Caveolin-1 is Associated with Tumor Progression and Confers a Multi-Modality Resistance Phenotype in Pancreatic Cancer

Suppression of hypoxia-induced CAV1 autophagic degradation enhances nanoalbumin-paclitaxel transcytosis and improves therapeutic activity in pancreatic cancer

Nanoalbumin-paclitaxel (nab-paclitaxel) is a standard chemotherapy for pancreatic cancer but has shown limited efficacy. However, the mechanism through which circulating nab-paclitaxel passes through the tumour vascular endothelium has not been determined. In our study, a new nonradioactive and highly sensitive method for analysing nab-paclitaxel transcytosis was established. Based on these methods, we found that hypoxia significantly enhanced the autophagic degradation of CAV1 and therefore attenuated caveolae-mediated nab-paclitaxel transcytosis across endothelial cells (ECs). In a proof-of-concept experiment, higher levels of CAV1, accompanied by lower levels of LC3B, were observed in the vascular endothelium of pancreatic cancer tissues collected from patients who showed a good response to nab-paclitaxel compared with those from patients who showed a poor response to nab-paclitaxel. Furthermore, both in vivo and in vitro studies confirmed that suppressing the autophagic degradation of CAV1 via EC-specific ATG5 knockdown or hydroxychloroquine sulfate (HCQ) treatment significantly enhanced nab-paclitaxel translocation across the endothelial barrier into pancreatic cancer cells and amplified the inhibitory effect of nab-paclitaxel on pancreatic tumour growth. The stimulation of CAV1 expression by EC-specific overexpression of exogenous CAV1 or administration of gemcitabine hydrochloride (GE) had the same effect. These results demonstrated that suppressing CAV1 autophagic degradation is a novel translatable strategy for enhancing nab-paclitaxel chemotherapeutic activity in the treatment of pancreatic cancer.

VHL mutation drives human clear cell renal cell carcinoma progression through PI3K/AKT-dependent cholesteryl ester accumulation

BACKGROUND

Cholesteryl ester (CE) accumulation in intracellular lipid droplets (LDs) is an essential signature of clear cell renal cell carcinoma (ccRCC), but its molecular mechanism and pathological significance remain elusive.

METHODS

Enabled by the label-free Raman spectromicroscopy, which integrated stimulated Raman scattering microscopy with confocal Raman spectroscopy on the same platform, we quantitatively analyzed LD distribution and composition at the single cell level in intact ccRCC cell and tissue specimens in situ without any processing or exogenous labeling. Since we found that commonly used ccRCC cell lines actually did not show the CE-rich signature, primary cancer cells were isolated from human tissues to retain the lipid signature of ccRCC with CE level as high as the original tissue, which offers a preferable cell model for the study of cholesterol metabolism in ccRCC. Moreover, we established a patient-derived xenograft (PDX) mouse model that retained the CE-rich phenotype of human ccRCC.

FINDINGS

Surprisingly, our results revealed that CE accumulation was induced by tumor suppressor VHL mutation, the most common mutation of ccRCC. Moreover, VHL mutation was found to promote CE accumulation by upregulating HIFα and subsequent PI3K/AKT/mTOR/SREBPs pathway. Inspiringly, inhibition of cholesterol esterification remarkably suppressed ccRCC aggressiveness in vitro and in vivo with negligible toxicity, through the reduced membrane cholesterol-mediated downregulations of integrin and MAPK signaling pathways.

INTERPRETATION

Collectively, our study improves current understanding of the role of CE accumulation in ccRCC and opens up new opportunities for treatment.

FUNDING

This work was supported by National Natural Science Foundation of China (No. U23B2046 and No. 62027824), National Key R&D Program of China (No. 2023YFC2415500), Fundamental Research Funds for the Central Universities (No. YWF-22-L-547), PKU-Baidu Fund (No. 2020BD033), Peking University First Hospital Scientific and Technological Achievement Transformation Incubation Guidance Fund (No. 2022CX02), and Beijing Municipal Health Commission (No. 2020-2Z-40713).

Exploring the role of sporadic BRAF and KRAS mutations during colorectal cancer pathogenesis: A spotlight on the contribution of the endosome-lysosome system

The highly heterogenous nature of colorectal cancer can significantly hinder its early and accurate diagnosis, eventually contributing to high mortality rates. The adenoma-carcinoma sequence and serrated polyp-carcinoma sequence are the two most common sequences in sporadic colorectal cancer. Genetic alterations in adenomatous polyposis coli (APC), v-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog (KRAS) and tumour protein 53 (TP53) genes are critical in adenoma-carcinoma sequence, whereas v-Raf murine sarcoma viral oncogene homolog B (BRAF) and MutL Homolog1 (MLH1) are driving oncogenes in the serrated polyp-carcinoma sequence. Sporadic mutations in these genes contribute differently to colorectal cancer pathogenesis by introducing distinct alterations in several signalling pathways that rely on the endosome-lysosome system. Unsurprisingly, the endosome-lysosome system plays a pivotal role in the hallmarks of cancer and contributes to specialised colon function. Thus, the endosome-lysosome system might be distinctively influenced by different mutations and these alterations may contribute to the heterogenous nature of sporadic colorectal cancer. This review highlights potential connections between major sporadic colorectal cancer mutations and the diverse pathogenic mechanisms driven by the endosome-lysosome system in colorectal carcinogenesis.

Nutrient scavenging-fueled growth in pancreatic cancer depends on caveolae-mediated endocytosis under nutrient-deprived conditions

Pancreatic ductal adenocarcinoma (PDAC) is characterized by its nutrient-scavenging ability, crucial for tumor progression. Here, we investigated the roles of caveolae-mediated endocytosis (CME) in PDAC progression. Analysis of patient data across diverse datasets revealed a strong association of high caveolin-1 (Cav-1) expression with higher histologic grade, the most aggressive PDAC molecular subtypes, and worse clinical outcomes. Cav-1 loss markedly promoted longer overall and tumor-free survival in a genetically engineered mouse model. Cav-1-deficient tumor cell lines exhibited significantly reduced proliferation, particularly under low nutrient conditions. Supplementing cells with albumin rescued the growth of Cav-1-proficient PDAC cells, but not in Cav-1-deficient PDAC cells under low glutamine conditions. In addition, Cav-1 depletion led to significant metabolic defects, including decreased glycolytic and mitochondrial metabolism, and downstream protein translation signaling pathways. These findings highlight the crucial role of Cav-1 and CME in fueling pancreatic tumorigenesis, sustaining tumor growth, and promoting survival through nutrient scavenging.

Low FHL1 expression indicates a good prognosis and drug sensitivity in ovarian cancer

Chemotherapy resistance is the main reason for the poor prognosis of ovarian cancer (OC). FHL1 is an important tumour regulator, but its relationship with the prognosis, drug resistance, and tumour microenvironment of OC is unknown. Immunohistochemistry was used to determine FHL1 expression in OC. Kaplan‒Meier plotter was used for survival analysis. The value of gene expression in predicting drug resistance was estimated using the area under the curve (AUC). Bivariate correlation was used to determine the coexpression of two genes. Functional cluster and pathway enrichment were used to uncover hidden signalling pathways. The relationship between gene levels and the tumour microenvironment was visualised through the ggstatsplot and pheatmap packages. The mRNA and protein levels of FHL1 were downregulated in 426 and 100 OC tissues, respectively. Low FHL1 expression was correlated with good progression-free survival (PFS), postprogression survival, and overall survival (OS) in 1815 OC patients, and was further confirmed to be associated with good OS by immunohistochemistry in 152 OC tissues. Furthermore, FHL1 was downregulated in drug-sensitive tissues, while its high expression predicted drug resistance (AUC > 0.65). Mechanistically, FHL1 was coexpressed with FLNC, CAV1, PPP1R12B, and FLNA at the mRNA and protein levels in 558 and 174 OC tissues, respectively, and their expression was downregulated in OC. Additionally, very strong coexpression of FHL1 with the four genes was identified in at least 23 different tumours. Low expression of the four genes was associated with good PFS, and the combination of FHL1 with the four genes provided better prognostic power. Meanwhile, the expression of all five genes was strongly and positively associated with the abundance of macrophages. Low FHL1 expression acts as a favourable factor in OC, probably via positive coexpression with FLNC, CAV1, PPP1R12B, and FLNA.

