Pathological characteristics of prostate cancer in elderly men.

PURPOSE: Recent guidelines recommend that men older than 75 years should not be screened for prostate cancer. However, increased life expectancy and the development of less invasive treatments have led to an interest in characterizing prostate cancer in elderly men. We determined how prostate cancer pathological characteristics differ in men older vs younger than 70 years. MATERIALS AND METHODS: We studied differences in prostate cancer pathological characteristics in autopsied glands from men 70 years old or older and compared findings to those in men younger than 70 years. All men died of causes unrelated to prostate cancer. Prostates were whole mounted at 4 mm intervals. Histological analysis was done to identify and characterize each cancer focus observed. Tumor volume was measured by computerized planimetry. Cancer was defined as clinically significant or insignificant based on established histological characteristics. RESULTS: Of 211 prostates evaluated 74 were from men 70 years old or older. We identified cancer in 33 men (45%) in this age group vs in 26 of 137 (19%) younger than 70 years (p <0.001). Men older than 70 years had significantly larger cancer and more clinically significant cancer (64% vs 23%, p <0.005). Older men had more advanced stage cancer and greater Gleason scores (p <0.001). CONCLUSIONS: In an autopsy study of men with no history of prostate cancer those older than 70 years were more likely to have larger and higher grade prostate cancer than younger men.

MnSOD genotype and prostate cancer risk as a function of NAT genotype and smoking status.

BACKGROUND: Cigarette smoke contains carcinogenic aromatic and heterocyclic amines that are metabolized by N-acetyltransferase (NAT). These carcinogens also produce reactive oxygen species that are metabolized by manganese superoxide dismutase (MnSOD). The association between prostate cancer (PCA) and the polymorphism of MnSOD and NAT, and cigarette smoking was investigated. PATIENTS AND METHODS: DNA samples from 187 PCA patients and 175 age-matched controls were genotyped for MnSOD, NAT1 and NAT2 by PCR restriction fragment length polymorphism analysis and DNA sequencing. RESULTS: MnSOD AA genotype, as compared to MnSOD VV and VA, was associated with PCA (odds ratio, 1.65; 95% confidence interval, 1.03-2.66. There was no association of PCA with NAT or smoking. Results of exploratory analyses of the data suggest that the association of PCA and MnSOD exists only in the subpopulation of rapid NAT1 genotypes and smokers. CONCLUSION: The present study demonstrates the association of PCA and MnSOD. Oxidative stress and cigarette smoking may play an important role in the carcinogenesis of the prostate in those who have MnSOD AA and rapid NAT1 genotypes.

Inspiring urology trainees to enter academic careers.

The physician-scientist in academic medical centers has been called as 'an endangered species'. Adverse socioeconomic pressures, lack of dedicated research time, and increasing difficulties in obtaining grant support, make it more and more difficult to attract talented individuals for this career path, and consequently to recruit and retain them in the urology departments. The challenges facing the young academic faculty, physician-scientists, and the research trainees represent a danger to the future of academic medicine. Only a concerted effort to balance the financial disincentives, providing a protected time, a nurturing environment, and the emphasis on outstanding mentors and role models, can secure the continued research and academic success of urology programs. The disproportionate representation of women and the minorities among academic faculty must be recognized and addressed.

Higher than expected association of clinical prostate and bladder cancers.

PURPOSE: In this study we evaluated the risk of a second malignancy of the bladder or prostate in patients with a previous diagnosis of prostate cancer (PCa) or urothelial cancer (TCC). MATERIALS AND METHODS: We retrospectively analyzed all cases of PCa and TCC diagnosed between January 1996 and June 2003. Only PCa diagnosed due to abnormal digital rectal examination or increased prostate specific antigen were included. All patients with TCC presented with hematuria or irritative voiding symptoms and the diagnoses were confirmed with a tissue diagnosis. The incidence of lung, colon and renal cancers was also analyzed. RESULTS: A total of 816 men were diagnosed with PCa and/or TCC. Of 673 men initially diagnosed with PCa 21 had TCC. Of 149 men initially diagnosed with TCC 18 had PCa. Average age at PCa and TCC diagnosis +/- SD was 68.2 +/- 7.9 and 68.2 +/- 10.4 years, respectively. The standardized incidence ratio (SIR) of TCC in patients with PCa (SIR 4.31, 95% CI 2.411 to 7.110) and of PCa in patients with TCC (SIR 3.83, 95% CI 1.911 to 6.858) was significantly increased. There was no statistical significant difference in SIR for TCC in men with or without radiotherapy. SIR for lung, renal or colon cancer was not significantly different from what was expected. CONCLUSIONS: Patients with PCa have higher incidence of bladder cancer and those with bladder cancer have a higher incidence of PCa. This study has clinical implications in the care of these patients and it may stimulate research interest that may identify common pathways of carcinogenesis.

