Thymidine phosphorylase expression in normal, hyperplastic and neoplastic prostates: correlation with tumour associated macrophages, infiltrating lymphocytes, and angiogenesis

1,3,4-Oxadiazole: An Emerging Scaffold to Inhibit the Thymidine Phosphorylase as an Anticancer Agent

Thymidine phosphorylase (TP), also referred to as "platelet-derived endothelial cell growth factor" is crucial to the pyrimidine salvage pathway. TP reversibly transforms thymidine into thymine and 2-deoxy-D-ribose-1-phosphate (dRib-1-P), which further degraded to 2-Deoxy-D-ribose (2DDR), which has both angiogenic and chemotactic activity. In several types of human cancer such as breast and colorectal malignancies, TP is abundantly expressed in response to biological disturbances like hypoxia, acidosis, chemotherapy, and radiation therapy. TP overexpression is highly associated with angiogenic factors such as vascular endothelial growth factor (VEGF), interleukins (ILs), matrix metalloproteases (MMPs), etc., which accelerate tumorigenesis, invasion, metastasis, immune response evasion, and resistant to apoptosis. Hence, TP is recognized as a key target for the development of new anticancer drugs. Heterocycles are the primary structural element of most chemotherapeutics. Even 75% of nitrogen-containing heterocyclic compounds are contributing to the pharmaceutical world. To create the bioactive molecule, medicinal chemists are concentrating on nitrogen-containing heterocyclic compounds such as pyrrole, pyrrolidine, pyridine, imidazole, pyrimidines, pyrazole, indole, quinoline, oxadiazole, benzimidazole, etc. The Oxadiazole motif stands out among all of them due to its enormous significance in medicinal chemistry. The main thrust area of this review is to explore the synthesis, SAR, and the significant role of 1,3,4-oxadiazole derivatives as a TP inhibitor for their chemotherapeutic effects.

Folylpoly-ɣ-glutamate synthetase association to the cytoskeleton: Implications to folate metabolon compartmentalization

Folates are essential for nucleotide biosynthesis, amino acid metabolism and cellular proliferation. Following carrier-mediated uptake, folates are polyglutamylated by folylpoly-ɣ-glutamate synthetase (FPGS), resulting in their intracellular retention. FPGS appears as a long isoform, directed to mitochondria via a leader sequence, and a short isoform reported as a soluble cytosolic protein (cFPGS). However, since folates are labile and folate metabolism is compartmentalized, we herein hypothesized that cFPGS is associated with the cytoskeleton, to couple folate uptake and polyglutamylation and channel folate polyglutamates to metabolon compartments. We show that cFPGS is a cytoskeleton-microtubule associated protein: Western blot analysis revealed that endogenous cFPGS is associated with the insoluble cellular fraction, i.e., cytoskeleton and membranes, but not with the cytosol. Mass spectrometry analysis identified the putative cFPGS interactome primarily consisting of microtubule subunits and cytoskeletal motor proteins. Consistently, immunofluorescence microscopy with cytosol-depleted cells demonstrated the association of cFPGS with the cytoskeleton and unconventional myosin-1c. Furthermore, since anti-microtubule, anti-actin cytoskeleton, and coatomer dissociation-inducing agents yielded perinuclear pausing of cFPGS, we propose an actin- and microtubule-dependent transport of cFPGS between the ER-Golgi and the plasma membrane. These novel findings support the coupling of folate transport with polyglutamylation and folate channeling to intracellular metabolon compartments. SIGNIFICANCE: FPGS, an essential enzyme catalyzing intracellular folate polyglutamylation and efficient retention, was described as a soluble cytosolic enzyme in the past 40 years. However, based on the lability of folates and the compartmentalization of folate metabolism and nucleotide biosynthesis, we herein hypothesized that cytoplasmic FPGS is associated with the cytoskeleton, to couple folate transport and polyglutamylation as well as channel folate polyglutamates to biosynthetic metabolon compartments. Indeed, using complementary techniques including Mass-spectrometry proteomics and fluorescence microscopy, we show that cytoplasmic FPGS is associated with the cytoskeleton and unconventional myosin-1c. This novel cytoskeletal localization of cytoplasmic FPGS supports the dynamic channeling of polyglutamylated folates to metabolon compartments to avoid oxidation and intracellular dilution of folates, while enhancing folate-dependent de novo biosynthesis of nucleotides and DNA/protein methylation.

