Angiogenesis in urological malignancy: prognostic indicator and therapeutic target

Tetraspanins as regulators of the tumour microenvironment: implications for metastasis and therapeutic strategies

One of the hallmarks of cancer is the ability to activate invasion and metastasis. Cancer morbidity and mortality are largely related to the spread of the primary, localized tumour to adjacent and distant sites. Appropriate management and treatment decisions based on predicting metastatic disease at the time of diagnosis is thus crucial, which supports better understanding of the metastatic process. There are components of metastasis that are common to all primary tumours: dissociation from the primary tumour mass, reorganization/remodelling of extracellular matrix, cell migration, recognition and movement through endothelial cells and the vascular circulation and lodgement and proliferation within ectopic stroma. One of the key and initial events is the increased ability of cancer cells to move, escaping the regulation of normal physiological control. The cellular cytoskeleton plays an important role in cancer cell motility and active cytoskeletal rearrangement can result in metastatic disease. This active change in cytoskeletal dynamics results in manipulation of plasma membrane and cellular balance between cellular adhesion and motility which in turn determines cancer cell movement. Members of the tetraspanin family of proteins play important roles in regulation of cancer cell migration and cancer-endothelial cell interactions, which are critical for cancer invasion and metastasis. Their involvements in active cytoskeletal dynamics, cancer metastasis and potential clinical application will be discussed in this review. In particular, the tetraspanin member, CD151, is highlighted for its major role in cancer invasion and metastasis.

LINKED ARTICLES

This article is part of a themed section on Cytoskeleton, Extracellular Matrix, Cell Migration, Wound Healing and Related Topics. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2014.171.issue-24.

Tumor Anti-angiogenic Gene Therapy with Microencapsulated Recombinant CHO Cells

Microencapsulation of recombinant cells is a novel promising approach to tumor therapy in which therapeutic protein is sustainable and long-term delivered by microencapsulated cells. The semi-permeable membrane of microcapsule can protect cell from host's immune rejection, increase the chemical stability of therapeutic protein and circumvent the problems of toxicity, limited half-lives and variation in circulating levels. Endostatin, a potent and specific angiogenesis inhibitor, could suppress the growth of primary and metastatic lesions in multiple murine tumor models. In this paper, APA microcapsules with high strength kept intact over 35 days and recombinant CHO cells kept the rapid proliferation viability and the continuous endostatin-expression function. The study of tumor treatment showed that the implantation of microencapsulated recombinant CHO cells decreased the neovascularization of tumor tissue by 59.4% and inhibited the B16 melanoma growth by 77.4%. Twenty days after tumor cell injection, 80% of animals treated with microencapsulated CHO-endo cells were alive compared to only 50% of animals in either control or mock control groups. Therefore, continuous delivery of endostatin from microencapsulated recombinant cells represents a feasible approach to tumor therapy.

The use of thalidomide in androgen-independent prostate cancer

More than 200,000 men will be diagnosed with prostate cancer during the year 2006. Approximately 20% to 30% of these cases may develop advanced disease, for which there currently is no cure. Although therapy for this disease has improved significantly over the past few years, with docetaxel treatment showing improved survival times in metastatic disease, there remains the need for improved treatment options. Dr. Folkman put forth the idea of angiogenesis in 1971, and, since that time, researchers have been trying to determine the best possible way to inhibit blood vessel formation. This review summarizes the use of thalidomide in androgen-independent prostate cancer and the results of trials conducted at the National Cancer Institute.

Results of a phase I trial of sorafenib (BAY 43-9006) in combination with oxaliplatin in patients with refractory solid tumors, including colorectal cancer

BACKGROUND

Sorafenib (BAY 43-9006), a multiple kinase inhibitor, has been shown to inhibit tumor growth and tumor angiogenesis by targeting Raf kinase, vascular endothelial growth factor receptor, and platelet-derived growth factor receptor. In phase I studies, sorafenib demonstrated single-agent activity in patients with advanced solid tumors and was successfully combined with oxaliplatin in preclinical studies. This phase I study investigated the safety, pharmacokinetics, and efficacy of sorafenib in combination with oxaliplatin.

PATIENTS AND METHODS

Twenty-seven patients with refractory solid tumors were enrolled in the initial dose-escalation part (cohorts 1, 2A, and 2B) and 10 additional patients with oxaliplatin-refractory colorectal cancer were subsequently enrolled in an extension part (cohort 3). Oxaliplatin 130 mg/m2 was given on day 1 of a 3-week cycle and oral sorafenib was administered continuously from day 4 of cycle 1 at 200 mg twice daily (cohort 1) or 400 mg twice daily (cohorts 2A, 2B, and 3).