Occult prostate cancer effects the results of case-control studies due to verification bias.

BACKGROUND: Epidemiological studies of prostate cancer (PCA) which are based on case control comparisons may be effected by verification bias. Verification bias exists when the experimental group has verified PCA, while the control group is presumed to be cancer free, but this is not histologically verified. MATERIALS AND METHODS: Review of the literature and our recent experience with case-control studies of PCA in an autopsy model. RESULTS: When autopsied prostates were evaluated for cancer based on prostatic specific antigen <4 ng/ml, negative biopsy or both criteria, the contamination rate was 22%, 15% or 12%, respectively. The effect of contamination by occult PCA alters the odds ratio and p-value of the results. CONCLUSION: It is important to recognize that contamination of the control population by occult carcinomas reduces the reliability of the results. Rigorous characterization of the experimental and control groups is needed in order to preserve the integrity of the conclusions.

The worldwide epidemiology of prostate cancer: perspectives from autopsy studies.

INTRODUCTION: Prostate cancer is the most frequently diagnosed non-skin cancer in the United States and the third leading cause of cancer deaths. International trends in the incidence, mortality and prevalence of prostate cancer are assessed. METHODS: Databases from the Surveillance, Epidemiology and End Results (SEER) program of the National Cancer Institute and the International Agency for Research on Cancer (IARC), and the literature on autopsy studies on prostate cancer were reviewed and summarized in the article. RESULTS: Prostate cancer remains an important public health concern in Western countries and an emerging malignancy in developing nations. Prostate cancer incidence is dependent on efforts to detect the disease. Autopsy studies provide accurate and useful information regarding comparative prevalence rates of the disease among regions of interest. CONCLUSIONS: Improved cancer registration is needed in developing nations. The prevalence of prostate cancer must be established to predict the expected incidence of the disease and in order to plan rational detection and treatment strategies. Clinically significant disease should be distinguished from insignificant disease which may pose little or no biological danger to the patient.

Shape Signatures: speeding up computer aided drug discovery.

Identifying potential lead molecules is becoming a more automated process. We review Shape Signatures, a tool that is effective and easy to use compared with most computer aided drug design techniques. Laboratory researchers can apply this in silico technique cost-effectively without the need for specialized computer backgrounds. Identifying a potential lead molecule requires database screening, and this becomes rate-limiting once the database becomes too large. The use of Shape Signatures eliminates this concern and offers molecule screening rates that are in advance of any currently available method. Shape Signatures provides a conduit for researchers to conduct rapid identification of potential active molecules, and studies with this tool can be initiated with only one bioactive lead or receptor site.

Inhibition of human liver catechol-O-methyltransferase by tea catechins and their metabolites: structure-activity relationship and molecular-modeling studies.

(-)-Epigallocatechin-3-gallate (EGCG) is the major polyphenol present in green tea. We previously demonstrated that EGCG was both a substrate and potent inhibitor of human liver cytosolic catechol-O-methyltransferease (COMT). We now report the structure-activity relationship for the inhibition of COMT-catalyzed O-methylation of catecholestrogens in human liver cytosol by tea catechins and some of their metabolites. The most potent inhibitors were catechins with a galloyl-type D-ring, including EGCG (IC(50)=0.07 microM), 4''-O-methyl-EGCG (IC(50)=0.10 microM), 4',4''-di-O-methyl-EGCG (4',4''-DiMeEGCG) (IC(50)=0.15 microM), and (-)-epicatechin-3-gallate (ECG) (IC(50)=0.20 microM). Catechins without the D-ring showed two to three orders of magnitude less inhibitory potency. Enzyme kinetic analyses revealed that EGCG behaved as a mixed inhibitor, whereas 4',4''-di-O-methyl-EGCG exhibited competitive kinetics for the S-adenosylmethionine (SAM), and noncompetitive kinetics for the catechol binding site. These compounds may represent a new type of COMT inhibitor. In silico molecular-modeling studies using a homology model of human COMT were conducted to aid in the understanding the catalytic and inhibitory mechanisms. Either D-ring or B-ring of EGCG could be accommodated to the substrate binding pocket of human COMT. However, the close proximity (2.6A) of 4''-OH to the critical residue Lys144, the higher acidity of the hydroxyl groups of the D-ring, and the hydrophobic interactions between the D-ring and residues in the binding pocket greatly facilitated the interaction of the D-ring with the enzyme, and resulted in increased inhibitory potency. These results provide mechanistic insight into the inhibition of COMT by commonly consumed tea catechins.

