Local anesthetics and immunotherapy: a novel combination to fight cancer

Intratumoral injection of oncolytic agents such as modified herpes simplex virus T-VEC or local administration of non-viral oncolytic therapies (such as radiofrequency, chemoembolization, cryoablation, or radiotherapy) can activate an anticancer immune response and hence trigger abscopal effects reducing secondary lesions. Preliminary data suggested that oncolytic treatments modulate tumor-infiltrating immune effectors and can be advantageously combined with the immune checkpoint inhibitors. Recent findings indicate that local anesthetics, which are usually used in the clinics to control surgical pain, also possess antineoplastic effects mimicking oncolytic treatments if they are injected into malignant lesions. Moreover, the association of local anesthetics with systemic immune checkpoint inhibition significantly improved overall survival in several preclinical tumor models. This may be explained by direct cytotoxic activity of local anesthetics and additional immune-related abscopal effects. We also summarize the molecular and cellular mechanisms by which the combination of local anesthetics and immunotherapy improves tumor control by the immune system.

Local anesthetics elicit immune-dependent anticancer effects

BACKGROUND

Retrospective clinical trials reported a reduced local relapse rate, as well as improved overall survival after injection of local anesthetics during cancer surgery. Here, we investigated the anticancer effects of six local anesthetics used in clinical practice.

RESULTS

In vitro, local anesthetics induced signs of cancer cell stress including inhibition of oxidative phosphorylation, and induction of autophagy as well as endoplasmic reticulum (ER) stress characterized by the splicing of X-box binding protein 1 (XBP1s) mRNA, cleavage of activating transcription factor 6 (ATF6), phosphorylation of eIF2α and subsequent upregulation of activating transcription factor 4 (ATF4). Both eIF2α phosphorylation and autophagy required the ER stress-relevant eukaryotic translation initiation factor 2 alpha kinase 3 (EIF2AK3, best known as PERK). Local anesthetics also activated two hallmarks of immunogenic cell death, namely, the release of ATP and high-mobility group box 1 protein (HMGB1), yet failed to cause the translocation of calreticulin (CALR) from the ER to the plasma membrane. In vivo, locally injected anesthetics decreased tumor growth and improved survival in several models of tumors established in immunocompetent mice. Systemic immunotherapy with PD-1 blockade or intratumoral injection of recombinant CALR protein, increased the antitumor effects of local anesthetics. Local anesthetics failed to induce antitumor effects in immunodeficient mice or against cancers unable to activate ER stress or autophagy due to the knockout of EIF2AK3/PERK or ATG5, respectively. Uncoupling agents that inhibit oxidative phosphorylation and induce autophagy and ER stress mimicked the immune-dependent antitumor effects of local anesthetics.

CONCLUSION

Altogether, these results indicate that local anesthetics induce a therapeutically relevant pattern of immunogenic stress responses in cancer cells.

Local anesthetics for the Nephrologist

Several specialists in medicine use local anesthetics. In patients with kidney disease, these agents are used during catheter insertions for hemodialysis and peritoneal dialysis, arteriovenous fistula and graft procedures, kidney transplantation, parathyroidectomy, kidney biopsies, and dental and skin procedures. Patients on chronic hemodialysis use a topical application prior to use of needles for arteriovenous fistula cannulation before starting dialysis. They are also used to manage acute and chronic pain conditions, in regional nerve blockade and in multi-modal enhanced recovery protocols. Despite their frequent use by both physicians and patients, data on the use of local anesthetics in patients with kidney impairment are not well reported. This review will summarize the use of local anesthetics in chronic kidney disease, describe their pharmacology and the impact of lower estimated glomerular filtration rate on their pharmacokinetics, and suggest dose regulation in those with kidney dysfunction.

Novel insights on the encapsulation mechanism of PLGA terminal groups on ropivacaine

Currently, the influences of free terminal groups (hydroxyl, carboxyl and ester) of PLGA on encapsulating active pharmaceutical ingredient are relatively ambiguous even though PLGA types were defined as critical quality attributes in vast majority of design of experiment process. In this study, emulsion method combined with premix membrane emulsification technique has been used to encapsulate ropivacaine (RVC), a small molecule local anesthetic in clinical. Based on the narrow particle size distribution, the influences and mechanisms of the terminal groups on properties of ropivacaine loaded microspheres have been investigated in detail. It was found that microspheres prepared by PLGA with hydroxyl or ester groups exhibited lower encapsulation efficiency but faster in vitro release rate than that of carboxyl groups. In the meanwhile, on microcosmic level analysis by quartz crystal microbalance with dissipation, atomic force microscope and confocal laser scanning microscopy, we attributed this distinction to the specific interaction between ropivacaine and different terminal groups. Subsequently, the reaction activation centers were verified by density functional simulation calculation and frontier molecular orbital theory at molecular level. Additionally, pharmacokinetics and pharmacodynamic research of infiltration anesthesia model were performed to compare sustained release ability, duration and intensity of the anesthetic effect in vivo. Finally, potential safety and toxicity were evaluated by the biochemical analysis. This study not only provides a novel mechanism of drug encapsulation process but also potential flexible selections in terms of various anesthesia indications in clinical.

Drug induced mitochondrial dysfunction: Mechanisms and adverse clinical consequences

Several commonly used medications impair mitochondrial function resulting in adverse effects or toxicities. Drug induced mitochondrial dysfunction may be a consequence of increased production of reactive oxygen species, altered mitochondrial permeability transition, impaired mitochondrial respiration, mitochondrial DNA damage or inhibition of beta-oxidation of fatty acids. The clinical manifestation depends on the specific drug and its effect on mitochondria. Given the ubiquitous presence of mitochondria and its central role in cellular metabolism, drug-mitochondrial interactions may manifest clinically as hepatotoxicity, enteropathy, myelosuppression, lipodystrophy syndrome or neuropsychiatric adverse effects, to name a few. The current review focuses on specific drug groups which adversely affect mitochondria, the mechanisms involved and the clinical consequences based on the data available from experimental and clinical studies. Knowledge of these adverse drug-mitochondrial interactions may help the clinicians foresee potential issues in individual patients, prevent adverse drug reactions or alter drug regimens to enhance patient safety.

Interaction of local anesthetics with biomembranes consisting of phospholipids and cholesterol: mechanistic and clinical implications for anesthetic and cardiotoxic effects

Despite a long history in medical and dental application, the molecular mechanism and precise site of action are still arguable for local anesthetics. Their effects are considered to be induced by acting on functional proteins, on membrane lipids, or on both. Local anesthetics primarily interact with sodium channels embedded in cell membranes to reduce the excitability of nerve cells and cardiomyocytes or produce a malfunction of the cardiovascular system. However, the membrane protein-interacting theory cannot explain all of the pharmacological and toxicological features of local anesthetics. The administered drug molecules must diffuse through the lipid barriers of nerve sheaths and penetrate into or across the lipid bilayers of cell membranes to reach the acting site on transmembrane proteins. Amphiphilic local anesthetics interact hydrophobically and electrostatically with lipid bilayers and modify their physicochemical property, with the direct inhibition of membrane functions, and with the resultant alteration of the membrane lipid environments surrounding transmembrane proteins and the subsequent protein conformational change, leading to the inhibition of channel functions. We review recent studies on the interaction of local anesthetics with biomembranes consisting of phospholipids and cholesterol. Understanding the membrane interactivity of local anesthetics would provide novel insights into their anesthetic and cardiotoxic effects.