaling molecule vascular endothelial growth factor (VEGF) and its cognate receptor (VEGF receptor 2 [VEGFR-2]) play a central role in angiogenesis and often are highly expressed in human cancers, and initial clinical efforts to develop antiangiogenic treatments focused largely on inhibiting VEGF/VEGFR signaling. Such approaches, however, often lead to transient responses and further disease progression because angiogenesis is regulated by multiple pathways that are able to compensate for each other when single pathways are inhibited. The platelet-derived growth factor (PDGF) and PDGF receptor (PDGFR) and fibroblast growth factor (FGF) and FGF receptor (FGFR) pathways, for example, provide potential escape mechanisms from anti-VEGF/VEGFR therapy that could facilitate resumption of tumor growth. Accordingly, more recent treatments have focused on inhibiting multiple signaling pathways simultaneously. This comprehensive review discusses the limitations of inhibiting VEGF signaling alone as an antiangiogenic strategy, the importance of other angiogenic pathways including PDGF/PDGFR and FGF/FGFR, and the novel current and emerging agents that target multiple angiogenic pathways for the treatment of advanced solid tumors.

IMPLICATIONS FOR PRACTICE

Significant advances in cancer treatment have been achieved with the development of antiangiogenic agents, the majority of which have focused on inhibition of the vascular endothelial growth factor (VEGF) pathway. VEGF targeting alone, however, has not proven to be as efficacious as originally hoped, and it is increasingly clear that there are many interconnected and compensatory pathways that can overcome VEGF-targeted inhibition of angiogenesis. Maximizing the potential of antiangiogenic therapy is likely to require a broader therapeutic approach using a new generation of multitargeted antiangiogenic agents.

PDGF receptors in tumor biology: prognostic and predictive potential

PDGF receptors (PDGFRs) exert cell type-specific effects in many different tumor types. They are emerging as key regulators of mesenchymal cells of the tumor microenvironment, and of many common malignancies, such as cancer of the breast, colon and prostate. In some tumor types PDGFRs are genetically activated and are thus directly involved in stimulation of malignant cell growth. Recent studies have uncovered clinically relevant variations in stromal PDGFR expression. High stromal PDGFRβ expression or activation is associated with poor prognosis in breast and prostate cancer. Indications of prognostic significance of stromal PDGFRβ expression in various GI tract tumor types also exist. The prognostic significance of PDGFRα and β in malignant cells of common epithelial tumor types should be further studied. Collectively data suggest that continued characterization of PDGFR expression in human tumors should present opportunities for improved accuracy in prognosis and also allow novel biomarker-based clinical studies exploring the efficacy of PDGFR-directed tumor therapies.

Platelet-derived growth factors induced lymphangiogenesis: evidence, unanswered questions and upcoming challenges

Crosstalk between angiogenesis and lymphangiogenesis in embryonic development continues during postnatal life and has specific mechanisms involving factors that initiate activation of the intracellular cascade for their specific receptors. Platelet-derived growth factors (PDGFs) and their corresponding receptors (PDGFRs) are known as important regulators of blood vessel development in both normal and pathologic angiogenesis. Despite some recent papers which reported a potential role of the PDGF/PDGFR axis in lymphatic spread of tumor cells, a few papers have suggested the potential role of PDGFs in tumor lymphangiogenesis development. The present paper summarizes the potential lymphangiogenic role of the PDGF/PDGFR axis, underlying upcoming challenges in the field.

Combining molecular targeted drugs to inhibit both cancer cells and activated stromal cells in gastric cancer

Recent studies have revealed that PDGF plays a role in promoting progressive tumor growth in several cancers, including gastric cancer. Cancer-associated fibroblasts, pericytes, and lymphatic endothelial cells in stroma express high levels of PDGF receptor (PDGF-R); cancer cells and vascular endothelial cells do not. Mammalian target of rapamycin (mTOR) is a serine/threonine kinase that increases the production of proteins that stimulate key cellular processes such as cell growth and proliferation, cell metabolism, and angiogenesis. In the present study, we examined the effects of PDGF-R tyrosine kinase inhibitor (nilotinib) and mTOR inhibitor (everolimus) on tumor stroma in an orthotopic nude mice model of human gastric cancer. Expression of PDGF-B and PDGF-Rβ mRNAs was associated with stromal volume. Treatment with nilotinib did not suppress tumor growth but significantly decreased stromal reactivity, lymphatic invasion, lymphatic vessel area, and pericyte coverage of tumor microvessels. In contrast, treatment with everolimus decreased tumor growth and microvessel density but not stromal reactivity. Nilotinib and everolimus in combination reduced both the growth rate and stromal reaction. Target molecule-based inhibition of cancer-stromal cell interaction appears promising as an effective antitumor therapy.

