Placental growth factor (PlGF) enhances breast cancer cell motility by mobilising ERK1/2 phosphorylation and cytoskeletal rearrangement

Excessive endometrial PlGF- Rac1 signalling underlies endometrial cell stiffness linked to pre-eclampsia

Cell stiffness is regulated by dynamic interaction between ras-related C3 botulinum toxin substrate 1 (Rac1) and p21 protein-activated kinase 1 (PAK1) proteins, besides other biochemical and molecular regulators. In this study, we investigated how the Placental Growth Factor (PlGF) changes endometrial mechanics by modifying the actin cytoskeleton at the maternal interface. We explored the global effects of PlGF in endometrial stromal cells (EnSCs) using the concerted approach of proteomics, atomic force microscopy (AFM), and electrical impedance spectroscopy (EIS). Proteomic analysis shows PlGF upregulated RhoGTPases activating proteins and extracellular matrix organization-associated proteins in EnSCs. Rac1 and PAK1 transcript levels, activity, and actin polymerization were significantly increased with PlGF treatment. AFM further revealed an increase in cell stiffness with PlGF treatment. The additive effect of PlGF on actin polymerization was suppressed with siRNA-mediated inhibition of Rac1, PAK1, and WAVE2. Interestingly, the increase in cell stiffness by PlGF treatment was pharmacologically reversed with pravastatin, resulting in improved trophoblast cell invasion. Taken together, aberrant PlGF levels in the endometrium can contribute to an altered pre-pregnancy maternal microenvironment and offer a unifying explanation for the pathological changes observed in conditions such as pre-eclampsia (PE).

Pharmacotranscriptomic profiling of resistant triple-negative breast cancer cells treated with lapatinib and berberine shows upregulation of PI3K/Akt signaling under cytotoxic stress

Triple-negative breast cancer (TNBC) is the most incurable type of breast cancer, accounting for 15-20% of breast cancer cases. Lapatinib is a dual tyrosine kinase inhibitor targeting EGFR and Her2, and berberine (BBR) is a plant-based alkaloid suggested to inhibit several cancer signaling pathways. We previously reported that lapatinib activates the Akt oncoprotein in MDA-MB231 TNBC cells. The present study determined the mechanism(s) of Akt activation in response to lapatinib, BBR, and capivasertib (Akt inhibitor) as well as the role of Akt signaling in chemoresistance in TNBC cells. Genetic profiles of 10 TNBC cell lines and patients were analyzed using datasets obtained from Gene Expression Omnibus and The Cancer Genome Atlas Database. Then, the effects of lapatinib, BBR, and capivasertib on treated MDA-MB231 and MCF-7 cell lines were studied using cytotoxicity, immunoblot, and RNA-sequencing analyses. For further confirmation, we also performed real-time PCR for genes associated with PI3K signaling. MDA-MB231 and MCF-7 cell lines were both strongly resistant to capivasertib largely due to significant Akt activation in both breast cancer cell lines, while lapatinib and BBR only enhanced Akt signaling in MDA-MB231 cells. Next-generation sequencing, functional enrichment analysis, and immunoblot revealed downregulation of CDK6 and DNMT1 in response to lapatinib and BBR lead to a decrease in cell proliferation. Expression of placental, fibroblast growth factor, and angiogenic biomarker genes, which are significantly associated with Akt activation and/or dormancy in breast cancer cells, was significantly upregulated in TNBC cells treated with lapatinib and BBR. Lapatinib and BBR activate Akt through upregulation of alternative signaling, which lead to chemoresistance in TNBC cell. In addition, lapatinib overexpresses genes related to PI3K signaling in resistant TNBC cell model.

Germline competent mesoderm: the substrate for vertebrate germline and somatic stem cells?

In vitro production of tissue-specific stem cells [e.g. haematopoietic stem cells (HSCs)] is a key goal of regenerative medicine. However, recent efforts to produce fully functional tissue-specific stem cells have fallen short. One possible cause of shortcomings may be that model organisms used to characterize basic vertebrate embryology (Xenopus, zebrafish, chick) may employ molecular mechanisms for stem cell specification that are not conserved in humans, a prominent example being the specification of primordial germ cells (PGCs). Germ plasm irreversibly specifies PGCs in many models; however, it is not conserved in humans, which produce PGCs from tissue termed germline-competent mesoderm (GLCM). GLCM is not conserved in organisms containing germ plasm, or even in mice, but understanding its developmental potential could unlock successful production of other stem cell types. GLCM was first discovered in embryos from the axolotl and its conservation has since been demonstrated in pigs, which develop from a flat-disc embryo like humans. Together these findings suggest that GLCM is a conserved basal trait of vertebrate embryos. Moreover, the immortal nature of germ cells suggests that immortality is retained during GLCM specification; here we suggest that the demonstrated pluripotency of GLCM accounts for retention of immortality in somatic stem cell types as well.

This article has an associated Future Leaders to Watch interview with the author of the paper.

Summary: Recent findings that germline and stem cell specification may differ between species may have important implications for regenerative medicine and the future of stem cell biology.

Long non-coding RNA ARAP1-AS1 contributes to cell proliferation and migration in clear cell renal cell carcinoma via the miR-361-3p/placental growth factor axis

Clear cell renal cell carcinoma (ccRCC) is an aggressive malignancy with a poor prognosis. Therefore, investigating the molecular mechanism of ccRCC is important for ccRCC treatment. Here, we aimed to explore the effect of the long non-coding RNA ARAP1-AS1/miR-361-3p/PGF axis on ccRCC. The expression of lncRNA ARAP1-AS1, miR-361-3p, and placental growth factor (PGF) in ccRCC cells was verified by real-time quantitative PCR (RT-qPCR). The influence of the ARAP1-AS1/miR-361-3p/PGF axis on ccRCC cells was identified using the Cell Counting Kit-8 (CCK-8) assay, colony formation assay, flow cytometry, and wound healing assay. The interaction between ARAP1-AS1, miR-361-3p, and PGF was confirmed by bioinformatics analysis and luciferase assay. The results showed that the levels of ARAP1-AS1 and PGF increased in ccRCC cells, while miR-361-3p expression decreased. Cell functional experiments showed that cell proliferation and migration were inhibited by silencing ARAP1-AS1 or PGF, while miR-361-3p inhibitor or PGF overexpression could relieve the inhibitory effect of silencing ARAP1-AS1 on ccRCC cells. Moreover, ARAP1-AS1 sponges miR-361-3p to increase PGF expression. In conclusion, our study revealed that ARAP1-AS1 enhanced the malignancy of ccRCC cells by regulating the miR-361-3p/PGF axis.

