Anti-caveolin-1 antibodies as anti-prostate cancer therapeutics

Caveolin-1: A promising therapeutic target for diverse diseases

The plasma membrane of eukaryotic cells contains small flask-shaped invaginations known as caveolae that are involved in the regulation of cellular signaling. Caveolin-1 is a 21-24kDa protein localized in the caveolar membrane. Caveolin-1 (Cav-1) has been considered as a master regulator among the various signaling molecules. It has been emerging as a chief protein regulating cellular events associated with homeostasis, caveolae formation, and caveolae trafficking. In addition to the physiological role of cav-1, it has a complex role in the progression of various diseases. Caveolin-1 has been identified as a prognosticator in patients with cancer and has a dual role in tumorigenesis. The expression of Cav-1 in hippocampal neurons and synapses is related to neurodegeneration, cognitive decline, and aging. Despite the ubiquitous association of caveolin-1 in various pathological processes, the mechanisms associated with these events are still unclear. Caveolin-1 has a significant role in various events of the viral cycle, such as viral entry. This review will summarize the role of cav-1 in the development of cancer, neurodegeneration, glaucoma, cardiovascular diseases, and infectious diseases. The therapeutic perspectives involving clinical applications of Caveolin-1 have also been discussed. The understanding of the involvement of caveolin-1 in various diseased states provides insights into how it can be explored as a novel therapeutic target.

Network-pharmacology-based identification of caveolin-1 as a key target of Oldenlandia diffusa to suppress breast cancer metastasis

BACKGROUND

Breast cancer remains the most common female malignancy and metastasis is the leading cause of death in breast cancer patients. Oldenlandia diffusa has been empirically and extensively used as an adjuvant therapy for metastatic breast cancer patients in Traditional Chinese Medicine (TCM) with proven efficacy. However, its anti-metastasis mechanism has been poorly revealed.

METHODS

Multiple molecular biology experiments as well as network pharmacology, bioinformatics analysis were conducted to investigate the anti-metastasis mechanism of Oldenlandia diffusa in breast cancer.

RESULTS

We demonstrated that ethanol extract of Oldenlandia diffusa (EEOD) significantly inhibited proliferation and induced apoptosis of high-metastatic breast cancer cell lines MDA-MB-231 and MDA-MB-453, while having no obvious cytotoxic effect on multiple nonmalignant cells. Furthermore, EEOD remarkably suppressed the migration and invasion capacities of the above breast cancer cells by modulating the matrix metalloproteinases (MMPs) and the epithelial-mesenchymal transition (EMT) pathway. More importantly, EEOD also significantly inhibited breast cancer metastasis in zebrafish xenotransplantation model in vivo. Network pharmacology and bioinformatics analysis further demonstrated that EEOD yielded 12 candidate compounds and 225 potential targets, and shared 85 putative targets associated with breast cancer metastasis. Mechanistically, RNA sequencing and experimental validation results suggested that EEOD might inhibit breast cancer metastasis by attenuating the expression of caveolin-1 (Cav-1) as overexpression of Cav-1 could weaken the anti-metastasis efficacy of EEOD.

CONCLUSIONS

Overall, our findings proved that EEOD could inhibit breast cancer metastasis by attenuating the expression of Cav-1, highlighting the use of EEOD as an adjunctive therapy for metastatic breast cancer patients. This study also provides novel insights into network pharmacology and bioinformatics analysis as effective tools to illuminate the scientific basis of TCM.

pH low insertion peptide mediated cell division cycle-associated protein 1 -siRNA transportation for prostatic cancer therapy targeted to the tumor microenvironment