Phenotypic Heterogeneity, Bidirectionality, Universal Cues, Plasticity, Mechanics, and the Tumor Microenvironment Drive Cancer Metastasis

Tumor diseases become a huge problem when they embark on a path that advances to malignancy, such as the process of metastasis. Cancer metastasis has been thoroughly investigated from a biological perspective in the past, whereas it has still been less explored from a physical perspective. Until now, the intraluminal pathway of cancer metastasis has received the most attention, while the interaction of cancer cells with macrophages has received little attention. Apart from the biochemical characteristics, tumor treatments also rely on the tumor microenvironment, which is recognized to be immunosuppressive and, as has recently been found, mechanically stimulates cancer cells and thus alters their functions. The review article highlights the interaction of cancer cells with other cells in the vascular metastatic route and discusses the impact of this intercellular interplay on the mechanical characteristics and subsequently on the functionality of cancer cells. For instance, macrophages can guide cancer cells on their intravascular route of cancer metastasis, whereby they can help to circumvent the adverse conditions within blood or lymphatic vessels. Macrophages induce microchannel tunneling that can possibly avoid mechanical forces during extra- and intravasation and reduce the forces within the vascular lumen due to vascular flow. The review article highlights the vascular route of cancer metastasis and discusses the key players in this traditional route. Moreover, the effects of flows during the process of metastasis are presented, and the effects of the microenvironment, such as mechanical influences, are characterized. Finally, the increased knowledge of cancer metastasis opens up new perspectives for cancer treatment.

Is there any diagnostic value of serum caveolin-1 levels on the determination of pancreatic adenocarcinoma?

BACKGROUND

Caveolin-1 (CAV-1) is a vital component in cancer pathogenesis, as its expression determines the survival of patients with cancer. This study investigates CAV-1 serum levels in pancreatic adenocarcinoma (PA) patients and their role in tumor progression and prognostic factors.

METHOD

The trial included 33 patients with pathologically confirmed pancreatic cancer (PC). The enzyme-linked immunosorbent assay (ELISA) method was used to measure the concentrations of CAV-1 in the blood. The study also included 20 healthy subjects. The statistical analysis was two-sided, and a P value of ≤ 0.05 was determined as statistically significant.

RESULTS

The median age of the subjects was 59 years (32-84 years) at the time of diagnosis. There were 13 (39%) female participants. In 21 (63%) patients, the primary focus was the pancreatic head. In 23 stage IV patients, hepatic metastasis (n = 19, 83%) was observed. Only one patient (3%) was still alive at the end of the study period. Palliative chemotherapy (CTx) was provided, with 39% of the 23 patients responding to it. The overall survival (OS) rate in this cohort was 41.3 ± 8.3 weeks at a 95% confidence interval (CI), after 25-58 weeks. Serum baseline CAV-1 values among patients with PA were significantly higher compared with controls (p = 0.009). Patients with poor performance status, a pancreatic head tumor, lower albumin levels, higher serum carcinoembryonic antigen (CEA) levels, and higher CA 19.9 levels had significantly higher serum CAV-1 levels (p = 0.01, P = 0.05, P = 0.03, P = 0.02, and P = 0.04, respectively). However, CAV-1 did not show any prognostic value (p = 0.75).

CONCLUSION

Although serum CAV-1 is a useful diagnostic marker in PC patients, it is not a prognostic or predictive marker.

Improved Targeting and Safety of Doxorubicin through a Novel Albumin Binding Prodrug Approach

Human serum albumin (HSA) improves the pharmacokinetic profile of drugs attached to it, making it an attractive carrier with proven clinical success. In our previous studies, we have shown that Caveolin-1 (Cav-1) and caveolae-mediated endocytosis play important roles in the uptake of HSA and albumin-bound drugs. Doxorubicin is an FDA-approved chemotherapeutic agent that is effective against multiple cancers, but its clinical applicability has been hampered by its high toxicity levels. In this study, a doxorubicin-prodrug was developed that could independently and avidly bind HSA in circulation, called IPBA-Dox. We first developed and characterized IPBA-Dox and confirmed that it can bind albumin in vitro while retaining a potent cytotoxic effect. We then verified that it efficiently binds to HSA in circulation, leading to an improvement in the pharmacokinetic profile of the drug. In addition, we tested our prodrug for Cav-1 selectivity and found that it preferentially affects cells that express relatively higher levels of Cav-1 in vitro and in vivo. Moreover, we found that our compound was well tolerated in vivo at concentrations at which doxorubicin was lethal. Altogether, we have developed a doxorubicin-prodrug that can successfully bind HSA, retaining a strong cytotoxic effect that preferentially targets Cav-1 positive cells while improving the general tolerability of the drug.

Identifying patients suitable for targeted adjuvant therapy: advances in the field of developing biomarkers for tumor recurrence following irradiation

Introduction

Radiation therapy (RT) is commonly used to treat cancer in conjunction with chemotherapy, immunotherapy, and targeted therapies. Despite the effectiveness of RT, tumor recurrence due to treatment resistance still lead to treatment failure. RT-specific biomarkers are currently lacking and remain challenging to investigate with existing data since, for many common malignancies, standard of care (SOC) paradigms involve the administration of RT in conjunction with other agents.

Areas Covered

Established clinically relevant biomarkers are used in surveillance, as prognostic indicators, and sometimes for treatment planning; however, the inability to intercept early recurrence or predict upfront resistance to treatment remains a significant challenge that limits the selection of patients for adjuvant therapy. We discuss attempts at intercepting early failure. We examine biomarkers that have made it into the clinic where they are used for treatment monitoring and management alteration, and novel biomarkers that lead the field with targeted adjuvant therapy seeking to harness these.

Expert Opinion

Given the growth of data correlating interventions with omic analysis toward identifying biomarkers of radiation resistance, more robust markers of recurrence that link to biology will increasingly be leveraged toward targeted adjuvant therapy to make a successful transition to the clinic in the coming years.

JNTX-101, a novel albumin-encapsulated gemcitabine prodrug, is efficacious and operates via caveolin-1-mediated endocytosis

Albumin is an attractive candidate carrier for the development of novel therapeutic drugs. Gemcitabine has been FDA approved for the treatment of solid tumors; however, new drugs that optimize gemcitabine delivery are not available for clinical use. The aim of this study was to test the efficacy of a novel albumin-encapsulated gemcitabine prodrug, JNTX-101, and investigate whether Cav-1 expression predicts the therapeutic efficacy of JNTX-101. We first determined the treatment efficacy of JNTX-101 in a panel of pancreatic/lung cancer cell lines and found that increases in Cav-1 expression resulted in higher uptake of albumin, while Cav-1 depletion attenuated the sensitivity of cells to JNTX-101. In addition, decreased Cav-1 expression markedly reduced JNTX-101-induced apoptotic cell death in a panel of cells, particularly in low-serum conditions. Furthermore, we tested the therapeutic efficacy of JNTX-101 in xenograft models and the role of Cav-1 in JNTX-101 sensitivity using a Tet-on-inducible tumor model in vivo. Our data suggest that JNTX-101 effectively inhibits cell viability and tumor growth, and that Cav-1 expression dictates optimal sensitivity to JNTX-101. These data indicate that Cav-1 correlates with JNTX-101 sensitivity, especially under nutrient-deprived conditions, and supports a role for Cav-1 as a predictive biomarker for albumin-encapsulated therapeutics such as JNTX-101.

A proteomic signature and potential pharmacological opportunities in the adaptive resistance to MEK and PI3K kinase inhibition in pancreatic cancer cells

Pancreatic cancer is one of the most lethal cancer types and is becoming a leading cause of cancer-related deaths. The limited benefit offered by chemotherapy agents has propelled the search for alternative approaches that target specific molecular drivers of cancer growth and progression. Mutant KRas and effector pathways Raf/MEK/ERK and PI3K/Akt are key players in pancreatic cancer; however, preclinical studies have shown adaptive tumour response to combined MEK and PI3K kinase inhibition leading to treatment resistance. There is a critical unmet need to decipher the molecular basis underlying adaptation to this targeted approach. Here, we aimed to identify common protein expression alterations associated with adaptive resistance in KRas-mutant pancreatic cancer cells, and test if it can be overcome by selected already available small molecule drugs. We found a group of 14 proteins with common expression change in resistant cells, including KRas, caveolin-1, filamin-a, eplin, IGF2R and cytokeratins CK-8, -18 and -19. Notably, several proteins have previously been observed in pancreatic cancer cells with intrinsic resistance to the combined kinase inhibition treatment, suggesting a proteomic signature. We also found that resistant cells are sensitive to small molecule drugs ERK inhibitor GDC-0994, S6K1 inhibitor DG2 and statins.

Endocytosis in cancer and cancer therapy

Endocytosis is a complex process whereby cell surface proteins, lipids and fluid from the extracellular environment are packaged, sorted and internalized into cells. Endocytosis is also a mechanism of drug internalization into cells. There are multiple routes of endocytosis that determine the fate of molecules, from degradation in the lysosomes to recycling back to the plasma membrane. The overall rates of endocytosis and temporal regulation of molecules transiting through endocytic pathways are also intricately linked with signalling outcomes. This process relies on an array of factors, such as intrinsic amino acid motifs and post-translational modifications. Endocytosis is frequently disrupted in cancer. These disruptions lead to inappropriate retention of receptor tyrosine kinases on the tumour cell membrane, changes in the recycling of oncogenic molecules, defective signalling feedback loops and loss of cell polarity. In the past decade, endocytosis has emerged as a pivotal regulator of nutrient scavenging, response to and regulation of immune surveillance and tumour immune evasion, tumour metastasis and therapeutic drug delivery. This Review summarizes and integrates these advances into the understanding of endocytosis in cancer. The potential to regulate these pathways in the clinic to improve cancer therapy is also discussed.