Borrelia burgdorferi-Induced Changes in the Class II Self-Immunopeptidome Displayed on HLA-DR Molecules Expressed by Dendritic Cells

The MHC class II antigen processing and presentation pathway has evolved to derive short amino acid peptides from proteins that enter the endocytic pathway, load them onto MHC class II molecules and display them on the surface of antigen presenting cells for recognition by CD4+ T cells. Under normal circumstances, peptides bound to MHC class II molecules are derived from host (self) proteins and not recognized by T cells due to tolerance mechanisms. Pathogens induce significant changes in the biology of antigen presenting cells, including upregulation of MHC processing and presentation. We therefore hypothesized that exposure to pathogens may alter the repertoire of self-peptides bound to MHC class II molecules. To test this hypothesis, we isolated monocyte-derived dendritic cells from healthy subjects, exposed them to the TLR-2 agonist lipoteichoic acid or live Borrelia burgdorferi, the causative agent of Lyme disease, and isolated and characterized HLA-DR associated peptides using mass spectrometry. Our results show that lipoteichoic acid-stimulated, B. burgdorferi-stimulated and unstimulated monocyte-derived dendritic cells largely derive their self-peptides from similar overlapping sets of host proteins. However, lipoteichoic acid and B. burgdorferi stimulation promote the processing and presentation of new sets of HLA-DR associated self-peptides derived from unique protein sources. Examination of processes and compartments these proteins reside in, indicate that activation of monocyte-derived dendritic cells changes the range of host self-proteins available for processing and presentation on MHC class II molecules. These findings reveal that the HLA-DR-bound self-immunopeptidome presented by mo-DCs is dynamic in nature and changes with activation state reflective of cellular function. In addition, among the repertoire of self-peptides bound to HLA-DR are several epitopes known to be recognized by autoreactive T cells. These studies are relevant to our basic understanding of pathogen-induced changes in monocyte-derived dendritic cell function, and the mechanisms involved in infection-induced autoimmune illnesses such as Lyme arthritis.

Thymidine Phosphorylase Expression and Microvascular Density Correlation Analysis in Canine Mammary Tumor: Possible Prognostic Factor in Breast Cancer

Purpose: The thymidine phosphorylase (TP) is a key enzyme involved in the metabolism of pyrimidines. Inhibition or downregulation of this enzyme causes accumulation of metabolites with consequences in DNA replication. TP regulates angiogenesis and chemotactic activity of endothelial cells. Different studies showed the presence of TP upregulation in human cancer but the correlation between TP expression and the microvascular density (MVD) in canine mammary tumors is unknown. The aim of this study was to investigate a possible correlation between the MVD and TP expression in tumor cells of canine mammary tumors of different degree of severity (G1–G3) by immunohistochemical analysis.

Methods: Sixty-eight samples of spontaneous mammary neoplasia of 5–12 cm in diameter were collected from purebred and mixed-breed dogs (mean aged = 9.5 ± 7), not subject to chemotherapy treatments in veterinary clinics. Histopathological analysis and immunostaining were performed.

Results: Carcinoma simple samples have been classified as 72.06% of tubule-papillary, 20.59% cysto-papillary, and 7.35% tubular carcinomas. Immunostainings revealed a marked cytoplasmic expression of TP in 30.88% of samples, mild in 32.35%, weaker in 22.07%, and negative in 14.70%. The correlation analysis and two-way ANOVA showed a linear correlation between MVD and TP with a coefficient of correlation (r) > 0.5 (p < 0.05) in G2 and G3. No correlation between variables was found in G1.

Conclusions: These findings suggest that cytoplasmic TP overexpression is correlated with microvascular density in canine mammary tumors, in severe grade, and it can be a potential prognostic factor in breast cancer.

The immune infiltrate in prostate, bladder and testicular tumors: An old friend for new challenges

In genito-urinary tumors immunotherapy has been administered for a long time: Calmette-Guèrin Bacillus as adjuvant treatment in high risk patients with non muscle invasive urothelial bladder cancer and interleukin-2 and interferon-α in metastatic kidney cancer. The vaccine Sipuleucel-T has been approved by United States Food and Drug Administration for the treatment of castration resistant prostate cancer patients with asymptomatic or minimally symptomatic disease, given the 22% reduction of mortality risk in this group. Recently immunotherapeutic agents targeting inhibitory immune checkpoint molecules lead to improved outcomes and lasting anti-tumor effects in a variety of hematological and solid malignancies, including urogenital tumors. The benefit from these treatments has been observed only in a proportion of subjects, raising a need in optimizing patients' selection for immune checkpoint blockade. The composition and activity of a pre-existing immune infiltrate may aid in identifying ideal candidates to immunotherapy, with possible implications for the clinical management of neoplastic diseases from earlier to later stages.

Metformin induces cytotoxicity by down-regulating thymidine phosphorylase and excision repair cross-complementation 1 expression in non-small cell lung cancer cells

Metformin is an antidiabetic drug recently shown to inhibit cancer cell proliferation and growth, although the involved molecular mechanisms have not been elucidated. In many cancer cells, high expression of thymidine phosphorylase (TP) and Excision repair cross-complementation 1 (ERCC1) is associated with poor prognosis. We used A549 and H1975 human non-small cell lung cancer (NSCLC) cell lines to investigate the role of TP and ERCC1 expression in metformin-induced cytotoxicity. Metformin treatment decreased cellular TP and ERCC1 protein and mRNA levels by down-regulating phosphorylated MEK1/2-ERK1/2 protein levels in a dose- and time-dependent manner. The enforced expression of the constitutively active MEK1 (MEK1-CA) vectors significantly restored cellular TP and ERCC1 protein levels and cell viability. Specific inhibition of TP and ERCC1 expression by siRNA enhanced the metformin-induced cytotoxicity and growth inhibition. Arachidin-1, an antioxidant stilbenoid, further decreased TP and ERCC1 expression and augmented metformin's cytotoxic effect, which was abrogated in lung cancer cells transfected with MEK1/2-CA expression vector. In conclusion, metformin induces cytotoxicity by down-regulating TP and ERCC1 expression in NSCLC cells.

