[Botulinum toxin type-A toxin activity on prostate cancer cell lines]

Bacterial Therapy of Cancer: A Way to the Dustbin of History or to the Medicine of the Future?

Bacteria are the constant companions of the human body throughout its life and even after its death. The history of a human disease such as cancer and the history of microorganisms, particularly bacteria, are believed to closely intertwined. This review was conceived to highlight the attempts of scientists from ancient times to the present day to discover the relationship between bacteria and the emergence or development of tumors in the human body. Challenges and achievements of 21st century science in forcing bacteria to serve for cancer treatment are considered. The future possibilities of bacterial cancer therapy, including the creation of bacterial microrobots, or "bacteriobots", are also discussed.

Microbiome and Prostate Cancer: A Novel Target for Prevention and Treatment

Growing evidence of the microbiome's role in human health and disease has emerged since the creation of the Human Microbiome Project. Recent studies suggest that alterations in microbiota composition (dysbiosis) may play an essential role in the occurrence, development, and prognosis of prostate cancer (PCa), which remains the second most frequent male malignancy worldwide. Current advances in biological technologies, such as high-throughput sequencing, transcriptomics, and metabolomics, have enabled research on the gut, urinary, and intra-prostate microbiome signature and the correlation with local and systemic inflammation, host immunity response, and PCa progression. Several microbial species and their metabolites facilitate PCa insurgence through genotoxin-mediated mutagenesis or by driving tumor-promoting inflammation and dysfunctional immunosurveillance. However, the impact of the microbiome on PCa development, progression, and response to treatment is complex and needs to be fully understood. This review addresses the current knowledge on the host-microbe interaction and the risk of PCa, providing novel insights into the intraprostatic, gut, and urinary microbiome mechanisms leading to PCa carcinogenesis and treatment response. In this paper, we provide a detailed overview of diet changes, gut microbiome, and emerging therapeutic approaches related to the microbiome and PCa. Further investigation on the prostate-related microbiome and large-scale clinical trials testing the efficacy of microbiota modulation approaches may improve patient outcomes while fulfilling the literature gap of microbial-immune-cancer-cell mechanistic interactions.

Recent advances in microbial toxin-related strategies to combat cancer

It is a major concern to treat cancer successfully, due to the distinctive pathophysiology of cancer cells and the gradual manifestation of resistance. Specific action, adverse effects and development of resistance has prompted the urgent requirement of exploring alternative anti-tumour treatment therapies. The naturally derived microbial toxins as a therapy against cancer cells are a promisingly new dimension. Various important microbial toxins such as Diphtheria toxin, Vibrio cholera toxin, Aflatoxin, Patulin, Cryptophycin-55, Chlorella are derived from several bacterial, fungal and algal species. These agents act on different biotargets such as inhibition of protein synthesis, reduction in cell growth, regulation of cell cycle and many cellular processes. Bacterial toxins produce actions primarily by targeting protein moieties and some immunomodulation and few acts through DNA. Fungal toxins appear to have more DNA damaging activity and affect the cell cycle. Algal toxins produce alteration in mitochondrial phosphorylation. In conclusion, microbial toxins and their metabolites appear to have a great potential to provide a promising option for the treatment and management to combat cancer.

Do Bacteria Provide an Alternative to Cancer Treatment and What Role Does Lactic Acid Bacteria Play?

Cancer is one of the leading causes of mortality and morbidity worldwide. According to 2022 statistics from the World Health Organization (WHO), close to 10 million deaths have been reported in 2020 and it is estimated that the number of cancer cases world-wide could increase to 21.6 million by 2030. Breast, lung, thyroid, pancreatic, liver, prostate, bladder, kidney, pelvis, colon, and rectum cancers are the most prevalent. Each year, approximately 400,000 children develop cancer. Treatment between countries vary, but usually includes either surgery, radiotherapy, or chemotherapy. Modern treatments such as hormone-, immuno- and antibody-based therapies are becoming increasingly popular. Several recent reports have been published on toxins, antibiotics, bacteriocins, non-ribosomal peptides, polyketides, phenylpropanoids, phenylflavonoids, purine nucleosides, short chain fatty acids (SCFAs) and enzymes with anticancer properties. Most of these molecules target cancer cells in a selective manner, either directly or indirectly through specific pathways. This review discusses the role of bacteria, including lactic acid bacteria, and their metabolites in the treatment of cancer.

