Effect of p53 status on tumor response to antiangiogenic therapy

Curcumin induces p53-independent necrosis in H1299 cells via a mitochondria-associated pathway

Curcumin has been shown to have various therapeutic and/or adjuvant therapeutic effects on human cancers, as it inhibits cancer cell proliferation and induces apoptosis through p53-dependent molecular pathways. However, numerous cancer cell types bear a mutant p53 gene, and whether curcumin has any therapeutic effects on p53-deficient/mutant cancer cells has remained elusive. The present study sought to determine whether curcumin exerts any anti-proliferative and cytotoxic effects on the p53-deficient H1299 human lung cancer cell line via a p53-independent mechanism. An MTT assay and flow cytometric analysis indicated that curcumin significantly decreased cell proliferation and induced necrotic cell death. Western blot analysis of the cytosolic and mitochondrial fractions of H1299 cells as well as a fluorometric caspase assay indicated that curcumin-induced necrosis was mitochondria- and caspase-dependent, and resulted in cytochrome c release. Of note, this necrotic cell death was reduced following inhibition of B-cell lymphoma‑2 (Bcl-2)‑associated X protein (Bax) or Bcl‑2 homologous antagonist killer (Bak) as well as overexpression of Bcl-2. In conclusion, the present study suggested that curcumin-induced necrotic cell death was mediated via a p53-independent molecular pathway, which was associated with Bax and Bak translocation, caspase activation and cytochrome c release.

Cellular signaling pathways implicated in metastasis of colorectal cancer and the associated targeted agents

Colorectal cancer (CRC) is the third leading cancer worldwide and CRC-related death is mainly attributed to metastasis. Many cellular signaling pathways have been demonstrated to be aberrant in colorectal tumors, and some of them lead to the acquisition of malignant phenotypes. Therefore, the evaluation of signaling pathways implicated in CRC metastasis is urgent for further understanding of CRC progression and pharmacotherapy. This review focuses on several novel cellular signaling pathways associated with CRC metastasis, including Wnt/β-catenin, p53, COX, TGF-β/Smad, NF-κB, Notch, VEGF and JAKs/STAT3 signaling pathways. Targeted agents developed based on these pathways are also briefly discussed.

Targeting hypoxia-inducible factor-1α (HIF-1α) in combination with antiangiogenic therapy: a phase I trial of bortezomib plus bevacizumab

Purpose

We hypothesized that bortezomib, an agent that suppresses HIF-1α transcriptional activity, when combined with bevacizumab, would obviate the HIF-1α resistance pathway. The objectives of this phase I trial were to assess safety and biological activity of this combination.

Experimental Design

Patients with advanced, refractory malignancies were eligible. Patients received bevacizumab and bortezomib (3-week cycle) with dose expansions permitted if responses were seen and for assessing correlates. Pharmacodynamic assessment included plasma VEGF, VEGFR2, 20S proteasome inhibition, dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI), and HIF-1α tumor expression.

Results

Ninety-one patients were treated (median=6 prior treatments). The FDA-approved doses of both drugs were safely reached, and the recommended phase 2 dose (RP2D) is bevacizumab 15 mg/kg with bortezomib 1.3 mg/m². Four patients attained partial response (PR) and seven patients achieved stable disease (SD) ≥6 months (Total SD≥6 months/PR=11 (12%)). The most common drug-related toxicities included thrombocytopenia (23%) and fatigue (19%). DCE-MRI analysis demonstrated no dose-dependent decreases in K^trans although analysis was limited by small sample size (N=12).

Conclusion

Combination bevacizumab and bortezomib is well-tolerated and has demonstrated clinical activity in patients with previously treated advanced malignancy. Pharmacodynamic assessment suggests that inhibition of angiogenic activity was achieved.

A systematic literature analysis of correlative studies in low-dose metronomic chemotherapy trials

Low-dose metronomic (LDM) chemotherapy is a beneficial and very well-tolerated form of chemotherapy utilization characterized by the frequent and uninterrupted administration of low doses of conventional chemotherapeutic agents over prolonged periods of time. While patients resistant to standard maximum tolerated dose (MTD) chemotherapy may still benefit from LDM chemotherapy, there is a lack of predictive markers of response to LDM chemotherapy. We searched the MEDLINE, EMBASE, CENTRAL and PubMed databases for correlative studies conducted as part of LDM chemotherapy trials in order to identify the most promising biomarker candidates. Given the antiangiogenic properties of LDM chemotherapy, angiogenesis-related biomarkers were most commonly studied. However, significant correlations between angiogenesis-related biomarkers and study end points were rare and variable, even so far as biomarkers correlating positively with an end point in some studies and negatively with the same end point in other studies. Pursuing biomarkers outside the angiogenesis field may be more promising.

The p53 family and the hypoxia-inducible factors (HIFs): determinants of cancer progression

HIFs have long been associated with resistance to therapy, metastasis, and poor survival rates in cancer patients. In parallel, although the tumor-suppressor p53 acts as the first barrier against tumor transformation, its inactivation also appears to be crucial for enabling cancer progression at advanced stages. p53 has been proposed to antagonize HIF, and emerging evidence suggests that the p53 siblings p63 and p73 also participate in this interplay. Crosstalk between HIFs and the p53 family acts as a determinant of cancer progression through regulating angiogenesis, the tumor microenvironment, dormancy, metastasis, and recurrence. We discuss the possible mechanisms underlying this regulation and the controversies in this field in an attempt to provide a unified view of current knowledge.

c-MET receptor tyrosine kinase as a molecular target in advanced hepatocellular carcinoma

c-MET is the membrane receptor for hepatocyte growth factor (HGF), also known as scatter factor or tumor cytotoxic factor, a mitogenic growth factor for hepatocytes. HGF is mainly produced by cells of mesenchymal origin and it mainly acts on neighboring epidermal and endothelial cells, regulating epithelial growth and morphogenesis. HGF/MET signaling has been identified among the drivers of tumorigenesis in human cancers. As such, c-MET is a recognized druggable target, and against it, targeted agents are currently under clinical investigation. c-MET overexpression is a common event in a wide range of human malignancies, including gastric, lung, breast, ovary, colon, kidney, thyroid, and liver carcinomas. Despite c-MET overexpression being reported by a large majority of studies, no evidence for a c-MET oncogenic addiction exists in hepatocellular carcinoma (HCC). In particular, c-MET amplification is a rare event, accounting for 4%–5% of cases while no mutation has been identified in c-MET oncogene in HCC. Thus, the selection of patient subgroups more likely to benefit from c-MET inhibition is challenging. Notwithstanding, c-MET overexpression was reported to be associated with increased metastatic potential and poor prognosis in patients with HCC, providing a rationale for its therapeutic inhibition. Here we summarize the role of activated HGF/MET signaling in HCC, its prognostic relevance, and the implications for therapeutic approaches in HCC.

