Long-term generation of antiPCSK9 antibody using a nanoliposome-based vaccine delivery system

Low Density Lipoprotein (LDL) Cholesterol as a Causal Role for Atherosclerotic Disease: Potential Role of PCSK9 Inhibitors

Proprotein convertase subtilisin/kexin type 9 (PCSK9)-related discoveries of the turn of the century have translated into substantial novelty in dyslipidemia treatment in the last 5 years. With chronic preventable atherosclerotic cardiovascular diseases (ASCVD) representing an epidemic of morbidity and mortality worldwide, low-density lipoprotein cholesterol (LDL-c) reduction represents a public health priority. By overcoming two major statin-related issues, namely intolerance and ineffectiveness, PCSK9 inhibitors have offered a safe and effective option in selected clinical settings where LDL-c reduction is required. Herein, we recapitulate recent findings, clinical applications, and ASCVD prevention potential of PCSK9 inhibition, with focus on anti-PCSK9 monoclonal antibodies, evolocumab and alirocumab.

Potential anti-tumor effect of a nanoliposomal antiPCSK9 vaccine in mice bearing colorectal cancer

INTRODUCTION

Inhibition of proprotein convertase subtilisin/kexin 9 (PCSK9) is an effective therapeutic tool for lowering low-density lipoprotein cholesterol (LDL-C). There is no available evidence on the efficacy and safety of PCSK9 inhibitors in non-cardiovascular diseases, particularly cancer. The present study aimed to evaluate the effect of PCSK9 inhibition on cancer endpoints in mice bearing colon carcinoma, using a nanoliposomal antiPCSK9 vaccine.

MATERIAL AND METHODS

The prepared nanoliposomal antiPCSK9 vaccine was subcutaneously inoculated in BALB/c mice four times with a biweekly interval. Two weeks after the last booster, the vaccinated and unvaccinated mice were subcutaneously inoculated with CT26 colon cancer cells into the right flank. After the tumor mass became palpable, the mice were randomly divided into three groups: (1) PBS (untreated control), (2) vaccine group, and (3) pegylated liposomal doxorubicin (PLD; positive control) group. Body weight, tumor size and survival of mice were monitored for 50 days.

RESULTS

The nanoliposomal antiPCSK9 vaccine could efficiently provoke specific antibodies against PCSK9 in BALB/c mice and thereby reduced the plasma level and function of PCSK9. Tumor volume was 77% and 87.7% lower (p < 0.0001) in the vaccinated mice when compared with Doxil (liposomal doxorubicin) and control mice, respectively. Tumor size analysis showed that time to reach the endpoint of the vaccine group (47 ±11 days) was slightly but not significantly higher than PLD (46 ±2.6 days) and the control (43 ±12 days) groups. The tumor growth rates in the vaccine and PLD groups were reduced by 9.3% and 7.3, respectively, when compared with the control group. The vaccinated mice survived slightly but not significantly longer than PLD and the control mice. The median survival of the vaccine, PLD and control groups were 51, 45, and 41 days, respectively. The vaccinated mice's life was prolonged by 24.4% as compared with the control mice, while it was increased by 9.8% in the PLD group.

CONCLUSIONS

Our results revealed that PCSK9 inhibition not only exerted no harmful effects but also could moderately inhibit tumor growth, and improve lifespan and survival in mice bearing colon cancer.

Effects of immunization against PCSK9 in an experimental model of breast cancer

INTRODUCTION

Inhibition of proprotein convertase subtilisin/kexin 9 (PCSK9) is an efficient strategy for lowering low-density lipoprotein cholesterol (LDL-C). There are, however, scant data on the efficacy and safety of PCSK9 inhibitors in non-cardiovascular diseases, particularly cancer. The present study aimed to evaluate the effect of PCSK9 inhibition using a nanoliposomal antiPCSK9 vaccine on cancer behavior and endpoints in mice bearing breast tumor.

MATERIAL AND METHODS

To induce antiPCSK9 antibody in vivo, a nanoliposomal antiPCSK9 vaccine absorbed on 0.4% alum adjuvant was used. To induce tumor, BALB/c mice were subcutaneously inoculated with 4T1 breast carcinoma cells. After the tumor mass was palpable (approximately 10 mm3), the mice were randomly divided into four groups and subjected to different treatment protocols: (1) PBS (untreated control), (2) vaccine group, (3) combination of vaccine and Doxil, and (4) Doxil (positive control) group. Vaccine was subcutaneously administered to mice four times at 2-week intervals. Two weeks after the last administration, the vaccinated and non-vaccinated mice were subcutaneously inoculated with 4T1 breast carcinoma cells. To evaluate therapeutic efficacy, mouse body weight, tumor size, and survival were monitored every other day for 60 days.

RESULTS

The nanoliposomal antiPCSK9 vaccine was found to efficiently induce specific antibodies against PCSK9 in BALB/c mice, thereby decreasing plasma levels of PCSK9 and inhibiting its function. Tumor size analysis showed that time to reach endpoint (TTE) of the vaccine, combination, Doxil, and control groups was 47 ±10, 57 ±4, 60 ±4 and 39 ±9 days, respectively. Rate of tumor growth in vaccine, combination and Doxil groups was decreased by 21%, 48% and 53%, respectively, compared to the control group. Lifespan was increased by 4.2% in the vaccine group, compared with the control group. Additionally, the survival in the combination and Doxil groups was significantly higher than the vaccine and control groups.

CONCLUSIONS

Our results revealed that PCSK9 inhibition may moderately improve breast cancer outcomes while having no harmful effects in tumor-bearing mice.