Multi-Omics Characterization of the 4T1 Murine Mammary Gland Tumor Model

Background: Tumor models are critical for our understanding of cancer and the development of cancer therapeutics. The 4T1 murine mammary cancer cell line is one of the most widely used breast cancer models. Here, we present an integrated map of the genome, transcriptome, and immunome of 4T1.

Results: We found Trp53 (Tp53) and Pik3g to be mutated. Other frequently mutated genes in breast cancer, including Brca1 and Brca2, are not mutated. For cancer related genes, Nav3, Cenpf, Muc5Ac, Mpp7, Gas1, MageD2, Dusp1, Ros, Polr2a, Rragd, Ros1, and Hoxa9 are mutated. Markers for cell proliferation like Top2a, Birc5, and Mki67 are highly expressed, so are markers for metastasis like Msln, Ect2, and Plk1, which are known to be overexpressed in triple-negative breast cancer (TNBC). TNBC markers are, compared to a mammary gland control sample, lower (Esr1), comparably low (Erbb2), or not expressed at all (Pgr). We also found testis cancer antigen Pbk as well as colon/gastrointestinal cancer antigens Gpa33 and Epcam to be highly expressed. Major histocompatibility complex (MHC) class I is expressed, while MHC class II is not. We identified 505 single nucleotide variations (SNVs) and 20 insertions and deletions (indels). Neoantigens derived from 22 SNVs and one deletion elicited CD8⁺ or CD4⁺ T cell responses in IFNγ-ELISpot assays. Twelve high-confidence fusion genes were observed. We did not observe significant downregulation of mismatch repair (MMR) genes or SNVs/indels impairing their function, providing evidence for 6-thioguanine resistance. Effects of the integration of the murine mammary tumor virus were observed at the genome and transcriptome level.

Conclusions: 4T1 cells share substantial molecular features with human TNBC. As 4T1 is a common model for metastatic tumors, our data supports the rational design of mode-of-action studies for pre-clinical evaluation of targeted immunotherapies.

Role of VEGFs/VEGFR-1 Signaling and its Inhibition in Modulating Tumor Invasion: Experimental Evidence in Different Metastatic Cancer Models

The vascular endothelial growth factor (VEGF) family members, VEGF-A, placenta growth factor (PlGF), and to a lesser extent VEGF-B, play an essential role in tumor-associated angiogenesis, tissue infiltration, and metastasis formation. Although VEGF-A can activate both VEGFR-1 and VEGFR-2 membrane receptors, PlGF and VEGF-B exclusively interact with VEGFR-1. Differently from VEGFR-2, which is involved both in physiological and pathological angiogenesis, in the adult VEGFR-1 is required only for pathological angiogenesis. Besides this role in tumor endothelium, ligand-mediated stimulation of VEGFR-1 expressed in tumor cells may directly induce cell chemotaxis and extracellular matrix invasion. Furthermore, VEGFR-1 activation in myeloid progenitors and tumor-associated macrophages favors cancer immune escape through the release of immunosuppressive cytokines. These properties have prompted a number of preclinical and clinical studies to analyze VEGFR-1 involvement in the metastatic process. The aim of the present review is to highlight the contribution of VEGFs/VEGFR-1 signaling in the progression of different tumor types and to provide an overview of the therapeutic approaches targeting VEGFR-1 currently under investigation.

PlGF signaling and macrophage repolarization contribute to the anti-neoplastic effect of metformin

Placental growth factor (PlGF) related signaling pathway has been shown to have close relationship with the progression of cancers. Metformin has been reported to have an inhibitory effect on PlGF expression in a breast cancer model. However, little is known about whether the anti-neoplastic activity of metformin is contributed by its inhibitory effect on PlGF expression. Protein, mRNA and secretion levels of PlGF were tested and the proliferation of cancer cells was determined. After treatment of metformin, BALB/c mice bearing 4T1 tumors were sacrificed and immunohistochemistry staining of the tumor sections was obtained. Baseline expression of autocrine PlGF varied between different breast cancer cell lines, while the expression of vascular endothelial growth factor receptor-1 (VEGFR-1) was comparable between cell lines. Other clinical data showed that the expression of PlGF other than VEGFR-1 had a prognostic value for patients with breast cancers. Metformin significantly decreased the secretion and mRNA levels of PlGF, which greatly contributed to its inhibitory effect on the proliferation of breast cancer cells with high P1GF expression. The unresponsiveness of tumor cells with low PlGF expression to genetic silencing was reversed by the supplementation of exogenous PlGF. Systemic metformin administration apparently inhibited the in vivo growth of 4T1 carcinoma, which was accompanied by the repolarization of macrophages from M2 to M1. These findings indicated that both autocrine and paracrine PlGF signaling and macrophage repolarization are involved in the progression of breast cancer, which could be targeted by metformin.

Aflibercept regulates retinal inflammation elicited by high glucose via the PlGF/ERK pathway

Diabetic retinopathy (DR) is a secondary complication of diabetes. DR can cause irreversible blindness, and its pathogenesis is considered multifactorial. DR can progress from non-proliferative DR to proliferative DR, characterized by retinal neovascularization. The main cause of vision loss in diabetic patients is diabetic macular edema, caused by vessel leakage and blood retinal barrier breakdown. Currently, aflibercept is an anti-VEGF approved for diabetic macular edema. Aflibercept can bind several members of vascular permeability factors, namely VEGF-A, B, and PlGF. We analyzed the aflibercept-PlGF complex at molecular level, through an in silico approach. In order to explore the role of PlGF in DR, we treated primary human retinal endothelial cells (HRECs) and mouse retinal epithelial cells (RPEs) with aflibercept and an anti-PlGF antibody. We explored the hypothesis that aflibercept has anti-inflammatory action through blocking of PlGF signaling and the ERK axis in an in vitro and in vivo model of DR. Both aflibercept and the anti-PlGF antibody exerted protective effects on retinal cells, by inhibition of the ERK pathway. Moreover, aflibercept significantly decreased (p < 0.05) the expression of TNF-α in an in vitro and in vivo model of DR. Therefore, our data suggest that inhibition of PlGF signaling, or a selective blocking, may be useful in the management of early phases of DR when the inflammatory process is largely involved.