Suppression of oxidative phosphorylation in mouse embryonic fibroblast cells deficient in apurinic/apyrimidinic endonuclease

The mammalian apurinic/apyrimidinic (AP) endonuclease 1 (APE1) is an essential DNA repair/gene regulatory protein. Decrease of APE1 in cells by inducible shRNA knockdown or by conditional gene knockout caused apoptosis. Here we succeeded in establishing a unique mouse embryonic fibroblast (MEF) line expressing APE1 at a level far lower than those achieved with shRNA knockdown. The cells, named MEF(la) (MEF(lowAPE1)), were hypersensitive to methyl methanesulfonate (MMS), and showed little activity for repairing AP-sites and MMS induced DNA damage. While these results were consistent with the essential role of APE1 in repair of AP sites, the MEF(la) cells grew normally and the basal activation of poly(ADP-ribose) polymerases in MEF(la) was lower than that in the wild-type MEF (MEF(wt)), indicating the low DNA damage stress in MEF(la) under the normal growth condition. Oxidative phosphorylation activity in MEF(la) was lower than in MEF(wt), while the glycolysis rates in MEF(la) were higher than in MEF(wt). In addition, we observed decreased intracellular oxidative stress in MEF(la). These results suggest that cells with low APE1 reversibly suppress mitochondrial respiration and thereby reduce DNA damage stress and increases the cell viability.

Advanced gynecologic malignancies treated with a combination of the VEGF inhibitor bevacizumab and the mTOR inhibitor temsirolimus

Background: Bevacizumab and temsirolimus are active agents in gynecologic tumors. Temsirolimus attenuates upregulation of HIF-1α levels, a resistance mechanism for antiangiogenics, and targets the PI3-kinase/AKT/mTOR axis, commonly aberrant in these tumors

Patients and Methods: We analyzed safety and responses in 41 patients with gynecologic cancers treated as part of a Phase I study of bevacizumab and temsirolimus.

Results: Median age of the 41 women was 60 years (range, 33-80 years); median number of prior systemic therapies was 4 (1-11). Grade 3 or 4 treatment-related toxicities included: thrombocytopenia (10%), mucositis (2%), hypertension (2%), hypercholesterolemia (2%), fatigue (7%), elevated aspartate aminotransferase (2%), and neutropenia (2%). Twenty-nine patients (71%) experienced no treatment-related toxicity greater than grade 2. Full FDA-approved doses of both drugs (bevacizumab 15mg/kg IV Q3weeks and temsirolimus 25mg IV weekly) were administered without dose-limiting toxicity. Eight patients (20%) achieved stable disease (SD) ≥ 6 months and 7 patients (17%), a partial response (PR) [total = 15/41 patients (37%)]. Eight of 13 patients (62%) with high-grade serous histology (ovarian or primary peritoneal) achieved SD ≥ 6 months/PR.

Conclusion: Bevacizumab and temsirolimus was well tolerated. Thirty-seven percent of heavily-pretreated patients achieved SD ≥ 6 months/PR, suggesting that this combination warrants further study.

Vascular endothelial growth factor a inhibition in gastric cancer

Angiogenesis is a vital process in the progression and metastasis of solids tumors including gastric adenocarcinoma. Tumors induce angiogenesis by secreting proangiogenic molecules such as vascular endothelial growth factor A (VEGF-A), and VEGF-A inhibition has become a common therapeutic strategy for many cancers. Several drugs targeting the VEGF-A pathway have been approved for clinical use in selected solid tumors, and several anti-VEGF-A strategies have been examined for gastric cancer. Phase II studies suggested that bevacizumab, an anti-VEGF antibody, can increase the efficacy of chemotherapy for advanced gastric cancer, but two international phase III trials failed to show an overall survival benefit. Two more recent international phase III trials have examined ramucirumab, an antibody targeting the primary receptor for VEGF-A, as second-line therapy for advanced gastric cancer and found a survival benefit both as single agent therapy and when combined with chemotherapy. Finally, correlative science studies suggest that the VEGF-A pathway may have varying importance in gastric cancer progression depending on ethnicity or race. This article will review the preclinical and clinical studies on the role of the VEGF-A pathway inhibition in gastric cancer.

Upregulation of ATG3 contributes to autophagy induced by the detachment of intestinal epithelial cells from the extracellular matrix, but promotes autophagy-independent apoptosis of the attached cells

Detachment of nonmalignant intestinal epithelial cells from the extracellular matrix (ECM) triggers their growth arrest and, ultimately, apoptosis. In contrast, colorectal cancer cells can grow without attachment to the ECM. This ability is critical for their malignant potential. We found previously that detachment-induced growth arrest of nonmalignant intestinal epithelial cells is driven by their detachment-triggered autophagy, and that RAS, a major oncogene, promotes growth of detached cells by blocking such autophagy. In an effort to identify the mechanisms of detachment-induced autophagy and growth arrest of nonmalignant cells we found here that detachment of these cells causes upregulation of ATG3 and that ATG3 upregulation contributes to autophagy and growth arrest of detached cells. We also observed that when ATG3 expression is artificially increased in the attached cells, ATG3 promotes neither autophagy nor growth arrest but triggers their apoptosis. ATG3 upregulation likely promotes autophagy of the detached but not that of the attached cells because detachment-dependent autophagy requires other detachment-induced events, such as the upregulation of ATG7. We further observed that those few adherent cells that do not die by apoptosis induced by ATG3 become resistant to apoptosis caused by cell detachment, a property that is critical for the ability of normal epithelial cells to become malignant. We conclude that cell-ECM adhesion can switch ATG3 functions: when upregulated in detached cells in the context of other autophagy-promoting events, ATG3 contributes to autophagy. However, when overexpressed in the adherent cells, in the circumstances not favoring autophagy, ATG3 triggers apoptosis.

Effects of prodigiosin family compounds from Pseudoalteromonas sp. 1020R on the activities of protein phosphatases and protein kinases

Pseudoalteromonas sp. strain 1020R produces prodigiosin and its closely related congeners, which differ in the length of their alkyl side chains. These red-pigmented compounds were found to exhibit cytotoxicity against human leukemia cell lines. The compounds also showed dose-dependent inhibitory effects on protein phosphatase 2A and protein tyrosine phosphatase 1B (PTP1B), while remaining relatively inactive against protein kinases, including protein tyrosine kinase, Ca(2+)/calmodulin-dependent protein kinase and protein kinases A and C. Comparative studies of the individual pigmented compounds on PTP1B inhibition showed that as the chain length of the alkyl group at the C-3 position of the compound increased, the inhibitory effect on PTP1B decreased. These results suggest that protein phosphatases but not protein kinases might be involved in the cytotoxicity of the prodigiosin family of compounds against malignant cells.

E2F1 suppresses cardiac neovascularization by down-regulating VEGF and PlGF expression

AIMS

The E2F transcription factors are best characterized for their roles in cell-cycle regulation, cell growth, and cell death. Here we investigated the potential role of E2F1 in cardiac neovascularization.