Bioactive Microbial Metabolites in Cancer Therapeutics: Mining, Repurposing, and Their Molecular Targets

The persistence and resurgence of cancer, characterized by abnormal cell growth and differentiation, continues to be a serious public health concern critically affecting public health, social life, and the global economy. Hundreds of putative drug molecules of synthetic and natural origin were approved for anticancer therapy in the last few decades. Although conventional anticancer treatment strategies have promising aspects, several factors such as their limitations, drug resistance, and side effects associated with them demand more effort in repositioning or developing novel therapeutic regimens. The rich heritage of microbial bioactive components remains instrumental in providing novel avenues for cancer therapeutics. Actinobacteria, Firmicutes, and fungi have a plethora of bioactive compounds, which received attention for their efficacy in cancer treatment targeting different pathways responsible for abnormal cell growth and differentiation. Yet the full potential remains underexplored to date, and novel compounds from such microbes are reported regularly. In addition, the advent of computational tools has further augmented the mining of microbial secondary metabolites and identifying their molecular targets in cancer cells. Furthermore, the drug-repurposing strategy has facilitated the use of approved drugs of microbial origin in regulating cancer cell growth and progression. The wide diversity of microbial compounds, different mining approaches, and multiple modes of action warrant further investigations on the current status of microbial metabolites in cancer therapeutics. Hence, in this review, we have critically discussed the untapped potential of microbial products in mitigating cancer progression. The review also summarizes the impact of drug repurposing in cancer therapy and discusses the novel avenues for future therapeutic drug development against cancer.

Subtilisin from Bacillus amyloliquefaciens induces apoptosis in breast cancer cells through ubiquitin-proteasome-mediated tubulin degradation

To search for novel proteases from environmental isolates which can induce apoptosis in cancer cells, we have purified subtilisin from Bacillus amyloliquefaciens and studied its anti-cancer properties. Subtilisin induced apoptosis in colon (HT29) and breast (MCF7) cancer cells but showed no effect on mouse peritoneal macrophages and normal breast cells (MCF10A). Western blot analysis showed that Bax, Bcl-2 level remained unchanged but tubulin level decreased significantly. Subtilisin does not induce the intrinsic pathway of apoptosis, rather it induced tubulin degradation in MCF-7 cells, whereas in normal cells (MCF-10A) tubulin degradation was not observed. Subtilisin activates ubiquitination and proteasomal-mediated tubulin degradation which was completely restored in presence of proteasome inhibitor MG-132. We further observed PARKIN, one of the known E3-ligase, is overexpressed and interacts with tubulin in subtilisin treated cells. Knockdown of PARKIN effectively downregulates ubiquitination and inhibits degradation of tubulin. PARKIN activation and tubulin degradation lead to ER-stress which in turn activates caspase-7 and PARP cleavage, thus guiding the subtilisin treated cells towards apoptosis. To our knowledge this is the first report of subtilisin induced apoptosis in cancer cells by proteasomal degradation of tubulin.