The metabolic interactions between tumor cells and tumor-associated stroma (TAS) in prostatic cancer

Tumor-associated stroma (TAS) is not simply a supporting element for cancer cells, but plays an important role in tumor growth, invasion and metastasis. Changes on the level of stromal constituents, such as loss of Caveolin-1 and increased thymidine phosphorylase (TP) expression, have been associated with tumor aggressiveness. The mutual cooperation between stromal fibroblasts and cancer cells is another distinguishing feature, which has recently emerged. In this investigation, both the loss of Caveolin-1 and the increased TP expression in the prostatic TAS was associated with high Gleason score (p = 0.0002 and 0.003, respectively); the two proteins were acting both independently and synergistically. In addition, TP was significantly associated with high stromal Ki-67 (MIB1) proliferation index (p = 0.03). Analysis of the metabolic interactions between stromal and epithelial elements showed that, while prostatic cancer cells express principally (> 91%) lactate dehydrogenase-5 (LDH-5) (anaerobic metabolism), the tumor-associated fibroblasts/myofibroblasts (TAFs) express largely (67.8%) LDH-1 (aerobic metabolism)-the terms TAFs and TAS are used interchangeably. These two isoenzyme pathways act complementary; the LDH-5 pathway converts pyruvate to lactate, whereas the LDH-1 enzyme system utilizes the secreted metabolite lactate to produce pyruvate, essential for continuous energy supply to tumor cells. Monocarboxylate transporter-1 (MCT-1)-the main facilitator of lactate uptake in tumor cells, was expressed exclusively in prostate cancer cells and related directly to LDH-5 overexpression. These findings support and extend our previous studies on energy recycling between the aerobic stroma and the anaerobic cancer cells within the framework of Warburg effect.

Up-regulation of extracellular signal-regulated kinase 1/2-dependent thymidylate synthase and thymidine phosphorylase contributes to cisplatin resistance in human non-small-cell lung cancer cells

Chemotherapy for advanced human non-small-cell lung cancer (NSCLC) includes platinum-containing compound such as cisplatin in combination with a second- or third-generation cytotoxic agent. 5-Fluorouracil (5-FU) belongs to antimetabolite chemotherapeutics, and its mechanism of cytotoxicity is involved in the inhibition of thymidylate synthase (TS). TS and thymidine phosphorylase (TP) are key enzymes of the pyrimidine salvage pathway. In this study, we have examined the molecular mechanism of TS and TP in regulating drug sensitivity to cisplatin in NSCLC cell lines. Cisplatin could increase the phosphorylation of mitogen-activated protein kinase kinase 1/2 (MKK1/2)-extracellular signal-regulated kinase 1/2 (ERK1/2) and the protein levels of TS and TP through enhancing the protein stability in A549 and H1975 cells. Blocking ERK1/2 activation by MKK1/2 inhibitor [U0126; 1,4-diamino-2,3-dicyano-1,4-bis(2-aminophenylthio)butadiene)] decreased TS and TP protein levels in both cell lines treated with cisplatin. Depletion of endogenous TS or TP expression by specific small interfering RNA transfection significantly increased cisplatin-induced cell death and growth inhibition. Combined treatment with 5-FU could decrease cisplatin-induced ERK1/2 activation and the induction of TS and TP, which subsequently resulted in synergistic cytotoxic effects. Enforced expression of constitutive active MKK1/2 vectors rescued the protein levels of phospho-ERK1/2, TS, and TP, and the cell viability that were decreased by cisplatin and 5-FU combination. In contrast, U0126 enhanced drug sensitivity to cisplatin and/or 5-FU in lung cancer cells. In conclusion, the up-regulation of ERK1/2-dependent TS and TP can protect human lung cancer cells from cisplatin-induced cytotoxicity.

Angiogenesis as a strategic target for prostate cancer therapy

It is becoming increasingly clear that angiogenesis plays a crucial role in prostate cancer (CaP) survival, progression, and metastasis. Tumor angiogenesis is a hallmark of advanced cancers and an attractive treatment target in multiple solid tumors. By understanding the molecular basis of resistance to androgen withdrawal and chemotherapy in CaP, the rational design of targeted therapeutics is possible. This review summarizes the recent advancements that have improved our understanding of the role of angiogenesis in CaP metastasis and the potential therapeutic efficacy of inhibiting angiogenesis in this disease. Current therapeutic options for patients with metastatic hormone-refractory CaP are very limited. Targeting vasculature is a developing area, which shows promise for the control of late stage and recurrent CaP disease and for overcoming drug resistance. We discuss angiogenesis and its postulated mechanisms and focus on the regulation of angiogenesis in CaP progression and the therapeutic beneficial effects associated with targeting of the CaP vasculature to overcome the resistance to current treatments and CaP recurrence.

