Why targeted therapy hasn't worked in advanced cancer

EGFR inhibitors, MHC expression and immune responses : Can EGFR inhibitors be used as immune response modifiers?

A recent study from our laboratory demonstrated that epidermal growth factor receptor (EGFR) inhibitors (EGFRIs) augment the expression of class I and class II MHC molecules. This finding provides an additional mechanism through which EGFRIs may exert anti-tumor effects and supports the notion that EGFRIs may influence adaptive immune responses by altering immune gene expression.

Oncogene Overdose: Too Much of a Bad Thing for Oncogene-Addicted Cancer Cells

Acquired resistance to targeted inhibitors remains a major, and inevitable, obstacle in the treatment of oncogene-addicted cancers. Newer-generation inhibitors may help overcome resistance mutations, and inhibitor combinations can target parallel pathways, but durable benefit to patients remains elusive in most clinical scenarios. Now, recent studies suggest a third approach may be available in some cases—exploitation of oncogene overexpression that may arise to promote resistance. Here, we discuss the importance of maintaining oncogenic signaling at “just-right” levels in cells, with too much signaling, or oncogene overdose, being potentially as detrimental as too little. This is highlighted in particular by recent studies of mutant-BRAF in melanoma and the fusion kinase nucleophosmin–anaplastic lymphoma kinase (NPM–ALK) in anaplastic large cell lymphoma. Oncogene overdose may be exploitable to prolong tumor control through intermittent dosing in some cases, and studies of acute lymphoid leukemias suggest that it may be specifically pharmacologically inducible.

Targeting angiogenesis in squamous non-small cell lung cancer

Non-small cell lung cancer (NSCLC) is the most common type of lung cancer, and can be further classified as nonsquamous carcinoma (including adenocarcinoma, which accounts for 40 % of NSCLCs) and squamous NSCLC, which makes up 30 % of NSCLC cases. The emergence of inhibitors of epidermal growth factor receptors, anaplastic lymphoma kinase, and vascular endothelial growth factors (VEGF) in the last decade has resulted in steady improvement in clinical outcomes for patients with advanced lung adenocarcinoma. However, improvements in the survival of patients with squamous NSCLC have remained elusive, presenting an urgent need for understanding and investigating therapeutically relevant molecular targets, specifically in squamous NSCLC. Although anti-VEGF therapy has been studied in squamous NSCLC, progress has been slow, in part due to issues related to pulmonary hemorrhage. In addition to these safety concerns, several phase III trials that initially included patients with squamous NSCLC failed to demonstrate improved overall survival (primary endpoint) with the addition of antiangiogenic therapy to chemotherapy compared with chemotherapy alone. Angiogenesis is an established hallmark of tumor progression and metastasis, and the role of VEGF signaling in angiogenesis is well established. However, some studies suggest that, while inhibiting VEGF signaling may be beneficial, prolonged exposure to VEGF/VEGF receptor (VEGFR) inhibitors may allow tumor cells to utilize alternative angiogenic mechanisms and become resistant. As a result, agents that target multiple angiogenic pathways simultaneously are also under evaluation. This review focuses on current and investigational antiangiogenic targets in squamous NSCLC, including VEGF/VEGFRs, fibroblast growth factor receptors, platelet-derived growth factor receptors, and angiopoietin. Additionally, clinical trials investigating VEGF- and multi-targeted antiangiogenic therapies are discussed.

Honokiol Eliminates Human Oral Cancer Stem-Like Cells Accompanied with Suppression of Wnt/ β -Catenin Signaling and Apoptosis Induction

Honokiol, an active compound of Magnolia officinalis, exerted many anticancer effects on various types of cancer cells. We explored its effects on the elimination of cancer stem-like side population (SP) cells in human oral squamous cell carcinoma SAS cells. The sorted SP cells possessed much higher expression of stemness genes, such as ABCG2, ABCC5, EpCAM, OCT-4, CD133, CD44, and β-catenin, and more clonogenicity as compared with the Non-SP cells. After 48 h of treatment, honokiol dose dependently reduced the proportion of SP from 2.53% to 0.09%. Apoptosis of honokiol-treated SP cells was evidenced by increased annexin V staining and cleaved caspase-3 as well as decreased Survivin and Bcl-2. Mechanistically, honokiol inhibited the CD44 and Wnt/β-catenin signaling of SP cells. The Wnt signaling transducers such as β-catenin and TCF-4 were decreased in honokiol-treated SP cells, while the β-catenin degradation promoting kinase GSK-3α/β was increased. Consistently, the protein levels of β-catenin downstream targets such as c-Myc and Cyclin D1 were also downregulated. Furthermore, the β-catenin-related EMT markers such as Slug and Snail were markedly suppressed by honokiol. Our findings indicate honokiol may be able to eliminate oral cancer stem cells through apoptosis induction, suppression of Wnt/β-catenin signaling, and inhibition of EMT.

