Combined c-Myc and caveolin-1 expression in human prostate carcinoma predicts prostate carcinoma progression

Caveolin-1: a tumor-promoting role in human cancer

PURPOSE

Caveolae are non-clathrin, flask-shaped invaginations of the plasma membrane. Caveolin-1 is an essential constituent of caveolae and as such acts as a regulator of caveolae-dependent lipid trafficking and endocytosis. Caveolin-1 interacts with a variety of cellular proteins and regulates cell-signaling events. Caveolin-1 appears to act as a tumor suppressor protein at early stages of cancer progression. However, a growing body of evidence indicates that caveolin-1 is up-regulated in several multidrug-resistant and metastatic cancer cell lines and human tumor specimens. Furthermore, caveolin-1 levels are positively correlated with tumor stage and grade in numerous cancer types.

CONCLUSION

The available experimental data support the tumor-promoting role of caveolin-1 in advanced-stage cancer.

Caveats of caveolin-1 in cancer progression

Caveolin-1, an essential scaffold protein of caveolae and cellular transport processes, lately gained recognition as a stage- and tissue-specific tumor modulator in vivo. Patient studies and rodent models corroborated its janus-faced role as a tumor suppressor in non-neoplastic tissue, its down-regulation (loss of function) upon transformation and its re-expression (regain of function) in advanced-stage metastatic and multidrug resistant tumors. This review is focussed on the role of caveolin-1 in metastasis and angiogenesis and its clinical implications as a prognostic marker in cancer progression.

Do the cholesterol-lowering properties of statins affect cancer risk?

The potential of 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors ('statins') to reduce the incidence and/or progression of certain malignancies remains uncertain. Some investigators have concluded that statins have no effects on malignancies of any kind. However, results of several epidemiologic studies, including four recent prospective cohort studies, suggest that long-term statin therapy inhibits the progression of prostate cancer. We argue that the principal mechanism of any anticancer effects from statin use arises from prolonged lowering of circulating cholesterol. Evidence suggests that prostate cancer might be particularly sensitive to this intervention. Our hypothesis provides a perspective from which mechanistic studies of cholesterol-lowering drugs and cancer, in addition to prospective trials in patients, might be designed.

Correlative evidence that tumor cell-derived caveolin-1 mediates angiogenesis in meningiomas

Since it has recently been reported that caveolin-1 (cav-1) may favor the progression of prostatic and renal cancers by stimulating tumor neoangiogenesis, we thought it of interest to analyze the correlation between cav-1 expression and tumor microvessel density (MVD) in meningiomas. In the present study we quantified cav-1 expression by immunohistochemistry and used CD105 immunohistochemical staining to measure MVD. Sixty-two formalin-fixed, paraffin-embedded, surgically resected meningiomas were submitted to the analysis. On the basis of cav-1 immuno-expression, cases were subdivided into meningiomas displaying a low (n = 34) and a high (n = 28) cav-1 immuno-expression, respectively. Mann-Whitney test showed that a significantly higher MVD was present in the cases with a high cav-1 expression than in those with a low expression (mean 24.44 vs. 41.28 microvessels/mm(2)) (P = 0.0001). Moreover, Spearman test revealed a significant positive correlation between cav-1 rate of expression and MVD counts in the meningiomas of our series (r = 0.390; P = 0.0023). Therefore, our study demonstrates the existence of an association between cav-1 expression and neoangiogenesis in meningiomas, suggesting that cav-1 may mediate the progression of these tumors by stimulating the angiogenic process. Besides, it is known that the progression of meningiomas is paralleled by an increase in MVD. The clarification of cav-1 role in the neoangiogensis of meningiomas may open new insights about the possibility of novel therapeutic strategies in these neoplasias.

Integrin regulation of caveolin function

Caveolae are unique organelles that are found in the plasma membrane of many cell types. They participate in various processes such as lipid recycling, cellular signalling and endocytosis. A variety of signalling molecules localize to caveolae in response to various stimuli, providing a potential mechanism for the spatial regulation of signal transduction pathways. Caveolin-1, a constitutive protein of caveolae, has been implicated in the regulation of cell growth, lipid trafficking, endocytosis and cell migration. Phosphorylation of caveolin-1 on Tyr 14 is involved in integrin-regulated caveolae trafficking and also in signalling at focal adhesions in migrating cells. In this review, we focus on recent studies that describe the role of caveolin-1 in integrin signal transduction, and how this interplay links extracellular matrix anchorage to cell proliferation, polarity and directional migration.

Caveolin-1 overexpression is associated with aggressive prostate cancer recurrence

BACKGROUND

Caveolin-1 protein suppresses apoptotic cell death in prostate cancer. The objectives of this study were to investigate the association of Caveolin-1 expression with established features of prostate cancer as well as overall and aggressive disease recurrence in patients treated with radical prostatectomy (RP).