Multifaceted Role of the Placental Growth Factor (PlGF) in the Antitumor Immune Response and Cancer Progression

The sharing of molecules function that affects both tumor growth and neoangiogenesis with cells of the immune system creates a mutual interplay that impairs the host’s immune response against tumor progression. Increasing evidence shows that tumors are able to create an immunosuppressive microenvironment by recruiting specific immune cells. Moreover, molecules produced by tumor and inflammatory cells in the tumor microenvironment create an immunosuppressive milieu able to inhibit the development of an efficient immune response against cancer cells and thus fostering tumor growth and progression. In addition, the immunoediting could select cancer cells that are less immunogenic or more resistant to lysis. In this review, we summarize recent findings regarding the immunomodulatory effects and cancer progression of the angiogenic growth factor namely placental growth factor (PlGF) and address the biological complex effects of this cytokine. Different pathways of the innate and adaptive immune response in which, directly or indirectly, PlGF is involved in promoting tumor immune escape and metastasis will be described. PlGF is important for building up vascular structures and functions. Although PlGF effects on vascular and tumor growth have been widely summarized, its functions in modulating the immune intra-tumoral microenvironment have been less highlighted. In agreement with PlGF functions, different antitumor strategies can be envisioned.

CYFRA 21-1 and Placental Growth Factor as Screening Markers for Endometriosis

Background

This study evaluated the performance of serum CYFRA 21-1 and placental growth factor (PIGF) as screening markers for endometriosis.

Material/Methods

In this prospective study included 81 female patients who underwent laparoscopy to treat benign ovarian tumors. Serum samples were obtained from all study patients before surgery. Serum marker levels, including CYFRA 21-1, PIGF, cancer antigen (CA)125, CA19-9, and human epididymis protein 4 (HE4) were measured using a fluorescence immunoassay technique.

Results

Forty of the patients were diagnosed with endometriosis (the study group) and 41 women were diagnosed with other benign ovarian tumors (the control group). Mean serum CYFRA 21-1 and PIGF levels were not different between these 2 groups (P=0.179 and P=0.865, respectively). Elevated serum CA125 levels (>35 U/mL) and lower CYFRA 21-1 levels (≤2.29 ng/mL) were more frequently observed in the endometriosis study group than in the control group (P<0.0001, and P=048, respectively). High serum PIGF levels (>14.2 pg/mL) were observed in both groups (P=0.226). Mean serum CA19-9 levels and HE4 levels, as well as the ROMA (risk of ovarian malignancy Algorithm) score were similar between the 2 groups. Sensitivity (95.0%) and negative predictive value (NPV) (80.0%) of CYFRA 21-1 for diagnosing endometriosis were higher than those of CA125 (sensitivity 67.5%, NPV 74.5%) and PIGF (sensitivity 20.0%, NPV 53.6%). However, the specificity (PIGF 90.2%, CA125 92.7%) and positive predictive value (PPV) (PIGF 66.7%, CA125 87.1%) of PIGF and CA125 for diagnosing endometriosis were higher than those of CYFRA 21-1 (specificity 19.5%, PPV 53.5%).

Conclusions

CYFRA 21-1 and PIGF may be promising markers to identify patients with and without ovarian endometriosis.

β-hCG promotes epithelial ovarian cancer metastasis through ERK/MMP2 signaling pathway

Epithelial ovarian cancer (EOC) is the most lethal gynecologic malignancy, with typically extensive intraperitoneal implantation leading to poor prognosis. Our previous study preliminarily demonstrated β-hCG can promote tumorigenesis in immortalized nontumorigenic ovarian epithelial cells. In this study, the roles and mechanisms of β-hCG in regulating EOC proliferation and metastasis were thoroughly explored. First, histologically, β-hCG was aberrantly overexpressed in human EOC metastatic tissues, and significantly correlated with FIGO stage, tumor size, differentiation, histologic grade and high grade serous ovarian carcinoma (HGSOC) (P < 0.05). However, serologically, β-hCG expression showed no significant difference between EOC and nonmalignant ovarian patients. Second, β-hCG was confirmed to have no significant effects on EOC proliferation in vitro and in vivo, while β-hCG upregulation was proven to promote migration and invasion ability in ES-2 and OVCAR-3 cells in vitro (P < 0.05), and β-hCG downregulation in SKOV3 cells had the opposite effect. Moreover, more invadopodia protrusions, mitochondria accumulations and cytoskeletal rearrangements were observed in β-hCG-overexpressing ES-2 cells, while β-hCG-depleted SKOV3 cells produced the opposite effect. Furthermore, β-hCG was confirmed to clearly facilitate intraperitoneal metastasis in nude mouse orthotopic ovarian xenograft models. Importantly, these effects of β-hCG were mediated by activation of the ERK/MMP2 signaling pathway, independently of luteinizing hormone/chorionic gonadotropin receptor (LHCGR) presence, and inhibition the pathway with the p-ERK1/2 inhibitor SCH772984 significantly impaired the tumor-promoting effects induced by β-hCG. Collectively, these data provide new insight into the roles and mechanisms of β-hCG in regulating EOC metastasis through ERK/MMP2 signaling pathway and may become a new target for therapeutic intervention.