Prognostic impact of major receptor tyrosine kinase expression in gastric cancer

BACKGROUND

Various kinds of molecular targeted drugs to inhibit receptor tyrosine kinases (RTKs) have been recently developed. The relationship between the expression status of major RTKs and prognosis in gastric cancer remains unclear. We conducted a multicenter study to evaluate the prognostic impact of the expression of epidermal growth factor receptor (EGFR), c-Met, platelet-derived growth factor receptor (PDGFR), and c-Kit in gastric cancer.

METHODS

This study included 153 gastric cancer patients who underwent gastrectomy at 9 institutions between 2000 and 2006. Expression status of EGFR, c-Met, PDGFR, and c-Kit were evaluated with immunohistochemistry (IHC) centrally. Overall survival based on RTK expression status was statistically compared. Cox multivariate analysis was conducted to adjust for potentially confounding factors.

RESULTS

The positive rates for EGFR, c-Met, PDGFR, and c-Kit were 14.4, 24.8, 41.2, and 11.1 %, respectively. Significant interactions with expression status were observed for pathological N stage with EGFR; HER2-status with c-Met; tumor location, histology, and pathological N stage with PDGFR; and no examined variables with c-Kit. Concomitant HER2 positivity was observed for 0.7 % of tumors positive for EGFR, 3.9 % for c-Met, 4.6 % for PDGFR, and 1.3 % for c-Kit. There were some differences in overall survival between patients with or without RTK expression, but only c-Kit expression showed a significant survival difference in Cox multivariate analysis (P = 0.046).

CONCLUSIONS

Our multicenter study indicated that IHC expression of 4 RTKs had some prognostic impact and that c-Kit-positive status may be a significant indicator of good prognosis in gastric cancer patients.

Targeting the PDGF signaling pathway in tumor treatment

Platelet-derived growth factor (PDGF) isoforms and PDGF receptors have important functions in the regulation of growth and survival of certain cell types during embryonal development and e.g. tissue repair in the adult. Overactivity of PDGF receptor signaling, by overexpression or mutational events, may drive tumor cell growth. In addition, pericytes of the vasculature and fibroblasts and myofibroblasts of the stroma of solid tumors express PDGF receptors, and PDGF stimulation of such cells promotes tumorigenesis. Inhibition of PDGF receptor signaling has proven to useful for the treatment of patients with certain rare tumors. Whether treatment with PDGF/PDGF receptor antagonists will be beneficial for more common malignancies is the subject for ongoing studies.

Angiogenesis stimulated by human kallikrein-related peptidase 12 acting via a platelet-derived growth factor B-dependent paracrine pathway

KLK12, a kallikrein peptidase, is thought to take part in the control of angiogenesis. Our analysis of the secretome of endothelial cells (ECs) that had been treated with KLK12 showed that KLK12 converts the extracellular matrix- or membrane-bound precursor of platelet-derived growth factor B (PDGF-B) into a soluble form. Both PDGF-B and vascular endothelial growth factor A (VEGF-A) take part in the induction of angiogenesis by KLK12 in a coculture model of angiogenesis that mimics endothelial tubule formation. We used a cellular approach to analyze the interplay between KLK12, PDGF-B, and VEGF-A and showed that release of PDGF-B by KLK12 leads to the fibroblast-mediated secretion of VEGF-A. This then stimulates EC differentiation and the formation of capillary tube-like structures. Thus, KLK12 favors the interaction of ECs and stromal cells. The released PDGF-B acts as a paracrine factor that modulates VEGF-A secretion by stromal cells, which ultimately leads to angiogenesis. Moreover, the genes encoding KLK12 and PDGFB are both expressed in ECs and up-regulated in tumor cells kept under hypoxic conditions, which is consistent with the physiological involvement of KLK12 in PDGF-B maturation.

The gastrointestinal tumor microenvironment

Over the past decade, the microenvironment of gastrointestinal tumors has gained increasing attention because it is required for tumor initiation, progression, and metastasis. The tumor microenvironment has many components and has been recognized as one of the major hallmarks of epithelial cancers. Although therapeutic strategies for gastrointestinal cancer have previously focused on the epithelial cell compartment, there is increasing interest in reagents that alter the microenvironment, based on reported interactions among gastrointestinal epithelial, stromal, and immune cells during gastrointestinal carcinogenesis. We review the different cellular components of the gastrointestinal tumor microenvironment and their functions in carcinogenesis and discuss how improving our understanding of the complex stromal network could lead to new therapeutic strategies.