Is Dysfunction of Caveolin-1 a Link Between Systemic Sclerosis and Breast Cancer, Opening a Window on Both Etiologies?

The importance of caveolins and caveolae to dermatology: Lessons from the caves and beyond

Caveolae are flask-shaped invaginations of the cell membrane rich in cholesterol and sphingomyelin, with caveolin proteins acting as their primary structural components that allow compartmentalization and orchestration of various signalling molecules. In this review, we discuss how pleiotropic functions of caveolin-1 (Cav1) and its intricate roles in numerous cellular functions including lipid trafficking, signalling, cell migration and proliferation, as well as cellular senescence, infection and inflammation, are integral for normal development and functioning of skin and its appendages. We then examine how disruption of the homeostatic levels of Cav1 can lead to development of various cutaneous pathophysiologies including skin cancers, cutaneous fibroses, psoriasis, alopecia, age-related changes in skin and aberrant wound healing and propose how levels of Cav1 may have theragnostic value in skin physiology/pathophysiology.

Caveolin-1 as a critical component in the pathogenesis of lung fibrosis of different etiology: Evidences and mechanisms

Caveolin is a structural protein of flask-shaped invaginations of the plasma membrane termed as caveolae and is widely expressed on the endothelial cells, smooth muscle cells and fibroblasts in the different parts of the body including the lung tissues. The expression of caveolin-1 in the lung tissues is important to prevent the fibrogenic actions of TGF-β1 in lung fibrosis of different etiology including idiopathic pulmonary fibrosis, systemic sclerosis-associated interstitial lung disease and allergen-induced airway remodeling. Caveolin-1-mediated internalization and degradation of TGF-β1 receptors may possibly account for the decreased actions of TGF-β1. Studies have shown that the deficiency of caveolin-1 is very important in inducing lung fibrosis and its upregulation is reported to prevent lung fibrosis. The biological actions of caveolin-1 involve signaling pathways including JNK signaling, IL-4, STAT-3, miR199a-5p, CXCR4⁺ and CXCL12. The present review discusses the key role of caveolin and associated signaling pathways in the pathogenesis of lung fibrosis of different etiology.

Intriguing Relationships Between Cancer and Systemic Sclerosis: Role of the Immune System and Other Contributors

Systemic sclerosis (SSc) is an autoimmune connective tissue disorder, characterized by multisystem involvement, vasculopathy, and fibrosis. An increased risk of malignancy is observed in SSc (including breast and lung cancers), and in a subgroup of patients with specific autoantibodies (i.e., anti-RNA polymerase III and related autoantibodies), SSc could be a paraneoplastic syndrome and might be directly related to an immune response against cancer. Herein, we reviewed the literature, focusing on the most recent articles, and shed light onto the potential relationship between cancer and scleroderma regarding temporal and immunological dimensions.

Systemic Sclerosis and Malignancy: A Review of Current Data

Systemic sclerosis (SSc) is associated with increased risk of malignancy. The organ systems most commonly affected are the lungs, the breasts and the hematological system. Risk factors predisposing a SSc patient for development of malignancy are not well defined, and the pathogenic basis of the association is yet to be explained. The incidence of malignancies in SSc patients is variable from one report to another, but most importantly, questions regarding the role of immunosuppressive therapies and the effect of autoantibodies have weak or sometimes contradictory answers in most of the currently available literature and physicians have no available guidelines to screen their SSc patients for malignancies. The lack of a concretely defined high-risk profile and the absence of malignancy screening guidelines tailored for SSc patients raise the importance of the need for more studies on the association of SSc and cancer and should incite rheumatology colleges to develop specific recommendations for the clinician to follow while approaching patients with SSc.

Association of anti-RNA polymerase III autoantibodies and cancer in scleroderma

INTRODUCTION

We assessed the profile and frequency of malignancy subtypes in a large single-centre UK cohort for patients with scleroderma (systemic sclerosis; SSc). We evaluated the cancer risk among SSc patients with different antibody reactivities and explored the temporal association of cancer with the duration between SSc onset and cancer diagnosis.