Predicting survival and immune microenvironment in colorectal cancer: a STAT signaling-related signature

BACKGROUND

Despite research advances, studies on predictive models of colorectal cancer (CRC) remain scarce and none have evaluated signal transducer and activator of transcription (STAT) signaling.

AIM

To develop an effective prognostic signature for and evaluate its association with immune microenvironment.

DESIGN

Comprehensive analysis based on The Cancer Genome Atlas and Gene Expression Omnibus databases with experimental validation.

METHODS

Gene expression and clinical profiles of CRC patients were extracted from the databases. Differentially expressed genes with prognostic values were used to construct a signature. Immune cell infiltration and composition were further evaluated by TIMER, single-sample gene set enrichment and CIBERSORT analyses. The impact of the hub gene Caveolin-1 (CAV1) on cell proliferation, apoptosis, senescence and tumor angiogenesis was experimentally validated.

RESULTS

The five-gene-based STAT signaling-related prognostic signature was significantly associated with CRC survival, and the nomogram was with improved prognostic efficacy than the conventional TNM stage. The STAT signaling-related signature was correlated with tumor immune microenvironment. CAV1 was further identified as the hub gene within the signature. CAV1 inhibits the proliferation and induces the apoptosis as well as senescence of CRC cells. In addition, the tumor angiogenesis of CRC can be suppressed by CAV1 overexpression.

CONCLUSIONS

The STAT signaling-related signature effectively predicts the prognosis and regulates tumor immune microenvironment in CRC. Our study underscores the role of STAT regulator, CAV1, as an important tumor suppressor in CRC carcinogenesis. Modulating STAT and its regulators could be a promising strategy for CRC in clinical practice.

Integrin β1 in Pancreatic Cancer: Expressions, Functions, and Clinical Implications

Simple Summary

Pancreatic cancer (PC) is a highly aggressive malignant tumor with an extremely poor prognosis. Early diagnosis and treatment are key to improving the survival rate of PC patients. Emerging studies show that integrins might contribute to the pathogenesis of PC. This review presents the various signaling pathways that are mediated by integrins in PC and emphasizes the multiple functions of integrin β1 in malignant behaviors of PC. It also discusses the clinical significance of integrin β1 as well as integrin β1-based therapy in PC patients.

Abstract

Pancreatic cancer (PC) is characterized by rapid progression and a high mortality rate. The current treatment is still based on surgical treatment, supplemented by radiotherapy and chemotherapy, and new methods of combining immune and molecular biological treatments are being explored. Despite this, the survival rate of PC patients is still very disappointing. Therefore, clarifying the molecular mechanism of PC pathogenesis and developing precisely targeted drugs are key to improving PC prognosis. As the most common β subunit of the integrin family, integrin β1 has been proved to be closely related to the vascular invasion, distant metastasis, and survival of PC patients, and treatment targeting integrin β1 in PC has gained initial success in animal models. In this review, we summarize the various signaling pathways by which integrins are involved in PC, focusing on the roles of integrin β1 in the malignant behaviors of PC. Additionally, recent studies regarding the feasibility of integrin β1 as a diagnostic and prognostic biomarker in PC are also discussed. Finally, we present the progress of several integrin β1-based clinical trials to highlight the potential of integrin β1 as a target for personalized therapy in PC.

mir-204-5p Acts as a Tumor Suppressor by Targeting DNM2 in Osteosarcoma Cells

Osteosarcoma is a malignant bone tumor composed of interstitial cells. We aim to seek the function of mir-204-5p/DNM2 in osteosarcoma cells. From April 2017 to August 2019, 58 cases of cancer tissues and paracancer tissues were obtained from patients with osteosarcoma in our hospital. qPCR was used to detect mir-204-5p in excisional cancer tissues and paracarcinoma tissues of osteosarcoma patients. The overexpression vector of mir-204-5p was established and transfected into osteosarcoma cells, and the propagation, invasiveness, migration, and apoptosis of osteosarcoma cells were observed. StarBase was employed to forecast the binding site of mir-204-5p and DNM2. The targeting connection of mir-204-5p with DNM2 was detected via double luciferase reporter gene. mir-204-5p was lessened in osteosarcoma (p < 0.05). mir-204-5p overexpression suppressed propagation and accelerated apoptosis of osteosarcoma cells (p < 0.05). The results of double luciferase reporter gene revealed that the fluorescence activity of mir-204-5p was obviously declined when binding to DNM2 (p < 0.05). mir-204-5p functions as a tumor inhibitor by targeting DNM2 in osteosarcoma cells. Our research is helpful to provide new ideas for clinical treatment.

Caveolae-Associated Molecules, Tumor Stroma, and Cancer Drug Resistance: Current Findings and Future Perspectives

Simple Summary

Cell membranes contain small invaginations called caveolae. They are a specialized lipid domain and orchestrate cellular signaling events, mechanoprotection, and lipid homeostasis. Formation of the caveolae depends on two classes of proteins, the caveolins and cavins, which form large complexes that allow their self-assembly into caveolae. Loss of either of these two proteins leads to distortion of the caveolae structure and disruption of many physiological processes that affect diseases of the muscle, metabolic states governing lipids, and the glucose balance as well as cancers. In cancers, the expression of caveolins and cavins is heterogenous, and they undergo alterations both in the tumors and the surrounding tumor microenvironment stromal cells. Remarkably, their expression and function has been associated with resistance to many cancer drugs. Here, we summarize the current knowledge of the resistance mechanisms and how this knowledge could be applied into the clinic in future.

Abstract

The discovery of small, “cave-like” invaginations at the plasma membrane, called caveola, has opened up a new and exciting research area in health and diseases revolving around this cellular ultrastructure. Caveolae are rich in cholesterol and orchestrate cellular signaling events. Within caveola, the caveola-associated proteins, caveolins and cavins, are critical components for the formation of these lipid rafts, their dynamics, and cellular pathophysiology. Their alterations underlie human diseases such as lipodystrophy, muscular dystrophy, cardiovascular disease, and diabetes. The expression of caveolins and cavins is modulated in tumors and in tumor stroma, and their alterations are connected with cancer progression and treatment resistance. To date, although substantial breakthroughs in cancer drug development have been made, drug resistance remains a problem leading to treatment failures and challenging translation and bench-to-bedside research. Here, we summarize the current progress in understanding cancer drug resistance in the context of caveola-associated molecules and tumor stroma and discuss how we can potentially design therapeutic avenues to target these molecules in order to overcome treatment resistance.

circFARP1 enables cancer-associated fibroblasts to promote gemcitabine resistance in pancreatic cancer via the LIF/STAT3 axis

Background

Cancer-associated fibroblasts (CAFs) are critically involved in gemcitabine (GEM) resistance in pancreatic ductal adenocarcinoma (PDAC). However, the underlying mechanism by which CAFs promote chemotherapy resistance remains unexplored. Here, we explored the role of circRNAs in CAF-induced GEM resistance in PDAC.

Methods

circRNA sequencing and quantitative real-time PCR (qRT–PCR) were utilized to screen CAF-specific circRNAs. The effects of CAF circFARP1 expression on GEM resistance in tumor cells were assessed in vitro and in vivo. RNA-seq, RNA pulldown, RNA immunoprecipitation, and luciferase reporter assays were used to screen the downstream target and underlying mechanism of circFARP1.

Results

circFARP1 (hsa_circ_0002557), a CAF-specific circRNA, was positively correlated with GEM chemoresistance and poor survival in an advanced PDAC cohort. Silencing or overexpressing circFARP1 in CAFs altered the ability of CAFs to induce tumor cell stemness and GEM resistance via leukemia inhibitory factor (LIF). Mechanistically, we found that circFARP1 directly binds with caveolin 1 (CAV1) and blocks the interaction of CAV1 and the E3 ubiquitin-protein ligase zinc and ring finger 1 (ZNRF1) to inhibit CAV1 degradation, which enhances LIF secretion. In addition, circFARP1 upregulated LIF expression by sponging miR-660-3p. Moreover, high circFARP1 levels were positively correlated with elevated serum LIF levels in PDAC and poor patient survival. Decreasing circFARP1 levels and neutralizing LIF significantly suppressed PDAC growth and GEM resistance in patient-derived xenograft models.

Conclusions

The circFARP1/CAV1/miR-660-3p/LIF axis is critical for CAF-induced GEM resistance in PDAC. Hence, circFARP1 may be a potential therapeutic target for PDAC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12943-022-01501-3.