METHODS AND RESULTS

We induced myocardial infarction (MI) by ligating the left anterior descending artery in wild-type (WT) and E2F1(-/-) mice. E2F1(-/-) mice demonstrated a significantly better cardiac function and smaller infarct sizes than WT mice. At infarct border zone, capillary density and endothelial cell (EC) proliferation were greater, apoptotic ECs were fewer, levels of VEGF and placental growth factor (PlGF) were higher, and p53 level was lower in E2F1(-/-) than in WT mice. Blockade of VEGF receptor 2 (VEGFR2) signalling with the selective inhibitor SU5416 or with the VEGFR2-blocking antibody DC101 abolished the differences between E2F1(-/-) mice and WT mice in cardiac function, infarct size, capillary density, EC proliferation, and EC apoptosis. In vitro, hypoxia-induced VEGF and PlGF up-regulation was significantly greater in E2F1(-/-) than in WT cardiac fibroblasts, and E2F1 overexpression suppressed PlGF up-regulation in both WT and p53(-/-) cells; however, VEGF up-regulation was suppressed only in WT cells. E2F1 interacted with and stabilized p53 under hypoxic conditions, and both E2F1 : p53 binding and the E2F1-induced suppression of VEGF promoter activity were absent in cells that expressed an N-terminally truncated E2F1 mutant.

CONCLUSION

E2F1 limits cardiac neovascularization and functional recovery after MI by suppressing VEGF and PlGF up-regulation through p53-dependent and -independent mechanisms, respectively.

The prevalent KRAS exon 2 c.35 G>A mutation in metastatic colorectal cancer patients: A biomarker of worse prognosis and potential benefit of bevacizumab-containing intensive regimens?

Bevacizumab-containing chemotherapy differently predict increased efficacy in KRAS exon 2 mutant and wild-type metastatic colorectal cancer (MCRC) patients. Mutant compared to wild-type status did not significantly affect progression-free survival (PFS) and overall survival (OS) in patients fit for first line bevacizumab-containing FIr-B/FOx regimen, and after progression. In patients unfit for intensive regimens, mutant status significantly affected PFS, while not OS. Codon 12 KRAS mutations differentially affect GTPase function, and confer worse clinical behaviour. Prognostic relevance of the prevalent c.35 G>A KRAS mutation was retrospectively evaluated. Fit c.35 G>A mutant patients showed significantly worse OS compared to wild-type and to other mutant. After progression and in unfit patients, c.35 G>A mutation affected significantly worse PFS and OS. c.35 G>A mutant status does not significantly affect worse PFS in patients fit for first line FIr-B/FOx, and it may depend upon effectiveness of anti-VEGF-containing intensive regimen.

Cellular intrinsic mechanism affecting the outcome of AML treated with Ara-C in a syngeneic mouse model

The mechanisms underlying acute myeloid leukemia (AML) treatment failure are not clear. Here, we established a mouse model of AML by syngeneic transplantation of BXH-2 derived myeloid leukemic cells and developed an efficacious Ara-C-based regimen for treatment of these mice. We proved that leukemic cell load was correlated with survival. We also demonstrated that the susceptibility of leukemia cells to Ara-C could significantly affect the survival. To examine the molecular alterations in cells with different sensitivity, genome-wide expression of the leukemic cells was profiled, revealing that overall 366 and 212 genes became upregulated or downregulated, respectively, in the resistant cells. Many of these genes are involved in the regulation of cell cycle, cellular proliferation, and apoptosis. Some of them were further validated by quantitative PCR. Interestingly, the Ara-C resistant cells retained the sensitivity to ABT-737, an inhibitor of anti-apoptosis proteins, and treatment with ABT-737 prolonged the life span of mice engrafted with resistant cells. These results suggest that leukemic load and intrinsic cellular resistance can affect the outcome of AML treated with Ara-C. Incorporation of apoptosis inhibitors, such as ABT-737, into traditional cytotoxic regimens merits consideration for the treatment of AML in a subset of patients with resistance to Ara-C. This work provided direct in vivo evidence that leukemic load and intrinsic cellular resistance can affect the outcome of AML treated with Ara-C, suggesting that incorporation of apoptosis inhibitors into traditional cytotoxic regimens merits consideration for the treatment of AML in a subset of patients with resistance to Ara-C.

Predictive biomarkers in renal cell cancer: insights in drug resistance mechanisms

INTRODUCTION

VEGF-targeted therapy is currently the first line treatment for patients with metastatic clear cell renal cell carcinoma (ccRCC), but most patients either display primary (intrinsic) resistance or acquire drug resistance. In recent years multiple mechanisms of resistance to VEGF-targeted therapy emerged from preclinical research, but it is currently unknown to what extent these drug resistance modalities play a role in the clinic. Here we reviewed the current literature on biomarkers that predict treatment outcome in patients with ccRCC to gain insight in clinical drug resistance mechanisms.

METHODS

A search syntax was compiled by combining different synonyms of "biomarker" AND "renal" AND "cancer". MEDLINE was accessed through PubMed, where this syntax was entered and used to search titles and abstracts of publications. Articles were selected based on three criteria: (1) description of patients with clear cell RCC, (2) treatment with VEGF targeted therapy and (3) discussion of biomarkers that were studied for potential association with treatment response.

RESULTS

The literature search was performed on March 4th 2014 and yielded 1882 articles. After carefully reading the titles and abstracts based on the three previously mentioned criteria, 103 publications were evaluated. Backward citation screening was performed on all eligible studies and revealed another 24 articles. This search revealed that (1) High glucose uptake and low contrast enhancement on PET- and CT-imaging before start of treatment may correlate with poor response to therapy, (2) Low dose intensity due to treatment intolerance is related to shorter progression free survival. (3) Acquired resistance appears to be associated with rebound vascularization based on both longitudinal monitoring of contrast enhancement by CT and blood vessel counts in tumor tissue, and (4) Based on plasma cytokine and single nucleotide polymorphism (SNP) studies, interleukin-8, VEGFR-3, FGFR2 and HGF/MET emerged as potential clinical markers for chemoresistance.

CONCLUSION

Low dose intensity, specific tumor-imaging techniques and potential biological biomarkers may be predictive for response to VEGF-targeted therapy in ccRCC. Some of these plausible biomarkers may also provide more insight into the underlying mechanisms of resistance such as altered glucose metabolism and rapid rebound vascularization.