Prostate cancer (PCa) is a common malignancy in male urinary system. Cell division cycle-associated protein 1 (CDCA1) is expressed highly in many cancer cells. Yet, whether CDCA1 play an important role in PCa progression is uncertain. pH low insertion peptide (pHLIP), a PH-induced transmembrane structure, can pass through the cell membrane into intracellular in an acidic environment. In this study, we try to confirm the expression status of CDCA1 in the PCa patients' tissues and PCa cell line. In addition, to make the CDCA1-siRNA efficiently targeting the PCa cells, pHLIP and CDCA1-siRNA were combined with disulfide bond to become effector molecules. By the characteristics of the pHLIP allosteric occurring in cancer tissue acidic microenvironment, CDCA1-siRNA may be transported specificity into prostatic cancer cells and released in the cytoplasm. The interference effect of the effector molecules on the CDCA1 was detected in vitro and in vivo. The results showed that CDCA1 was highly expressed in PCa cell line and human PCa clinical samples. Knock down CDCA1 significantly inhibit the growth and promote the apoptosis of prostatic cancer cells. In the intracellular translocation experiment, CDCA1-siRNA could be delivered into cytoplasma at pH 6.2, but not at pH 7.4. In the in vivo test, the tumor size was reduced obviously in the NOD/SCID mice treated with pHLIP-CDCA1-siRNA compared to the CDCA1-siRNA and the bioluminescent signal of Cy5-pHLIP-CDCA1-siRNA was focused detected in the tumor site. Our findings indicated that CDCA1 might be a very key molecule regulating survival and proliferation of PCa. pHLIP-CDCA1-siRNA might be a promising targeting therapy for PCa.

Deregulation of E-cadherin, β-catenin, APC and Caveolin-1 expression occurs in canine prostate cancer and metastatic processes

Prostate cancer is a heterogeneous disease with high levels of clinical and gene heterogeneity, consequently offering several targets for therapy. Dogs with naturally occurring prostate cancer are useful models for molecular investigations and studying new treatment efficacy. Three genes and proteins associated with the WNT pathway (β-catenin, APC and E-cadherin) and Caveolin-1 (CAV-1) were evaluated in canine pre-neoplastic proliferative inflammatory atrophy (PIA), prostate cancer and metastatic disease. The APC gene methylation status was also investigated. As in human prostate cancer, cytoplasmic and nuclear β-catenin, which are fundamental for activating the canonical WNT pathway, were found in canine prostate cancer and metastasis. Membranous E-cadherin was also lost in these lesions, allowing cellular migration to the stroma and nuclear localization of β-catenin. In contrast to human prostate tumours, no APC downregulation or hypermethylation was found in canine prostate cancer. The CAV-1 gene and protein overexpression were found in canine prostate cancer, and as in humans, the highest levels were found in Gleason scores ≥8. In conclusion, as with human prostate cancer, β-catenin and E-cadherin in the WNT pathway, as well as Caveolin-1, are molecular drivers in canine prostate cancer. These findings provide additional evidence that dogs are useful models for studying new therapeutic targets in prostate cancer.

Caveolins as Regulators of Stress Adaptation

Caveolins have been recognized over the past few decades as key regulators of cell physiology. They are ubiquitously expressed and regulate a number of processes that ultimately impact efficiency of cellular processes. Though not critical to life, they are central to stress adaptation in a number of organs. The following review will focus specifically on the role of caveolin in stress adaptation in the heart, brain, and eye, three organs that are susceptible to acute and chronic stress and that show as well declining function with age. In addition, we consider some novel molecular mechanisms that may account for this stress adaptation and also offer potential to drive the future of caveolin research.

Prognostic value of Caveolin-1 in patients treated with radical prostatectomy: a multicentric validation study

OBJECTIVE

To validate Caveolin-1 as an independent prognostic marker of biochemical recurrence (BCR) in a large multi-institutional cohort of patients with prostate cancer treated with radical prostatectomy (RP).

PATIENTS AND METHODS

Caveolin-1 expression was evaluated by immunochemistry on a tissue microarray in 3 117 patients treated with RP for prostate cancer at five institutions. Univariable and multivariable Cox proportional hazards regression models assessed the association of Caveolin-1 status with BCR. Harrell's c-index quantified prognostic accuracy.