METHODS

Caveolin-1 immunostaining was performed on a tissue microarray containing prostatectomy specimen cores from 232 consecutive patients treated with RP for clinically localized prostatic adenocarcinoma. Caveolin-1 over-expression was defined as more than 50% of cells staining positively for Caveolin-1. Patients were categorized as having features of aggressive disease recurrence if they had a positive metastatic work-up, post-recurrence PSA doubling time less than 10 months, and/or failure to respond to local salvage radiation therapy.

RESULTS

Seventy patients (30.2%) exhibited over-expression of Caveolin-1. Caveolin-1 over-expression was associated with higher pathologic Gleason sum (P=0.038) and higher pre-operative PSA level (P=0.024). Patients with Caveolin-1 over-expression were at increased risk of PSA recurrence after surgery (P=0.023) in univariate but not in standard post-operative multivariate analysis. However, patients with Caveolin-1 over-expression were at increased risk of aggressive prostate cancer recurrence in both univariate and multivariate analysis (P<0.001 and P=0.001, respectively).

CONCLUSIONS

Over-expression of Caveolin-1 was associated with established features of prostate cancer and aggressive PSA recurrence. Caveolin-1 might help identify patients at high risk of developing aggressive prostate cancer recurrence, thus allowing selection of patients who might benefit from early systemic therapeutic intervention.

The multiple faces of caveolae

Caveolae are a highly abundant but enigmatic feature of mammalian cells. They form remarkably stable membrane domains at the plasma membrane but can also function as carriers in the exocytic and endocytic pathways. The apparently diverse functions of caveolae, including mechanosensing and lipid regulation, might be linked to their ability to respond to plasma membrane changes, a property that is dependent on their specialized lipid composition and biophysical properties.

Caveolin-1 in meningiomas: expression and clinico-pathological correlations

Caveolin-1 (Cav-1) protein has been documented in several neoplasms with a controversial role in cell proliferation, tumour development and progression. The aim of the present study was to investigate the Cav-1 immunohistochemical expression in human meningiomas. Sixty-two cases, classified as 11 meningothelial (17%), 12 transitional (19%), 5 fibrous (8%), 3 microcystic (5%), 3 secretory (5%), 1 clear cell (2%), 1 chordoid (2%) and 26 (42%) atypical meningiomas, were selected from our pathological files. Clinico-pathological data, including Ki-67 values and survival data were also available. Ten leptomeningeal samples were utilized as normal tissue control. For each case, a polyclonal antibody against Cav-1 was applied and an intensity distribution (ID) score was determined. The Cav-1 immunoexpression was found in 95% of meningiomas with a variable ID score, while only minimal, not uniform, reactivity was noted in non-neoplastic meninges. Of note, higher Cav-1 ID score was significantly correlated with tumour site, Simpson's grade, histological type, higher histologic grade, Ki-67 labelling index > or = 4% and clinical course. Kaplan-Meier curves demonstrated a significantly worse survival in patients with higher Cav-1 ID score, Ki-67 > or = 4% and 2-3 Simpson grade. Multivariate analysis indicated that only Ki-67 was an independent prognostic factor. Increased immunoexpression of the Cav-1 seems to be associated with the biological aggressiveness of meningiomas, reflecting a worse prognosis.

Molecular markers in the diagnosis of prostate cancer

The genetic alterations leading to prostate cancer are gradually being discovered. A wide variety of genes have been associated with prostate cancer development as well as tumor progression. Knowledge of gene polymorphisms associated with disease aid in the understanding of important pathways involved in this process and may result in the near future in clinical applications. Urinary molecular markers will soon be available to aid in the decision of repeat prostate biopsies. Recent findings suggest the importance of androgen signaling in disease development and progression. The further understanding of interaction of inflammation, diet, and genetic predisposition will improve risk stratification in the near future.

Development of a "reverse capture" autoantibody microarray for studies of antigen-autoantibody profiling

Diagnosing cancers based on serum profiling is a particularly attractive concept. However, the technical challenges to analysis of the serum proteome arise from the dynamic range of protein amounts. Cancer sera contain antibodies that react with a unique group of autologous cellular antigens, which affords a dramatic amplification of signal in the form of antibodies relative to the amount of the corresponding antigens. The serum autoantibody repertoire from cancer patients might, therefore, be exploited for antigen-antibody profiling. To date, studies of antigen-antibody reactivity using microarrays have relied on recombinant proteins or synthetic peptides as arrayed features. However, recombinant proteins and/or synthetic peptides may fail to accurately detect autoantibody binding due to the lack of proper PTMs. Here we describe the development and use of a "reverse capture" autoantibody microarray. Our "reverse capture" autoantibody microarray is based on the dual-antibody sandwich immunoassay platform of ELISA, which allows the antigens to be immobilized in their native configuration. As "proof-of-principle", we demonstrate its use for antigen-autoantibody profiling with sera from patients with prostate cancer and benign prostate hyperplasia.