RESULTS

Adverse events were generally mild to moderate and the maximum tolerated dose was not reached. Common adverse events were diarrhea (52% of patients in the dose-escalation part and 20% in the extension part), sensory neuropathy (44% and 20%), and dermatologic toxicities (41% and 80%). No pharmacokinetic interaction between sorafenib and oxaliplatin was detectable. Two patients with gastric cancer had a partial response. Forty-three percent of patients in cohorts 1 and 2A/B and 78% of patients in cohort 3 exhibited stable disease for >or=10 weeks.

CONCLUSION

Continuous oral sorafenib 400 mg twice daily was safely combined with oxaliplatin without detectable drug interactions and showed preliminary antitumor activity in this phase I study. This dose is recommended for phase II studies.

Antiangiogenesis: A Possible Treatment Option for Prostate Cancer?

With a need for effective treatment modalities in prostate cancer, angiogenesis is a likely target for the interference of tumor progression. Angiogenesis promotes the vasculature of a tumor, allowing for tumor progression and for cancer cells to metastasize and spread throughout the circulatory system. To date, there are > 20 antiangiogenic drugs undergoing preclinical and clinical investigation alone and in conjunction with other treatment options to determine the validity of antiangiogenic agents in the treatment of prostate cancer. This article reviews several aspects of antiangiogenesis and its relationship to the treatment of prostate cancer.

Cotargeting tumor and tumor endothelium effectively inhibits the growth of human prostate cancer in adenovirus-mediated antiangiogenesis and oncolysis combination therapy

Tumor-endothelial interaction contributes to local prostate tumor growth and distant metastasis. In this communication, we designed a novel approach to target both cancer cells and their "crosstalk" with surrounding microvascular endothelium in an experimental hormone refractory human prostate cancer model. We evaluated the in vitro and in vivo synergistic and/or additive effects of a combination of conditional oncolytic adenovirus plus an adenoviral-mediated antiangiogenic therapy. In the in vitro study, we demonstrated that human umbilical vein endothelial cells (HUVEC) and human C4-2 androgen-independent (AI) prostate cancer cells, when infected with an antiangiogenic adenoviral (Ad)-Flk1-Fc vector secreting a soluble form of Flk1, showed dramatically inhibited proliferation, migration and tubular formation of HUVEC endothelial cells. C4-2 cells showed maximal growth inhibition when coinfected with Ad-Flk1-Fc and Ad-hOC-E1, a conditional replication-competent Ad vector with viral replication driven by a human osteocalcin (hOC) promoter targeting both prostate cancer epithelial and stromal cells. Using a three-dimensional (3D) coculture model, we found that targeting C4-2 cells with Ad-hOC-E1 markedly decreased tubular formation in HUVEC, as visualized by confocal microscopy. In a subcutaneous C4-2 tumor xenograft model, tumor volume was decreased by 40-60% in animals treated with Ad-Flk1-Fc or Ad-hOC-E1 plus vitamin D3 alone and by 90% in a combined treatment group, compared to untreated animals in an 8-week treatment period. Moreover, three of 10 (30%) pre-established tumors completely regressed when animals received combination therapy. Cotargeting tumor and tumor endothelium could be a promising gene therapy strategy for the treatment of both localized and metastatic human prostate cancer.

Transition of an androgen-dependent human prostate cancer cell line into an androgen-independent subline is associated with increased angiogenesis

BACKGROUND

Androgen-independent prostate cancer is today an incurable disease, but increased understanding of the mechanisms for the transition into an androgen-independent state may increase the possibilities for more efficient strategies in the future.

METHODS

An androgen-independent subline, LNCaP-19, to the androgen-dependent prostate cancer cell line LNCaP was developed in vitro under standard culture conditions. The characteristics of LNCaP-19 regarding androgen responsiveness, PSA, and VEGF secretion was studied in vitro. The growth in vivo and the microvessel density (MVD) of the tumors were studied after inoculation in nude mice.

RESULTS

LNCaP-19 grows equally well in dextran-charcoal stripped FBS (DCC-FBS) as in normal FBS, and rapidly gives rise to tumors in both intact and castrated mice, indicating a true androgen-independent growth. The PSA secretion from LNCaP-19 cells was lower than from LNCaP cells, while the VEGF level was comparable to the secretion from LNCaP cells without androgen stimulation. The MVD was increased in the LNCaP-19 tumors, and the vessels also displayed a changed morphology with exclusively small microvessels without lumen.