RESULTS

Caveolin-1 was overexpressed in 644 (20.6%) patients and was associated with higher pathological Gleason sum (P = 0.002) and lymph node metastases (P = 0.05). Within a median (interquartile range) follow-up of 38 (21-66) months, 617 (19.8%) patients experienced BCR. Patients with overexpression of Caveolin-1 had worse BCR-free survival than those with normal expression (log-rank test, P = 0.004). Caveolin-1 was an independent predictor of BCR in multivariable analyses that adjusted for the effects of standard clinicopathological features (hazard ratio 1.21, P = 0.037). Addition of Caveolin-1 in a model for prediction of BCR based on these standard prognosticators did not significantly improve the predictive accuracy of the model. In subgroup analyses, Caveolin-1 was associated with BCR in patients with favourable pathological features (pT2pN0 and Gleason score = 6; P = 0.021).

CONCLUSIONS

We confirmed that overexpression of Caveolin-1 is associated with adverse pathological features in prostate cancer and independently predicts BCR after RP, especially in patients with favourable pathological features. However, it did not add prognostically relevant information to established predictors of BCR, limiting its use in clinical practice.

Endothelial Caveolin-1 regulates the radiation response of epithelial prostate tumors

The membrane protein caveolin-1 (Cav1) recently emerged as a novel oncogene involved in prostate cancer progression with opposed regulation in epithelial tumor cells and the tumor stroma. Here we examined the role of stromal Cav1 for growth and radiation response of MPR31-4 prostate cancer xenograft tumors using Cav1-deficient C57Bl/6 mice. Syngeneic MPR31-4 tumors grew faster when implanted into Cav1-deficient mice. Increased tumor growth on Cav1-deficient mice was linked to decreased integration of smooth muscle cells into the wall of newly formed blood vessels and thus with a less stabilized vessel phenotype compared with tumors from Cav1 wild-type animals. However, tumor growth delay of MPR31-4 tumors grown on Cav1 knockout mice to a single high-dose irradiation with 20 Gray was more pronounced compared with tumors grown on wild-type mice. Increased radiation-induced tumor growth delay in Cav1-deficient mice was associated with an increased endothelial cell apoptosis. In vitro studies using cultured endothelial cells (ECs) confirmed that the loss of Cav1 expression increases sensitivity of ECs to radiation-induced apoptosis and reduces their clonogenic survival after irradiation. Immunohistochemical analysis of human tissue specimen further revealed that although Cav1 expression is mostly reduced in the tumor stroma of advanced and metastatic prostate cancer, the vascular compartment still expresses high levels of Cav1. In conclusion, the radiation response of MPR31-4 prostate tumors is critically regulated by Cav1 expression in the tumor vasculature. Thus, Cav1 might be a promising therapeutic target for combinatorial therapies to counteract radiation resistance of prostate cancer at the level of the tumor vasculature.

Caveolin-1 is a risk factor for postsurgery metastasis in preclinical melanoma models

Melanomas are highly lethal skin tumours that are frequently treated by surgical resection. However, the efficacy of such procedures is often limited by tumour recurrence and metastasis. Caveolin-1 (CAV1) has been attributed roles as a tumour suppressor, although in late-stage tumours, its presence is associated with enhanced metastasis. The expression of this protein in human melanoma development and particularly how the presence of CAV1 affects metastasis after surgery has not been defined. CAV1 expression in human melanocytes and melanomas increases with disease progression and is highest in metastatic melanomas. The effect of increased CAV1 expression can then be evaluated using B16F10 murine melanoma cells injected into syngenic immunocompetent C57BL/6 mice or human A375 melanoma cells injected into immunodeficient B6Rag1−/− mice. Augmented CAV1 expression suppresses tumour formation upon a subcutaneous injection, but enhances lung metastasis of cells injected into the tail vein in both models. A procedure was initially developed using B16F10 melanoma cells in C57BL/6 mice to mimic better the situation in patients undergoing surgery. Subcutaneous tumours of a defined size were removed surgically and local tumour recurrence and lung metastasis were evaluated after another 14 days. In this postsurgery setting, CAV1 presence in B16F10 melanomas favoured metastasis to the lung, although tumour suppression at the initial site was still evident. Similar results were obtained when evaluating A375 cells in B6Rag1−/− mice. These results implicate CAV1 expression in melanomas as a marker of poor prognosis for patients undergoing surgery as CAV1 expression promotes experimental lung metastasis in two different preclinical models.