Model-Based Anticancer Effect of Botulinum Neurotoxin Type A1 on Syngeneic Melanoma Mice

In recent, Botulinum Neurotoxin A1 (BoNT/A1) has been suggested as a potential anticancer agent due to neuronal innervation in tumor cells. Although potential BoNT/A1's mechanism of action for the tumor suppression has been gradually revealed so far, there were no reports to figure out the exposure-response relationships because of the difficulty of its quantitation in the biological matrix. The main objectives of this study were to measure the anticancer effect of BoNT/A1 using a syngeneic mouse model transplanted with melanoma cells (B16-F10) and developed a kinetic-pharmacodynamic (K-PD) model for quantitative exposure-response evaluation. To overcome the lack of exposure information, the K-PD model was implemented by the virtual pharmacokinetic compartment link to the pharmacodynamic compartment of Simeoni's tumor growth inhibition model and evaluated using curve-fitting for the tumor growth-time profile after intratumoral injection of BoNT/A1. The final K-PD model was adequately explained for a pattern of tumor growth depending on represented exposure parameters and simulation studies were conducted to determine the optimal dose under various scenarios considering dose strength and frequency. The optimal dose range and regimen of ≥13.8 units kg^-1 once a week or once every 3 days was predicted using the final model in B16-F10 syngeneic model and it was demonstrated with an extra in-vivo experiment. In conclusion, the K-PD model of BoNT/A1 was well developed to optimize the dosing regimen for evaluation of anticancer effect and this approach could be expandable to figure out quantitative interpretation of BoNT/A1's efficacy in various xenograft and/or syngeneic models.

Botulinum toxin in cancer therapy-current perspectives and limitations

Abstract

Different serotypes of botulinum toxins (BoNTs) act upon different types of SNARE proteins. This property is used in aesthetic medicine to treat certain eye disorders such as crossed eyes (strabismus) and uncontrolled blinking (blepharospasm), to treat muscle spasms or movement disorders, and, for the two last decades, more and more often, to provide support in cancer therapy, especially so as to obtain analgesic effects upon spastic conditions. The limited literature data also suggests that the addition of BoNTs to the culture of cancer cell lines reduces cell growth, and mitotic activity, and promotes their apoptosis. BoNTs have several advantages that can be emphasized: BoNTs act on both perfusion and oxygenation; moreover, BoNTs are considered to be safe and free of systemic side effects upon administration. Recently, advances in molecular biology techniques have allowed a wide variety of novel BoNT constructs with alternative functions. These constructs could be assessed as potential new classes of anti-cancer drugs. This creates new potential perspectives in the wider use of non-toxic modified BoNT constructs in cancer therapy. In the light of the mentioned premises and existing literature reports, the aim of this review is to summarize current data and reports considering BoNT use in cancer therapy.

Key points

•Botulinum toxin (BoNTs) may be useful in cancer treatment.

•Botulinum toxin can serve as an analgesic after cancer radiotherapy.

•Botulinum toxin has the ability to inhibit tumor growth and promote apoptosis of neoplastic cells.

Prostate Microbiota and Prostate Cancer: A New Trend in Treatment

Although the incidence and mortality of prostate cancer have gradually begun to decline in the past few years, it is still one of the leading causes of death from malignant tumors in the world. The occurrence and development of prostate cancer are affected by race, family history, microenvironment, and other factors. In recent decades, more and more studies have confirmed that prostate microflora in the tumor microenvironment may play an important role in the occurrence, development, and prognosis of prostate cancer. Microorganisms or their metabolites may affect the occurrence and metastasis of cancer cells or regulate anti-cancer immune surveillance. In addition, the use of tumor microenvironment bacteria in interventional targeting therapy of tumors also shows a unique advantage. In this review, we introduce the pathway of microbiota into prostate cancer, focusing on the mechanism of microorganisms in tumorigenesis and development, as well as the prospect and significance of microorganisms as tumor biomarkers and tumor prevention and treatment.