The miRNA network: micro-regulator of cell signaling in cancer

The dysregulation of cell signaling plays a pivotal role in tumorigenesis and progression. miRNAs have been linked to almost all known aspects of physiological and pathological processes. It is well known that the miRNA network is linked at several and unexpected levels with cancer-related signaling pathways. Our understanding of the roles and regulation of the miRNA network has been extended to include classical cell signaling, termed miRNA network complements cell signaling in cancer. As a transcription factor, tumor suppressor p53 plays a central role in tumor prevention. Recent studies have demonstrated that miRNAs may regulate the expression of the p53 pathway or be regulated by the p53 pathway. These findings added a new and challenging layer of complexity to the p53 pathway and prompted us to contemplate the use of the compensatory mechanisms in therapeutics against cancer. In this review, we have therefore summarized the p53 tumor suppressive pathway as a typical paradigm to elucidate the advances of the compensatory mechanisms. We then go on to critically discuss how the compensatory mechanisms can be used to enable better cancer diagnosis and prognosis and to serve as potential therapeutic targets.

Somatic mutation load of estrogen receptor-positive breast tumors predicts overall survival: an analysis of genome sequence data

Breast cancer is one of the most commonly diagnosed cancers in women. While there are several effective therapies for breast cancer and important single gene prognostic/predictive markers, more than 40,000 women die from this disease every year. The increasing availability of large-scale genomic datasets provides opportunities for identifying factors that influence breast cancer survival in smaller, well-defined subsets. The purpose of this study was to investigate the genomic landscape of various breast cancer subtypes and its potential associations with clinical outcomes. We used statistical analysis of sequence data generated by the Cancer Genome Atlas initiative including somatic mutation load (SML) analysis, Kaplan–Meier survival curves, gene mutational frequency, and mutational enrichment evaluation to study the genomic landscape of breast cancer. We show that ER⁺, but not ER⁻, tumors with high SML associate with poor overall survival (HR = 2.02). Further, these high mutation load tumors are enriched for coincident mutations in both DNA damage repair and ER signature genes. While it is known that somatic mutations in specific genes affect breast cancer survival, this study is the first to identify that SML may constitute an important global signature for a subset of ER⁺ tumors prone to high mortality. Moreover, although somatic mutations in individual DNA damage genes affect clinical outcome, our results indicate that coincident mutations in DNA damage response and signature ER genes may prove more informative for ER⁺ breast cancer survival. Next generation sequencing may prove an essential tool for identifying pathways underlying poor outcomes and for tailoring therapeutic strategies.

The role of antiangiogenic agents in the treatment of patients with advanced colorectal cancer according to K-RAS status

Colorectal cancer (CRC) is the fourth most commonly diagnosed cancer worldwide. Recently, it has been found that about 40 % of patients with CRC have mutations in the K-RAS gene. Several clinical trials have showed that patients with metastatic colorectal cancer (mCRC) who present tumour-promoting mutations in signalling pathways involving the epidermal growth factor receptor (EGFR), which includes activating K-RAS mutations, do not respond to anti-EGFR drugs such as panitumumab and cetuximab. Hence, K-RAS status is now considered an important negative predictive factor for response to anti-EGFR drugs. Moreover, K-RAS status seems to have also a prognostic role in CRC, but this fact is somewhat controversial. Activity of antiangiogenic agents seems not to be influenced by K-RAS gene status. Tumour angiogenesis has attracted interest in attempts to improve the management of mCRC. The vascular endothelial growth factor (VEGF) pathway is fundamental to the regulation of angiogenesis, and research has focused on developing agents that selectively target it. In this way, the anti-VEGF antibody bevacizumab in combination with chemotherapy has provided important clinical benefits in terms of response rate, progression-free survival and overall survival to patients with mCRC. Efficacy data of bevacizumab in K-RAS wild-type patients seem to be comparable with the efficacy data observed with anti-EGFR therapies in a cross-trial comparison. Although there is a lack of prospective and randomized data in this setting, the combination of chemotherapy plus antiangiogenic agents could be considered as an effective alternative for the treatment of mCRC with independence of K-RAS gene status. Here, we review the available data we have in the literature of the use of antiangiogenic strategies in the treatment of mCRC nowadays.

Sunitinib resistance in renal cell carcinoma

Of the many targeted therapies introduced since 2006, sunitinib has carved its way to become the most commonly used first-line therapy for the treatment of metastatic renal cell carcinoma (RCC). Despite significant improvements in progression-free survival, 30% of the patients are intrinsically resistant to sunitinib and the remaining 70% who respond initially will eventually become resistant in 6-15 months. While the molecular mechanisms of acquired resistance to sunitinib have been unravelling at a rapid rate, the mechanisms of intrinsic resistance remain elusive. Combination therapy, sunitinib rechallenge and sequential therapy have been investigated as means to overcome resistance to sunitinib. Of these, sequential therapy appears to be the most promising strategy. This mini review summarises our emerging understanding of the molecular mechanisms, and the strategies employed to overcome sunitinib resistance.

Cancer nanotechnology: the impact of passive and active targeting in the era of modern cancer biology

Cancer nanotherapeutics are progressing at a steady rate; research and development in the field has experienced an exponential growth since early 2000's. The path to the commercialization of oncology drugs is long and carries significant risk; however, there is considerable excitement that nanoparticle technologies may contribute to the success of cancer drug development. The pace at which pharmaceutical companies have formed partnerships to use proprietary nanoparticle technologies has considerably accelerated. It is now recognized that by enhancing the efficacy and/or tolerability of new drug candidates, nanotechnology can meaningfully contribute to create differentiated products and improve clinical outcome. This review describes the lessons learned since the commercialization of the first-generation nanomedicines including DOXIL® and Abraxane®. It explores our current understanding of targeted and non-targeted nanoparticles that are under various stages of development, including BIND-014 and MM-398. It highlights the opportunities and challenges faced by nanomedicines in contemporary oncology, where personalized medicine is increasingly the mainstay of cancer therapy. We revisit the fundamental concepts of enhanced permeability and retention effect (EPR) and explore the mechanisms proposed to enhance preferential "retention" in the tumor, whether using active targeting of nanoparticles, binding of drugs to their tumoral targets or the presence of tumor associated macrophages. The overall objective of this review is to enhance our understanding in the design and development of therapeutic nanoparticles for treatment of cancers.

Anti-angiogenic therapy for cancer: current progress, unresolved questions and future directions

Tumours require a vascular supply to grow and can achieve this via the expression of pro-angiogenic growth factors, including members of the vascular endothelial growth factor (VEGF) family of ligands. Since one or more of the VEGF ligand family is overexpressed in most solid cancers, there was great optimism that inhibition of the VEGF pathway would represent an effective anti-angiogenic therapy for most tumour types. Encouragingly, VEGF pathway targeted drugs such as bevacizumab, sunitinib and aflibercept have shown activity in certain settings. However, inhibition of VEGF signalling is not effective in all cancers, prompting the need to further understand how the vasculature can be effectively targeted in tumours. Here we present a succinct review of the progress with VEGF-targeted therapy and the unresolved questions that exist in the field: including its use in different disease stages (metastatic, adjuvant, neoadjuvant), interactions with chemotherapy, duration and scheduling of therapy, potential predictive biomarkers and proposed mechanisms of resistance, including paradoxical effects such as enhanced tumour aggressiveness. In terms of future directions, we discuss the need to delineate further the complexities of tumour vascularisation if we are to develop more effective and personalised anti-angiogenic therapies.

