Engineering extracellular vesicles to deliver CRISPR ribonucleoprotein for gene editing

Clustered regularly interspaced palindromic repeats (CRISPR) is a gene editing tool with tremendous therapeutic potential. Recently, ribonucleoprotein (RNP) complex-based CRISPR systems have gained momentum due to their reduction of off-target editing. This has coincided with the emergence of extracellular vesicles (EVs) as a therapeutic delivery vehicle due to its low immunogenicity and high capacity for manipulation. EVs are cell-derived membranous nanoparticles which mediate the intercellular transfer of molecular components. Current technologies achieve CRISPR RNP encapsulation into EVs through EVs biogenesis, thereby avoiding unnecessary physical, chemical or biological manipulations to the vesicles directly. Herein, we identify sixteen EVs-based CRISPR RNP encapsulation strategies, each with distinct genetic features to encapsulate CRISPR RNP. According to the molecular mechanism facilitating the encapsulation process, there are six strategies of encapsulating Cas9 RNP into virus-like particles based on genetic fusion, seven into EVs based on protein tethering, and three based on sgRNA-coupled encapsulation. Additionally, the incorporation of a targeting moiety to the EVs membrane surface through EVs biogenesis confers tropism and increases delivery efficiency to specific cell types. The targeting moieties include viral envelope proteins, recombinant proteins containing a ligand peptide, single-chain fragment variable (scFv) antibodies, and integrins. However, current strategies still have a number of limitations which prevent their use in clinical trials. Among those, the incorporation of viral proteins for encapsulation of Cas9 RNP have raised issues of biocompatibility due to host immune response. Future studies should focus on genetically engineering the EVs without viral proteins, enhancing EVs delivery specificity, and promoting EVs-based homology directed repair. Nevertheless, the integration of CRISPR RNP encapsulation and tropism technologies will provide strategies for the EVs-based delivery of CRISPR RNP in gene therapy and disease treatment.

Src family kinases engage differential pathways for encapsulation into extracellular vesicles

Extracellular vesicles (EVs) are heterogeneous biological nanoparticles secreted by all cell types. Identifying the proteins preferentially encapsulated in secreted EVs will help understand their heterogeneity. Src family kinases including Src and Fyn are a group of tyrosine kinases with fatty acylation modifications and/or multiple lysine residues (contributing charge interaction) at their N-terminus. Here, we demonstrate that Src and Fyn kinases were preferentially encapsulated in EVs and fatty acylation including myristoylation and palmitoylation facilitated their encapsulation. Genetic loss or pharmacological inhibition of myristoylation suppressed Src and/or Fyn kinase levels in EVs. Similarly, loss of palmitoylation reduced Fyn levels in EVs. Additionally, mutation of lysine at sites 5, 7, and 9 of Src kinase also inhibited the encapsulation of myristoylated Src into EVs. Knockdown of TSG101, which is a protein involved in the endosomal sorting complexes required for transport (ESCRT) protein complex mediated EVs biogenesis and led to a reduction of Src levels in EVs. In contrast, filipin III treatment, which disturbed the lipid raft structure, reduced Fyn kinase levels, but not Src kinase levels in EVs. Finally, elevated levels of Src protein were detected in the serum EVs of host mice carrying constitutively active Src-mediated prostate tumors in vivo. Collectively, the data suggest that different EVs biogenesis pathways exist and can regulate the encapsulation of specific proteins into EVs. This study provides an understanding of the EVs heterogeneity created by different EVs biogenesis pathways.

Postdiagnosis dietary factors, supplement use and breast cancer prognosis: Global Cancer Update Programme (CUP Global) systematic literature review and meta-analysis

Little is known about how diet might influence breast cancer prognosis. The current systematic reviews and meta-analyses summarise the evidence on postdiagnosis dietary factors and breast cancer outcomes from randomised controlled trials and longitudinal observational studies. PubMed and Embase were searched through 31st October 2021. Random-effects linear dose-response meta-analysis was conducted when at least three studies with sufficient information were available. The quality of the evidence was evaluated by an independent Expert Panel. We identified 108 publications. No meta-analysis was conducted for dietary patterns, vegetables, wholegrains, fish, meat, and supplements due to few studies, often with insufficient data. Meta-analysis was only possible for all-cause mortality with dairy, isoflavone, carbohydrate, dietary fibre, alcohol intake and serum 25-hydroxyvitamin D (25(OH)D), and for breast cancer-specific mortality with fruit, dairy, carbohydrate, protein, dietary fat, fibre, alcohol intake and serum 25(OH)D. The results, with few exceptions, were generally null. There was limited-suggestive evidence that predefined dietary patterns may reduce the risk of all-cause and other causes of death; that isoflavone intake reduces the risk of all-cause mortality (relative risk (RR) per 2 mg/day: 0.96, 95% confidence interval (CI): 0.92-1.02), breast cancer-specific mortality (RR for high vs low: 0.83, 95% CI: 0.64-1.07), and recurrence (RR for high vs low: 0.75, 95% CI: 0.61-0.92); that dietary fibre intake decreases all-cause mortality (RR per 10 g/day: 0.87, 95% CI: 0.80-0.94); and that serum 25(OH)D is inversely associated with all-cause and breast cancer-specific mortality (RR per 10 nmol/L: 0.93, 95% CI: 0.89-0.97 and 0.94, 95% CI: 0.90-0.99, respectively). The remaining associations were graded as limited-no conclusion.