METHODS

We conducted a retrospective study of a well-characterised cohort of SSc patients attending a large tertiary referral centre, with clinical data collected from our clinical database and by review of patient records. We evaluated development of all cancers in this cohort, and comparison was assessed with the SSc cohort without cancer. The effect of demographics and clinical details, including antibody reactivities, were explored to find associations relevant to the risk for development of cancer in SSc patients.

RESULTS

Among 2,177 patients with SSc, 7.1% had a history of cancer, 26% were positive for anticentromere antibodies (ACAs), 18.2% were positive for anti-Scl-70 antibodies and 26.6% were positive for anti-RNA polymerase III (anti-RNAP) antibody. The major malignancy cancer subtypes were breast (42.2%), haematological (12.3%), gastrointestinal (11.0%) and gynaecological (11.0%). The frequency of cancers among patients with RNAP (14.2%) was significantly increased compared with those with anti-Scl-70 antibodies (6.3%) and ACAs (6.8%) (P < 0.0001 and P < 0.001, respectively). Among the patients, who were diagnosed with cancer within 36 months of the clinical onset of SSc, there were more patients with RNAP (55.3%) than those with other autoantibody specificities (ACA = 23.5%, P < 0.008; and anti-Scl-70 antibodies = 13.6%, P < 0.002, respectively). Breast cancers were temporally associated with onset of SSc among patients with anti-RNAP, and SSc patients with anti-RNAP had a twofold increased hazard ratio for cancers compared to patients with ACAs (P < 0.0001).

CONCLUSIONS

Our study independently confirms, in what is to the best of our knowledge the largest population examined to date, that there is an association with cancer among SSc patients with anti-RNAP antibodies in close temporal relationship to onset of SSc, which supports the paraneoplastic phenomenon in this subset of SSc cases. An index of cautious suspicion should be maintained in these cases, and investigations for underlying malignancy should be considered when clinically appropriate.

Apoptosis modulation as a promising target for treatment of systemic sclerosis

Diffuse systemic sclerosis (SSc) is a fatal autoimmune disease characterized by an excessive ECM deposition inducing a loss of function of skin and internal organs. Apoptosis is a key mechanism involved in all the stages of the disease: vascular damage, immune dysfunction, and fibrosis. The purpose of this paper is to gather new findings in apoptosis related to SSc, to highlight relations between apoptosis and fibrosis, and to identify new therapeutic targets.

Hydrogen peroxide fuels aging, inflammation, cancer metabolism and metastasis: the seed and soil also needs "fertilizer"

In 1889, Dr. Stephen Paget proposed the "seed and soil" hypothesis, which states that cancer cells (the seeds) need the proper microenvironment (the soil) for them to grow, spread and metastasize systemically. In this hypothesis, Dr. Paget rightfully recognized that the tumor microenvironment has an important role to play in cancer progression and metastasis. In this regard, a series of recent studies have elegantly shown that the production of hydrogen peroxide, by both cancer cells and cancer-associated fibroblasts, may provide the necessary "fertilizer," by driving accelerated aging, DNA damage, inflammation and cancer metabolism, in the tumor microenvironment. By secreting hydrogen peroxide, cancer cells and fibroblasts are mimicking the behavior of immune cells (macrophages/neutrophils), driving local and systemic inflammation, via the innate immune response (NFκB). Thus, we should consider using various therapeutic strategies (such as catalase and/or other anti-oxidants) to neutralize the production of cancer-associated hydrogen peroxide, thereby preventing tumor-stroma co-evolution and metastasis. The implications of these findings for overcoming chemo-resistance in cancer cells are also discussed in the context of hydrogen peroxide production and cancer metabolism.