The dual role of thymidine phosphorylase in cancer development and chemotherapy

Thymidine phosphorylase (TP), also known as "platelet-derived endothelial cell growth factor" (PD-ECGF), is an enzyme, which is upregulated in a wide variety of solid tumors including breast and colorectal cancers. TP promotes tumor growth and metastasis by preventing apoptosis and inducing angiogenesis. Elevated levels of TP are associated with tumor aggressiveness and poor prognosis. Therefore, TP inhibitors are synthesized in an attempt to prevent tumor angiogenesis and metastasis. TP is also indispensable for the activation of the extensively used 5-fluorouracil prodrug capecitabine, which is clinically used for the treatment of colon and breast cancer. Clinical trials that combine capecitabine with TP-inducing therapies (such as taxanes or radiotherapy) suggest that increasing TP expression is an adequate strategy to enhance the antitumoral efficacy of capecitabine. Thus, TP plays a dual role in cancer development and therapy: on the one hand, TP inhibitors can abrogate the tumorigenic and metastatic properties of TP; on the other, TP activity is necessary for the activation of several chemotherapeutic drugs. This duality illustrates the complexity of the role of TP in tumor progression and in the clinical response to fluoropyrimidine-based chemotherapy.

Antiangiogenic and antitumor activity of 6-(2-aminoethyl)amino-5-chlorouracil, a novel small-molecule inhibitor of thymidine phosphorylase, in combination with the vascular endothelial growth factor-trap

PURPOSE

Tumors produce multiple proangiogenic factors, making it unlikely that agents targeting a single angiogenic pathway will be sufficient to treat the spectrum of tumors that occur clinically. Platelet-derived endothelial cell growth factor has angiogenic activity in vitro and in vivo and is overexpressed in most human cancers, where its expression has been correlated with increased microvessel density, more aggressive tumors, and poorer patient prognosis. Platelet-derived endothelial cell growth factor is identical to the enzyme thymidine phosphorylase (TP), and unlike other angiogenic factors, the proangiogenic actions of TP are dependent on its enzyme activity.

EXPERIMENTAL DESIGN

A potent and specific small-molecule inhibitor of the catalytic activity of TP, 6-(2-aminoethyl)amino-5-chlorouracil (AEAC), was tested for antiangiogenic and antitumor activity in human cancer xenografts in vivo.

RESULTS

Oral administration of AEAC caused 40% to 50% reductions in the growth of A549 non-small cell lung cancer and PANC-1 pancreatic cancer xenografts, but it was not active against a second pancreatic tumor, BxPC-3. AEAC reduced the microvessel density in the tumors, providing evidence for an antiangiogenic action. Equal or better activity was seen when the mice were treated with the vascular endothelial growth factor (VEGF)-Trap, a soluble VEGF decoy receptor, and the combination of AEAC and VEGF-Trap produced additive antitumor activity that was significantly greater than the VEGF-Trap alone. In the A549 tumors, the combination produced tumor regressions.

CONCLUSION

These studies show antitumor activity for a drug targeting TP and suggest that inhibitors of TP could be used to augment the clinical efficacy of drugs targeting the VEGF pathway.

(188)Re-HEDP combined with capecitabine in hormone-refractory prostate cancer patients with bone metastases: a phase I safety and toxicity study

Purpose

¹⁸⁸Re-HEDP is indicated for the treatment of pain in patients with painful osteoblastic bone metastases, including hormone-refractory prostate cancer patients. Efficacy may be improved by adding chemotherapy to the treatment regimen as a radiation sensitizer. The combination of ¹⁸⁸Re-HEDP and capecitabine (Xeloda®) was tested in a clinical phase I study.

Methods

Patients with hormone-refractory prostate cancer were treated with capecitabine for 14 days (oral twice daily in a dose escalation regimen with steps of 1/3 of 2,500 mg/m² per day in cohorts of three to six patients, depending on toxicity). Two days later patients were treated with 37 MBq/kg ¹⁸⁸Re-HEDP as an intravenous injection. Six hours after treatment post-therapy scintigraphy was performed. Urine was collected for 8 h post-injection. Follow-up was at least 8 weeks. The primary end-point was to establish the maximum tolerable dose (MTD) of capecitabine when combined with ¹⁸⁸Re-HEDP. Secondary end-points included the effect of capecitabine on the biodistribution and pharmacokinetics of ¹⁸⁸Re-HEDP.

Results

Three patients were treated in the first and second cohorts, each without unacceptable toxicity. One of six patients in the highest cohort experienced unacceptable toxicity (grade 4 thrombopaenia). The MTD proved to be the maximum dose of 2,500 mg/m² per day capecitabine. No unexpected toxicity occurred. Capecitabine had no effect on uptake or excretion of ¹⁸⁸Re-HEDP.