Association of MnSOD AA Genotype with the Progression of Prostate Cancer.

PURPOSE: To investigate whether manganese superoxide dismutase (MnSOD) genetic polymorphism is associated with the clinical significance of prostate cancer. MATERIALS AND METHODS: Prostates were obtained from 194 deceased men 45 years or older who did not have a history of prostate cancer. Serial sections and histological examinations of the prostate were performed. The MnSOD genotypes of the specimens were determined by polymerase chain reaction restriction fragment length polymorphism analysis. RESULTS: Of the 194 men, 31 and 26 had clinically insignificant and significant prostate cancer. Clinically significant cancer comprised 29% and 58% of the cancers in men <70 and >70 years old, respectively. The age-specific proportion of significant cancer significantly increased with the advance of age (p<0.001). MnSOD AA, as compared with the other genotypes (VA and VV together), was associated with significant prostate cancer across all ages, odds ratio (OR) 2.34, 95% confidence interval (CI) 0.99-5.49, and in men older than 69 years (OR 4.89, 95% CI 1.51-15.8), but not in men younger than 70 years. The genotype was not associated with clinically insignificant cancer regardless of age. The comparison between significant and insignificant cancer, the OR (95% CI) for MnSOD AA was 5.04 (1.05-24.2) (sensitivity 0.57, specificity 0.78, positive predictive value 0.78) in men older than 69 years. CONCLUSIONS: MnSOD polymorphism is strongly associated with the clinical significance of prostate cancer in men older than 69 years, but not in men younger than 70 years suggesting that oxidative stress may be involved in the progression of the disease. MnSOD may be a clinically useful marker to predict the potential of progression of prostate cancer.

Antitumor Effect on Murine Renal Cell Carcinoma by Autologous Tumor Vaccines Genetically Modified with Granulocyte-Macrophage Colony-Stimulating Factor and Interleukin-6 Cells.

SUMMARY: The authors evaluted the efficacy of vaccination with murine renal cell carcinoma (Renca) secreting the granulocyte-macrophage colony-stimulating factor (GM-CSF) gene and interleukin-6 (IL-6) gene for the treatment of Renca tumor. Murine GM-CSF and murine IL-6 genes were introduced and expressed in Renca cells (Renca-GM-CSF and Renca-IL-6). For a prevaccination study, wild-type Renca cells were injected subcutaneously into Balb/c mice that had been vaccinated three times with inactivated wild-type Renca, Renca-GM-CSF, Renca-IL-6, or a mixture of Renca-GM-CSF and Renca-IL-6 cells 7, 14, and 21 days before this tumor inoculation. For vaccination experiments, Renca tumor-bearing (8 to 10 mm) mice were injected subcutaneously weekly for 3 weeks with inactivated wild-type Renca cells, or either one or a combination of Renca-GM-CSF and Renca-IL-6. A nonvaccinated control was included in all experiments. The animals were monitored for survival and tumor development for 8 weeks. Mice inoculated with wild-type Renca alone died from the tumor within 35 days. Renca-IL-6 grew slower than wild-type Renca (p < 0.05). No tumor was produced by Renca-GM-CSF. Prevaccination with the combination of Renca-GM-CSF and Renca-IL-6 prevented subsequently inoculated wild-type Renca from forming tumors, and prevaccination with either one of them, compared with prevaccination with wild-type Renca, retarded tumor growth and prolonged survival time. Tumor-bearing mice vaccinated with wild-type Renca died within 42 days. Vaccination with Renca-GM-CSF or Renca-IL-6 alone prolonged the survival time, but only Renca-GM-CSF drastically reduced the tumor size. Vaccination with the combination of them achieved complete remission. Neither of the cytokine-secreting cells enhanced the expression of MHC class I or II molecules. Autologous tumor cell vaccine secreting GM-CSF is effective in preventing and treating established tumors. Its efficacy is enhanced by the cosecretion of IL-6.