CONCLUSIONS

LNCaP-19 shows characteristics resembling those of androgen-independent prostate cancer. An increased MVD and changed vessel morphology in the tumor, makes it an interesting model system for studies regarding angiogenesis in the context of the acquisition of androgen independence.

Randomized phase II trial of docetaxel plus thalidomide in androgen-independent prostate cancer

PURPOSE

Both docetaxel and thalidomide have demonstrated activity in androgen-independent prostate cancer (AIPC). We compared the efficacy of docetaxel to docetaxel plus thalidomide in patients with AIPC.

METHODS

Seventy-five patients with chemotherapy-naïve metastatic AIPC were randomly assigned to receive either docetaxel 30 mg/m(2) intravenously every week for 3 consecutive weeks, followed by a 1-week rest period (n = 25); or docetaxel at the same dose and schedule, plus thalidomide 200 mg orally each day (n = 50). Prostate-specific antigen (PSA) consensus criteria and radiographic scans were used to determine the proportion of patients with a PSA decline, and time to progression.

RESULTS

After a median potential follow-up time of 26.4 months, the proportion of patients with a greater than 50% decline in PSA was higher in the docetaxel/thalidomide group (53% in the combined group, 37% in docetaxel-alone arm). The median progression-free survival in the docetaxel group was 3.7 months and 5.9 months in the combined group (P =.32). At 18 months, overall survival in the docetaxel group was 42.9% and 68.2% in the combined group. Toxicities in both groups were manageable after administration of prophylactic low-molecular-weight heparin in the combination group.

CONCLUSION

In this randomized phase II trial, the addition of thalidomide to docetaxel resulted in an encouraging PSA decline rate and overall median survival rate in patients with metastatic AIPC. After the prophylactic low-molecular-weight heparin was instituted to prevent venous thromboses, the combination regimen was well tolerated. Larger randomized trials are warranted to assess the impact of this combination.

The Combination of Antiangiogenic and Cytotoxic Agents in the Treatment of Prostate Cancer

Metastatic prostate cancer is one of the leading causes of cancer death in men. Although initially responsive to hormone therapy, it eventually progresses in almost all patients. For this reason, there has been a search for novel agents to use in the fight against androgen-independent prostate cancer. Antiangiogenesis is a relatively new antitumor strategy that has been employed in the treatments of many malignancies. As prostate cancer is likely dependent on angiogenesis for its growth and progression, it would logically serve as a good target for this modality. Initially met with great enthusiasm, antiangiogenic drugs have seen only limited success when used as single agents. This has been attributed to many possible etiologies including lack of cytotoxicity and use in situations of large tumor burden. In order to overcome these problems, many investigators are combining antiangiogenic agents with more traditional cytotoxic chemotherapy regimens in hope of augmenting the effects of either drug alone. This article will review the background of angiogenesis inhibition and the use of such combinations in metastatic prostate cancer.

Angiogenesis in prostate cancer: its role in disease progression and possible therapeutic approaches

The interaction between cancer cells and their microenvironment is a promising area for the development of novel therapeutic anti-cancer modalities. The formation of new blood vessels, angiogenesis, is an important step in cancer progression. Angiogenesis is a complex multistep process involving close orchestration of endothelial cells, extracellular matrix, and soluble factors. Essentially every step has been found to be regulated by inducers and inhibitors. Prostate cancer has the ability to produce angiogenic factors such as metalloproteinases, vascular endothelial growth factor, fibroblast growth factor 2, transforming growth factor-beta and cyclooxygenase-2. In several studies in prostate cancer an increased microvessel density is associated with poorer prognosis. On the other hand several endogenous inhibitors of angiogenesis have been described in prostate cancer e.g., angiostatin, endostatin, prostate specific antigen (PSA), thrombospondin-1, interleukin 10, interferons and retinoids. The expanding insight in the process of angiogenesis has resulted in a large number of pharmaceutical agents that have been tested in preclinical studies and are currently tested in clinical trials. These agents inhibit endothelial cell proliferation or migration and induce apoptosis. This ultimately will affect the formation of new vessels thereby inducing tumor dormancy. Because antiangiogenic treatment is cytostatic rather than cytotoxic, patients will need long-term therapy to prevent regrowth of the tumor. Prostate cancer is an ideal tumor for antiangiogenic studies because of the availability of a reliable tumor marker, PSA, the indolent clinical course of this cancer and the low rate of proliferation even in metastatic sites. Furthermore, clinical studies showed limited side effects, which is advantageous in this elderly patient group. Whether the ultimate antiangiogenic treatment is effective as a single agent or in combination with radiation therapy, chemotherapy or immunotherapy remains to be determined.

