Effects of immunisation against PCSK9 in mice bearing melanoma

The Causal Relationship between PCSK9 Inhibitors and Malignant Tumors: A Mendelian Randomization Study Based on Drug Targeting

Objective: This study explores the potential causal association between proprotein convertase subtilisin/kexin 9 (PCSK9) inhibitors and tumor development using Mendelian randomization (MR) based on drug targets. Methods: Instrumental variables within ±100 kb of the PCSK9 gene locus, impacting low-density lipoprotein cholesterol (LDL-C), were utilized for MR analysis. Coronary heart disease (CHD) served as a positive control to validate the causal relationship between PCSK9 inhibitors and various cancers. We employed reverse MR to address the reverse causation concerns. Data from positive controls and tumors were sourced from OpenGWAS. Results: MR analysis suggested a negative causal relationship between PCSK9 inhibitors and both breast and lung cancers (95%CIBreast cancer 0.81~0.99, p = 2.25 × 10-2; 95%CILung cancer 0.65~0.94, p = 2.55 × 10-3). In contrast, a positive causal link was observed with gastric, hepatic, and oral pharyngeal cancers and cervical intraepithelial neoplasia (95%CIGastric cancer 1.14~1.75, p = 1.88 × 10-2; 95%CIHepatic cancer 1.46~2.53, p = 1.16 × 10-2; 95%CIOral cavity and pharyngeal cancer 4.49~6.33, p = 3.36 × 10-4; 95%CICarcinoma in situ of cervix uteri 4.56~7.12, p = 6.91 × 10-3), without heterogeneity or pleiotropy (p > 0.05). Sensitivity analyses confirmed these findings. The results of MR of drug targets suggested no causal relationship between PCSK9 inhibitors and bladder cancer, thyroid cancer, pancreatic cancer, colorectal cancer, malignant neoplasms of the kidney (except for renal pelvis tumors), malignant neoplasms of the brain, and malignant neoplasms of the esophagus (p > 0.05). Reverse MR helped mitigate reverse causation effects. Conclusions: The study indicates a divergent causal relationship of PCSK9 inhibitors with certain cancers. While negatively associated with breast and lung cancers, a positive causal association was observed with gastric, hepatic, oral cavity, and pharyngeal cancers and cervical carcinoma in situ. No causal links were found with bladder, thyroid, pancreatic, colorectal, certain kidney, brain, and esophageal cancers.

Targeting proprotein convertase subtilisin/kexin type 9 (PCSK9): from bench to bedside

Proprotein convertase subtilisin/kexin type 9 (PCSK9) has evolved as a pivotal enzyme in lipid metabolism and a revolutionary therapeutic target for hypercholesterolemia and its related cardiovascular diseases (CVD). This comprehensive review delineates the intricate roles and wide-ranging implications of PCSK9, extending beyond CVD to emphasize its significance in diverse physiological and pathological states, including liver diseases, infectious diseases, autoimmune disorders, and notably, cancer. Our exploration offers insights into the interaction between PCSK9 and low-density lipoprotein receptors (LDLRs), elucidating its substantial impact on cholesterol homeostasis and cardiovascular health. It also details the evolution of PCSK9-targeted therapies, translating foundational bench discoveries into bedside applications for optimized patient care. The advent and clinical approval of innovative PCSK9 inhibitory therapies (PCSK9-iTs), including three monoclonal antibodies (Evolocumab, Alirocumab, and Tafolecimab) and one small interfering RNA (siRNA, Inclisiran), have marked a significant breakthrough in cardiovascular medicine. These therapies have demonstrated unparalleled efficacy in mitigating hypercholesterolemia, reducing cardiovascular risks, and have showcased profound value in clinical applications, offering novel therapeutic avenues and a promising future in personalized medicine for cardiovascular disorders. Furthermore, emerging research, inclusive of our findings, unveils PCSK9's potential role as a pivotal indicator for cancer prognosis and its prospective application as a transformative target for cancer treatment. This review also highlights PCSK9's aberrant expression in various cancer forms, its association with cancer prognosis, and its crucial roles in carcinogenesis and cancer immunity. In conclusion, this synthesized review integrates existing knowledge and novel insights on PCSK9, providing a holistic perspective on its transformative impact in reshaping therapeutic paradigms across various disorders. It emphasizes the clinical value and effect of PCSK9-iT, underscoring its potential in advancing the landscape of biomedical research and its capabilities in heralding new eras in personalized medicine.