Angiogenesis in spontaneous tumors and implications for comparative tumor biology

Blood supply is essential for development and growth of tumors and angiogenesis is the fundamental process of new blood vessel formation from preexisting ones. Angiogenesis is a prognostic indicator for a variety of tumors, and it coincides with increased shedding of neoplastic cells into the circulation and metastasis. Several molecules such as cell surface receptors, growth factors, and enzymes are involved in this process. While antiangiogenic therapy for cancer has been proposed over 20 years ago, it has garnered much controversy in recent years within the scientific community. The complex relationships between the angiogenic signaling cascade and antiangiogenic substances have indicated the angiogenic pathway as a valid target for anticancer drug development and VEGF has become the primary antiangiogenic drug target. This review discusses the basic and clinical perspectives of angiogenesis highlighting the importance of comparative biology in understanding tumor angiogenesis and the integration of these model systems for future drug development.

Inhibition of autophagy enhances the anticancer activity of silver nanoparticles

Silver nanoparticles (Ag NPs) are cytotoxic to cancer cells and possess excellent potential as an antitumor agent. A variety of nanoparticles have been shown to induce autophagy, a critical cellular degradation process, and the elevated autophagy in most of these situations promotes cell death. Whether Ag NPs can induce autophagy and how it might affect the anticancer activity of Ag NPs has not been reported. Here we show that Ag NPs induced autophagy in cancer cells by activating the PtdIns3K signaling pathway. The autophagy induced by Ag NPs was characterized by enhanced autophagosome formation, normal cargo degradation, and no disruption of lysosomal function. Consistent with these properties, the autophagy induced by Ag NPs promoted cell survival, as inhibition of autophagy by either chemical inhibitors or ATG5 siRNA enhanced Ag NPs-elicited cancer cell killing. We further demonstrated that wortmannin, a widely used inhibitor of autophagy, significantly enhanced the antitumor effect of Ag NPs in the B16 mouse melanoma cell model. Our results revealed a novel biological activity of Ag NPs in inducing cytoprotective autophagy, and inhibition of autophagy may be a useful strategy for improving the efficacy of Ag NPs in anticancer therapy.

Treating hepatocellular carcinoma progression following first-line sorafenib: therapeutic options and clinical observations

Despite the established efficacy of sorafenib in advanced hepatocellular carcinoma (HCC), a significant number of sorafenib-treated patients experience disease progression. Current guidelines recommend either best supportive care or clinical trial enrollment for this population. As such, there remains an unmet need for tolerable, life-prolonging strategies in the second-line setting. New information regarding the molecular pathogenesis of resistance to antiangiogenic therapy and positive post-progression experience with antiangiogenics in other tumor types has led to trials investigating the effect of continued use of sorafenib, alone or combined with other agents. Trials investigating the effect of switching from sorafenib to alternate antiangiogenic agents, phosphatidylinositol 3 kinase/AKT/mammalian target of rapamycin inhibitors, or cMet inhibitors are also underway. As these data emerge, clinicians may consider a new paradigm for managing advanced HCC. This article briefly reviews the mechanisms of disease resistance to antiangiogenic therapy as a vehicle for discussing clinical strategies to prolong survival in patients with advanced HCC that are currently employed at our institutions or are under investigation. Key ongoing trials investigating the use of molecularly targeted therapies in patients with progressive disease are also highlighted.

Changes in tumour vessel density upon treatment with anti-angiogenic agents: relationship with response and resistance to therapy

Background:

We examine how changes in a surrogate marker of tumour vessel density correlate with response and resistance to anti-angiogenic therapy.

Methods:

In metastatic renal cancer patients treated with anti-angiogenic tyrosine kinase inhibitors, arterial phase contrast-enhanced computed tomography was used to simultaneously measure changes in: (a) tumour size, and (b) tumour enhancement (a surrogate marker of tumour vessel density) within individual lesions.

Results:

No correlation between baseline tumour enhancement and lesion shrinkage was observed, but a reduction in tumour enhancement on treatment was strongly correlated with reduction in lesion size (r=0.654, P<0.0001). However, close examination of individual metastases revealed different types of response: (1) good vascular response with significant tumour shrinkage, (2) good vascular response with stabilisation of disease, (3) poor vascular response with stabilisation of disease and (4) poor vascular response with progression. Moreover, contrasting responses between different lesions within the same patient were observed. We also assessed rebound vascularisation in tumours that acquired resistance to treatment. The amplitude of rebound vascularisation was greater in lesions that had a better initial response to therapy (P=0.008).

Interpretation:

Changes in a surrogate marker of tumour vessel density correlate with response and resistance to anti-angiogenic therapy. The data provide insight into the mechanisms that underlie response and resistance to this class of agent.

Tumor dynamics in response to antiangiogenic therapy with oral metronomic topotecan and pazopanib in neuroblastoma xenografts

Metronomic chemotherapy, combined with targeted antiangiogenic drugs, has demonstrated significant anticancer efficacy in various studies. Though, tumors do acquire resistance. Here, we have investigated the effect of prolonged therapy with oral metronomic topotecan and pazopanib on tumor behavior in a neuroblastoma mouse xenograft model. SK-N-BE(2) xenograft-bearing mice were treated with either of the following regimens (daily, orally): vehicle (control), 150 mg/kg pazopanib, 1.0 mg/kg topotecan, and combination of topotecan and pazopanib. Planned durations of treatment for each regimen were 28, 56, and 80 days or until the end point, after which animals were sacrificed. We found that only combination-treated animals survived until 80 days. Combination halted tumor growth for up to 50 days, after which gradual growth was observed. Unlike single agents, all three durations of combination significantly lowered microvessel densities compared to the control. However, the tumors treated with the combination for 56 and 80 days had higher pericyte coverage compared to control and those treated for 28 days. The proliferative and mitotic indices of combination-treated tumors were higher after 28 days of treatment and comparable after 56 days and 80 days of treatment compared to control. Immunohistochemistry, Western blot, and real-time polymerase chain reaction revealed that combination treatment increased the hypoxia and angiogenic expression. Immunohistochemistry for Glut-1 and hexokinase II expression revealed a metabolic switch toward elevated glycolysis in the combination-treated tumors. We conclude that prolonged combination therapy with metronomic topotecan and pazopanib demonstrates sustained antiangiogenic activity but also incurs resistance potentially mediated by elevated glycolysis.