MiR-507 inhibits the migration and invasion of human breastcancer cells through Flt-1 suppression

Vascular endothelial growth factor receptor-1/fms-related tyrosine kinase-1 (VEGFR-1/Flt-1) is a tyrosine kinase receptor that binds placental growth factor (PlGF). Flt-1 is also highly expressed in breast-cancer tissues and breast-cancer cell lines. However, the molecular mechanism by which Flt-1 promotes breast-cancer invasion and metastasis by binding to PlGF-1 is unclear. In this study, we discovered that PlGF-1 and Flt-1 played a key role in the migration and invasion of breast cancer. Flt-1 promoted the migration and chemotaxis of breast-cancer cells by binding to PlGF-1. In addition, Flt-1 was confirmed to be a direct target gene of miR-507. miR-507 up-regulation inhibited the invasion and metastasis of breast-cancer cells in vitro and in vivo. Flt-1 overexpression rescued the invasion partially caused by the ectopic expression of miR-507. miR-507 expression in breast-cancer tissues and cell lines was lower than that in adjacent non-neoplastic tissues and normal cells. Clinical analysis indicated that miR-507 was negatively correlated with tumor differentiation, lymphatic metastasis, and the expression of Flt-1 in breast cancer. Furthermore, we showed that miR-507 down-regulation was due to the hypermethylation of its promotor region. Our results indicated that miR-507 represented potential therapeutic targets in breast cancer by modulating Flt-1.

A new angiogenesis prognostic index with VEGFA, PlGF, and angiopoietin1 predicts survival in patients with advanced gastric cancer

BACKGROUND/AIM

The role of angiogenic factors in gastric cancer is not clear. We aimed to assess the role of vascular endothelial growth factor A (VEGFA), angiopoietin 1 (Ang-1), and placental growth factor (PlGF) in the prognosis of patients with advanced gastric cancer.

MATERIALS AND METHODS

Thirty consecutive patients treated with a modified DCF (docetaxel, cisplatin, and fluorouracil) regimen were included in the study. The plasma VEGFA, Ang-1, and PlGF levels of the patients before treatment and following two cycles of chemotherapy were measured and evaluated as prognostic factors.

RESULTS

Poor performance status and lower Ang-1 levels were correlated with poor overall survival (OS). No significant correlation between VEGFA or PlGF and OS was found. An angiogenesis prognostic index (API) based on the levels of VEGFA, Ang-1, and PlGF was found to be highly correlated with OS. Performance status and API were found as independent prognostic factors for OS. Furthermore, a decrease in VEGFA by 25% from the pretreatment level was also found as a prognostic factor for OS independent of response to DCF regimen.

CONCLUSION

Our results support the use of the new API including VEGFA, Ang-1, and PlGF levels in patients with advanced gastric cancer as a predictor of survival.

Placental Kisspeptins Differentially Modulate Vital Parameters of Estrogen Receptor-Positive and -Negative Breast Cancer Cells

Kisspeptins (KPs) are major regulators of trophoblast and cancer invasion. Thus far, limited and conflicting data are available on KP-mediated modulation of breast cancer (BC) metastasis; mostly based on synthetic KP-10, the most active fragment of KP. Here, we report for the first time comprehensive functional effects of term placental KPs on proliferation, adhesion, Matrigel invasion, motility, MMP activity and pro-inflammatory cytokine production in MDA-MB-231 (estrogen receptor-negative) and MCF-7 (estrogen receptor-positive). KPs were expressed at high level by term placental syncytiotrophoblasts and released in soluble form. Placental explant conditioned medium containing KPs (CM) significantly reduced proliferation of both cell types compared to CM without (w/o) KP (CM-w/o KP) in a dose- and time-dependent manner. In MDA-MB-231 cells, placental KPs significantly reduced adhesive properties, while increased MMP9 and MMP2 activity and stimulated invasion. Increased invasiveness of MDA-MB-231 cells after CM treatment was inhibited by KP receptor antagonist, P-234. CM significantly reduced motility of MCF-7 cells at all time points (2–30 hr), while it stimulated motility of MDA-MB-231 cells. These effects were reversed by P-234. Co-treatment with selective ER modulators, Tamoxifen and Raloxifene, inhibited the effect of CM on motility of MCF-7 cells. The level of IL-6 in supernatant of MCF-7 cells treated with CM was higher compared to those treated with CM-w/o KP. Both cell types produced more IL-8 after treatment with CM compared to those treated with CM-w/o KP. Taken together, our observations suggest that placental KPs differentially modulate vital parameters of estrogen receptor-positive and -negative BC cells possibly through modulation of pro-inflammatory cytokine production.

PlGF knockdown inhibited tumor survival and migration in gastric cancer cell via PI3K/Akt and p38MAPK pathways

The molecular signalling of placental growth factor (PlGF), a member of the vascular endothelial growth factor family, was not uncovered in human adenocarcinoma gastric cell line (AGS). The purpose of this study was to examine the inhibitory effects of PlGF knockdown on cell proliferation, apoptosis and migration through p38 mitogen-activated protein kinase (p38MAPK) and PI3K pathways in human adenocarcinoma gastric cell line (AGS). To study PlGF knockdown effect, AGS cells were treated with 40 pmol of small interfering RNA (siRNA) related to PlGF gene and also a scrambled siRNA as control. Trypan Blue and Anexin V staining of AGS cells treated with PlGF-specific siRNA showed induction of apoptosis. Wound healing assay and zymography indicated that cellular migration and matrix metalloproteinases activities were reduced in response to PlGF knockdown. Phosphorylation of Akt and p38MAPK was reduced in AGS cells treated with PlGF-specific siRNA. PlGF knockdown decreased transcripts of PI3K, Akt, p38MAPK, PCNA, Caspase-3, OCT3/OCT4 and CD44, but elevated p53 and SOX2 transcripts. Our results indicated that PlGF knockdown decreased migration and induced apoptosis through PI3K/Akt1 and p38MAPK signal transduction in AGS cells.

Antiangiogenic mechanisms and factors in breast cancer treatment

Breast cancer is known to metastasize in its latter stages of existence. The different angiogenic mechanisms and factors that allow for its progression are reviewed in this article. Understanding these mechanisms and factors will allow researchers to design drugs to inhibit angiogenic behaviors and control the rate of tumor growth.