Prognostic impact of angiogenic markers in non-small-cell lung cancer is related to tumor size

BACKGROUND

It is thought that different families of angiogenic factors stimulate angiogenesis at different stages of tumor development. Our aim was to study whether the prognostic impact of vascular endothelial growth factors (VEGFs) and receptors (VEGFRs), platelet-derived growth factors (PDGFs) and receptors (PDGFRs) and fibroblast growth factor-2 (FGF-2) were associated with tumor size in non-small-cell lung cancer (NSCLC).

PATIENTS AND METHODS

Tumor tissue samples were obtained from 335 patients who had undergone resection for stage I-IIIA NSCLC, and tissue microarrays (TMAs) were constructed. Immunohistochemical techniques were used to evaluate the expression of VEGF-A, VEGF-C, VEGFR-2, VEGFR-3, PDGF-A, PDGF-B, PDGFR-α, PDGFR-β, and FGF-2. Tumor size was categorized using the same cutoffs as in the 7th TNM classification for lung cancer.

RESULTS

In multivariate analysis, high VEGFR-2 (HR, 1.87, [95% CI, 1.02-3.45]; P = .043), VEGFR-3 (HR, 2.18 [95% CI, 1.28-3.71]; P = .004) and the combination of high VEGF-A and high VEGFR-2 expression (low/low vs. high/high; HR, 3.28 [95% CI, 1.47-7.31]; P = .004) were independent negative prognostic factors in T2a tumors. High PDGF-B expression (HR, 11.72 [95% CI, 3.07-44.76]; P < .001) was an independent prognostic factor in T2b tumors.

CONCLUSION

The prognostic impact of angiogenic factors depend in part on tumor size. VEGF-A/VEGFR-2 and VEGFR-3 seem to have their main impact in T2a tumors, while PDGF-B is a strong and independent prognostic factor in T2b tumors.

Novel angiogenesis inhibitors: addressing the issue of redundancy in the angiogenic signaling pathway

Angiogenesis, the formation of new blood vessels from established vasculature, is a fundamental process in the growth and metastasis of solid tumours. It is a complex, tightly regulated process that requires the coordinated action of antiangiogenic and proangiogenic factors, the balance of which becomes disturbed during tumour development. Vascular endothelial growth factor (VEGF) and its receptor are the key mediators of angiogenesis and targets for multiple pharmacologic agents. Many patients treated with VEGF inhibitors survive for a longer period; however, eventual resistance is associated with progressive disease and death. Multiple approaches to overcome resistance have been investigated with varying success, including the use of agents that target multiple angiogenic factors or co-administration of angiogenesis inhibitors with standard chemotherapy or radiotherapy. It would appear that the future of angiogenic inhibitors lies in the intelligent combination of multiple targeted agents with other angiogenic inhibitors, as well as more conventional therapies to maximise therapeutic effect.

Novel antiangiogenic agents in dermatology

Because angiogenesis underlies the pathogenesis of numerous conditions (cancer, psoriasis, macular degeneration), there is a pressing need for continued investigations into angiogenic signaling and potential drug targets. Antiangiogenic agents can be classified as either direct or indirect. Direct antiangiogenics act on untransformed endothelial cells to prevent differentiation and proliferation; indirect antiangiogenics act to inhibit factors involved in proangiogenic signaling. Agents currently available with dermatologic indications are few; while several established and novel biologics targeting various proangiogenic factors are currently being investigated for potential dermatologic uses, but the jury is still out on their efficacy and safety. In this review, we highlight our experience with a group of existing and novel, small molecules that combine several modes of action against angiogenesis in addition to other properties--triarylmethane dyes and fulvene derivatives.

META060 inhibits osteoclastogenesis and matrix metalloproteinases in vitro and reduces bone and cartilage degradation in a mouse model of rheumatoid arthritis

OBJECTIVE

The multikinase inhibitor META060 has been shown to inhibit NF-kappaB activation and expression of markers of inflammation. This study was undertaken to investigate the effect of META060 on biomarkers associated with bone and cartilage degradation in vitro and its antiinflammatory efficacy in vivo in both acute and chronic inflammation models.