Role of caveolin-1 as a biomarker for radiation resistance and tumor aggression in lung cancer

Radiation therapy plays a major role in the treatment of lung cancer patients. However, cancer cells develop resistance to radiation. Tumor radioresistance is a complex multifactorial mechanism which may be dependent on DNA damage and repair, hypoxic conditions inside tumor microenvironment, and the clonal selection of radioresistant cells from the heterogeneous tumor site, and it is a major cause of treatment failure in non-small cell lung cancer (NSCLC). In the present investigation caveolin-1 (CAV-1) has been observed to be highly expressed in radiation resistant A549 lung cancer cells. CRISPR-Cas9 knockout of CAV-1 reverted the cells to a radio sensitive phenotype. In addition, CAV-1 overexpression in parental A549 cells, led to radiation resistance. Further, gene expression analysis of A549 parental, radiation resistant, and caveolin-1 overexpressed cells, exhibited overexpression of DNA repair genes RAD51B, RAD18, SOX2 cancer stem cell marker, MMPs, mucins and cytoskeleton proteins in resistant and caveolin-1 over expressed A549 cells, as compared to parental A549 cells. Bioinformatic analysis shows upregulation of BRCA1, Nuclear Excision DNA repair, TGFB and JAK/STAT signaling pathways in radioresistant and caveolin-1 overexpressed cells, which may functionally mediate radiation resistance. Immunohistochemistry data demonstrated heterogeneous expression of CAV-1 gene in human lung cancer tissues, which was analogous to its enhanced expression in human lung cancer cell line model and mouse orthotopic xenograft lung cancer model. Also, TCGA PanCancer clinical studies have demonstrated amplification, deletions and missense mutation in CAV-1 gene in lung cancer patients, and that CAV-1 alteration has been linked to poor prognosis, and poor survival in lung cancer patients. Interestingly, we have also optimized ELISA assay to measure caveolin-1 protein in the blood of A549 radiation resistant human xenograft preclinical mouse model and discovered higher level of caveolin-1 (950 pg/ml) in tumor bearing animals treated with radiation, as compared to xenograft with radiosensitive lung cancer cells (450 pg/ml). Thus, we conclude that caveolin-1 is involved in radio-resistance and contributes to tumor aggression, and it has potential to be used as prognostic biomarker for radiation treatment response, and tumor progression for precision medicine in lung cancer patients.

Prognostic significance and therapeutic implications of Caveolin-1 in gastrointestinal tract malignancies

Caveolin-1 (CAV1) is expressed in several solid tumors both in cancerous cells as well as in tumor stroma and is reported to be related to cancer progression, metastasis, therapy resistance and clinical outcomes. Many studies report contrasting functions of this protein depending on the tumor cell model, the tumor type, or the stage of cancer studied. This protein is reported to function both as tumor suppressor and as tumor promoter. In this review, we aim to summarize translational and clinical studies that provide evidence of the role of CAV1 in tumor progression and survival outcome focusing on tumors of the gastrointestinal (GI) tract. Towards this aim, a detailed search has been performed for studies on the expression and the role of CAV1 in oesophageal, gastric, colorectal, pancreatic cancer and cholangiocarcinoma prognosis. We also review and discuss the implication of CAV1 in the outcome of pharmacological interventions. We conclude that CAV1 has the potential to become an important prognostic, and possibly predictive, biomarker in GI malignancies. It may also become a novel target towards the development of improved cancer therapies. However, it is obvious that there remains a lack of consensus on important issues such as the methodologies and cut-off levels in caveolin assessment. This ultimately result in many studies being contradictory not only in terms of the role of CAV1 as a tumor-promoting or suppressing gene but also in terms of the tumor compartment in which the levels of this protein may be of clinical significance. Addressing these important technical issues, in conjunction with a further elucidation of the role of CAV1 in tumor formation and progression, will delineate the importance of CAV1 in prognostic and therapeutic perspectives.

A Novel Ferroptosis-Related Gene Signature Predicts Recurrence in Patients With Pancreatic Ductal Adenocarcinoma

Background: Recurrence after surgery is largely responsible for the extremely poor outcomes for patients with pancreatic ductal adenocarcinoma (PDAC). Ferroptosis is implicated in chemotherapy sensitivity and tumor recurrence, we aimed to find out survival-associated ferroptosis-related genes and use them to build a practical risk model with the purpose to predict PDAC recurrence. Methods: Univariate Cox regression analysis was conducted to obtain prognostic ferroptosis-related genes in The Cancer Genome Atlas (TCGA, N = 140) cohort. Multivariate Cox regression analysis was employed to construct a reliable and credible gene signature. The prognostic performance was verified in a MTAB-6134 (N = 286) validation cohort and a PACA-CA (N = 181) validation cohort. The stability of the signature was tested in TCGA and MTAB-6134 cohorts by ROC analyses. Pathway enrichment analysis was adopted to preliminary illuminate the biological relevance of the gene signature. Results: Univariate and multivariate Cox regression analyses identified a 5-gene signature that contained CAV1, DDIT4, SLC40A1, SRXN1 and TFAP2C. The signature could efficaciously stratify PDAC patients with different recurrence-free survival (RFS), both in the training and validation cohorts. Results of subgroup receiver operating characteristic curve (ROC) analyses confirmed the stability and the independence of this signature. Our signature outperformed clinical indicators and previous reported models in predicting RFS. Moreover, the signature was found to be closely associated with several cancer-related and drug response pathways. Conclusion: This study developed a precise and concise prognostic model with the clinical implication in predicting PDAC recurrence. These findings may facilitate individual management of postoperative recurrence in patients with PDAC.

A novel protein-drug conjugate, SSH20, demonstrates significant efficacy in caveolin-1-expressing tumors

In recent years, human serum albumin (HSA) has been characterized as an ideal drug carrier in the cancer arena. Caveolin-1 (Cav-1) has been established as the principal structural protein of caveolae and, thus, critical for caveolae-mediated endocytosis. Cav-1 has been shown to be overexpressed in cancers of the lung and pancreas, among others. We found that Cav-1 expression plays a critical role in both HSA uptake and response to albumin-based chemotherapies. As such, developing a novel albumin-based chemotherapy that is more selective for tumors with high Cav-1 expression or high levels of caveolar-endocytosis could have significant implications in biomarker-directed therapy. Herein, we present the development of a novel and effective HSA-SN-38 conjugate (SSH20). We find that SSH20 uptake decreases significantly by immunofluorescence assays and western blotting after silencing of Cav-1 expression through RNA interference. Decreased drug sensitivity occurs in Cav-1-depleted cells using cytotoxicity assays. Importantly, we find significantly reduced sensitivity to SSH20 in Cav-1-silenced tumors compared to Cav-1-expressing tumors in vivo. Notably, we show that SSH20 is significantly more potent than irinotecan in vitro and in vivo. Together, we have developed a novel HSA-conjugated chemotherapy that is potent, effective, safe, and demonstrates improved efficacy in high Cav-1-expressing tumors.

Retrospective Cohort Study of Caveolin-1 Expression as Prognostic Factor in Unresectable Locally Advanced or Metastatic Pancreatic Cancer Patients

Caveolin-1 (Cav-1) plays a key role in various neoplastic diseases and is upregulated in different cancers, including pancreatic ductal adenocarcinoma (PDAC). Furthermore, Cav-1 is critical for the uptake of albumin as well as nab-paclitaxel in PDAC cells. Here, we investigated the prognostic impact of Cav-1 expression in a cohort of 39 metastatic PDAC patients treated with different first-line chemotherapy regimens. We also assessed the predictive value of Cav-1 in patients treated with gemcitabine and nab-paclitaxel. Cav-1 expression was evaluated by immunohistochemistry staining in neoplastic and stromal cells, using metastatic sites or primary tumor tissue specimens. Higher levels of Cav-1 expression were associated with significantly worse overall survival (OS) and progression-free survival (PFS). No differences in OS were found between patients treated with gemcitabine + nab-paclitaxel vs. other chemotherapy options. Multivariate analysis for OS and PFS confirmed the independent prognostic role of Cav-1 expression. Our study evidenced a negative prognostic role of Cav-1 in patients affected by metastatic/locally advanced unresectable PDAC. Moreover, Cav-1 expression seems not to predict different response rates to different types of first-line treatment. Future prospective trials will be necessary to confirm the prognostic role of Cav-1 and explore Cav-1 specific inhibitors as a therapeutic option for advanced PDAC patients.

Role of caveolin-1 in human organ function and disease: friend or foe?

Caveolin-1 (Cav-1) is a structural protein component of caveolae, which are invaginations of the plasma membrane involved in various cellular processes, including endocytosis, extracellular matrix organization, cholesterol distribution, cell migration, and signaling. Mounting evidence over the last 10-15 years has demonstrated a central role of Cav-1 in many diseases, such as cancer, diabetes, and fibrosis. Cav-1 plays positive and negative roles in various diseases through its different regulation pathways. Here, we review the current knowledge on Cav-1 in different diseases and discuss the role of this protein in human organs and diseases.