The hypoxia-inducible genes VEGF and CA9 are differentially regulated in superficial vs invasive bladder cancer

Regulation by hypoxia may underlie the expression of vascular endothelial growth factor in bladder cancer. We have compared the distribution of vascular endothelial growth factor mRNA with a hypoxia marker, carbonic anhydrase 9 (CA IX). vascular endothelial growth factor mRNA was analysed by in situ hybridisation and CA IX by immunochemistry in 22 cases of bladder cancer. The relationship of microvessels to the distribution of CA IX was determined. In a separate series of 49 superficial tumours, CA IX immunostaining was compared with clinico-pathological outcome. In superficial and invasive disease there was overlap in the expression of vascular endothelial growth factor and CA IX, CA IX being more widespread. Both were expressed predominantly on the luminal surface, and surrounding areas of necrosis (invasive tumours). Expression of both factors was greater in superficial disease. Expression was absent within approximately 80 microm of microvessels. Unlike vascular endothelial growth factor, CA IX did not predict outcome in superficial disease. Differential responses to reoxygenation provide one explanation: vascular endothelial growth factor mRNA declined rapidly, while CA IX expression was sustained for >72 h. Expression of vascular endothelial growth factor mRNA in bladder tumours is consistent with hypoxic regulation and suggests differential regulation in superficial vs invasive disease. The expression of CA IX on the luminal surface justifies investigation of its utility as a therapeutic target/prognostic indicator.

Blood vessels are regulators of growth, diagnostic markers and therapeutic targets in prostate cancer

The vasculature plays an important role in the normal and malignant prostate. Under basal conditions both glandular epithelial and stromal prostate cells produce an abundance of blood flow and angiogenesis regulating substances and the expression of these is generally increased in prostate tumors. The proportion of proliferating endothelial cells is high in the normal prostate compared to other tissues in the body. After castration effects on the vasculature, such as decreased blood flow and vascular regression, precede effects on the glandular compartment. Correspondingly, hormone induced prostate growth is characterized by early effects on the vasculature such as increased blood flow and endothelial cell proliferation, thus indicating that the vasculature may be involved in the androgenic regulation of the prostate. Prostatic intraepithelial neoplasia (PIN) and prostate cancer are associated with increased vascular density and in experimental models prostate cancer growth is apparently angiogenesis-dependent since tumor growth and progression can be inhibited by antiangiogenic treatment. Moreover, vascular density has been related to prognosis in prostate cancer patients. A better understanding of the pathways regulating angiogenesis in the normal prostate and how these pathways change during malignant transformation can hopefully lead to better prognostic markers and therapies for the large group of patients with prostate cancer. The purpose of this review is therefore to summarize the current knowledge on the role and regulation of the vasculature in the prostate and its potential clinical applications.

Angiogenesis and lymphangiogenesis in stage 1 germ cell tumours of the testis

OBJECTIVE

To determine whether angiogenesis can be used as an additional prognostic indicator in patients with stage 1 germ cell tumours of the testis.

PATIENTS AND METHODS

Paraffin sections were assessed immunohistochemically from 51 patients with clinical stage 1 germ cell tumours of the testis (28 seminoma, 23 teratoma) treated by orchidectomy and surveillance only. Sections were analysed for microvascular density (MVD), and expression of the angiogenic factors vascular endothelial growth factor (VEGF) and thymidine phosphorylase (TP). In addition, in the seminoma cases the presence of mRNA for the lymphangiogenic factor VEGF-C was examined by in situ hybridization, and its corresponding receptor VEGFR-3 by immunohistochemistry.

RESULTS

Teratoma specimens had a significantly higher mean (range) MVD (85, 26-163; P < 0.01) than both seminoma (37, 16-91) and four normal specimens (26, 18-30). Teratoma specimens also had significantly higher VEGF expression than both seminoma and normal specimens (P < 0.01). Despite these differences between groups, and indeed individual tumours, there was no significant correlation between MVD and VEGF, or between either MVD or VEGF and relapse-free survival. TP expression was significantly greater in tumours than in normal specimens (P < 0.02) but with very little inter-tumour variation. VEGF-C mRNA and VEGFR-3 protein were detected in a third to a half of cases, with expression mostly around endothelial vessels.