KRAS as prognostic biomarker in metastatic colorectal cancer patients treated with bevacizumab: a pooled analysis of 12 published trials

The significance of KRAS in advanced colorectal cancer (CRC) treated with bevacizumab (B) is not well understood. We conducted a systematic review and pooled analysis of published trials with the aim to assess the predictive and prognostic role of KRAS status in patients treated with B. We performed a systematic search of PubMed, EMBASE, Web of Science, and Cochrane Register of Controlled Trials. The primary endpoints included objective response rate (RR), progression-free survival (PFS), and overall survival (OS). The odds ratio (OR) for RR and hazard ratios (HRs) were calculated or extracted by published data either using a fixed effect model or a random effect model. A total of 12 studies were included. A total of 2,266 patients were analysed (54 % were KRAS wt). The pooled RRs for KRAS wild-type (wt) versus mutated (mut) patients were 54.8 and 48.3 %, respectively (OR 1.42, P = 0.02). Median PFS was significantly longer in KRAS wt patients compared with that in KRAS mut patients (HR = 0.85; 95 % confidence interval (CI) 0.74-0.98; P = 0.02). Similarly, median OS was significantly better in wt KRAS patients compared with that in mut KRAS patients (HR = 0.65; 95 % CI 0.46-0.92; P = 0.01). This pooled analysis of 12 published studies shows that KRAS wt status is a good prognostic factor for B-based chemotherapy. Also, KRAS wt CRC is associated with a better RR with B plus chemotherapy than mut counterpart.

Tumor stroma: a complexity dictated by the hypoxic tumor microenvironment

A lot of effort has been done to study how cancer cells react to low-oxygen tension, a condition known as hypoxia. Indeed, abnormal and dysfunctional blood vessels in the tumor are incapable to restore oxygenation, therefore perpetuating hypoxia, which, in turn, will fuel tumor progression, metastasis and resistance to antitumor therapies. Nevertheless, how stromal components including blood and lymphatic endothelial cells, pericytes and fibroblasts, as well as hematopoietic cells, respond to low-oxygen tension in comparison with their normoxic counterparts has been a matter of investigation in the last few years only and, to date, this field of research remains poorly understood. In general, opposing phenotypes can arise from the same stromal component when embedded in different tumor microenvironments, and, vice versa, different stromal components can have opposite reaction to the same tumor microenvironment. In this article, we will discuss the emerging link between tumor stroma and hypoxia, and how this complexity is translated at the molecular level.

Effects of HDM2 antagonism on sunitinib resistance, p53 activation, SDF-1 induction, and tumor infiltration by CD11b+/Gr-1+ myeloid derived suppressor cells

Background

The studies reported herein were undertaken to determine if the angiostatic function of p53 could be exploited as an adjunct to VEGF-targeted therapy in the treatment of renal cell carcinoma (RCC).

Methods

Nude/beige mice bearing human RCC xenografts were treated with various combinations of sunitinib and the HDM2 antagonist MI-319. Tumors were excised at various time points before and during treatment and analyzed by western blot and IHC for evidence of p53 activation and function.

Results

Sunitinib treatment increased p53 levels in RCC xenografts and transiently induced the expression of p21^waf1, Noxa, and HDM2, the levels of which subsequently declined to baseline (or undetectable) with the emergence of sunitinib resistance. The development of resistance and the suppression of p53-dependent gene expression temporally correlated with the induction of the p53 antagonist HDMX. The concurrent administration of MI-319 markedly increased the antitumor and anti-angiogenic activities of sunitinib and led to sustained p53-dependent gene expression. It also suppressed the expression of the chemokine SDF-1 (CXCL12) and the influx of CD11b⁺/Gr-1⁺ myeloid-derived suppressor cells (MDSC) otherwise induced by sunitinib. Although p53 knockdown markedly reduced the production of the angiostatic peptide endostatin, the production of endostatin was not augmented by MI-319 treatment.

Conclusions

The evasion of p53 function (possibly through the expression of HDMX) is an essential element in the development of resistance to VEGF-targeted therapy in RCC. The maintenance of p53 function through the concurrent administration of an HDM2 antagonist is an effective means of delaying or preventing the development of resistance.

Microvessel density and p53 mutations in advanced-stage epithelial ovarian cancer

We planned to determine the relationship between angiogenesis and p53 mutational status in advanced-stage epithelial ovarian cancer. Using 190 tumor samples from patients with stage III and IV ovarian cancer we performed p53 sequencing, immunohistochemistry, and CD31 microvessel density (MVD) determination. MVD was elevated in tumors with p53 null mutations compared to p53 missense mutation or no mutation. Disease recurrence was increased with higher MVD in both unadjusted and adjusted analyses. In adjusted analysis, p53 null mutation was associated with increased recurrence and worse overall survival. Worse overall survival and increased recurrence risk were also associated with the combination of CD31 MVD values >25 vessels/HPF and any p53 mutation. P53 mutation status and MVD may have prognostic significance in patients with advanced-stage ovarian cancer. Tumors with p53 null mutations are likely to be more vascular, contributing to decreased survival and increased recurrence probability.

Delta like ligand 4 induces impaired chemo-drug delivery and enhanced chemoresistance in pancreatic cancer

The stubborn chemoresistance of pancreatic ductal adenocarcinoma (PDA) is simultaneously influenced by tumor parenchymal and stromal factors, and the ctritical role of Notch ligand Delta-like 4 (DLL4) in the regulation of tumor malignancies has been observed. DLL4 positive expression ratio between duct cells from clinical tumor and adjacent tissues was statistically significant, and the overactivation of DLL4/Notch pathway enhanced the phenotype of EMT and cancer stem cell, even can induce multi-chemoresistance in vitro. Notably, the accompanied defective angiogenesis directly induced inefficient chemo-drug delivery in vivo. Collectively, overexpressed DLL4 on neoplastic cells can enhance chemoresistance through angiogenesis-dependent/independent mechanisms in PDA.

Targeting tumor neovasculature in non-small-cell lung cancer

Recent insight into the molecular biology of cancer and mechanisms of tumorigenesis, has allowed for the identification of several potential molecular targets and the development of novel "targeted therapies". One of the most active research fields in NSCLC is the discovery of therapies that target angiogenesis. The vascular endothelial growth factor (VEGF) pathway represents a crucial component of the tumor angiogenesis process. Two different strategies have been developed in clinical practice in order to restrict tumor vasculature development; either the use of monoclonal antibodies against VEGF or small molecule tyrosine kinase inhibitors to target the tyrosine kinase domain of VEGF receptor. Among these agents that have been tested bevacizumab, a monoclonal antibody against VEGF, has been approved for the treatment of metastatic NSCLC in combination with chemotherapy, while several other agents are under phase III investigation. Moreover, several issues such as predictive biomarkers of response to antiangiogenic therapy and mechanisms of resistance to these agents remain to be elucidated. The purpose of this paper is to present the current status of antiangiogenic therapies in the treatment of NSCLC and to discuss these issues.