Tailor-Made Nanomaterials for Diagnosis and Therapy of Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest cancers worldwide due to its aggressiveness and the challenge to early diagnosis and treatment. In recent decades, nanomaterials have received increasing attention for diagnosis and therapy of PDAC. However, these designs are mainly focused on the macroscopic tumor therapeutic effect, while the crucial nano-bio interactions in the heterogeneous microenvironment of PDAC remain poorly understood. As a result, the majority of potent nanomedicines show limited performance in ameliorating PDAC in clinical translation. Therefore, exploiting the unique nature of the PDAC by detecting potential biomarkers together with a deep understanding of nano-bio interactions that occur in the tumor microenvironment is pivotal to the design of PDAC-tailored effective nanomedicine. This review will introduce tailor-made nanomaterials-enabled laboratory tests and advanced noninvasive imaging technologies for early and accurate diagnosis of PDAC. Moreover, the fabrication of a myriad of tailor-made nanomaterials for various PDAC therapeutic modalities will be reviewed. Furthermore, much preferred theranostic multifunctional nanomaterials for imaging-guided therapies of PDAC will be elaborated. Lastly, the prospects of these nanomaterials in terms of clinical translation and potential breakthroughs will be briefly discussed.

The Biomarker Potential of Caveolin-1 in Penile Cancer

Various types of human cancers were characterized by an altered expression of epithelial or stromal caveolin-1 (CAV1). However, the clinical significance of CAV1 expression in penile cancer remains largely unknown. Here the expression patterns of CAV1 were analyzed in a retrospective cohort (n=43) of penile squamous cell carcinomas (SCC). Upon penile cancer progression, significantly increased CAV1-levels were determined within the malignant epithelium, whereas within the tumor stroma, namely the fibroblastic tumor compartment harboring activated and/or cancer associated fibroblasts, CAV1 levels significantly decline. Concerning the clinicopathological significance of CAV1 expression in penile cancer as well as respective epithelial-stromal CAV1 distributions, high expression within the tumor cells as well as low expression of CAV1 within the stromal compartment were correlated with decreased overall survival of penile cancer patients. Herein, CAV1 expressions and distributions at advanced penile cancer stages were independent of the immunohistochemically proven tumor protein p53 status. In contrast, less differentiated p16-positive tumor epithelia (indicative for human papilloma virus infection) were characterized by significantly decreased CAV1 levels. Conclusively, we provide further and new evidence that the characteristic shift in stromal‐epithelial CAV1 being functionally relevant to tumor progression even occurs in penile SCC.

Significance of caveolin-1 immunohistochemical staining differences in biopsy samples from kidney recipients with BK virus viremia

BK virus infections which usually remains asymptomatic in healthy adults may have different clinical manifestations in immunocompromised patient population. BK virus reactivation can cause BK virus nephropathy in 8% of kidney transplant patients and graft loss may be seen if not treated. Clathrin or Caveolar system is known to be required for the transport of many viruses from Polyomaviruses family including BK viruses. In this study, kidney transplant patients with BK virus viremia were divided into two groups according to the BK virus nephropathy found in kidney biopsy (Group I: Viremia+, Nephropathy+ / Group II: Viremia+, Nephropathy-). Kidney biopsies were examined with immunohistochemical staining to determine the distribution and density of the Caveolin-1 and Clathrin molecules. Immunohistochemical staining of the 31 pathologic specimens with anti-caveolin-1 immunoglobulin revealed statistically significant difference between group-I and group-II. The number of the specimens stained with anti-caveolin-1 was less in group I. On the other hand, we did not find any difference between the groups regarding the anti-clathrin immunochemical analysis. According to these findings, caveolin-1 expression differences in kidney transplant patients may be important in disease progression.

Disseminated cancer cells in breast cancer: Mechanism of dissemination and dormancy and emerging insights on therapeutic opportunities

Metastatic spread in breast cancer patients is the major driver of cancer-related deaths. A unique subset of cells disseminated from pre-invasive or primary tumor lesions are recognized as the main seeds for metastatic outgrowth. Disseminated cancer cells (DCCs) can migrate to distant organs and settle in a dormant state for a prolonged period until they emerge to overt metastases. Understanding the biology of breast cancer cells dissemination, dormancy and reactivation to form overt metastases has become an important focus. In this review, we discuss the recent advancements of molecular pathways involving breast cancer cell dissemination, role of chemokine-chemokine receptor networks in DCCs migration, DCCs phenotypic heterogeneity and unique genes signatures in tumor dormancy, microenvironmental regulation and specific niches that favors DCCs homing and dormancy. In addition, we also discuss recent findings relating to the role of immune response on DCC dissemination and dormancy. With recent advances in the field of immunotherapy/targeted therapy and its beneficial effects in cancer treatment, this review will focus on their impact on DCCs, reversal of stemness, tumor dormancy and metastatic relapse.

Morphological Heterogeneity in Pancreatic Cancer Reflects Structural and Functional Divergence

Simple Summary

Pancreatic cancer has a poor prognosis, which is largely due to resistance to treatment. Tumor heterogeneity is a known cause for treatment failure and has been studied at the molecular level. Morphological heterogeneity is common but has not been investigated, despite the fact that pathology examination is an integral part of clinical diagnostics. This study assessed whether morphological heterogeneity reflects structural and functional diversity in key cancer biological processes. Using archival tissues from resected pancreatic cancer, we selected four common and distinct morphological phenotypes and demonstrated that these differed significantly for a panel of 26 structural and functional features of the cancer-cell and stromal compartments. The strong link between these features and morphological phenotypes allowed prediction of the latter based on the results for the panel of features. The findings of this study indicate that morphological heterogeneity reflects biological diversity and that its assessment may potentially provide clinically relevant information.

Abstract

Inter- and intratumor heterogeneity is an important cause of treatment failure. In human pancreatic cancer (PC), heterogeneity has been investigated almost exclusively at the genomic and transcriptional level. Morphological heterogeneity, though prominent and potentially easily assessable in clinical practice, remains unexplored. This proof-of-concept study aims at demonstrating that morphological heterogeneity reflects structural and functional divergence. From the wide morphological spectrum of conventional PC, four common and distinctive patterns were investigated in 233 foci from 39 surgical specimens. Twenty-six features involved in key biological processes in PC were analyzed (immuno-)histochemically and morphometrically: cancer cell proliferation (Ki67) and migration (collagen fiber alignment, MMP14), cancer stem cells (CD44, CD133, ALDH1), amount, composition and spatial arrangement of extracellular matrix (epithelial proximity, total collagen, collagen I and III, fibronectin, hyaluronan), cancer-associated fibroblasts (density, αSMA), and cancer-stroma interactions (integrins α2, α5, α1; caveolin-1). All features differed significantly between at least two of the patterns. Stromal and cancer-cell-related features co-varied with morphology and allowed prediction of the morphological pattern. In conclusion, morphological heterogeneity in the cancer-cell and stromal compartments of PC correlates with structural and functional diversity. As such, histopathology has the potential to inform on the operationality of key biological processes in individual tumors.

Altered Gemcitabine and Nab-paclitaxel Scheduling Improves Therapeutic Efficacy Compared with Standard Concurrent Treatment in Preclinical Models of Pancreatic Cancer

PURPOSE

Concurrent gemcitabine and nab-paclitaxel treatment is one of the preferred chemotherapy regimens for metastatic and locally advanced pancreatic ductal adenocarcinoma (PDAC). Previous studies demonstrate that caveolin-1 (Cav-1) expression is critical for nab-paclitaxel uptake into tumors and correlates with response. Gemcitabine increases nab-paclitaxel uptake by increasing Cav-1 expression. Thus, we hypothesized that pretreatment with gemcitabine would further enhance the sensitivity of PDAC to nab-paclitaxel by increasing Cav-1 expression and nab-paclitaxel uptake.

EXPERIMENTAL DESIGN

We investigated the sensitivity of different gemcitabine and nab-paclitaxel treatment regimens in a panel of PDAC cell lines and orthotopic xenograft models. The sensitivity of different treatment regimens was compared with the standard concurrent treatment.

RESULTS

Pretreatment with gemcitabine before nab-paclitaxel increased Cav-1 and albumin uptake and significantly decreased proliferation and clonogenicity compared with concurrent treatment, which correlated with increased levels of apoptosis. Cav-1 silencing reduced the uptake of albumin, and therapeutic advantage was observed when cells were pretreated with gemcitabine prior to nab-paclitaxel. In addition, we observed that pretreatment with gemcitabine resulted in partial synchronization of cells in the G2-M-phase at the time of nab-paclitaxel treatment, providing another mechanism for the benefit of altered scheduling. In heterotopic and orthotopic xenograft models, the altered schedule of gemcitabine prior to nab-paclitaxel significantly delayed tumor growth compared with concurrent delivery without added toxicity.

CONCLUSIONS

Pretreatment with gemcitabine significantly increased nab-paclitaxel uptake and correlated with an increased treatment efficacy and survival benefit in preclinical models, compared with standard concurrent treatment. These results justify preclinical and clinical testing of this altered scheduling combination.