Effect of proprotein convertase subtilisin/kexin type 9 inhibition on cancer events: A pooled, post hoc, competing risk analysis of alirocumab clinical trials

OBJECTIVE

Assess the risk of new and worsening cancer events among participants who received the lipid-lowering therapy alirocumab, a proprotein convertase subtilisin/kexin type 9 inhibitor.

DESIGN

Pooled post hoc analysis.

SETTING

Six phase 3 or phase 4 placebo-controlled randomised trials with alirocumab.

PARTICIPANTS

A total of 24,070 patients from the safety population with complete dosing data (alirocumab, n = 12,533; placebo, n = 11,537).

INTERVENTION

Alirocumab 75 mg, alirocumab 150 mg, alirocumab 75 mg increasing to 150 mg if low-density lipoprotein cholesterol <50 mg/dL not achieved, or placebo, all every 2 weeks. All participants received background high-intensity or maximum-tolerated statin therapy.

OUTCOMES AND MEASURES

The first new or worsening incident cancer events were assessed during the treatment-emergent adverse event period. Four outcomes were evaluated: any-neoplasm, malignant neoplasms, broad definition of hormone-sensitive cancers, and stricter definition of hormone-sensitive cancers. Sub-distribution hazard ratios and 95% confidence intervals (CIs) were estimated using a competing risk framework, with death as a competing risk.

RESULTS

Considering both treatment arms in aggregate, 969 (4.03%), 779 (3.24%), 178 (0.74%) and 167 (0.69%) patients developed any neoplasm, malignant neoplasms, broad definition of hormone-sensitive cancer and strict definition of hormone-sensitive cancer events, respectively. There was no significant difference in the risk of having any neoplasm in the alirocumab versus the placebo group (sub-distribution hazards ratio [95% CI], 0.93 [0.82-1.1]; p = 0.28). A nominally lower risk of having any neoplasms with alirocumab was observed among subjects aged ≥64 years (sub-distribution hazards ratio 0.83; 95% CI, 0.70-0.99).

CONCLUSIONS

Intensive low-density lipoprotein cholesterol lowering with a proprotein convertase subtilisin/kexin type 9 inhibitor combined with statin does not appear to increase the risk of new or worsening cancer events.

The evolving landscape of PCSK9 inhibition in cancer

Cancer is a disease with a significant global burden in terms of premature mortality, loss of productivity, healthcare expenditures, and impact on mental health. Recent decades have seen numerous advances in cancer research and treatment options. Recently, a new role of cholesterol-lowering PCSK9 inhibitor therapy has come to light in the context of cancer. PCSK9 is an enzyme that induces the degradation of low-density lipoprotein receptors (LDLRs), which are responsible for clearing cholesterol from the serum. Thus, PCSK9 inhibition is currently used to treat hypercholesterolemia, as it can upregulate LDLRs and enable cholesterol reduction through these receptors. The cholesterol-lowering effects of PCSK9 inhibitors have been suggested as a potential mechanism to combat cancer, as cancer cells have been found to increasingly rely on cholesterol for their growth needs. Additionally, PCSK9 inhibition has demonstrated the potential to induce cancer cell apoptosis through several pathways, increase the efficacy of a class of existing anticancer therapies, and boost the host immune response to cancer. A role in managing cancer- or cancer treatment-related development of dyslipidemia and life-threatening sepsis has also been suggested. This review examines the current evidence regarding the effects of PCSK9 inhibition in the context of different cancers and cancer-associated complications.

Preclinical toxicity assessment of a peptide-based antiPCSK9 vaccine in healthy mice

BACKGROUND

Proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibition is a novel cholesterol-lowering treatment for decreasing the risk of atherosclerosis. We have previously shown that active immunization using the antiPCSK9 vaccine could decrease hypercholesterolemia and impede the development of atherosclerotic lesions in the experimental model of atherosclerosis. Here, we evaluated the toxicity of the vaccine in healthy mice.

METHODS

Forty male and female albino mice were divided into 4 experimental groups, including vaccine female (10 mice) and male (10 mice) groups receiving the antiPCSK9 vaccine as well as the corresponding control female (10 mice) and male (10 mice) groups receiving the phosphate buffer. Vaccination was planned based on 4 subcutaneous injections of the vaccine formulation (10 µg/mouse) in bi-weekly intervals. The toxicity study was performed by the subacute protocol, 28 days after the last vaccine injection. To this end, the plasma levels of lipid indexes, urea, creatinine, AST, ALT, ALP, and fasting plasma glucose (FPG), as well as the CBC test were measured. To evaluate histopathological alterations, various tissues including the heart, liver, kidney, spleen, and brain were studied using hematoxylin & eosin (H&E) staining by an expert pathologist. The severity of damage to the tissue was considered based on the standard classification; grade 1 as light damage, grade 2 as moderate damage, grade 3 as near intense damage, and grade 4 as intense damage.