Conclusion

Capecitabine may be safely used in combination with ¹⁸⁸Re-HEDP in a dose of 2,500 mg/m² per day and 37 MBq/kg, respectively. Efficacy will be further studied in a phase II study using these dosages.

Tumor-associated macrophages: effectors of angiogenesis and tumor progression

Tumor-associated macrophages (TAMs) are a prominent inflammatory cell population in many tumor types residing in both perivascular and avascular, hypoxic regions of these tissues. Analysis of TAMs in human tumor biopsies has shown that they express a variety of tumor-promoting factors and evidence from transgenic murine tumor models has provided unequivocal evidence for the importance of these cells in driving angiogenesis, lymphangiogenesis, immunosuppression, and metastasis. This review will summarize the mechanisms by which monocytes are recruited into tumors, their myriad, tumor-promoting functions within tumors, and the influence of the tumor microenvironment in driving these activities. We also discuss recent attempts to both target/destroy TAMs and exploit them as delivery vehicles for anti-cancer gene therapy.

Efficacy of the oral fluorouracil pro-drug capecitabine in cancer treatment: a review

Capecitabine (Xeloda) was developed as a pro-drug of fluorouracil (FU), with the aim of improving tolerability and intratumor drug concentrations through its tumorspecific conversion to the active drug. The purpose of this paper is to review the available information on capecitabine, focusing on its clinical effectiveness against various carcinomas. Identification of all eligible English trails was made by searching the PubMed and Cochrane databases from 1980 to 2007. Search terms included capecitabine, Xeloda and cancer treatment. Nowadays, FDA has approved the use of capecitabine as a first line therapy in patients with metastatic colorectal cancer when single-agent fluoropyrimidine is preferred. The drug is also approved for use as a single agent in metastatic breast cancer patients who are resistant to both anthracycline and paclitaxel-based regimens or when further anthracycline treatment is contraindicated. It is also approved in combination with docetaxel after failure of prior anthracycline-based chemotherapy. In patients with prostate, pancreatic, renal cell and ovarian carcinomas, capecitabine as a single-agent or in combination with other drugs has also shown benefits. Improved tolerability and comparable efficacy, compared with the intravenous FU/LV combination, in addition to its oral administration, make capecitabine an attractive option for the treatment of several types of carcinomas.

Targeting platelet-derived endothelial cell growth factor/thymidine phosphorylase for cancer therapy

Thymidine phosphorylase (TP) is a key enzyme in the pyrimidine nucleoside salvage pathway, but it also recognizes and inactivates various anti-cancer chemotherapeutic agents. Moreover, TP is identical to platelet-derived endothelial cell growth factor (PD-ECGF), an angiogenic factor with anti-apoptotic properties. Increased expression of PD-ECGF/TP is found in many tumor and stromal cells, and elevated TP levels are associated with aggressive disease and/or poor prognosis. Thus, progression and metastasis of TP-expressing tumors might be abrogated by TP inhibitors that are used as single agents or in combination with (TP-sensitive) nucleoside analogues. On the other hand, increased TP activity in tumors may be exploited for the tumor-specific activation of fluoropyrimidine prodrugs, such as capecitabine. This review will focus on the different biological activities of PD-ECGF/TP and their implications for cancer progression and treatment.

5'-O-tritylated nucleoside derivatives: inhibition of thymidine phosphorylase and angiogenesis

Thymidine phosphorylase (TPase) is one of the key enzymes involved in the pyrimidine nucleoside salvage pathway. However, TPase also stimulates angiogenesis, and its expression correlates well with microvessel density and metastasis in a variety of human tumors. We have shown recently that 5'-O-trityl-inosine (KIN59) allosterically inhibits TPase enzymatic activity. KIN59 also inhibits TPase-induced angiogenesis in the chick chorioallantoic membrane (CAM) assay. The trityl group was found to be instrumental to preserve both the anti-TPase and antiangiogenic effect. We have now synthesized a variety of novel 5'-O-trityl nucleoside derivatives. Enzyme activity studies showed that the anti-TPase activity is significantly improved by replacement of the hypoxanthine base by thymine [3.5-fold; i.e., 5'-O-tritylthymidine (KIN6)] and the introduction of chloride on the trityl group [7-fold; i.e., 5'-O-(4-chlorotrityl)-inosine (TP136)], whereas removal of 2'-hydroxyl in the ribose did not significantly alter the anti-TPase activity. Enzyme kinetic studies also demonstrated that 1-(5'-O-trityl-beta-d-ribofuranosyl)-thymine (TP124), like KIN59, inhibits TPase in a noncompetitive fashion both with respect to phosphate and thymidine. Most KIN59 analogs markedly inhibited TPase-induced angiogenesis in the CAM assay. In vitro studies showed that the antiangiogenic effect of these compounds is not attributed to endothelial cell toxicity. For several compounds, there was no stringent correlation between their anti-TPase and antiangiogenic activity, indicating that these compounds may also act on other angiogenesis mediators. The antiangiogenic 5'-O-trityl nucleoside analogs also caused degradation of pre-existing, immature vessels at the site of drug exposure. Thus, 5'-O-trityl nucleoside derivatives combine antiangiogenic and vascular-targeting activities, which opens perspectives for their potential use as anticancer agents.