Caveolin-1 promotes radioresistance via IRGM-regulated autophagy in lung cancer

Background

Radiotherapy is the standard therapeutic approach for non-small cell lung cancers (NSCLCs). However, radiotherapy resistance accounts for major treatment failures in NSCLC patients. Recently, targeting autophagy-related signaling has shown potential to improve radiotherapy. Furthermore, some studies have reported that caveolin-1 (Cav1), a primary scaffolding protein of caveolae, is positively associated with NSCLC progression and cell autophagy. However, the function of Cav1-mediated autophagy in NSCLC radioresistance remains largely unknown.

Methods

The NSCLC irradiation (IR)-resistant cell lines H358-IRR and A549-IRR were used for in vitro analysis. Real-time quantitative PCR (qPCR), western blot, cell counting kit-8 (CCK-8), colony formation and transmission electron microscopy analyses were performed to explore the relationship between Cav1 and immunity-related GTPase family M protein (IRGM)-regulated autophagy in the radiation resistance of lung cancers.

Results

Cav1 was significantly overexpressed in H358-IRR and A549-IRR cells compared to their parental counterparts. Knockdown of Cav1 significantly decreased the proliferation of IR-resistant NSCLC cells. Combinational treatment of IR and siRNA of Cav1 showed enhanced inhibition of the cell viability and colony formation of IR-resistant NSCLC cells. In addition, Cav1 overexpression could upregulate the autophagic proteins microtubule associated protein 1 light chain 3 II (LC3 II), Beclin-1 and Sequestosome 1 (SQSTM1/p62) in parental NSCLC cells, while Cav1 downregulation by siRNA inhibited the expression of LC3 II, Beclin-1 and p62 and the formation of autophagosomes in IR-resistant NSCLC cells. Furthermore, we observed that IRGM was downregulated after knockdown of Cav1 in IR-resistant NSCLC cells. Thus, Cav1 was observed to promote autophagy and increase IR-resistant cell survival by targeting IRGM.

Conclusions

The results of our study showed that Cav1 is involved in the development of IR resistance in NSCLC through IRGM-regulated autophagy and can be considered as a potential therapeutic target for improving the radiosensitivity of NSCLC.

Caveolin1 Tyrosine-14 Phosphorylation: Role in Cellular Responsiveness to Mechanical Cues

The plasma membrane is a dynamic lipid bilayer that engages with the extracellular microenvironment and intracellular cytoskeleton. Caveolae are distinct plasma membrane invaginations lined by integral membrane proteins Caveolin1, 2, and 3. Caveolae formation and stability is further supported by additional proteins including Cavin1, EHD2, Pacsin2 and ROR1. The lipid composition of caveolar membranes, rich in cholesterol and phosphatidylserine, actively contributes to caveolae formation and function. Post-translational modifications of Cav1, including its phosphorylation of the tyrosine-14 residue (pY14Cav1) are vital to its function in and out of caveolae. Cells that experience significant mechanical stress are seen to have abundant caveolae. They play a vital role in regulating cellular signaling and endocytosis, which could further affect the abundance and distribution of caveolae at the PM, contributing to sensing and/or buffering mechanical stress. Changes in membrane tension in cells responding to multiple mechanical stimuli affects the organization and function of caveolae. These mechanical cues regulate pY14Cav1 levels and function in caveolae and focal adhesions. This review, along with looking at the mechanosensitive nature of caveolae, focuses on the role of pY14Cav1 in regulating cellular mechanotransduction.

Triptolide-induced apoptosis in non-small cell lung cancer via a novel miR204-5p/Caveolin-1/Akt-mediated pathway

Lung cancer is one of the most prevalent malignancies world-wide with non-small cell lung cancer (NSCLC) comprising nearly 80% of all cases. Unfortunately, many lung cancer patients are diagnosed at advanced stages of the disease with an associated poor prognosis. Recently, the Chinese herb root extract Triptolide/Minnelide (TL) has shown significant promise as a therapeutic agent for NSCLC treatment both in vitro and in vivo. The aim of this study was to investigate the underlying mechanism(s) of action regarding TL-induced cytotoxicity in NSCLC. We demonstrate that triptolide treatment of A549 and H460 NSCLC cells decreases Caveolin-1 (CAV-1) mRNA/protein expression, resulting in activation of the Akt/Bcl-2-mediated mitochondrial apoptosis pathway. CAV-1 down-regulation was triggered by Micro-RNA 204-5p (miR204-5p) up-regulation and could be significantly blocked by pre-treatment with both Sirt-1/Sirt-3 specific siRNA and SIRT-1/SIRT-3 enzyme inhibitors, EX-527 and nicotinamide. Overall, our results provide evidence for a novel mechanism by which TL exerts its cytotoxic effects on NSCLC via CAV-1 down-regulation. Furthermore, these findings demonstrate a pivotal role for TL induction of the Akt/Bax pathway in apoptosis of human lung cancer.

Caveolae: Formation, dynamics, and function

Caveolae are abundant surface pits formed by the assembly of cytoplasmic proteins on a platform generated by caveolin integral membrane proteins and membrane lipids. This membranous assembly can bud off into the cell or can be disassembled releasing the cavin proteins into the cytosol. Disassembly can be triggered by increased membrane tension, or by stress stimuli, such as UV. Here, we discuss recent mechanistic studies showing how caveolae are formed and how their unique properties allow them to function as multifunctional protective and signaling structures.

Metabolic reprogramming of normal oral fibroblasts correlated with increased glycolytic metabolism of oral squamous cell carcinoma and precedes their activation into carcinoma associated fibroblasts

Cancers show a metabolic shift towards aerobic glycolysis. By "corrupting" their microenvironment, carcinoma cells are able to obtain energy substrates to "fuel" their mitochondrial metabolism and cell growth in an autophagy-associated, paracrine manner. However, the metabolic changes and role of normal fibroblasts in this process remain unclear. We devised a novel, indirect co-culture system to elucidate the mechanisms of metabolic coupling between stromal cells and oral squamous cell carcinoma (OSCC) cells. Here, we showed that normal oral fibroblasts (NOFs) and OSCC become metabolically coupled through several processes before acquiring an activated phenotype and without inducing senescence. We observed, for the first time, that NOFs export mitochondria towards OSCCs through both direct contact and via indirect mechanisms. NOFs are activated and are able to acquire a cancer-associated fibroblasts metabolic phenotype when co-cultivation with OSSC cells, by undergoing aerobic glycolysis, secreting more reactive oxygen species (ROS), high L-lactate and overexpressing lactate exporter MCT-4, leading to mitochondrial permeability transition pore (mPTP) opening, hypoxia, and mitophagy. On the other hand, Cav-1-low NOFs generate L-lactate to "fuel" mitochondrial metabolism and anabolic growth of OSCC. Most interestingly, the decrease in AMPK activity and PGC-1α expression might involve in regulation of ROS that functions to maintain final energy and metabolic homeostasis. This indicated, for the first time, the existence of ATP and ROS homeostasis during carcinogenesis. Our study suggests that an efficient therapeutical approach has to target the multiple mechanisms used by them to corrupt the normal surrounding stroma and metabolic homeostasis.

Mycobacterium tuberculosis and myeloid-derived suppressor cells: Insights into caveolin rich lipid rafts

Mycobacterium tuberculosis (M.tb) is likely the most successful human pathogen, capable of evading protective host immune responses and driving metabolic changes to support its own survival and growth. Ineffective innate and adaptive immune responses inhibit effective clearance of the bacteria from the human host, resulting in the progression to active TB disease. Many regulatory mechanisms exist to prevent immunopathology, however, chronic infections result in the overproduction of regulatory myeloid cells, like myeloid-derived suppressor cells (MDSC), which actively suppress protective host T lymphocyte responses among other immunosuppressive mechanisms. The mechanisms of M.tb internalization by MDSC and the involvement of host-derived lipid acquisition, have not been fully elucidated. Targeted research aimed at investigating MDSC impact on phagocytic control of M.tb, would be advantageous to our collective anti-TB arsenal. In this review we propose a mechanism by which M.tb may be internalized by MDSC and survive via the manipulation of host-derived lipid sources.

Modelling of pancreatic cancer biology: transcriptomic signature for 3D PDX-derived organoids and primary cell line organoid development

With a five-year survival rate of 9%, pancreatic ductal adenocarcinoma (PDAC) is the deadliest of all cancers. The rapid mortality makes PDAC difficult to research, and inspires a resolve to create reliable, tractable cellular models for preclinical cancer research. Organoids are increasingly used to model PDAC as they maintain the differentiation status, molecular and genomic signatures of the original tumour. In this paper, we present novel methodologies and experimental approaches to develop PDAC organoids from PDX tumours, and the simultaneous development of matched primary cell lines. Moreover, we also present a method of recapitulating primary cell line cultures to organoids (CLOs). We highlight the usefulness of CLOs as PDAC organoid models, as they maintain similar transcriptomic signatures as their matched patient-derived organoids and patient derived xenografts (PDX)s. These models provide a manageable, expandable in vitro resource for downstream applications such as high throughput screening, functional genomics, and tumour microenvironment studies.