RESULTS

The results showed non-significant changes of total cholesterol, LDL-C, triglyceride, HDL-C, FBS, creatinine, urea, AST, ALP, ALT, and PAB in the vaccinated mice when compared with control mice. The CBS test indicated that there were no significant changes in the levels of WBC, RBC, HGB, HCT, MCH, MCHC, PLT, LYM, NEUT, MCV, RDW-S, PDW, and MPV in the vaccinated mice when compared with control mice. Evaluating histopathological alterations in various tissues indicated no significant adverse effects in vaccinated mice when compared to control mice.

CONCLUSION

The findings of the present study indicate that antiPCSK9 is safe and exerts no adverse effects on the function of different organs and blood levels of cellular and biochemical biomarkers in healthy mice.

PCSK9 facilitates melanoma pathogenesis via a network regulating tumor immunity

BACKGROUND

PCSK9 regulates cholesterol homeostasis and promotes tumorigenesis. However, the relevance of these two actions and the mechanisms underlying PCSK9's oncogenic roles in melanoma and other cancers remain unclear.

METHODS

PCSK9's association with melanoma was analysed using the TCGA dataset. Empty vector (EV), PCSK9, gain-of-function (D374Y), and loss-of-function (Q152H) PCSK9 mutant were stably-expressed in murine melanoma B16 cells and studied for impact on B16 cell-derived oncogenesis in vitro and in vivo using syngeneic C57BL/6 and Pcsk9^-/- mice. Intratumoral accumulation of cholesterol was determined. RNA-seq was performed on individual tumor types. Differentially-expressed genes (DEGs) were derived from the comparisons of B16 PCSK9, B16 D374Y, or B16 Q152H tumors to B16 EV allografts and analysed for pathway alterations.

RESULTS

PCSK9 expression and its network negatively correlated with the survival probability of patients with melanoma. PCSK9 promoted B16 cell proliferation, migration, and growth in soft agar in vitro, formation of tumors in C57BL/6 mice in vivo, and accumulation of intratumoral cholesterol in a manner reflecting its regulation of the low-density lipoprotein receptor (LDLR): Q152H, EV, PCSK9, and D374Y. Tumor-associated T cells, CD8 + T cells, and NK cells were significantly increased in D374Y tumors along with upregulations of multiple immune checkpoints, IFNγ, and 143 genes associated with T cell dysfunction. Overlap of 36 genes between the D374Y DEGs and the PCSK9 DEGs predicted poor prognosis of melanoma and resistance to immune checkpoint blockade (ICB) therapy. CYTH4, DENND1C, AOAH, TBC1D10C, EPSTI1, GIMAP7, and FASL (FAS ligand) were novel predictors of ICB therapy and displayed high level of correlations with multiple immune checkpoints in melanoma and across 30 human cancers. We observed FAS ligand being among the most robust biomarkers of ICB treatment and constructed two novel and effective multigene panels predicting response to ICB therapy. The profiles of allografts produced by B16 EV, PCSK9, D374Y, and Q152H remained comparable in C57BL/6 and Pcsk9^-/- mice.

CONCLUSIONS

Tumor-derived PCSK9 plays a critical role in melanoma pathogenesis. PCSK9's oncogenic actions are associated with intratumoral cholesterol accumulation. PCSK9 systemically affects the immune system, contributing to melanoma immune evasion. Novel biomarkers derived from the PCSK9-network effectively predicted ICB therapy responses.

The effect of PCSK9 immunization on the hepatic level of microRNAs associated with the PCSK9/LDLR pathway

INTRODUCTION

MicroRNAs (miRNAs) are a class of gene expression epigenetic regulators that play roles in regulating genes involved in cholesterol homeostasis, including low-density lipoprotein receptor (LDLR) and PCSK9; therefore, miRNAs have been suggested as potential therapeutic targets for treating cardiometabolic disorders. Thus, the present study aimed to assess the effect of immunotherapy with the PCSK9 peptide vaccine on the hepatic expression levels of microRNAs associated with the LDLR pathway, including miRNA-27a, miRNA-30c, and miRNA-191, in normal vaccinated mice.