Resistance and escape from antiangiogenesis therapy: clinical implications and future strategies

Angiogenesis has long been considered an important target for cancer therapy. Initial efforts have primarily focused on targeting of endothelial and tumor-derived vascular endothelial growth factor signaling. As evidence emerges that angiogenesis has significant mechanistic complexity, therapeutic resistance and escape have become practical limitations to drug development. Here, we review the mechanisms by which dynamic changes occur in the tumor microenvironment in response to antiangiogenic therapy, leading to drug resistance. These mechanisms include direct selection of clonal cell populations with the capacity to rapidly upregulate alternative proangiogenic pathways, increased invasive capacity, and intrinsic resistance to hypoxia. The implications of normalization of vasculature with subsequently improved vascular function as a result of antiangiogenic therapy are explored, as are the implications of the ability to incorporate and co-opt otherwise normal vasculature. Finally, we consider the extent to which a better understanding of the biology of hypoxia and reoxygenation, as well as the depth and breadth of systems invested in angiogenesis, may offer putative biomarkers and novel therapeutic targets. Insights gained through this work may offer solutions for personalizing antiangiogenesis approaches and improving the outcome of patients with cancer.

Immunomodulatory effects of low dose chemotherapy and perspectives of its combination with immunotherapy

Given that cancer is one of the main causes of death worldwide, many efforts have been directed toward discovering new treatments and approaches to cure or control this group of diseases. Chemotherapy is the main treatment for cancer; however, a conventional schedule based on maximum tolerated dose (MTD) shows several side effects and frequently allows the development of drug resistance. On the other side, low dose chemotherapy involves antiangiogenic and immunomodulatory processes that help host to fight against tumor cells, with lower grade of side effects. In this review, we present evidence that metronomic chemotherapy, based on the frequent administration of low or intermediate doses of chemotherapeutics, can be better than or as efficient as MTD. Finally, we present some data indicating that noncytotoxic concentrations of antineoplastic agents are able to both up-regulate the immune system and increase the susceptibility of tumor cells to cytotoxic T lymphocytes. Taken together, data from the literature provides us with sufficient evidence that low concentrations of selected chemotherapeutic agents, rather than conventional high doses, should be evaluated in combination with immunotherapy.

Oxidative stress in apoptosis and cancer: an update

The oxygen paradox tells us that oxygen is both necessary for aerobic life and toxic to all life forms. Reactive oxygen species (ROS) touch every biological and medical discipline, especially those involving proliferative status, supporting the idea that active oxygen may be increased in tumor cells. In fact, metabolism of oxygen and the resulting toxic byproducts can cause cancer and death. Efforts to counteract the damage caused by ROS are gaining acceptance as a basis for novel therapeutic approaches, and the field of prevention of cancer is experiencing an upsurge of interest in medically useful antioxidants. Apoptosis is an important means of regulating cell numbers in the developing cell system, but it is so important that it must be controlled. Normal cell death in homeostasis of multicellular organisms is mediated through tightly regulated apoptotic pathways that involve oxidative stress regulation. Defective signaling through these pathways can contribute to both unbalance in apoptosis and development of cancer. Finally, in this review, we discuss new knowledge about recent tools that provide powerful antioxidant strategies, and designing methods to deliver to target cells, in the prevention and treatment of cancer.

Targeting angiogenesis in lung cancer - Pitfalls in drug development

In non-small-cell lung cancer, anti-angiogenic strategies like bevacizumab have developed into standard treatment options. New anti-angiogenic drugs like tyrosine kinase inhibitors generated optimistic results in phase II trials, but failed to translate into positive results in phase III trials. In this overview some critical aspects of the biology of tumor angiogenesis and potential pitfalls of anti-angiogenic drug development are discussed. These include the design of clinical trials, dosage of investigational drugs or the choice of combinational drugs, the lack of validated biomarkers and the complexity of the patho-biology of tumor angiogenesis. Future trials should also direct attention to the role of cigarette smoke and the stage of the disease, which is investigated.

Angiogenesis in cancer: Anti-VEGF escape mechanisms

It is now widely accepted that tumor-angiogenesis plays a crucial role in tumor growth, tumor propagation and metastasis formation. Among several angiogenic activators, the vascular endothelial growth factor (VEGF) and its receptors represent one of the major inducers of tumor angiogenesis. Thus, this system has become the focus of therapeutic interventions, which led to the approval of the anti-VEGF blocking antibody bevacizumab and the VEGFR-2 pathway inhibitors pazopanib, sorafenib and sunitinib. However, not every cancer patient benefits from such treatment or finally becomes resistant to anti-VEGF approaches; others are suffering from adverse effects. Thus, there is an urgent need for a better understanding of VEGF-independent mechanisms leading to angiogenesis in cancer. This review focuses on anti-VEGF escape mechanisms of tumor cells and its microenvironment.

Identification of colorectal cancer metastasis markers by an angiogenesis-related cytokine-antibody array

AIM: To investigate the angiogenesis-related protein expression profile characterizing metastatic colorectal cancer (mCRC) with the aim of identifying prognostic markers.

METHODS: The expression of 44 angiogenesis-secreted factors was measured by a novel cytokine antibody array methodology. The study evaluated vascular endothelial growth factor (VEGF) and its soluble vascular endothelial growth factor receptor (sVEGFR)-1 protein levels by enzyme immunoassay (EIA) in a panel of 16 CRC cell lines. mRNA VEGF and VEGF-A isoforms were quantified by quantitative reverse-transcription polymerase chain reaction (Q-RT-PCR) and vascular endothelial growth factor receptor (VEGFR)-2 expression was analyzed by flow cytometry.

RESULTS: Metastasis-derived CRC cell lines expressed a distinctive molecular profile as compared with those isolated from a primary tumor site. Metastatic CRC cell lines were characterized by higher expression of angiopoietin-2 (Ang-2), macrophage chemoattractant proteins-3/4 (MCP-3/4), matrix metalloproteinase-1 (MMP-1), and the chemokines interferon γ inducible T cell α chemoattractant protein (I-TAC), monocyte chemoattractant protein I-309, and interleukins interleukin (IL)-2 and IL-1α, as compared to primary tumor cell lines. In contrast, primary CRC cell lines expressed higher levels of interferon γ (IFN-γ), insulin-like growth factor-1 (IGF-1), IL-6, leptin, epidermal growth factor (EGF), placental growth factor (PlGF), thrombopoietin, transforming growth factor β1 (TGF-β1) and VEGF-D, as compared with the metastatic cell lines. VEGF expression does not significantly differ according to the CRC cellular origin in normoxia. Severe hypoxia induced VEGF expression up-regulation but contrary to expectations, metastatic CRC cell lines did not respond as much as primary cell lines to the hypoxic stimulus. In CRC primary-derived cell lines, we observed a two-fold increase in VEGF expression between normoxia and hypoxia as compared to metastatic cell lines. CRC cell lines express a similar pattern of VEGF isoforms (VEGF₁₂₁, VEGF₁₆₅ and VEGF₁₈₉) despite variability in VEGF expression, where the major transcript was VEGF₁₂₁. No relevant expression of VEGFR-2 was found in CRC cell lines, as compared to that of human umbilical vein endothelial cells and sVEGFR-1 expression did not depend on the CRC cellular origin.