Dexamethasone Inhibits Spheroid Formation of Thyroid Cancer Cells Exposed to Simulated Microgravity

Detachment and the formation of spheroids under microgravity conditions can be observed with various types of intrinsically adherent human cells. In particular, for cancer cells this process mimics metastasis and may provide insights into cancer biology and progression that can be used to identify new drug/target combinations for future therapies. By using the synthetic glucocorticoid dexamethasone (DEX), we were able to suppress spheroid formation in a culture of follicular thyroid cancer (FTC)-133 cells that were exposed to altered gravity conditions on a random positioning machine. DEX inhibited the growth of three-dimensional cell aggregates in a dose-dependent manner. In the first approach, we analyzed the expression of several factors that are known to be involved in key processes of cancer progression such as autocrine signaling, proliferation, epithelial–mesenchymal transition, and anoikis. Wnt/β-catenin signaling and expression patterns of important genes in cancer cell growth and survival, which were further suggested to play a role in three-dimensional aggregation, such as NFKB2, VEGFA, CTGF, CAV1, BCL2(L1), or SNAI1, were clearly affected by DEX. Our data suggest the presence of a more complex regulation network of tumor spheroid formation involving additional signal pathways or individual key players that are also influenced by DEX.

Replication Study: Biomechanical remodeling of the microenvironment by stromal caveolin-1 favors tumor invasion and metastasis

As part of the Reproducibility Project: Cancer Biology we published a Registered Report (Fiering et al., 2015) that described how we intended to replicate selected experiments from the paper 'Biomechanical remodeling of the microenvironment by stromal caveolin-1 favors tumor invasion and metastasis' (Goetz et al., 2011). Here we report the results. Primary mouse embryonic fibroblasts (pMEFs) expressing caveolin 1 (Cav1WT) demonstrated increased extracellular matrix remodeling in vitro compared to Cav1 deficient (Cav1KO) pMEFs, similar to the original study (Goetz et al., 2011). In vivo, we found higher levels of intratumoral stroma remodeling, determined by fibronectin fiber orientation, in tumors from cancer cells co-injected with Cav1WT pMEFs compared to cancer cells only or cancer cells plus Cav1KO pMEFs, which were in the same direction as the original study (Supplemental Figure S7C; Goetz et al., 2011), but not statistically significant. Primary tumor growth was similar between conditions, like the original study (Supplemental Figure S7Ca; Goetz et al., 2011). We found metastatic burden was similar between Cav1WT and Cav1KO pMEFs, while the original study found increased metastases with Cav1WT (Figure 7C; Goetz et al., 2011); however, the duration of our in vivo experiments (45 days) were much shorter than in the study by Goetz et al. (2011) (75 days). This makes it difficult to interpret the difference between the studies as it is possible that the cells required more time to manifest the difference between treatments observed by Goetz et al. We also found a statistically significant negative correlation of intratumoral remodeling with metastatic burden, while the original study found a statistically significant positive correlation (Figure 7Cd; Goetz et al., 2011), but again there were differences between the studies in terms of the duration of the metastasis studies and the imaging approaches that could have impacted the outcomes. Finally, we report meta-analyses for each result.

Caveolin-1 Modulates Mechanotransduction Responses to Substrate Stiffness through Actin-Dependent Control of YAP

The transcriptional regulator YAP orchestrates many cellular functions, including tissue homeostasis, organ growth control, and tumorigenesis. Mechanical stimuli are a key input to YAP activity, but the mechanisms controlling this regulation remain largely uncharacterized. We show that CAV1 positively modulates the YAP mechanoresponse to substrate stiffness through actin-cytoskeleton-dependent and Hippo-kinase-independent mechanisms. RHO activity is necessary, but not sufficient, for CAV1-dependent mechanoregulation of YAP activity. Systematic quantitative interactomic studies and image-based small interfering RNA (siRNA) screens provide evidence that this actin-dependent regulation is determined by YAP interaction with the 14-3-3 protein YWHAH. Constitutive YAP activation rescued phenotypes associated with CAV1 loss, including defective extracellular matrix (ECM) remodeling. CAV1-mediated control of YAP activity was validated in vivo in a model of pancreatitis-driven acinar-to-ductal metaplasia. We propose that this CAV1-YAP mechanotransduction system controls a significant share of cell programs linked to these two pivotal regulators, with potentially broad physiological and pathological implications.

Involvement of the TGF-β1 pathway in caveolin-1-associated regulation of head and neck tumor cell metastasis

Head and neck squamous cell carcinoma (HNSCC) is the sixth most frequent malignancy with a 5-year survival rate of 54%. Therefore, disease management improvement is required. The present study aimed to assess the role of caveolin-1 (Cav-1) in the metastasis of head and neck tumor cells. Short hairpin RNA was used to silence Cav-1 expression in Tu686 cells. Proliferation, migration, invasion, morphology and the levels of effector proteins were assessed in cells. Upon Cav-1 silencing, E-cadherin levels were decreased, while vimentin levels were significantly increased. Cell migration, quantified by wound healing and Transwell assays, was significantly increased. Meanwhile, Cav-1 and transforming growth factor β1 (TGF-β1) receptor were identified to be co-localized. In addition, Cav-1-knockdown resulted in increased phosphorylation of SMAD family member 2 (P<0.05), a downstream effector of TGF-β signaling. In addition, there was a mutual regulation, with increasing TGF-β1 levels leading to a dose-dependent decrease of Cav-1 expression levels (P<0.05). These findings indicate that Cav-1 inhibits cell metastasis in HNSCC, suggesting the involvement of the TGF-β signaling pathway.

Pyruvate Kinase M2: a Metabolic Bug in Re-Wiring the Tumor Microenvironment

Metabolic reprogramming is a newly emerged hallmark of cancer attaining a recent consideration as an essential factor for the progression and endurance of cancer cells. A prime event of this altered metabolism is increased glucose uptake and discharge of lactate into the cells surrounding constructing a favorable tumor niche. Several oncogenic factors help in promoting this consequence including, pyruvate kinase M2 (PKM2) a rate-limiting enzyme of glycolysis in tumor metabolism via exhibiting its low pyruvate kinase activity and nuclear moon-lightening functions to increase the synthesis of lactate and macromolecules for tumor proliferation. Not only its role in cancer cells but also its role in the tumor microenvironment cells has to be understood for developing the small molecules against it which is lacking with the literature till date. Therefore, in this present review, the role of PKM2 with respect to various tumor niche cells will be clarified. Further, it highlights the updated list of therapeutics targeting PKM2 pre-clinically and clinically with their added limitations. This upgraded understanding of PKM2 may provide a pace for the reader in developing chemotherapeutic strategies for better clinical survival with limited resistance.

MicroRNA‑192 inhibits cell proliferation and induces apoptosis in human breast cancer by targeting caveolin 1

It has been demonstrated that microRNA-192 (miR-192) serves important roles in different cancer types, including breast cancer, prostate cancer and colorectal cancer. However, its biological role and function in breast cancer remains largely unknown. The present study aimed to determine the role of miR-192 in breast cancer. In the present study, one normal breast and two breast tumor cells lines were used, which included the normal mammary fibroblast cell line Hs578Bst, a more aggressive breast tumor cell line MDA-MB-231 and a less aggressive breast tumor cell line MCF-7. The effect of miR-192 on proliferation of breast cancer cells was detected with an MTT assay. Western blot analysis was performed to determine protein expression of caveolin 1 (CAV1). A lentiviral vector that overexpresses pre-miR-192 and control lentiviral packaging plasmids were used in the present study. The Student's t-test was performed to analyze the significance of differences between samples. In the present study, it was determined that the expression of miR-192 is downregulated in breast cancer, compared with the adjacent normal tissues. Overexpression of miR-192 significantly inhibited cell proliferation, and induced cell apoptosis and cell cycle arrest in MCF7 and MDA-MB-231 cells. Using a bioinformatics method, CAV1 was considered a potential target of miR-192. Furthermore, it was demonstrated that CAV1 is a direct target of miR-192 and its protein expression is negatively regulated by miR-192. Therefore, the present study demonstrated that miR-192 serves an important role as a regulator in breast cancer and the miR-192/CAV1 axis has a potential as a therapeutic target for treatment of breast cancer.