Double primary cancers of the prostate and bladder: a literature review.

A number of studies report a high frequency of double primary cancers of the bladder and prostate. The coincidence was as high as 70% for prostate cancers in patients with bladder cancer, and 3.4% for bladder cancers in patients with prostate cancer. Two studies reviewing medical records reported a significant risk of bladder cancer after prostate cancer and of prostate cancer after bladder cancer. Only 1 of 3 cancer registry studies reported a significantly increased risk of prostate cancer after bladder cancer, and 3 of 11 studies reported a significantly increased risk in bladder cancer after prostate cancer. There was an association between DNA repair and N-acetyltransferase polymorphisms and risk of prostate and bladder cancer. These data suggest that these cancers may share a common carcinogenic process or that these patients are particularly susceptible to both cancers. Because of the association between these cancers, patients who are diagnosed with prostate or bladder cancer should be followed closely for the detection of the second urologic malignancy.

Differential gene expression in human prostate cancer cells adapted to growth in bone in Beige mice.

OBJECTIVE: A metastasis model was used to identify genes potentially related to the growth of human prostate cancer in the bone. Injection of the human prostate cancer line PC3 into the femurs of Beige mice induced tumors that ruptured the femurs in 4 to 6 weeks. MATERIALS AND METHODS: The subline PC3a was cultured in vitro from one of these PC3 bone tumors. PC3a cells were reinjected into femurs, and the subline PC3b was then cultured from a resulting PC3a tumor. Likewise, PC3c was derived from a PC3b bone tumor. The PC3 tumors were osteolytic, invasive and metastatic. RESULTS: Analysis of gene expression in these PC3 sublines by differential-display RT-PCR identified two groups of transcripts whose steady state levels differed substantially from the original PC3 line. One group of transcripts increased with progressive adaptation to tumor formation in bone. The second group showed the reverse pattern. They progressively diminished in subsequent sublines, and were virtually absent in PC3b and PC3c. Two in this group were fibroblast growth factor receptor-2 and caveolin-1. They were strongly expressed in non-malignant prostate tissue. CONCLUSION: These two downregulated genes, which have been reported to play a role in the development of androgen independence and malignant progression, may reflect molecular changes in growth regulation of PC3 cells during readaptation to an intra-osseal environment.

Correlation of the genotypes for N-acetyltransferases 1 and 2 with double bladder and prostate cancers in a case-comparison study.

BACKGROUND: The arylamine N-acetyltransferases play a major role in the metabolic activation of carcinogenic amines that are present in cigarette smoke and a variety of other exogenous sources. The objective of this study was to determine the association of rapid or slow arylamine N-acetyltransferase (NAT) genotypes with smoking history and the risk for developing both bladder and prostate cancer. PATIENTS AND METHODS: The subjects analyzed were a case group of 17 double-cancer patients and 34 age-matched controls who had benign prostatic hypertrophy, but were asymptomatic for prostate or bladder cancers. Genotyping of NAT1 and NAT2 alleles was done by restriction fragment length polymorphism and/or sequencing of NAT genes amplified from genomic DNAs by the polymerase chain reaction (PCR). RESULTS: No significant correlation was found between NAT1 genotypes, double cancer, and smoking history. While NAT2-smoking interaction gave an odds ratio of only 1.70 (p = 0.117), a disproportionate number of cancer cases were genotypically rapid: 12 of 17 cancer cases vs. 13 of 34 controls (odds ratio 3.88; p = 0.040). CONCLUSION: Rapid NAT2 genotype correlated significantly with the development of double prostate-bladder cancer.

Combination of radiation and vaccination with autologous tumor cells expressing IL-2, IFN-gamma and GM-CSF for treatment of murine renal carcinoma.