MATERIAL AND METHODS

PCSK9 immunogenic peptide and 0.4% alum adjuvant were mixed at a 1 : 1 ratio and used as a vaccine formulation. Male albino mice were randomly assigned to the vaccine or control group. Mice in the vaccine group were injected four times at two-week intervals with a PCSK9 peptide vaccine, and mice in the control group were injected with phosphate-buffered saline (PBS). Animal livers were sampled 2 weeks after the last injection to assess miRNA expression levels. The hepatic expression levels of miRNA-27a, miRNA-30c, and miRNA-191 were evaluated by SYBR Green real-time PCR, quantified by a comparative (2^{- Δ Δ CT}) method (fold change (FC)) and normalized to U6 small nuclear RNA (U6snRNA) expression as an internal control.

RESULTS

The hepatic expression level of miRNA-27a was significantly lower in mice following immunotherapy with the PCSK9 peptide vaccine compared to the control group (FC: 0.731 ±0.1, p = 0.027). Also, there was a borderline significantly lower hepatic expression level of miRNA-30c in the vaccinated group compared to the control (FC: 0.569 ±0.1, p = 0.078). However, no significant differences were found in the hepatic expression level of miRNA-191 between the two studied groups (FC: 0.852 ±0.1, p = 0.343).

CONCLUSIONS

According to the findings, the PCSK9 peptide vaccine could effectively reduce the hepatic expression level of miRNA-27a and may be helpful in the management of LDL-C level and atherosclerosis, which may be mediated through the LDLR pathway.

PCSK9 in Liver Cancers at the Crossroads between Lipid Metabolism and Immunity

Metabolic rewiring and defective immune responses are considered to be the main driving forces sustaining cell growth and oncogenesis in many cancers. The atypical enzyme, proprotein convertase subtilisin/kexin type 9 (PCSK9), is produced by the liver in large amounts and plays a major role in lipid metabolism via the control of the low density lipoprotein receptor (LDLR) and other cell surface receptors. In this context, many clinical studies have clearly demonstrated the high efficacy of PCSK9 inhibitors in treating hyperlipidemia and cardiovascular diseases. Recent data implicated PCSK9 in the degradation of major histocompatibility complex I (MHC-I) receptors and the immune system as well as in other physiological activities. This review highlights the complex crosstalk between PCSK9, lipid metabolism and immunosuppression and underlines the latest advances in understanding the involvement of this convertase in other critical functions. We present a comprehensive assessment of the different strategies targeting PCSK9 and show how these approaches could be extended to future therapeutic options to treat cancers with a main focus on the liver.

Antitumor activity and molecular mechanism of proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibition

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a member of the proprotein convertase family of proteins that activate other proteins in cells. Functionally, PCSK9 binds to the receptor of low-density lipoprotein particles (LDL) to regulate cholesterol metabolism and lipoprotein homeostasis in human body. PCSK9 inhibition is a novel pharmacological strategy to control hypercholesterolemia and cardiovascular diseases. Recently accumulating evidence realizes that PCSK9 possesses other roles in cells, such as regulation of tissue inflammatory response, intratumoral immune cell infiltration, and tumor progression. This review discussed the advancement of PCSK9 research on its role and underlying mechanisms in tumor development and progression. For example, PCSK9 inhibition could attenuate progression of breast cancer, glioma, colon tumor, hepatocellular cancer, prostate cancer, and lung adenocarcinoma and promote apoptosis of glioma, prostate cancer, and hepatocellular cancer cells. PCSK9 deficiency could reduce liver metastasis of B16F1 melanoma cells by lowering the circulating cholesterol levels. PCSK9 gene knockdown substantially attenuated mouse tumor growth in vivo by activation of cytotoxic T cells, although PCSK9 knockdown had no effect on morphology and growth rate of different mouse cancer cell lines in vitro. PCSK9 inhibition thus can be used to control human cancers. Future preclinical and clinical studies are warranted to define anti-tumor activity of PCSK9 inhibition.