CONCLUSION: A distinct angiogenesis-related expression pattern characterizes metastatic CRC cell lines. Factors other than VEGF appear as prognostic markers and intervention targets in the metastatic CRC setting.

A phase 1 trial of E7974 administered on day 1 of a 21-day cycle in patients with advanced solid tumors

BACKGROUND

E7974, a synthetic analog of hemiasterlin, interacts with the tubulin molecule and overcomes resistance to other antitubulin drugs (taxanes and vinca alkaloids).

METHODS

In a phase 1 study, E7974 was given intravenously over a 2- to 5-minute infusion on day 1 of every 21-day cycle. Adult patients with advanced refractory solid tumors who had adequate organ function and Eastern Cooperative Oncology Group performance status 0 to 2 were eligible for this study. A modified Fibonacci schema was used. The maximal tolerated dose (MTD) was the dose where <2 of 6 patients developed a dose-limiting toxicity (DLT).

RESULTS

Twenty-eight patients (19 men and 9 women; median age, 64 years) treated at different cohort dose levels (0.18 mg/m(2) , 0.27 mg/m(2) , 0.36 mg/m(2) , 0.45 mg/m(2) , and 0.56 mg/m(2) ) received a total of 66 courses of E7974. The MTD was established at 0.45 mg/m(2) , where 1 of 6 patients experienced DLT (grade 4 febrile neutropenia). Of the 17 refractory colon cancer patients with a median of 3 prior treatments, stable disease was seen in 7 patients (41%). There were no tumor responses. Median progression-free survival was 1.2 months, and median overall survival was 6.7 months. In pharmacokinetic analysis, E7974 was characterized by a fast and moderately large distribution (37.95-147.93 L), slow clearance (2.23-7.15 L/h), and moderate to slow elimination (time to half-life, 10.4-30.5 hours).

CONCLUSIONS

This study shows that E7974 once every 21-day cycle shows antitumor activity in patients with refractory solid tumors. The recommended phase 2 dose is 0.45 mg/m(2).

Increased expression of histone demethylase JHDM1D under nutrient starvation suppresses tumor growth via down-regulating angiogenesis

Histone demethylase JHDM1D (also known as KDM7A) modifies the level of methylation in histone and participates in epigenetic gene regulation; however, the role of JHDM1D in tumor progression is unknown. Here, we show that JHDM1D plays a tumor-suppressive role by regulating angiogenesis. Expression of JHDM1D was increased in mouse and human cancer cells under long-term nutrient starvation in vitro. Expression of JHDM1D mRNA was increased within avascular tumor tissue at the preangiogenic switch, along with increased expression of angiogenesis-regulating genes such as Vegf-A. Stable expression of JHDM1D cDNA or siRNA silencing of JHDM1D in cancer cells did not affect cell proliferation, anchorage-independent cell growth, or cell cycle progression in vitro. Notably, JHDM1D-expressing mouse melanoma (B16) and human cervical carcinoma (HeLa) cells exhibited significantly slower tumor growth in vivo compared with the original cells. This reduction in tumor growth was associated with decreased formation of CD31(+) blood vessels and reduced infiltration of CD11b(+) macrophage linage cells into tumor tissues. Expression of multiple angiogenic factors such as VEGF-B and angiopoietins was decreased in tumor xenografts of JHDM1D-expressing B16 and HeLa cells. Our results provide evidence that increased JHDM1D expression suppressed tumor growth by down-regulating angiogenesis under nutrient starvation.

Mechanisms of resistance to vascular endothelial growth factor blockade

Angiogenesis is essential for the growth of primary tumors and for their metastasis. This process is induced by factors, such as vascular endothelial growth factors (VEGFs), that bind to transmembrane VEGF receptors (VEGFRs). VEGF-A is the primary factor involved with angiogenesis; it binds to both VEGFR-1 and VEGFR-2. The inhibition of angiogenesis by obstructing VEGF-A signaling has been investigated as a method to treat solid tumors, but the development of resistance to this blockade has complicated treatment. The major mechanisms of this resistance to VEGF-A blockade include signaling by redundant receptors, such as the fibroblast growth factors, angiopoietin-1, ephrins, and other forms of VEGF. Other major mechanisms of resistance are increased metastasis of hypoxia-resistant tumor cells, recruitment of cell types capable of promoting VEGF-independent angiogenesis, and increased circulation of nontumor proangiogenic factors. Additional mechanisms of resistance to VEGF-A blockade include heterogeneity of responsiveness among tumor cells, use of anti-VEGF-A agents at insufficient doses or for insufficient duration, altered sensitivity to anti-VEGF-A agents by mutations in endothelial cells or vascular remodeling, maintenance of vascular sleeves that allow for easy regrowth of tumor vasculature upon discontinuation of therapy, vascular cooption, and intussusceptive angiogenesis. An understanding of these mechanisms may lead to the development of targeted therapies that overcome this resistance. Some of these approaches include the combined inhibition of redundant angiogenic pathways, proper patient selection for various therapies based on gene expression profiles, blockade of cellular migration by inhibition of colony-stimulating factor, or the use of agents to disrupt vascular architecture.

Mechanisms of resistance to anti-angiogenic therapy and development of third-generation anti-angiogenic drug candidates

The concept of inhibiting tumor neovessels has taken the hurdle from the bench to the bedside and now represents an extra pillar of anticancer treatment. So far, anti-angiogenic therapy prolongs survival in the order of months in some settings while failing to induce a survival benefit in others, in part because of intrinsic refractoriness or evasive escape. This review provides an update on recent mechanisms via which tumor and stromal cells induce resistance and discusses recent evolutions in the (pre)clinical development of novel third-generation anti-angiogenic agents to overcome this problem.

Angiogenesis in head and neck cancer: a review of the literature

Angiogenesis is a necessary process for tumor growth, progression and diffusion. In the last years many efforts have been made to understand the mechanisms necessary to the formation of new vessels in tumor tissue and how to integrate these findings in the treatment of different type of cancer. Thanks to these studies there are today many anti-angiogenic drugs with established activity in cancer and approved in clinical practice. Head and neck cancer is a common tumor worldwide that often has advanced stage at diagnosis and poor prognosis. Angiogenesis has a well recognized role in head and neck cancer progression and resistance to drugs and radiotherapy and many clinical trials has been conducted with antiangiogenic agents in this disease, even if they often showed limited efficacy. In this review we summarize the main trials published about angiogenesis in head and neck cancer with particular attention to factors involved in this process and the available data on the efficacy of treatment with anti-angiogenic agents in this disease.