BACKGROUND: We previously showed, in a murine renal cell carcinoma (RCC) model, that lung irradiation plus vaccination with autologous tumor cells producing recombinant interleukin-2 (IL-2), interferon-gamma (IFN-gamma) and granulocyte-macrophage colony-stimulating factor (GM-CSF) (Renca/cytokine) reduces the number of lung metastases by over 90%. The present study investigates the host cellular mechanisms mediating this anti-tumor activity. MATERIALS AND METHODS: Lung metastases were produced by injection of BALB/c mice i.v. with wild-type Renca cells (wt Renca) on day 0. The mice were then injected s.c. with irradiated Renca/cytokine vaccine cells on days 4, 8 and 11. Lungs were irradiated (300 rads) on day 7. Natural killer (NK) cells or T cells were depleted by injection i.p. with an antibody against anti-asialo GM1 or Thy1.2, respectively. Polyinosinic-polycytidylic acid (poly I:C) was injected i.p. to activate NK cells. Lung tumors were enumerated on day 21. RESULTS: The anti-asialo GM I antibody totally abolished the antitumor activity elicited by the combined vaccination/radiation treatment regime. In contrast, anti-Thyl.2 antibody did not significantly decrease treatment efficacy. Poly I:C elicited over 95% reduction in lung metastases and strong NK activation as assayed against YAC-1 cells in vitro. CONCLUSIONS: It appears that NK cells and granulocytes are predominantly involved in the antitumor action elicited by the cytokine-secreting autologous tumor cell vaccine in this metastatic RCC model.

Instillation of mitomycin C after transurethral resection of bladder cancer impairs wound healing: an animal model.

BACKGROUND: Mitomycin C is used in the immediate post-operative period to prevent tumor re-implantation, but it has adverse effects on the bladder. This study devised an animal model to investigate the effects of intravesical mitomycin C on wound healing. METHODS AND MATERIALS: A cystotomy was made in the dome of the bladder of female rats. The mucosa of the posterior wall was scratch with closed forceps. The bladder was closed and 0.2 ml of saline with or without 0.4 mg mitomycin C was instilled into the bladder transurethrally. The rats were sacrificed 30 and 60 days after the treatment and the bladder was examined grossly and microscopically. RESULTS: The most frequent histological findings in the bladder were chronic inflammation and fibrosis. Fibrosis but not chronic inflammation was significantly associated with the exposure to MMC and it persisted even 60 days after the exposure to mitomycin C. CONCLUSION: Mitomycin C produces chronic fibrosis in rat bladder that is often seen in patients receiving prophylactic treatment with this drug.

IRX-2 increases the T cell-specific immune response to protein/peptide vaccines.

Therapeutic cancer vaccines are attractive due to the prospect of specificity and their lack of toxicity; however, their clinical development has been hampered by several biologic and clinical challenges. One of the most important biologic challenges is the relative lack of effective cellular immune adjuvants. Effective physiologic immune responses are characterized by the local generation of a complex cytokine environment that activates and regulates multiple immune cell types. IRX-2 is a primary cell-derived biologic with physiological levels of multiple active cytokine components, produced under pharmaceutical standards. The hypothesis that IRX-2 amplifies the T cell response to defined antigens was assessed in mice by measuring the T cell-specific peptide response to a dominant mouse peptide (NFT) derived from human prostate-specific membrane antigen (PSMA). IRX-2 enhances the T cell response to NFT when antigens were delivered either via irradiated cells expressing human PSMA, NFT peptide in Incomplete Freund's adjuvant (IFA) or NFT peptide conjugated to KLH. The T cell-specific activity was measured in spleen or lymph nodes cells by IFN-γ ELISpot and/or IFN-γ secretion over 6 days or in vivo by peptide-specific delayed-type hypersensitivity reaction (DTH). Further more, a single administration of IRX-2 with the antigen was not active as compared to 4 or 9 additional administrations which were sufficient to enhance the T cell response to antigens. The influence of IRX-2 on the B cell response to ovalbumin when it was used as a carrier protein was measured by ELISA. IRX-2 was compared to a commercially available combination adjuvant (MPL+TDM in squalene/Tween 80) which based on the literature is a potent adjuvant in murine systems. In the T cell assay IRX-2 was superior to the commercially available combination adjuvant and while IRX-2 also increased antibody titer, it was not as potent as the combination adjuvant. Mice immunized with IRX-2 and antigen also exhibited delayed tumor progression following challenge with PSMA-expressing tumor cells. These studies demonstrate that IRX-2 is an immunomodulator with adjuvant activity which preferentially enhances the T cell-specific responses to tumor associated antigens. Based on these studies, IRX-2 is a candidate for evaluation as a T cell adjuvant in a variety of preclinical vaccine delivery systems as well as in human clinical trials with cancer vaccine candidates.