CONCLUSIONS

The marked differences between normal testis and tumours implicate angiogenesis in the biology of germ cell tumours of the testis. In addition, the detection of factors involved in lymphangiogenesis in some seminomas, tumours which initially metastasize primarily to lymph nodes, indicate that although not prognostic in this study, further studies are warranted in both these areas in the search for further prognostic indicators and therapeutic targets.

Three-dimensional contrast-enhanced power Doppler ultrasonography and conventional examination methods: the value of diagnostic predictors of prostate cancer

OBJECTIVE

To investigate the value of three-dimensional contrast-enhanced power Doppler ultrasonography (3D-CE-PDU) in the diagnosis of prostate cancer and to compare 3D-CE-PDU with digital rectal examination (DRE), prostate-specific antigen (PSA) levels, grey-scale ultrasonography (GSU) and PDU.

PATIENTS AND METHODS

The study comprised 30 patients with localized prostate cancer scheduled to undergo radical prostatectomy and 29 with clinical BPH scheduled to undergo transurethral microwave thermotherapy. The 3D-CE-PDU examinations were carried out using 2.5 g of microbubble ultrasound contrast medium; the images were stored digitally to allow off-line analysis. All the reconstructed 3D images of the prostate were evaluated blindly in random order by two investigators (one expert and one novice). The images were scored according to asymmetry (0-2) and vessel distribution (0-3). Marked asymmetry (2) and/or a focal increase in vascularity (> 2) were considered as suspicious for prostate malignancy. Diagnostic predictions using the DRE, PSA level, GSU, PDU, 3D-CE-PDU and their combinations were investigated using receiver operating characteristic (ROC) curves.

RESULTS

True-positive and true-negative rates of the 3D-CE-PDU were 87% (26/30) and 79% (23/29), respectively, for the expert observer. The sensitivity of 3D-CE-PDU was higher than that of DRE, GSU and PDU, but not PSA level, and the specificity was lower, again except for PSA level. However, when compared with those of the other modalities in single-test evaluations, 3D-CE-PDU, and a combination of 3D-CE-PDU and PSA level, had the largest area under the ROC curve (0. 830 and 0.933, respectively). The diagnostic agreement between the examiners was 76% (Cohen kappa statistic, 0.5).

CONCLUSION

In this selected group of patients, 3D-CE-PDU alone was a better diagnostic tool than the DRE, PSA level, GSU or PDU alone. The most suitable diagnostic predictor for prostate cancer was a combination of 3D-CE-PDU and PSA level.

Vascular endothelial growth factor and its correlation with superficial bladder cancer recurrence rates and stage progression

Because of the heterogeneous behavior of superficial bladder cancer, the development of additional simple diagnostic and prognostic tests will be invaluable. The authors have demonstrated significantly elevated levels of urinary VEGF in patients with active bladder cancer. The sensitivity and specificity of urinary VEGF for diagnosing primary or recurrent bladder cancer were superior when compared with the results of cytology, which remains the most widely used noninvasive diagnostic investigation. These results and the authors' previous findings at the mRNA and protein level strongly implicate VEGF in the pathogenesis of bladder cancer recurrence and progression. The potential exists for anti-VEGF strategies in the treatment of, or prophylaxis against, recurrent superficial bladder cancer.

Elevated serum vascular endothelial growth factor in patients with hormone-escaped prostate cancer

OBJECTIVE

To investigate the role of serum vascular endothelial growth factor (VEGF) in the assessment of patients with prostate cancer. Patients, subjects and methods Serum from 78 men was assayed for VEGF using a commercially available enzyme-linked immunosorbent assay kit. Forty-eight patients had a histopathological diagnosis of prostate cancer (16 local disease, 32 metastatic), nine had benign prostatic hyperplasia (BPH) and 21 were healthy controls.

RESULTS

The mean serum VEGF level was significantly higher in patients with hormone-escaped prostate cancer than in all other groups (P </= 0. 02). There were no significant differences in serum VEGF levels among the other groups. In 18 patients with serial measurements there was no significant difference in serum VEGF level during either response to or escape from hormonal therapy.

CONCLUSIONS

The significantly higher serum VEGF level in patients with hormone-escaped prostate cancer suggests a role in the pathogenesis of advanced disease. However, the lack of significant differences among the other groups and the failure to indicate either response to or escape from hormonal therapy suggests that serum VEGF in this setting is of limited use.