Performance of Circulating Placental Growth Factor as A Screening Marker for Diagnosis of Ovarian Endometriosis: A Pilot Study

Background

The aim of this study is to compare the circulating placental growth factor (PlGF) concentration in women with and without endometrioma to verify the performance of this marker to diagnose the disease.

Materials and Methods

In this case-control study, thirteen women with histological diagnosis of ovarian endometriosis were compared with women without endometriosis disease. PlGF plasma levels of endometriotic patients and controls were investigated using a fluorescence immunoassay technique.

Results

PlGF showed a direct correlation with body mass index (BMI) only in the control group (P=0.013). After adjustment for BMI values, PlGF median value in endometriosis group (14.7 pg/mL) resulted higher than in control group (13.8 pg/ mL, P=0.004).

Conclusion

PlGF is a promising peripheral blood marker that can discriminate between patients with and without ovarian endometriosis.

VEGFR-1 Pseudogene Expression and Regulatory Function in Human Colorectal Cancer Cells

A large number of pseudogenes have been found to be transcribed in human cancers. However, only a few pseudogenes are functionally characterized. Here, we identified a transcribed pseudogene of VEGFR1, or fms-related tyrosine kinase 1 (FLT1), in human colorectal cancer cells. Interestingly, this pseudogene (designated as FLT1P1) was found to be transcribed bidirectionally and functionally modulated cognate VEGFR1 protein expression in the cells. Mechanistically, expression of FLT1P1 antisense transcript not only inhibited the VEGFR1 expression, but also inhibited non-cognate VEGF-A expression through interaction with miR-520a. Perturbation of FLT1P1 expression by RNA interference (RNAi) markedly inhibited tumor cell proliferation and xenograft tumor growth. This study identifies FLT1P1 antisense as a critical regulator of VEGFR1 and VEGF-A expression in colorectal cancer cells, and highlights its role in regulation of the pathogenesis of colorectal cancer.

IMPLICATIONS

The VEGFR1 pseudogene, FLT1P1, is a novel and functional regulator of VEGF signaling and its targeting could be an alternative strategy to modulate its cognate/target gene expression and downstream activity in cancer.

Reproduction and breast cancer risk

Reproduction is doubtlessly one of the main biological meanings of life. It is therefore not surprising that various aspects of reproduction impact on breast cancer risk. Various developmental levels may become targets of breast tumorigenesis. This review follows the chronologic sequence of events in the life of a female at risk, starting with the intrauterine development. Furthermore, the influence of both contraceptive measures and fertility treatment on breast cancer development is dealt with, as well as various pregnancy-associated factors, events, and perinatal outcomes. Finally, the contribution of breast feeding to a reduced breast cancer risk is discussed.

ERK1/2 and AKT are vital factors in regulation of the migration of rat Schwann cells

After peripheral nerve injury, Wallerian degeneration (WD) occurs in the distal nerve segment. During the process of degeneration, Schwann cells (SCs) dedifferentiate, proliferate and migrate to align in “bands of Büngner”, providing structural guidance and growth-promoting substrates to regenerating axons. The molecular signals that trigger SCs migration remain unclear. Here, we explored the molecular characteristics of the migration of cultured SCs prepared from rat sciatic nerves that had degenerated. The results revealed that elevated p-ERK1/2 was coupled with the migration of SCs, activated either by nerve degeneration or the addition of placenta growth factor. However, the inhibition of ERK1/2 activity, which activated the PI3K pathway, did not show a significant negative effect on SC migratory potential. Combined inhibition of ERK1/2 and AKT activity resulted in a significant decrease in SCs motility. These molecular characteristics suggest that both the ERK1/2 and AKT signals are involved in the migratory potential of SCs. It may be helpful to understand the process of nerve regeneration and perspective on promoting peripheral nerve regeneration.

Value of oncogenes for the prediction of brain metastases at initial diagnosis: a review of published data

Identifying cancer patients who are at high risk of developing brain metastases at initial diagnosis and applying effective intervention or monitoring strategies is of vital importance. Recent advances in the biology of brain metastases revealed that some oncogenes from primary tumors may be potential markers for identifying cancer patients likely to metastasize to the brain. We here summarize data on the mechanisms of brain metastases supporting the involvement of oncogene changes in the brain metastatic evolution. We also review the available evidence on clinical studies of oncogenes in the prediction of cancer patients with high incidence of brain metastases.

Placenta growth factor promotes migration through regulating epithelial-mesenchymal transition-related protein expression in cervical cancer

Epithelial-mesenchymal transition (EMT) plays an important role in cancer invasion and metastasis by enabling cancer cells to depart from the primary tumor, invade surrounding tissue and disseminate to distant organs. The existence and function of EMT in cervical cancer is poorly understood. Placental growth factor (PLGF) has been shown to associate with EMT in various cancers. However, whether PLGF is involved in EMT in cervical cancer remains unclear. Thus the present study examined the relationship between PLGF expression and EMT-related proteins in 110 cervical lesions samples. We detected that PLGF was expressed in 61.8% cervical lesion sections. In addition, PLGF expression is positively correlated with low expression level of E-cadherin and high expression level of vimentin. Serum samples and cervical lavage samples were collected from patients with pre-invasive and invasive lesion of uterine cervix or normal control group, the PLGF levels were determined by enzyme-linked immunosorbent assay (ELISA). We found that a significantly high level of PLGF could be detected both in serum and vaginal lavage compared with normal women group, and there is no significant difference between serum and lavage in PLGF level. In addition, whatever in lavage or in serum, the PLGF level in stage I and II was significantly higher than it in CINIII or cancer in situ. However, there is no significant difference between the stage I and stage II; we also found that exogenous PLGF promotes molecular changes of epithelial-mesenchymal transition (EMT) in siha cells. In addition, application of a specific EKR1/2 inhibitor could reverse the effects of PLGF. These findings suggested that PLGF could regulate the expression of EMT-related proteins and promote migration of siha cells through ERK/MAPK signaling pathway. Therapies that targets PLGF/Flt-1/ERK/MAPK signaling pathway may be beneficial in treatment of cervical cancer.