CAV1 - GLUT3 signaling is important for cellular energy and can be targeted by Atorvastatin in Non-Small Cell Lung Cancer

Background: The development of molecular targeted therapies, such as EGFR-TKIs, has positively impacted the management of EGFR mutated NSCLC. However, patients with innate and acquired resistance to EGFR-TKIs still face limited effective therapeutic options. Statins are the most frequently prescribed anti-cholesterol agents and have been reported to inhibit the progression of various malignancies, including in lung. However, the mechanism by which statin exerts its anti-cancer effects is unclear. This study is designed to investigate the anti-proliferative effects and identify the mechanism-of-action of statins in NSCLC. Methods: In this study, the anti-tumoral properties of Atorvastatin were investigated in NSCLC utilizing cell culture system and in vivo models. Results: We demonstrate a link between elevated cellular cholesterol and TKI-resistance in NSCLC, which is independent of EGFR mutation status. Atorvastatin suppresses growth by inhibiting Cav1 expression in tumors in cell culture system and in in vivo models. Subsequent interrogations demonstrate an oncogenic physical interaction between Cav1 and GLUT3, and glucose uptake found distinctly in TKI-resistant NSCLC and this may be due to changes in the physical properties of Cav1 favoring GLUT3 binding in which significantly stronger Cav1 and GLUT3 physical interactions were observed in TKI-resistant than in TKI-sensitive NSCLC cells. Further, the differential effects of atorvastatin observed between EGFR-TKI resistant and sensitive cells suggest that EGFR mutation status may influence its actions. Conclusions: This study reveals the inhibition of oncogenic role of Cav1 in GLUT3-mediated glucose uptake by statins and highlights its potential impact to overcome NSCLC with EGFR-TKI resistance.

Cell Intrinsic and Extrinsic Mechanisms of Caveolin-1-Enhanced Metastasis

Caveolin-1 (CAV1) is a scaffolding protein with a controversial role in cancer. This review will initially discuss earlier studies focused on the role as a tumor suppressor before elaborating subsequently on those relating to function of the protein as a promoter of metastasis. Different mechanisms are summarized illustrating how CAV1 promotes such traits upon expression in cancer cells (intrinsic mechanisms). More recently, it has become apparent that CAV1 is also a secreted protein that can be included into exosomes where it plays a significant role in determining cargo composition. Thus, we will also discuss how CAV1 containing exosomes from metastatic cells promote malignant traits in more benign recipient cells (extrinsic mechanisms). This ability appears, at least in part, attributable to the transfer of specific cargos present due to CAV1 rather than the transfer of CAV1 itself. The evolution of how our perception of CAV1 function has changed since its discovery is summarized graphically in a time line figure.

Deletion of caveolin scaffolding domain alters cancer cell migration

Caveolin-1 (Cav-1) is an integral membrane protein that plays an important role in proliferative and terminally differentiated cells. As a structural component of Caveolae, Cav-1 interacts with signaling molecules via a caveolin scaffolding domain (CSD) regulating cell signaling. Recent reports have shown that Cav-1 is a negative regulator in tumor metastasis. Therefore, we hypothesize that Cav-1 inhibits cell migration through its CSD. HeLa cells were engineered to overexpress Cav-1 (Cav-1 OE), Cav-1 without a functional CSD (∆CSD), or enhanced green fluorescent protein (EGFP) as a control. HeLa cell migration was suppressed in Cav-1 OE cells while ∆CSD showed increased migration, which corresponded to a decrease in the tight junction protein, zonula occludens (ZO-1). The migration phenotype was confirmed in multiple cancer cell lines. Phosphorylated STAT-3 was decreased in Cav-1 OE cells compared to control and ∆CSD cells; reducing STAT-3 expression alone decreased cell migration. ∆CSD blunted HeLa proliferation by increasing the number of cells in the G2/M phase of the cell cycle. Overexpressing the CSD peptide alone suppressed HeLa cell migration and inhibited pSTAT3. These findings suggest that Cav-1 CSD may be critical in controlling the dynamic phenotype of cancer cells by facilitating the interaction of specific signal transduction pathways, regulating STAT3 and participating in a G2/M checkpoint. Modulating the CSD and targeting specific proteins may offer potential new therapies in the treatment of cancer metastasis.

Caveolin-1 and dynamin-2 overexpression is associated with the progression of bladder cancer

Caveolae-mediated endocytosis regulates cell adhesion and growth in an anchorage-dependent manner. Studies of the endocytic function of caveolae have suggested a wide-ranging list of cargoes, including a number of receptors and extracellular proteins, ligands and nutrients from the extracellular matrix. Disruption of the processes of caveolae-mediated endocytosis mediated by signaling proteins is critical to cellular integrity. Caveolin-1 and dynamin-2 are the 2 major proteins associated with endocytotic function. Mechanistically, dynamin-2 has a co-equal role with caveolin-1 in terms of caveolae-derived endosome formation. Recent studies have revealed the pathological outcomes associated with the dysregulation of caveolin-1 and dynamin-2 expression. Increased expression levels of the gene for caveolin, Cav-1, resulting in augmented cellular metastasis and invasion, have been demonstrated in various types of cancer, and overexpression of the gene for dynamin-2, DNM2, has been associated with tumorigenesis in cervical, pancreatic and lung cancer. An increased expression of Cav-1 and DNM2 is known to be associated with the invasive behavior of cancer cells, and with cancer progression. Furthermore, it has been previously demonstrated that, in caveolar assembly and caveolae mediated endocytosis, Cav-1 interacts directly with DNM2 during the processes. Altered expression of the 2 genes is critical for the normal function of the cell. The expression patterns of Cav-1 and DNM2 have been previously examined in bladder cancer cell lines, and were each demonstrated to be overexpressed. In the present study, the expression levels of these 2 genes in bladder cancer samples were quantified. The gene expression levels of Cav-1 and DNM2 were identified to be increased 8.88- and 8.62-fold, respectively, in tumors compared with the normal controls. Furthermore, high-grade tumors exhibited significantly increased expression levels of Cav-1 and DNM2 (both P<0.0001) compared with the low-grade tumors. In addition, compared with normal control samples, the expression of the 2 genes in tumor samples was observed to be highly significant (P<0.0001), with a marked positive correlation identified for the tumors (Pearson's correlation coefficient, r=0.80 for the tumor samples vs. r=0.32 in the normal control samples). Taken together, the results of the present study demonstrated that the overexpression of Cav-1 and DNM2 genes, and a determination of their correlation coefficients, may be a potential risk factor for bladder cancer, in addition to other clinical factors.

Secalonic acid D induces cell apoptosis in both sensitive and ABCG2-overexpressing multidrug resistant cancer cells through upregulating c-Jun expression

Secalonic acid D (SAD) could inhibit cell growth in not only sensitive cells but also multidrug resistant (MDR) cells. However, the molecular mechanisms need to be elucidated. Here, we identified that SAD possessed potent cytotoxicity in 3 pairs of MDR and their parental sensitive cells including S1-MI-80 and S1, H460/MX20 and H460, MCF-7/ADR and MCF-7 cells. Furthermore, SAD induced cell G2/M phase arrest via the downregulation of cyclin B1 and the increase of CDC2 phosphorylation. Importantly, JNK pathway upregulated the expression of c-Jun in protein level and increased c-Jun phosphorylation induced by SAD, which was linked to cell apoptosis via c-Jun/Src/STAT3 pathway. To investigate the mechanisms of upregulation of c-Jun protein by SAD, the mRNA expression level and degradation of c-Jun were examined. We found that SAD did not alter the mRNA level of c-Jun but inhibited its proteasome-dependent degradation. Taken together, these results implicate that SAD induces cancer cell death through c-Jun/Src/STAT3 signaling axis by inhibiting the proteasome-dependent degradation of c-Jun in both sensitive cells and ATP-binding cassette transporter sub-family G member 2 (ABCG2)-mediated MDR cells.

Simvastatin delays castration‑resistant prostate cancer metastasis and androgen receptor antagonist resistance by regulating the expression of caveolin‑1

The failure of androgen deprivation therapy in prostate cancer treatment mainly results from drug resistance to androgen receptor antagonists. Although an aberrant caveolin‑1 (Cav‑1) expression has been reported in multiple tumor cell lines, it is unknown whether it is responsible for the progression of castration‑resistant prostate cancer (CRPC). Thus, the aim of the present study was to determine whether Cav‑1 can be used as a key molecule for the prevention and treatment of CRPC, and to explore its mechanism of action in CRPC. For this purpose, tissue and serum samples from patients with primary prostate cancer and CRPC were analyzed using immunohistochemistry and enzyme‑linked immunosorbent assay, which revealed that Cav‑1 was overexpressed in CRPC. Furthermore, Kaplan‑Meier survival analysis and univariate Cox proportional hazards regression analysis demonstrated that Cav‑1 expression in tumors was an independent risk factor for the occurrence of CRPC and was associated with a shorter recurrence‑free survival time in patients with CRPC. Receiver operating characteristic curves suggested that serum Cav‑1 could be used as a diagnostic biomarker for CRPC (area under the curve, 0.876) using a cut‑off value of 0.68 ng/ml (with a sensitivity of 82.1% and specificity of 80%). In addition, it was determined that Cav‑1 induced the invasion and migration of CRPC cells by the activation of the H‑Ras/phosphoinositide‑specific phospholipase Cε signaling cascade in the cell membrane caveolae. Importantly, simvastatin was able to augment the anticancer effects of androgen receptor antagonists by downregulating the expression of Cav‑1. Collectively, the findings of this study provide evidence that Cav‑1 is a promising predictive biomarker for CRPC and that lowering cholesterol levels with simvastatin or interfering with the expression of Cav‑1 may prove to be a useful strategy with which to prevent and/or treat CRPC.