Mechanical ventilation promotes lung tumor spread by modulation of cholesterol cell content

Mechanical stretch of cancer cells can alter their invasiveness. During mechanical ventilation, lungs may be exposed to an increased amount of stretch, but the consequences on lung tumors have not been explored. To characterize the influence of mechanical ventilation on the behavior of lung tumors, invasiveness assays and transcriptomic analyses were performed in cancer cell lines cultured in static conditions or under cyclic stretch. Mice harbouring lung melanoma implants were submitted to mechanical ventilation and metastatic spread was assessed. Additional in vivo experiments were performed to determine the mechano-dependent specificity of the response. Incidence of metastases was studied in a cohort of lung cancer patients that received mechanical ventilation compared with a matched group of non-ventilated patients. Stretch increases invasiveness in melanoma B16F10luc2 and lung adenocarcinoma A549 cells. We identified a mechanosensitive upregulation of pathways involved in cholesterol processing in vitro, leading to an increase in PCSK9 and LDLR expression, a decrease in intracellular cholesterol and preservation of cell stiffness. A course of mechanical ventilation in mice harboring melanoma implants increased brain and kidney metastases two weeks later. Blockade of PCSK9 using a monoclonal antibody increased cell cholesterol and stiffness and decreased cell invasiveness in vitro and metastasis in vivo In patients, mechanical ventilation increased PCSK9 abundance in lung tumors and the incidence of metastasis, thus decreasing survival. Our results suggest that mechanical stretch promote invasiveness of cancer cells, which may have clinically relevant consequences. Pharmacological manipulation of cholesterol endocytosis could be a novel therapeutic target in this setting.

PCSK9 as a new player in cancer: New opportunity or red herring?

Initially described as a factor involved in liver regeneration and neuronal differentiation, proprotein convertase subtilisin/kexin type 9 (PCSK9) has become one of the key regulators of low-density lipoprotein cholesterol. Besides that, a number of studies have suggested PCSK9 may play a role in cancer biology. This is particularly true for gastroenteric (gastric and liver cancers) and lung cancers, where higher PCSK9 levels were associated with the increased ability of the tumor to develop and give metastasis as well as with reduced overall survival. Accordingly, monoclonal antibodies blocking PCSK9 were recently shown to synergize with immunotherapy in different types of cancers to achieve tumor growth suppression through an increased intratumoral infiltration of cytotoxic T cells. Anti-PCSK9 vaccines have been tested in animal models with encouraging results only in colon carcinoma. As most of this evidence is based on pre-clinical studies, this has led to some controversies and inconsistencies, thus suggesting that additional research is needed to clarify the topic. Finally, modulation of intracellular PCSK9 levels by silencing RNA (siRNA) may help understand the physiological and pathological mechanisms of PCSK9.

Surfactin exerts an anti-cancer effect through inducing allergic reactions in melanoma skin cancer

Surfactin is a mast cell degranulator, that increases the immune response via the degranulation of mast cells. Recently, numerous studies reported that allergic reactions play an important role in the reduction of melanoma development. So, this study aimed to investigate the anti-cancer effects of surfactin in a melanoma skin cancer in vivo model and a melanoma cell line, B16F10. Oral administration of surfactin significantly increased survival rate and reduced tumor growth and tumor weight on melanoma skin cancer in vivo model. Surfactin significantly increased infiltration of mast cells and levels of histamine. Surfactin significantly enhanced levels of IgE and immune-enhancing mediators, such as interferon-γ, interleukin (IL)-2, IL-6, IL-12, and tumor necrosis factor-α in serum and melanoma tissues. Activities of caspase-3, 8, and 9 were significantly enhanced by oral administration of surfactin. In vitro model, surfactin significantly increased B16F10 cell death via activation of caspase-3, 8, and 9 in a dose-dependent manner. Overall, our results indicate that surfactin has a significant anti-cancer effect on melanoma skin cancer through indirectly or directly inducing apoptosis of B16F10 melanoma cells. Also, these findings suggest that it will contribute to a novel perception into the role of allergic reactions in melanoma.

Pro-protein convertase subtilisin/kexin type 9 promotes intestinal tumor development by activating Janus kinase 2/signal transducer and activator of transcription 3/SOCS3 signaling in ApcMin/+ mice

Introduction

Pro-protein convertase subtilisin/kexin type 9 (PCSK9) regulates lipoprotein homeostasis in humans. Evolocumab is a selective PCSK9 inhibitor that can reduce low-density lipoprotein cholesterol (LDLC) level and decrease hypercholesterolemia. The current study aimed to explore whether PCSK9 increases the risk of colorectal cancer.

Methods

First, we utilized the classic intestinal tumor Apc^Min/+ mouse model and PCSK9 knock-in (KI) mice to establish Apc^Min/+PCSK9(KI) mice. Then, we investigated the effect of PCSK9 overexpression in Apc^Min/+PCSK9(KI) mice and PCSK9 inhibition using evolocumab on the progression of intestinal tumors in vivo by hematoxylin and eosin (HE) staining, Western blot, and immunohistochemistry (IHC) assay.