GABA(A) receptor pi (GABRP) stimulates basal-like breast cancer cell migration through activation of extracellular-regulated kinase 1/2 (ERK1/2)

Breast cancer is a heterogeneous disease comprised of distinct subtypes predictive of patient outcome. Tumors of the basal-like subtype have a poor prognosis due to inherent aggressiveness and the lack of targeted therapeutics. Basal-like tumors typically lack estrogen receptor-α, progesterone receptor and HER2/ERBB2, or in other words they are triple negative (TN). Continued evaluation of basal-like breast cancer (BLBC) biology is essential to identify novel therapeutic targets. Expression of the pi subunit of the GABA(A) receptor (GABRP) is associated with the BLBC/TN subtype, and herein, we reveal its expression also correlates with metastases to the brain and poorer patient outcome. GABRP expression in breast cancer cell lines also demonstrates a significant correlation with the basal-like subtype suggesting that GABRP functions in the initiation and/or progression of basal-like tumors. To address this postulate, we stably silenced GABRP in two BLBC cell lines, HCC1187 and HCC70 cells. Decreased GABRP reduces in vitro tumorigenic potential and migration concurrent with alterations in the cytoskeleton, specifically diminished cellular protrusions and expression of the BLBC-associated cytokeratins, KRT5, KRT6B, KRT14, and KRT17. Silencing GABRP also decreases phosphorylation of extracellular regulated kinase 1/2 (ERK1/2) in both cell lines and selective inhibition of ERK1/2 similarly decreases the basal-like cytokeratins as well as migration. Combined, these data reveal a GABRP-ERK1/2-cytokeratin axis that maintains the migratory phenotype of basal-like breast cancer. GABRP is a component of a cell surface receptor, thus, these findings suggest that targeting this new signaling axis may have therapeutic potential in BLBC.

Interaction of mesenchymal stem cells with fibroblast-like synoviocytes via cadherin-11 promotes angiogenesis by enhanced secretion of placental growth factor

Bone marrow-derived mesenchymal stem cells (MSC) exist in the synovium of patients with rheumatoid arthritis (RA), yet the role of MSC in RA is elusive. Placental growth factor (PlGF) expression is increased in RA synovial fluids, and blocking of PlGF attenuates progression of arthritis in mice. In this study, we observed that PlGF induced chemotaxis of MSC in a dose-dependent manner, which was blocked by anti-vascular endothelial growth factor receptor-1 peptide. MSC exposed to PlGF elicited increased phosphorylation of Akt and p38 MAPK. PlGF-mediated chemotaxis was inhibited by PI3K inhibitor (LY294002) and p38 MAPK inhibitor (SB203580), but not by ERK1/2 inhibitor (PD98059). Fibroblast-like synoviocytes (FLS) constitutively produced PlGF, but MSC released negligible amounts of PlGF. Of note, when FLS of RA patients and MSC were cocultured, PlGF production by FLS was significantly increased; such an increase was dependent on the number of added MSC. Moreover, coculture conditioned medium promoted chemotaxis of MSC and increased angiogenesis in Matrigel plugs assay, and these were suppressed by preincubation of the medium with anti-PlGF Ab. Transwell experiments revealed that MSC to FLS contact was required for the increase in PlGF production by coculture. Cadherin-11 was expressed both in FLS and MSC, and small interfering RNA knockdown of cadherin-11 in FLS significantly abrogated the enhanced PlGF production under coculture conditions. These data indicate that increased levels of PlGF in RA joints could induce the migration of MSC to the synovium, and interaction of migrated MSC with FLS via cadherin-11 may contribute to angiogenesis and chronic synovitis by enhancing the secretion of PlGF.

Unlocking Doors without Keys: Activation of Src by Truncated C-terminal Intracellular Receptor Tyrosine Kinases Lacking Tyrosine Kinase Activity

One of the best examples of the renaissance of Src as an open door to cancer has been the demonstration that just five min of Src activation is sufficient for transformation and also for induction and maintenance of cancer stem cells [1]. Many tyrosine kinase receptors, through the binding of their ligands, become the keys that unlock the structure of Src and activate its oncogenic transduction pathways. Furthermore, intracellular isoforms of these receptors, devoid of any tyrosine kinase activity, still retain the ability to unlock Src. This has been shown with a truncated isoform of KIT (tr-KIT) and a truncated isoform of VEGFR-1 (i₂₁-VEGFR-1), which are intracellular and require no ligand binding, but are nonetheless able to activate Src and induce cell migration and invasion of cancer cells. Expression of the i₂₁-VEGFR-1 is upregulated by the Notch signaling pathway and repressed by miR-200c and retinoic acid in breast cancer cells. Both Notch inhibitors and retinoic acid have been proposed as potential therapies for invasive breast cancer.

Protective effects of placental growth factor on retinal neuronal cell damage

Placental growth factor (PlGF) is a member of the vascular endothelial growth factor family. Although it has been reported that PlGF protects against neuronal damage in the brain, little is known about the effects of PlGF in the retina. Therefore, we investigated the effects of PlGF on retinal neuronal cells. To evaluate the effects of PlGF against L-buthionine-(S,R)-sulfoximine (BSO)/glutamate cell death, oxygen-glucose deprivation (OGD)-induced cell death, and light-induced cell death, RGC-5 and 661W cells were used. We evaluated the mechanism responsible for the protective effects of PlGF against retinal neuronal cell death by performing the examinations with U1026, which is a mitogen-activated protein kinase (MEK) inhibitor, and LY294002, which is a phosphoinositide 3-kinase (PI3K) inhibitor. In addition, we measured caspase-3/7 activity in RGC-5 cells and 661W cells. PlGF protected against RGC-5 cell death induced by BSO/glutamate and OGD and against 661W cell death induced by light irradiation. Moreover, an anti-PlGF antibody negated these protective effects. The protective effects of PlGF against OGD-induced RGC-5 cell death and light-induced 661W cell death were suppressed by using an anti-PlGF antibody, U1026, and LY294002. Treatment with PlGF suppressed caspase-3/7 activity in both cell lines. We demonstrated for the first time that PlGF exerts a protective effect by inhibiting the activation of caspase-3/7 through the MEK and PI3K pathway in retinal neuronal cells. These data suggest that PlGF may be an important protective factor in the retina.