Association of prostate cancer and manganese superoxide dismutase AA genotype influenced by presence of occult cancer in control group.

OBJECTIVES: To investigate whether the inclusion of occult cancer in the control group can influence the association of prostate cancer and the polymorphism of manganese superoxide dismutase (MnSOD). METHODS: Prostate specimens and sera were obtained from 194 deceased men who did not have a history of prostate cancer. Eighteen-core biopsy specimens and whole-mount sections were evaluated histologically. The MnSOD genotype of the specimens was determined by polymerase chain reaction restriction fragment length polymorphism analysis. RESULTS: Tumors were present in 57 of the prostates, and biopsy detected 33 (including 1 false-positive finding). It detected 17 (1 false-positive finding) and missed 14 tumors in the subgroup of 135 specimens with a prostatic-specific antigen <4 ng/mL. The MnSOD AA genotype was associated with prostate cancer found in the step-sectioned specimens vs the control group in whom the absence of occult prostate cancer had been verified. However, no association was found if the control group consisted of subjects with negative biopsy results from the overall group or the subgroup with a prostatic-specific antigen level of <4 ng/mL. CONCLUSIONS: The MnSOD AA genotype was associated with prostate cancer in our study; however, contamination of occult prostate cancer in the control group reduced the power of analysis and might yield seemingly negative results. Epidemiologic studies should strive to include control groups with a verified absence of occult cancer.

Structural model reveals key interactions in the assembly of the pregnane X receptor/corepressor complex.

The human pregnane X receptor (PXR), also known as steroid and xenobiotic receptor, is a member of the orphan nuclear receptors and mediates the mammalian xenobiotic response with broad specificity and implications for drug clearance. The mouse pregnane X receptor is highly similar to the human ortholog in structure but with subtle species differentiation in the ligand binding domain (LBD). The C-terminal helix named alphaAF or AF-2 helix in other nuclear receptors is responsible for transcription activation by recruiting coactivators through conformational change. In the absence of ligands, PXR can also repress gene expression by interacting with transcriptional corepressors, such as the silencing mediator for retinoid and thyroid hormone receptor (SMRT). We first constructed homology models of the complete LBD with two SMRT nuclear receptor (NR)-interacting domains (ID1 and ID2), respectively. We then performed energy minimization and molecular dynamics simulations on these systems to study the specific interactions between the interacting domains and LBD. Further experimental results supported and validated the observed preference of SMRT toward ID2 over ID1. Our modeling results revealed the key interactions that account for the binding preference. Here, we propose structural models of the PXR-LBD/SMRT-ID1 and PXR-LBD/SMRT-ID2 complexes to understand their molecular interactions and potential inhibitory mechanism.

Expression of prostate-specific membrane antigen in normal and malignant human tissues.

BACKGROUND: Prostate-specific membrane antigen (PSMA) is upregulated in androgen-dependent prostate carcinoma and it has been targeted for immunotherapy and diagnosis of this cancer. However, this protein is also expressed in other tissues. The objective of this study is to investigate its expression in normal and malignant human tissues. METHODS: Using monoclonal antibodies 24.4E6 (specific for residues 638-657) and 7E11.C5 (specific for the transmembrane domain of PSMA), immunohistochemical detection of PSMA was performed in surgical specimens. RESULTS: Prostate-specific membrane antigen was detected in the epithelium of prostate, urinary bladder, proximal tubules of kidney, liver, esophagus, stomach, small intestine, colon, breast, fallopian tubes and testicular seminiferous tubules, hippocampal neurons and astrocytes, ependyma, cortex and medulla of the adrenal gland, and ovary stroma. It was also detected in neoplasms of the prostate, kidney, urinary bladder, stomach, small intestine, colon, lung, adrenal gland, and testis. It was not detected in normal seminal vesicles or the lung. CONCLUSIONS: These findings demonstrate that PSMA is widely distributed in normal tissues, and, depending on the tumors, its expression is up- or down-regulated, or unchanged. The broad distribution of PSMA may make it suitable for the diagnosis and therapy of a wide variety of tumors.