Results

Apc^Min/+PCSK9(KI) mice had higher numbers and larger sizes of adenomas, with 83.3% of these mice developing adenocarcinoma (vs. 16.7% of Apc^Min/+ mice). However, treatment with evolocumab reduced the number and size of adenomas and prevented the development of adenocarcinomas in Apc^Min/+ mice. PCSK9 overexpression reduced tumor cell apoptosis, the Bax/bcl-2 ratio, and the levels of cytokine signaling 3 protein (SOCS3) suppressors, but activated Janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) signaling in intestinal tumors. In contrast, evolocumab treatment had the opposite effect on Apc^Min/+mice.

Conclusion

PCSK9 might act as an oncogene or have an oncogenic role in the development and progression of colorectal cancer in vivo via activation of JAK2/STAT3/SOCS3 signaling.

Proprotein convertase subtilisin/kexin type 9 (PCSK9): A potential multifaceted player in cancer

Proprotein convertase subtilisin/kexin type 9 (PCSK9) has emerged as a novel pharmacological target for hypercholesterolemia and associated cardiovascular diseases owing to its function to mediate the degradation of low-density lipoprotein receptor (LDLR). Findings over the past two decades have identified novel binding partners and cellular functions of PCSK9. Notably, PCSK9 is aberrantly expressed in a broad spectrum of cancers and apparently contributes to disease prognosis, indicating that PCSK9 could be a valuable cancer biomarker. Experimental studies demonstrate the contribution of PCSK9 in various aspects of cancer, including cell proliferation, apoptosis, invasion, metastasis, anti-tumor immunity and radioresistance, strengthening the idea that PCSK9 could be a promising therapeutic target. Here, we comprehensively review the involvement of PCSK9 in cancer, summarizing its aberrant expression, association with disease prognosis, biological functions and underlying mechanisms in various malignancies. Besides, we highlight the potential of PCSK9 as a future therapeutic target in personalized cancer medicine.

PCSK9 and cancer: Rethinking the link

BACKGROUND

Cancer is emerging as a major problem globally, as it accounts for the second cause of death despite medical advances. According to epidemiological and basic studies, cholesterol is involved in cancer progression and there are abnormalities in cholesterol metabolism of cancer cells including prostate, breast, and colorectal carcinomas. However, the importance of cholesterol in carcinogenesis and thereby the role of cholesterol homeostasis as a therapeutic target is still a debated area in cancer therapy. Proprotein convertase subtilisin/kexin type-9 (PCSK9), a serine protease, modulates cholesterol metabolism by attachment to the LDL receptor (LDLR) and reducing its recycling by targeting the receptor for lysosomal destruction. Published research has shown that PCSK9 is also involved in degradation of other LDLR family members namely very-low-density-lipoprotein receptor (VLDLR), lipoprotein receptor-related protein 1 (LRP-1), and apolipoprotein E receptor 2 (ApoER2). As a result, this protein represents an interesting therapeutic target for the treatment of hypercholesterolemia. Interestingly, clinical trials on PCSK9-specific monoclonal antibodies have reported promising results with high efficacy in lowering LDL-C and in turn reducing cardiovascular complications. It is important to note that PCSK9 mediates several other pathways apart from its role in lipid homeostasis, including antiviral activity, hepatic regeneration, neuronal apoptosis, and modulation of various signaling pathways. Furthermore, recent literature has illustrated that PCSK9 is closely associated with incidence and progression of several cancers. In a number of studies, PCSK9 siRNA was shown to effectively suppress the proliferation and invasion of the several studied tumor cells. Hence, a novel application of PCSK9 inhibitors/silencers in cancer/metastasis could be considered. However, due to poor data on effectiveness and safety of PCSK9 inhibitors in cancer, the impact of PCSK9 inhibition in these pathological conditions is still unknown.

SEARCH METHODS

A vast literature search was conducted to find intended studies from 1956 up to 2020, and inclusion criteria were original peer-reviewed publications.

PURPOSE OF REVIEW

To date, PCSK9 has been scantly investigated in cancer. The question that needs to be discussed is "How does PCSK9 act in cancer pathophysiology and what are the risks or benefits associated to its inhibition?". We reviewed the available publications highlighting the contribution of this proprotein convertase in pathways related to cancer, with focus on the potential implications of its long-term pharmacological inhibition in cancer therapy.