Vascular endothelial growth factor receptor-1 activation promotes migration and invasion of breast cancer cells through epithelial-mesenchymal transition

Vascular endothelial growth factor receptor-1 (VEGFR-1 or Flt-1), a tyrosine kinase receptor, is highly expressed in breast cancer tissues, but near absent in normal breast tissue. While VEGFR-1 expression is associated with poor prognosis of women with breast cancer, it is not clear whether it is involved in the aggressiveness of breast cancer. Thus, the present study examined whether VEGFR-1 activation is associated with the invasiveness of breast cancer. We reported that VEGFR-1 was detected in 60.6% of invasive breast carcinoma tissue sections. In addition, VEGFR-1 expression positively correlated with lymph node-positive tumor status, low expression level of membranous E-cadherin, and high expression levels of N-cadherin and Snail. We found that PlGF-mediated VEGFR-1 activation promoted migration and invasion in MCF-7 (luminal) cells and led to morphologic and molecular changes of epithelial-mesenchymal transition (EMT). This was blocked by the down-regulation of VEGFR-1. Conversely, down-regulation of VEGFR-1 in MDA-MB-231 (post-EMT) cells resulted in morphologic and molecular changes similar to mesenchymal-epithelial transition (MET), and exogenous PlGF could not reverse these changes. Moreover, VEGFR-1 activation led to an increase in nuclear translocation of Snail. Finally, MDA-MB-231 cells expressing shRNA against VEGFR-1 significantly decreased the tumor growth and metastasis capacity in a xenograft model. Histological examination of VEGFR-1/shRNA-expressing tumor xenografts showed up-regulation of E-cadherin and down-regulation of N-cadherin and Snail. These findings suggest that VEGFR-1 may promote breast cancer progression and metastasis, and therapies that target VEGFR-1 may be beneficial in the treatment of breast cancer patients.

Placental growth factor supports neuroendocrine tumor growth and predicts disease prognosis in patients

Placental growth factor (PlGF), a VEGF-homolog implicated in tumor angiogenesis and adaptation to antiangiogenic therapy, is emerging as candidate target in malignancies. Here, we addressed the expression, function, and prognostic value of PlGF in neuroendocrine tumors (NETs). PlGF was determined in NET patients' sera collected retrospectively (n=88) and prospectively (n=87) using Roche-Elecsys and correlated with clinicopathological data. Tumoral PlGF was evaluated by immunohistochemistry, effects of PlGF on proliferation and migration in vitro were assessed using different NET cell lines and effects on tumor growth in vivo in orthotopic xenografts. Circulating and tumoral PlGF was elevated in patients with pancreatic NETs (pNETs) compared with control sera and respective healthy tissue. De novo PlGF expression occurred primarily in the tumor stroma, suggesting paracrine stimulatory circuits. Indeed, PlGF enhanced NET proliferation and migration in vitro and, conversely, neutralizing antibodies to PlGF reduced tumor growth in vivo. Elevated circulating PlGF levels in NET patients correlated with advanced tumor grading and were associated with reduced tumor-related survival in pNETs. Subsequent determinations confirmed and extended our observation of elevated PlGF levels in a prospective cohort of grade 1 and grade 2 pNETs (n=30) and intestinal NETs (n=57). In low-grade pNETs, normal circulating PlGF levels were associated with better survival. In intestinal NETs, circulating PlGF above median emerged as an independent prognostic factor for shorter time-to-progression in multivariate analyses. These data assign to PlGF a novel function in the pathobiology of NETs and propose PlGF as a prognostic parameter and therapeutic target.

PlGF: a multitasking cytokine with disease-restricted activity

Placental growth factor (PlGF) is a member of the vascular endothelial growth factor (VEGF) family that also comprises VEGF-A (VEGF), VEGF-B, VEGF-C, and VEGF-D. Unlike VEGF, PlGF is dispensable for development and health but has diverse nonredundant roles in tissue ischemia, malignancy, inflammation, and multiple other diseases. Genetic and pharmacological gain-of-function and loss-of-function studies have identified molecular mechanisms of this multitasking cytokine and characterized the therapeutic potential of delivering or blocking PlGF for various disorders.

Protein expression changes during human triple negative breast cancer cell line progression to lymph node metastasis in a xenografted model in nude mice

Triple negative breast cancers (TNBC) lacking hormone receptors and HER-2 amplification are very aggressive tumors. Since relevant differences between primary tumors and metastases could arise during tumor progression as evidenced by phenotypic discordances reported for hormonal receptors or HER-2 expression, in this analysis we studied changes that occurred in our TNBC model IIB-BR-G throughout the development of IIB-BR-G-_MTS6 metastasis to the lymph nodes (LN) in nude mice, using an antibody-based protein array to characterize their expression profile. We also analyzed their growth kinetics, migration, invasiveness and cytoskeleton structure in vitro and in vivo.

In vitro IIB-BR-G-_MTS6 cells grew slower but showed higher anchorage independent growth. In vivo IIB-BR-G-_MTS6 tumors grew significantly faster and showed a 100% incidence of LN metastasis after s.c. inoculation, although no metastasis was observed for IIB-BR-G. CCL3, IL1β, CXCL1, CSF2, CSF3, IGFBP1, IL1α, IL6, IL8, CCL20, PLAUR, PlGF and VEGF were strongly upregulated in IIB-BR-G-_MTS6 while CCL4, ICAM3, CXCL12, TNFRSF18, FIGF were the most downregulated proteins in the metastatic cell line. IIB-BR-G-_MTS6 protein expression profile could reflect a higher NFκB activation in these cells. In vitro, IIB-BR-G displayed higher migration but IIB-BR-G-_MTS6 had more elevated matrigel invasion ability. In agreement with that observation, IIB-BR-G-_MTS6 had an upregulated expression of MMP1, MMP9, MMP13, PLAUR and HGF. IIB-BR-G-_MTS6 tumors presented also higher local lymphatic invasion than IIB-BR-G but similar lymphatic vessel densities. VEGFC and VEGFA/B expression were higher both in vitro and in vivo for IIB-BR-G-_MTS6. IIB-BR-G-_MTS6 expressed more vimentin than IB-BR-G cells, which was mainly localized in the cellular extremities and both cell lines are E-cadherin negative.