Mechanisms of Disease: angiogenesis in urologic malignancies

Angiogenesis is critical for growth of tumors and their metastasis. In this article we review the literature on studies of angiogenesis pathways and markers for renal cancer, prostate cancer and bladder cancer. Overall, there is clear evidence that markers of angiogenesis and expression of angiogenic factors are associated with adverse outcomes in each of these tumor types. Relatively few angiogenic pathways have been investigated so far, although over 50 factors are known to be involved, and little has been studied on the antiangiogenic pathways and their suppression. The failing in many of the studies is small size and lack of suitable statistical analysis. Nevertheless, this review demonstrates the importance of these pathways and the need to develop selection criteria for patients who are candidates for antiangiogenic therapies. On the basis of the expression profiles reported so far, therapies that target vascular endothelial growth factor should be considered for the treatment of renal, prostate and bladder cancers. As most tumors express factors that are involved in multiple angiogenic pathways, further research is needed to determine which are coregulated and what the most common patterns are.

Phase II study of oral capecitabine in patients with hormone-refractory prostate cancer

BACKGROUND

Currently available treatment for hormone refractory prostate cancer is limited in efficacy and associated with significant toxicity. This phase II study was performed to assess the efficacy of the oral fluoropyrimidine capecitabine in advanced prostate cancer.

PATIENTS AND METHODS

Patients who had a rising prostate-specific antigen (PSA) despite androgen withdrawal, but who remained free from cancer-related symptoms. In total, 14 patients received oral capecitabine 1250 mg/m2 twice daily for two weeks of a three-week cycle. Tumour response was assessed using serum PSA measurement at 3-weekly intervals and, where present, imaging of soft tissue metastases.

RESULTS

One of 14 patients experienced a partial response as assessed by both PSA and imaging of liver metastases. In seven other patients (50%), treatment decreased the rate of PSA rise. The duration of PSA stabilisation was generally short, but in 5/14 patients (36%) was sustained beyond 18 weeks, and in one patient to 24 weeks. Toxicity was significant but manageable, the most common adverse events being nausea, mucositis and hand-foot syndrome, each occurring in 50% of patients. Other common side effects were diarrhoea and lymphopenia. All toxicities were grade 1 or 2, except for grade 3 hand-foot syndrome occurring in one patient, and no dose reduction was required because of toxicity.

CONCLUSION

Capecitabine has limited activity as a single agent in prostate cancer, but appears to modulate tumour biology. Considering the added convenience of oral administration, these results support further evaluation of combinations containing capecitabine in hormone-refractory prostate cancer.

Proliferating fibroblasts at the invading tumour edge of colorectal adenocarcinomas are associated with endogenous markers of hypoxia, acidity, and oxidative stress

BACKGROUND

Stroma frequently forms at sites of active tumour invasion, and may be important for tumour growth and progression. The term "stromatogenesis" is used to describe this unique process that involves host peritumorous fibroblasts and is very different to reactive fibrosis.

AIMS/METHODS

To investigate the activation status of host fibroblasts at the invading tumour edge, assessed as MIB1 proliferation index and thymidine phosphorylase (TP) expression. Results were related to vascular density and certain properties of invading cancer cells-MIB1 proliferation activity, TP expression, expression of endogenous markers of hypoxia (hypoxia inducible factor-1alpha; HIF1alpha) and acidity (lactate dehydrogenase-5; LDH5). Standard immunohistochemical techniques were applied to 150 colorectal adenocarcinomas.

RESULTS

Normal fibroblasts at the tumour edge had a median MIB1 index of 2%-significantly higher than normal submucosal fibroblasts (0.3%) and significantly lower than cancer cells (40%). Normal peritumorous fibroblasts with a proliferation rate above the median strongly expressed TP and were supported by an increased vascular network. Cancer cells close to these fibroblasts had a high MIB1 proliferative index, high HIF1alpha and LDH5 reactivity, and a clear trend to extramural extension. All associations were significant.

CONCLUSIONS

These results suggest that activated fibroblastic status at the invading tumour front sets the stage for stromatogenesis and new blood vessel formation, facilitating deep transmural invasion in colorectal adenocarcinomas. This complicity of peritumorous fibroblasts in the overall aggressiveness/invasive and metastatic ability of colorectal tumours, occurring within the framework of cancer-stromal cell interactions, is probably favoured by the altered microenvironmental conditions of hypoxia and acidity.

Capecitabine: a review

BACKGROUND

Fluorouracil (FU) is an antimetabolite with activity against numerous types of neoplasms, including those of the breast, esophagus, larynx, and gastrointestinal and genitourinary tracts. Systemic toxicity, including neutropenia, stomatitis, and diarrhea, often occur due to cytotoxic nonselectivity. Capecitabine was developed as a prodrug of FU, with the goal of improving tolerability and intratumor drug concentrations through tumor-specific conversion to the active drug.