METHODS

Glycogen synthase kinase 3beta (GSK3beta)-dependent beta-catenin phosphorylation was evaluated in RAW 264.7 macrophages to assess kinase inhibition. The inhibition of osteoclastogenesis and tartrate-resistant acid phosphatase (TRAP) activity was evaluated in RANKL-treated RAW 264.7 cells. The inhibition of interleukin-1beta (IL-1beta)-mediated markers of inflammation was analyzed in human rheumatoid arthritis synovial fibroblasts (RASFs). Mice with carrageenan-induced acute inflammation and collagen-induced arthritis (CIA) were used to assess efficacy.

RESULTS

META060 inhibited the activity of kinases (spleen tyrosine kinase [Syk], Bruton's tyrosine kinase [Btk], phosphatidylinositol 3-kinase [PI 3-kinase], and GSK3) associated with RA and inhibited beta-catenin phosphorylation. META060 inhibited osteoclastogenesis, as indicated by decreased transformation of RAW 264.7 cells to osteoclasts and reduced TRAP activity, and inhibited IL-1beta-activated prostaglandin E(2), matrix metalloproteinase 3, IL-6, IL-8, and monocyte chemotactic protein 1 in RASFs. In mice with acute inflammation, oral administration of META060 reduced paw swelling similar to the effect of aspirin. In mice with CIA, META060 significantly reduced the arthritis index and decreased bone, joint, and cartilage degradation. Serum IL-6 concentrations in these mice were inhibited in a dose-dependent manner.

CONCLUSION

Our findings indicate that META060 reduces swelling in a model of acute inflammation and inhibits bone and cartilage destruction in a model of chronic inflammation. Its efficacy is associated with the inhibition of multiple protein kinases, including Syk, Btk, PI 3-kinase, and GSK3. These results warrant further clinical testing of META060 for its therapeutic potential in the treatment of inflammatory diseases.

Prognostic impact of fibroblast growth factor 2 in non-small cell lung cancer: coexpression with VEGFR-3 and PDGF-B predicts poor survival

PURPOSE

Fibroblast growth factor 2 (FGF2; basic fibroblast growth factor, b-FGF) and its main receptor FGFR-1 are important in both hemangiogenesis and lymphangiogenesis. Murine studies have indicated a close interplay between both FGF2 and platelet-derived growth factor-B (PDGF-B) as well as FGF2 and vascular endothelial growth factor-3 (VEGFR-3). This study investigates the prognostic impact of FGF2 and FGFR-1 in tumor cells and tumor stroma of resected non-small cell lung carcinomas (NSCLC) and explores the importance of their coexpression with VEGFR-3 or PDGF-B.

METHODS

Tumor tissue samples from 335 resected patients with stage I to IIIA NSCLC were obtained and tissue microarrays were constructed from duplicate cores of tumor cells and tumor-related stroma from each specimen. Immunohistochemistry was used to evaluate the expression of the molecular markers FGF2, FGFR-1, VEGFR-3, and PDGF-B.

RESULTS

In univariate analyses, high tumor cell FGF2 expression (p = 0.015) was a negative prognostic indicator for disease-specific survival. In tumor stroma, high FGF2 (p = 0.024) expression correlated with good prognosis. In multivariate analyses, high expression of FGF2 in tumor cells (p = 0.038) was an independent negative prognostic factor whereas increased FGF2 in stroma (p = 0.015) was a positive prognosticator. Tumor cell coexpressions of FGF2/VEGFR-3 (p < 0.001) and FGFR-1/PDGF-B (p = 0.002) were significant indicators of poor prognosis.

CONCLUSIONS

Expression of FGF2 in tumor cells is an independent negative prognostic factor, and the coexpressions of FGF2/VEGFR-3 and FGFR-1/PDGF-B are strongly associated with poor survival in NSCLC patients.

Honokiol, a multifunctional antiangiogenic and antitumor agent

Honokiol is a small-molecule polyphenol isolated from the genus Magnolia. It is accompanied by other related polyphenols, including magnolol, with which it shares certain biologic properties. Recently, honokiol has been found to have antiangiogenic, antiinflammatory, and antitumor properties in preclinical models, without appreciable toxicity. These findings have increased interest in bringing honokiol to the clinic as a novel chemotherapeutic agent. In addition, mechanistic studies have tried to find the mechanism(s) of action of honokiol, for two major reasons. First, knowledge of the mechanisms of action may assist development of novel synthetic analogues. Second, mechanistic actions of honokiol may lead to rational combinations with conventional chemotherapy or radiation for enhanced response to systemic cancers. In this review, we describe the findings that honokiol has two major mechanisms of action. First, it blocks signaling in tumors with defective p53 function and activated ras by directly blocking the activation of phospholipase D by activated ras. Second, honokiol induces cyclophilin D, thus potentiating the mitochondrial permeability transition pore, and causing death in cells with wild-type p53. Knowledge of the dual activities of honokiol can assist with the development of honokiol derivatives and the design of clinical trials that will maximize the potential benefit of honokiol in the patient setting.