Postdiagnosis body fatness, recreational physical activity, dietary factors and breast cancer prognosis: Global Cancer Update Programme (CUP Global) summary of evidence grading

Based on the Global Cancer Update Programme, formally known as the World Cancer Research Fund/American Institute for Cancer Research Continuous Update Project, we performed systematic reviews and meta-analyses to investigate the association of postdiagnosis body fatness, physical activity and dietary factors with breast cancer prognosis. We searched PubMed and Embase for randomised controlled trials and longitudinal observational studies from inception to 31 October 2021. We calculated summary relative risks (RRs) and 95% confidence intervals (CIs) using random-effects meta-analyses. An independent Expert Panel graded the quality of evidence according to predefined criteria. The evidence on postdiagnosis body fatness and higher all-cause mortality (RR per 5 kg/m2 in body mass index: 1.07, 95% CI: 1.05-1.10), breast cancer-specific mortality (RR: 1.10, 95% CI: 1.06-1.14) and second primary breast cancer (RR: 1.14, 95% CI: 1.04-1.26) was graded as strong (likelihood of causality: probable). The evidence for body fatness and breast cancer recurrence and other nonbreast cancer-related mortality was graded as limited (likelihood of causality: limited-suggestive). The evidence on recreational physical activity and lower risk of all-cause (RR per 10 metabolic equivalent of task-hour/week: 0.85, 95% CI: 0.78-0.92) and breast cancer-specific mortality (RR: 0.86, 95% CI: 0.77-0.96) was judged as limited-suggestive. Data on dietary factors was limited, and no conclusions could be reached except for healthy dietary patterns, isoflavone and dietary fibre intake and serum 25(OH)D concentrations that were graded with limited-suggestive evidence for lower risk of the examined outcomes. Our results encourage the development of lifestyle recommendations for breast cancer patients to avoid obesity and be physically active.

Postdiagnosis body fatness, weight change and breast cancer prognosis: Global Cancer Update Program (CUP global) systematic literature review and meta-analysis

Previous evidence on postdiagnosis body fatness and mortality after breast cancer was graded as limited-suggestive. To evaluate the evidence on body mass index (BMI), waist circumference, waist-hip-ratio and weight change in relation to breast cancer prognosis, an updated systematic review was conducted. PubMed and Embase were searched for relevant studies published up to 31 October, 2021. Random-effects meta-analyses were conducted to estimate summary relative risks (RRs). The evidence was judged by an independent Expert Panel using pre-defined grading criteria. One randomized controlled trial and 225 observational studies were reviewed (220 publications). There was strong evidence (likelihood of causality: probable) that higher postdiagnosis BMI was associated with increased all-cause mortality (64 studies, 32 507 deaths), breast cancer-specific mortality (39 studies, 14 106 deaths) and second primary breast cancer (11 studies, 5248 events). The respective summary RRs and 95% confidence intervals per 5 kg/m2 BMI were 1.07 (1.05-1.10), 1.10 (1.06-1.14) and 1.14 (1.04-1.26), with high between-study heterogeneity (I2  = 56%, 60%, 66%), but generally consistent positive associations. Positive associations were also observed for waist circumference, waist-hip-ratio and all-cause and breast cancer-specific mortality. There was limited-suggestive evidence that postdiagnosis BMI was associated with higher risk of recurrence, nonbreast cancer deaths and cardiovascular deaths. The evidence for postdiagnosis (unexplained) weight or BMI change and all outcomes was graded as limited-no conclusion. The RCT showed potential beneficial effect of intentional weight loss on disease-free-survival, but more intervention trials and well-designed observational studies in diverse populations are needed to elucidate the impact of body composition and their changes on breast cancer outcomes.

Vitamin D and Breast Cancer: Mechanistic Update

The presence of the vitamin D receptor (VDR) in mammary gland and breast cancer has long been recognized, and multiple preclinical studies have demonstrated that its ligand, 1,25-dihydroxyvitamin D (1,25D), modulates normal mammary gland development and inhibits growth of breast tumors in animal models. Vitamin D deficiency is common in breast cancer patients, and some evidence suggests that low vitamin D status enhances the risk for disease development or progression. Although many 1,25D-responsive targets in normal mammary cells and in breast cancers have been identified, validation of specific targets that regulate cell cycle, apoptosis, autophagy, and differentiation, particularly in vivo, has been challenging. Model systems of carcinogenesis have provided evidence that both VDR expression and 1,25D actions change with transformation, but clinical data regarding vitamin D responsiveness of established tumors is limited and inconclusive. Because breast cancer is heterogeneous, the relevant VDR targets and potential sensitivity to vitamin D repletion or supplementation will likely differ between patient populations. Detailed analysis of VDR actions in specific molecular subtypes of the disease will be necessary to clarify the conflicting data. Genomic, proteomic, and metabolomic analyses of in vitro and in vivo model systems are also warranted to comprehensively understand the network of vitamin D-regulated pathways in the context of breast cancer heterogeneity. This review provides an update on recent studies spanning the spectrum of mechanistic (cell/molecular), preclinical (animal models), and translational work on the role of vitamin D in breast cancer. © 2021 The Author. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.