Prognostic significance of tumor/stromal caveolin-1 expression in breast cancer patients

Caveolin-1 (Cav-1) has been extensively characterized in cancer biological research. However, the role of Cav-1 in the interaction between tumor and stromal cells remains unclear. In the present study, we examined Cav-1 expression in tumor cells and stromal cells in breast cancer tissue by immunohistochemical analysis and evaluated its prognostic value in a training cohort. Immunohistochemical analysis of Cav-1 expression was scored as (++), (+) or (-) according to the proportion of positively stained tumor cells (T) and stromal cells (S). Correlation analysis between tumor/stromal Cav-1 expression and clinicopathological parameters revealed that only T(++) Cav-1 status was positively associated with tumor size and histological nodal status (P = 0.019 and 0.021, respectively). Univariate analysis revealed that combined T(++)/S(-) status was significantly correlated with unfavorable prognostic outcomes (P < 0.001). Multivariate analysis demonstrated that this combined status is an independent prognostic factor for primary breast cancer (P = 0.002). Clinical outcomes in different subgroups of breast cancer patients were also strictly dependent on this combined status (P < 0.05). The prognostic value of T(++)/S(-) Cav-1 status was also validated in the testing cohort. Collectively, our data indicate that high Cav-1 expression in tumor cells and lack of this expression in stromal cells could help identify a particular subgroup of breast cancer patients with potentially poor survival. Further studies are required to understand the regulatory mechanism of Cav-1 in the tumor microenvironment.

Molecular profiling of a lethal tumor microenvironment, as defined by stromal caveolin-1 status in breast cancers

Breast cancer progression and metastasis are driven by complex and reciprocal interactions, between epithelial cancer cells and their surrounding stromal microenvironment. We have previously shown that a loss of stromal Cav-1 expression is associated with an increased risk of early tumor recurrence, metastasis and decreased overall survival. To identify and characterize the signaling pathways that are activated in Cav-1 negative tumor stroma, we performed gene expression profiling using laser microdissected breast cancer-associated stroma. Tumor stroma was laser capture microdissected from 4 cases showing high stromal Cav-1 expression and 7 cases with loss of stromal Cav-1. Briefly, we identified 238 gene transcripts that were upregulated and 232 gene transcripts that were downregulated in the stroma of tumors showing a loss of Cav-1 expression (p ≤ 0.01 and fold-change ≥ 1.5). Gene set enrichment analysis (GSEA) revealed "stemness," inflammation, DNA damage, aging, oxidative stress, hypoxia, autophagy and mitochondrial dysfunction in the tumor stroma of patients lacking stromal Cav-1. Our findings are consistent with the recently proposed "Reverse Warburg Effect" and the "Autophagic Tumor Stroma Model of Cancer Metabolism." In these two complementary models, cancer cells induce oxidative stress in adjacent stromal cells, which then forces these stromal fibroblasts to undergo autophagy/mitophagy and aerobic glycolysis. This, in turn, produces recycled nutrients (lactate, ketones and glutamine) to feed anabolic cancer cells, which are undergoing oxidative mitochondrial metabolism. Our results are also consistent with previous biomarker studies showing that the increased expression of known autophagy markers (such as ATG16L and the cathepsins) in the tumor stroma is specifically associated with metastatic tumor progression and/or poor clinical outcome.

Extracellular signals in young and aging breast epithelial cells and possible connections to age-associated breast cancer development

Aging of human breast tissue is accompanied by certain structural and functional variations and several studies suggest a possible contribution of these changes to an aging-related breast cancer development. At the cellular level, aging of human mammary epithelial cells is associated with significant morphological and functional alterations such as an increased cell size and a reduced proliferation. Cellular senescence of HMEC cannot be explained by a single mechanism but represents an interaction of numerous extra- and intracellular events and the complexity of such orchestrating pathways is still hardly understood. Besides the contribution of reactive oxygen species and telomere dysfunction to aging, it is the aim of this mini-review, to compare distinct changes to extracellular signals by certain matrix metalloproteinases including MMP-7 and associated growth factor pathways mediated by HB-EGF activation in young and aging HMEC. Such changes can alter hormone receptor levels within aged HMEC, induce tissue fibrosis and promote epithelial-to-mesenchymal transition as a potential prerequisite for breast cancer development. Moreover, an accumulation of aging cells during the normal life span of the breast tissue may also substantially effect and interact with adjacent neighboring populations in the local microenvironment to provide optimized growth conditions which would also support neoplastic cells.