Effect of Caveolin-1 on growth of human gastric cancer cell Line MGC803

AIM: To investigate the effect of Caveolin-1 on the proliferation and differentiation of gastric carcinoma cell line MGC803, and explore the probability that Caveolin-1 can be used for gene therapy.

METHODS: Caveolin-1 gene and Pcl-neo control plasmid were transfected into human MGC803 cell line by lipofectin, respectively. The positive clones were selected by G418. We also stabled a positive control group which was treated with PD98059 for 48 hours. Then the expression of Caveolin-1 in each group was detected by Western blot. Cell morphology was observed under optical microscope. Cell population doubling time was determined by cell counting method and cell cycle was analyzed by flow cytometry.

RESULTS: The expression of Caveolin-1 was significantly higher in the cells treated with Caveolin-1 or PD98059 than that in the empty controls (P < 0.001, q = 23.067 or 13.3376). Furthermore, Caveolin-1 expression was also markedly higher in the cells transfected with Caveolin-1 than that in the positive controls (P < 0.001, q = 9.7294). Under light microscope, marked changes occurred in cell morphous after gene transfection. Before transfection, the cells had a significant heteromorphism, with the features of large cell body, little cytoplasm, obvious karyokinesis. While in Caveolin-1-transfected MGC803 cells, the cell malignancy declined as the cellular heteromorphism diminished, with the ratio of nuclear-to-cytoplasm decreased, and the karyokinesis disappeared. Caveolin-1-transfected cells had an extended doubling time (65.46 h vs 46.67 h, P < 0.05, q = 4.8695). At same time, the population of Caveolin-1-transfected cells in G₀/G₁ phase was obviously increased (P < 0.01, q = 9.1824) while that in S phase was decreased (P < 0.01, q = 7.827). There were also notable differences in cell cycle distribution between Caveolin-1-transfected cells and the positive controls (G₀/G₁: P < 0.01, q = 4.9323; S: P < 0.05, q = 3.3295).

CONCLUSION: Caveolin-1 not only induces the differentiation of MGC803 cells, but also blocks them at in G₀/G₁ phase. Caveolin-1 can inhibit the proliferation of MGC803 cells in vitro by prolonging the cell doubling time.

Divergent expression and roles for caveolin-1 in mouse hepatocarcinoma cell lines with varying invasive ability

Caveolin-1 is the major component protein of caveolae and associated with a lot of cellular events such as endocytosis, cholesterol homeostasis, signal transduction, and tumorigenesis. The majority of results suggest that caveolin-1 might not only act as a tumor suppressor gene but also a promoting metastasis gene. In this study, the divergent expression and roles of caveolin-1 were investigated in mouse hepatocarcinoma cell lines Hca-F, Hca-P, and Hepa1-6, which have high, low, and no metastatic potential in the lymph nodes, as compared with normal mouse liver cell line IAR-20. The results showed that expression of caveolin-1 mRNA and protein along with the amount of caveolae number in Hca-F cells was higher than that in Hca-P cells, but was not detectable in Hepa1-6 cells. When caveolin-1 expression in Hca-F cells was down-regulated by RNAi approach, Hca-F cells proliferation rate in vitro declined and the expression of lymphangiogenic factor VEGFA in Hca-F decreased as well. Furthermore, in vivo implantation assay indicated that reduction of caveolin-1 expression in Hca-F prevented the lymphatic metastasis tumor burden of Hca-F cells in 615 mice. These results suggest that caveolin-1 facilities the lymphatic metastasis ability of mouse hepatocarcinoma cells via regulation tumor cell growth and VEGFA expression.

Recent advances on multiple tumorigenic cascades involved in prostatic cancer progression and targeting therapies

Recent advances on differently-expressed gene products and their functions during the progression from localized androgen-dependent states into androgen-independent and metastatic forms of prostate cancer are reported. The expression levels of numerous oncogenes and tumor suppressor genes in distinct prostatic cancer epithelial cell lines and tissues relative to normal prostate cells are described. This is carried out to identify the signaling elements that are altered during the initiation, progression and metastatic process of prostate cancer. Additional information on the interactions between certain deregulated signaling pathways such as androgen receptor (AR), estrogen receptors, epidermal growth factor receptor (EGFR), hedgehog and Wnt/beta-catenin cascades in controlling the proliferation, survival and invasion of tumor prostate epithelial cells during the disease progression is described. The emphasis is on the critical functions of the AR and EGF-EGFR systems at all stages during prostate carcinogenesis. Of therapeutic interest, new strategies for the diagnosis and treatment of localized and metastatic forms of prostate cancer by targeting multiple tumorigenic signaling elements are also reported.