Caveola-forming proteins caveolin-1 and PTRF in prostate cancer

The expression of caveola-forming proteins is dysregulated in prostate cancer. Caveolae are flask-shaped invaginations of the plasma membrane that have roles in membrane trafficking and cell signalling. Members of two families of proteins--caveolins and cavins--are known to be required for the formation and functions of caveolae. Caveolin-1, the major structural protein of caveolae, is overexpresssed in prostate cancer and has been demonstrated to be involved in prostate cancer angiogenesis, growth and metastasis. Polymerase I and transcript release factor (PTRF) is the only cavin family member necessary for caveola formation. When exogenously expressed in prostate cancer cells, PTRF reduces aggressive potential, probably via both caveola-mediated and caveola-independent mechanisms. In addition, stromal PTRF expression decreases with progression of the disease. Evaluation of caveolin-1 antibodies in the clinical setting is underway and it is hoped that future studies will reveal the mechanisms of PTRF action, allowing its targeting for therapeutic purposes.

PTRF/cavin-1 neutralizes non-caveolar caveolin-1 microdomains in prostate cancer

Caveolin-1 has a complex role in prostate cancer and has been suggested to be a potential biomarker and therapeutic target. As mature caveolin-1 resides in caveolae, invaginated lipid raft domains at the plasma membrane, caveolae have been suggested as a tumor-promoting signaling platform in prostate cancer. However, caveola formation requires both caveolin-1 and cavin-1 (also known as PTRF; polymerase I and transcript release factor). Here, we examined the expression of cavin-1 in prostate epithelia and stroma using tissue microarray including normal, non-malignant and malignant prostate tissues. We found that caveolin-1 was induced without the presence of cavin-1 in advanced prostate carcinoma, an expression pattern mirrored in the PC-3 cell line. In contrast, normal prostate epithelia expressed neither caveolin-1 nor cavin-1, while prostate stroma highly expressed both caveolin-1 and cavin-1. Utilizing PC-3 cells as a suitable model for caveolin-1-positive advanced prostate cancer, we found that cavin-1 expression in PC-3 cells inhibits anchorage-independent growth, and reduces in vivo tumor growth and metastasis in an orthotopic prostate cancer xenograft mouse model. The expression of α-smooth muscle actin in stroma along with interleukin-6 (IL-6) in cancer cells was also decreased in tumors of mice bearing PC-3-cavin-1 tumor cells. To determine whether cavin-1 acts by neutralizing caveolin-1, we expressed cavin-1 in caveolin-1-negative prostate cancer LNCaP and 22Rv1 cells. Caveolin-1 but not cavin-1 expression increased anchorage-independent growth in LNCaP and 22Rv1 cells. Cavin-1 co-expression reversed caveolin-1 effects in caveolin-1-positive LNCaP cells. Taken together, these results suggest that caveolin-1 in advanced prostate cancer is present outside of caveolae, because of the lack of cavin-1 expression. Cavin-1 expression attenuates the effects of non-caveolar caveolin-1 microdomains partly via reduced IL-6 microenvironmental function. With circulating caveolin-1 as a potential biomarker for advanced prostate cancer, identification of the molecular pathways affected by cavin-1 could provide novel therapeutic targets.