OBJECTIVES

The purpose of this article is to review the available information on capecitabine with respect to clinical pharmacology, mechanism of action, pharmacokinetic and pharmacodynamic properties, clinical efficacy for breast and colorectal cancer adverse-effect profile, documented drug interactions, dosage and administration, and future directions of ongoing research.

METHODS

Relevant English-language literature was identified through searches of PubMed (1966 to August 2004), International Pharmaceutical Abstracts (1977 to August 2004), and the Proceedings of the American Society of Clinical Oncology (January 1995 to August 2004). Search terms included capecitabine, Xeloda, breast cancer, and colorectal cancer. The references of the identified articles were reviewed for additional sources. In addition, product information was obtained from Roche Pharmaceuticals. Studies from the identified literature that addressed this article's objectives were selected for review, with preference given to Phase II/III trials.

RESULTS

Capecitabine is an oral prodrug that is converted to its only active metabolite, FU, by thymidine phosphorylase. Higher levels of this enzyme are found in several tumors and the liver, compared with normal healthy tissue. In adults, capecitabine has a bioavailability of approximately 100% with a Cmax of 3.9 mg/L, Tmax of 1.5 to 2 hr, and AUC of 5.96 mg.h/L. The predominant route of elimination is renal, and dosage reduction of 75% is recommended in patients with creatinine clearance (CrCl) of 30 to 50 mL/min. The drug is contraindicated if CrCl is < 30 mL/min. Capecitabine has shown varying degrees of efficacy with acceptable tolerability in numerous cancers including prostate, renal cell, ovarian, and pancreatic, with the largest amount of evidence in metastatic breast and colorectal cancer. Single-agent capecitabine was compared with IV FU/leucovorin (LV) using the bolus Mayo Clinic regimen in 2 Phase III trials as first-line treatment for patients with metastatic colorectal cancer. Overall response rate (RR) favored the capecitabine arm (26% vs 17%, P < 0.001); however, this did not translate into a difference in time to progression (TTP) (4.6 months vs 4.7 months) or overall survival (OS) (12.9 months vs 12.8 months). In Phase II noncomparative trials, combinations of capecitabine with oxaliplatin or irinotecan have produced results similar to regimens combining FU/LV with the same agents in patients with colorectal cancer. In metastatic breast cancer patients who had received prior treatment with an anthracycline-based regimen, a Phase III trial comparing the combination of capecitabine with docetaxel versus docetaxel alone demonstrated superior objective tumor RR (42% vs 30%, P = 0.006), median TTP (6.1 months vs 4.2 months, P < 0.001), and median OS (14.5 months vs 11.5 months, P = 0.013) with the combination treatment. Noncomparative Phase II studies have also supported efficacy in patients with metastatic breast cancer pretreated with both anthracyclines and taxanes, yielding an overall RR of 15% to 29% and median OS of 9.4 to 15.2 months. The most common dose-limiting adverse effects associated with capecitabine monotherapy are hyperbilirubinemia, diarrhea, and hand-foot syndrome. Myelosuppression, fatigue and weakness, abdominal pain, and nausea have also been reported. Compared with bolus FU/LV, capecitabine was associated with more hand-foot syndrome but less stomatitis, alopecia, neutropenia requiring medical management, diarrhea, and nausea. Capecitabine has been reported to increase serum phenytoin levels and the international normalized ratio in patients receiving concomitant phenytoin and warfarin, respectively. The dose of capecitabine approved by the US Food and Drug Administration (FDA) for both metastatic colorectal and breast cancer is 1250 Mg/M2 given orally twice per day, usually separated by 12 hours for the first 2 weeks of every 3-week cycle.

CONCLUSIONS

Capecitabine is currently approved by the FDA for use as first-line therapy in patients with metastatic colorectal cancer when single-agent fluoropyrimidine therapy is preferred. The drug is also approved for use as (1) a single agent in metastatic breast cancer patients who are resistant to both anthracycline- and paclitaxel-based regimens or in whom further anthracycline treatment is contra indicated and (2) in combination with docetaxel after failure of prior anthracycline-based chemotherapy. Single-agent and combination regimens have also shown benefits in patients with prostate, pancreatic, renal cell, and ovarian cancers. Improved tolerability and comparable efficacy compared with IV FU/LV in addition to oral administration make capecitabine an attractive option for the treatment of several types of cancers as well as the focus of future trials.