Our results suggest that IIB-BR-G-_MTS6 cells have acquired a pronounced epithelial-to-mesenchymal transition phenotype. Protein expression changes observed between primary tumor-derived IIB-BR-G and metastatic IIB-BR-G-_MTS6 TNBC cells suggest potential targets involved in the control of metastasis.

Inhibition of placenta growth factor with TB-403: a novel antiangiogenic cancer therapy

INTRODUCTION

There is clinical evidence that therapies targeting the vascular endothelial growth factor pathway are effective in delaying cancer progression. However, tumors may be either intrinsically resistant or evolve resistance to such therapies. Hence, there is a need for new therapies targeting angiogenesis.

AREAS COVERED

The data are obtained by searching in the PubMed database. The search terms used included antiangiogenic therapy, TB-403 (RO5323441), placenta growth factor (PlGF) and VEGFR-1 (Flt-1). We review preclinical data concerning the function and inhibition of PlGF and summarize data on expression of PlGF in cancer patients. Data from early-phase clinical trials of TB-403 (RO5323441), a monoclonal antibody inhibiting PlGF, are discussed. Future development strategies, therapeutic potentials and limitations of TB-403 are further evaluated.

EXPERT OPINION

There are some conflicting data on the function of PlGF and the importance of its role in primary tumor growth. Data from some preclinical models of PlGF inhibition and early-phase clinical trials with TB-403 are, however, promising, although the true potential of the drug is yet to be determined. Further clinical development should be preceded by molecular studies in the context of well-designed preclinical models and/or small translational studies. Future challenges involve identifying predictive biomarkers.

Prognostic impact of placenta growth factor and vascular endothelial growth factor A in patients with breast cancer

Placenta growth factor (PlGF) and vascular endothelial growth factor A (VEGF-A) are angiogenic growth factors interacting competitively with the same receptors. VEGF-A is essential in both normal and pathologic conditions, but the functions of PlGF seem to be restricted to pathologic conditions such as ischemic heart disease, arthritis and tumor growth. Angiogenesis is a complex process with several growth factors involved. Because PlGF modulates VEGF-A responses, we investigated their mutual relationship and impact on breast cancer prognosis. Quantitative PlGF and VEGF-A levels were measured in 229 tumor tissue specimen from primarily operated patients with unilateral breast cancer. Non-malignant breast tissue was also dissected near the tumor and quantitative measurements were available for 211 patients. PlGF and VEGF-A protein levels in homogenized tissue lysates were analyzed using the Luminex system. We found significantly higher median levels of PlGF and VEGF-A in tumor tissue compared to non-malignant tissue (PlGF: 69.8 vs. 31.4 pg/mg, p < 0.001 and VEGF-A: 1148.2 vs. 163.5 pg/mg, p < 0.001). PlGF and VEGF-A were correlated in both malignant tissue (r = 0.41, p < 0.001) and in non-malignant tissue (r = 0.69, p < 0.001). The proportion of node positive patients was higher with high PlGF expression (61.4%) than with low PlGF expression (45.6%) in tumor tissue, p = 0.024. High levels of PlGF and VEGF-A in tumor tissue were associated with significant shorter recurrence-free survival (RFS) in both univariate analysis (PlGF: p = 0.023; VEGF-A: p = 0.047) and in multivariate analysis (PlGF: p = 0.026; VEGF-A: p = 0.036). Neither PlGF nor VEGF-A expression in non-malignant tissue were predictors for RFS. In conclusion, our results support the mutual relationship between PlGF and VEGF-A and encourage further investigations as prognostic markers in breast cancer patients.

Signal transduction by vascular endothelial growth factor receptors

VEGFs (vascular endothelial growth factors) control vascular development during embryogenesis and the function of blood vessels and lymphatic vessels in the adult. There are five related mammalian ligands, which act through three receptor tyrosine kinases. Signalling is modulated through neuropilins, which act as VEGF co-receptors. Heparan sulfate and integrins are also important modulators of VEGF signalling. Therapeutic agents that interfere with VEGF signalling have been developed with the aim of decreasing angiogenesis in diseases that involve tissue growth and inflammation, such as cancer. The present review will outline the current understanding and consequent biology of VEGF receptor signalling.

Loss or inhibition of stromal-derived PlGF prolongs survival of mice with imatinib-resistant Bcr-Abl1(+) leukemia

Imatinib has revolutionized the treatment of Bcr-Abl1(+) chronic myeloid leukemia (CML), but, in most patients, some leukemia cells persist despite continued therapy, while others become resistant. Here, we report that PlGF levels are elevated in CML and that PlGF produced by bone marrow stromal cells (BMSCs) aggravates disease severity. CML cells foster a soil for their own growth by inducing BMSCs to upregulate PlGF, which not only stimulates BM angiogenesis, but also promotes CML proliferation and metabolism, in part independently of Bcr-Abl1 signaling. Anti-PlGF treatment prolongs survival of imatinib-sensitive and -resistant CML mice and adds to the anti-CML activity of imatinib. These results may warrant further investigation of the therapeutic potential of PlGF inhibition for (imatinib-resistant) CML.

Vascular endothelial growth factors and receptors: anti-angiogenic therapy in the treatment of cancer

Vascular endothelial growth factors (VEGFs) are critical regulators of vascular and lymphatic function during development, in health and in disease. There are five mammalian VEGF ligands and three VEGF receptor tyrosine kinases. In addition, several VEGF co-receptors that lack intrinsic catalytic activity, but that indirectly modulate the responsiveness to VEGF contribute to the final biological effect. This review describes the molecular features of VEGFs, VEGFRs and co-receptors with focus on their role in the treatment of cancer.