Unexpected autocrine role of vascular endothelial growth factor in squamous cell carcinoma

Mirones et al. demonstrate that keratinocytes deficient in VEGF are capable of forming tumors but use a distinct form of aneuploidy and signaling to form tumors. This knowledge is important because inhibitors of VEGF, including bevacizumab (anti-VEGF antibodies) and sorafenib (Braf/VEGFR2 kinase inhibitor), have already entered the clinic. These agents may "remodel" tumor signaling.

Differential roles of PDGFR-alpha and PDGFR-beta in angiogenesis and vessel stability

Preclinical and clinical evaluations of individual proangiogenic/arteriogenic factors for the treatment of ischemic myocardium and skeletal muscle have produced unfulfilled promises. The establishment of functional and stable arterial vascular networks may require combinations of different angiogenic and arteriogenic factors. Using in vivo angiogenesis and ischemic hind-limb animal models, we have compared the angiogenic and therapeutic activities of fibroblast growth factor 2 (FGF-2) in combinations with PDGF-AA and PDGF-AB, two members of the platelet-derived growth factor (PDGF) family, with distinct receptor binding patterns. We show that both PDGF-AA/FGF-2 and PDGF-AB/FGF-2 in combinations synergistically induce angiogenesis in the mouse cornea. FGF-2 up-regulates PDGFR-alpha and -beta expression levels in the newly formed blood vessels. Interestingly, PDGF-AB/FGF-2, but not PDGF-AA/FGF-2, is able to stabilize the newly formed vasculature by recruiting pericytes, and an anti-PDGFR-beta neutralizing antibody significantly blocks PDGF-AB/FGF-2-induced vessel stability. These findings demonstrate that PDGFR-beta receptor is essential for vascular stability. Similarly, PDGF-AB/FGF-2 significantly induces stable collateral growth in the rat ischemic hind limb. The high number of collaterals induced by PDGF-AB/FGF-2 leads to dramatic improvement of the paw's skin perfusion. Immunohistochemical analysis of the treated skeletal muscles confirms that a combination of PDGF-AB and FGF-2 significantly induces arteriogenesis in the ischemic tissue. A combination of PDGF-AB and FGF-2 would be optimal proangiogenic agents for the treatment of ischemic diseases.

FIP1L1/PDGFRalpha synergizes with SCF to induce systemic mastocytosis in a murine model of chronic eosinophilic leukemia/hypereosinophilic syndrome

Expression of the fusion gene FIP1-like 1/platelet-derived growth factor receptor alpha (FIP1L1/PDGFRalpha, F/P) and dysregulated c-kit tyrosine kinase activity are associated with systemic mastocytosis (SM) and chronic eosinophilic leukemia (CEL)/hypereosinophilic syndrome (HES). We analyzed SM development and pathogenesis in a murine CEL model induced by F/P in hematopoietic stem cells and progenitors (HSCs/Ps) and T-cell overexpression of IL-5 (F/P-positive CEL mice). These mice had more mast cell (MC) infiltration in the bone marrow (BM), spleen, skin, and small intestine than control mice that received a transplant of IL-5 transgenic HSCs/Ps. Moreover, intestinal MC infiltration induced by F/P expression was severely diminished, but not abolished, in mice injected with neutralizing anti-c-kit antibody, suggesting that endogenous stem cell factor (SCF)/c-kit interaction synergizes with F/P expression to induce SM. F/P-expressing BM HSCs/Ps showed proliferation and MC differentiation in vitro in the absence of cytokines. SCF stimulated greater migration of F/P-expressing MCs than mock vector-transduced MCs. F/P-expressing bone marrow-derived mast cells (BMMCs) survived longer than mock vector control BMMCs in cytokine-deprived conditions. The increased proliferation and survival correlated with increased SCF-induced Akt activation. In summary, F/P synergistically promotes MC development, activation, and survival in vivo and in vitro in response to SCF.

Incorporating molecular tools into early-stage clinical trials

The author discusses the implications of a new phase I trial investigating the role of rapamycin in patients with glioblastoma.