Angiogenic Profile of Breast Carcinoma Determines Leukocyte Infiltration

To study the relationship between the angiogenic profile and leukocyte infiltration of tumors, single cell suspensions of archival frozen medullary and ductal breast cancer tissues were analyzed by flow cytometry. The amount of leukocytes and endothelial cells was measured, as well as the expression of intercellular adhesion molecule-1 (ICAM-1) on the endothelial cell fraction. A significantly higher number (3.2-fold) of infiltrating leukocytes was observed in medullary carcinoma. The composition of this infiltrate was similar to that seen in ductal carcinomas. The more intense infiltrate was explained by the ∼3-fold enhanced endothelial ICAM-1 expression in medullary carcinoma. The angiogenic profile of all tumors was assessed by quantitative real-time reverse transcription-PCR analysis. Vascular endothelial growth factor (VEGF)-C and VEGF-D, but not VEGF-A, basic fibroblast growth factor, placental growth factor, and angiopoietins 1, 2, and 3 showed a relatively higher level of expression in ductal carcinoma than in medullary carcinoma. In vitro, both VEGF-C and VEGF-D were found to decrease endothelial ICAM-1 expression in the presence of basic fibroblast growth factor. These data suggest that in vivo angiogenic stimuli prevent the formation of an effective leukocyte infiltrate in tumors by suppressing endothelial ICAM-1 expression.

"Stromatogenesis" and tumor progression

"Stromatogenesis" is the formation of new stroma occurring, in parallel with the neoplastic process, at sites of active tumor invasion, i.e., at the free surface of a developing exophytic tumor, at the invading tumor front of an advancing endophytic tumor, and at sites of tumor metastasis, wherein the newly formed stroma disrupts the continuity of normal structures, cleaving paths for the invading tumor cells. Stroma is also present at the heart of the tumor, but only as a secondary event following tumor advancement and subsequent incorporation of its periphery into inner tumor areas. The new stroma, composed of stromal cells and extracellular matrix (ECM), is loose and edematous at the expanding tumor fronts, and rather dense in central tumor areas and sites of tumor metastasis. The stromal cells facing tumor invasion are intensely proliferating (high MIB-1 index) spindle-shaped cells, alpha-smooth muscle actin positive, and loaded with thymidine phosphorylase (TP) and SPARC (secreted protein acidic and rich in cysteine). The associated ECM is rich in collagen III, SPARC, and new blood vessels (CD31) but is depleted of collagen I and fibronectin. These constitutional changes render stromatogenesis amenable to tumor cell invasion and are, in cases of incipient neoplasia, a prospective criterion of early stromal invasion. Other stromal cell or ECM constituents, such as the lactate dehydrogenase-5 (LDH-5), the acidic fibroblast growth factor (aFGF), the basic FGF (bFGF), and the collagens II and IV, remain unchanged, and others are negative: myosin, desmin, S-100 protein and epidermal growth factor receptor (EGFR). The mechanism of stromatogenesis is obscure but is probably stimulated by specific stromatogenic growth factors, released by neoplastic and inflammatory cells. It appears that the process is neither neoplastic nor reactive, but rather is a, hereto unexplained, phenomenon of host's complicity in tumor progression.

Expression of the angiogenic factor thymidine phosphorylase in THP-1 monocytes: induction by autocrine tumor necrosis factor-alpha and inhibition by aspirin

The angiogenic factor thymidine phosphorylase (TP) is highly expressed in human monocytes and macrophages, and its expression has been linked to the pathology and progression of solid tumors, rheumatoid arthritis, and gastric ulcers. In this study, TP mRNA and enzyme activity were found to be up-regulated upon the induction of differentiation of the human monocyte cell line THP-1 by phorbol 12-myristate 13-acetate (PMA). TP expression in THP-1 cells was similarly increased by tumor necrosis factor-alpha (TNFalpha). Because monocytes and macrophages are a predominant source of TNFalpha, the up-regulation of TP upon THP-1 differentiation could have been caused by the autocrine production of TNFalpha. In support of this hypothesis, PMA increased TNFalpha mRNA levels; furthermore, the increase in TP expression with PMA treatment was partially blocked by a neutralizing antibody to TNFalpha, particularly at the earlier time points. This data also suggested there may be additional mechanisms regulating TP expression upon PMA treatment of the cells. The induction of TP by TNFalpha was mimicked by an antibody to the TNFalpha receptor R2 (TNF-R2; p75), but not by an antibody to TNF-R1 (p55), suggesting that the TNF-R2 plays a role in the regulation of TP expression. The PMA-induced increase in TP expression was blocked by aspirin but not by the related agent indomethacin, suggesting that aspirin's effect was not caused by the inhibition of cellular cyclooxygenases. An alternative mechanism by which aspirin inhibits gene expression is the modulation of the transcription factor NFkappaB, and the TNFalpha-induced increase in TP mRNA was blocked by a cell-permeable NFkappaB inhibitory peptide. Furthermore, TNFalpha increased and aspirin (but not indomethacin) decreased NFkappaB DNA-binding activity in THP-1 cells. In conclusion, the modulation of TP expression in monocytes by pro- and anti-inflammatory agents suggests that its angiogenic-related actions could contribute to the inflammatory response associated with a number of pathophysiological conditions.

Immunopathological prognostic and predictive factors in prostate cancer

Prostate cancer is the leading male malignancy in the Western world. Patients with prostate cancer have an unpredictable clinical course, as three biologically different types of tumor exist. This review summarises some of the recent progress made in understanding the biology of prostate cancer with special reference to the prognostic and predictive role of immunohistochemical markers. The prognostic value of established prognostic variables is also discussed.