The Mechanisms of Action of Botulinum Toxin Type A in Nociceptive and Neuropathic Pathways in Cancer Pain

BACKGROUND

Botulinum toxin type A (BoNT-A) is widely employed for cosmetic purposes and in the treatment of certain diseases such as strabismus, hemifacial spasm and focal dystonia among others. BoNT-A effect mainly acts at the muscular level by inhibiting the release of acetylcholine at presynaptic levels consequently blocking the action potential in the neuromuscular junction. Despite the great progress in approval and pharmaceutical usage, improvement in displacing BoNT-A to other pathologies has remained very limited. Patients under diagnosis of several types of cancer experience pain in a myriad of ways; it can be experienced as hyperalgesia or allodynia, and the severity of the pain depends, to some degree, on the place where the tumor is located. Pain relief in patients diagnosed with cancer is not always optimal, and as the disease progresses, transition to more aggressive drugs, like opioids is sometimes unavoidable. In recent years BoNT-A employment in cancer has been explored, as well as an antinociceptive drug; experiments in neuropathic, inflammatory and acute pain have been carried out in animal models and humans. Although its mechanism has not been fully known, evidence has shown that BoNT-A inhibits the secretion of pain mediators (substance P, Glutamate, and calcitonin gene related protein) from the nerve endings and dorsal root ganglion, impacting directly on the nociceptive transmission through the anterolateral and trigeminothalamic systems.

AIM

The study aimed to collect available literature regarding molecular, physiological and neurobiological evidence of BoNT-A in cancer patients suffering from acute, neuropathic and inflammatory pain in order to identify possible mechanisms of action in which the BoNT-A could impact positively in pain treatment.

CONCLUSION

BoNT-A could be an important neo-adjuvant and coadjuvant in the treatment of several types of cancer, to diminish pro-tumor activity and secondary pain.

Microbes as Medicines: Harnessing the Power of Bacteria in Advancing Cancer Treatment

Conventional anti-cancer therapy involves the use of chemical chemotherapeutics and radiation and are often non-specific in action. The development of drug resistance and the inability of the drug to penetrate the tumor cells has been a major pitfall in current treatment. This has led to the investigation of alternative anti-tumor therapeutics possessing greater specificity and efficacy. There is a significant interest in exploring the use of microbes as potential anti-cancer medicines. The inherent tropism of the bacteria for hypoxic tumor environment and its ability to be genetically engineered as a vector for gene and drug therapy has led to the development of bacteria as a potential weapon against cancer. In this review, we will introduce bacterial anti-cancer therapy with an emphasis on the various mechanisms involved in tumor targeting and tumor suppression. The bacteriotherapy approaches in conjunction with the conventional cancer therapy can be effective in designing novel cancer therapies. We focus on the current progress achieved in bacterial cancer therapies that show potential in advancing existing cancer treatment options and help attain positive clinical outcomes with minimal systemic side-effects.

Bacteria and bacterial anticancer agents as a promising alternative for cancer therapeutics

Cancer is the leading cause of deaths worldwide, though significant advances have occurred in its diagnosis and treatment. The development of resistance against chemotherapeutic agents, their side effects, and non-specific toxicity urge to screen for the novel anticancer agent. Hence, the development of novel anticancer agents with a new mechanism of action has become a major scientific challenge. Bacteria and bacterially produced bioactive compounds have recently emerged as a promising alternative for cancer therapeutics. Bacterial anticancer agents such as antibiotics, bacteriocins, non-ribosomal peptides, polyketides, toxins, etc. These are adopted different mechanisms of actions such as apoptosis, necrosis, reduced angiogenesis, inhibition of translation and splicing, and obstructing essential signaling pathways to kill cancer cells. Also, live tumor-targeting bacteria provided a unique therapeutic alternative for cancer treatment. This review summarizes the anticancer properties and mechanism of actions of the anticancer agents of bacterial origin and antitumor bacteria along with their possible future applications in cancer therapeutics.

Clostridium botulinum neurotoxin A induces apoptosis and mitochondrial oxidative stress via activation of TRPM2 channel signaling pathway in neuroblastoma and glioblastoma tumor cells

BACKGROUND

The Clostridium botulinum neurotoxin A (BTX) is a polypeptide produced by the bacterium Clostridium botulinum. In addition to the therapeutic actions of BTX against pain and neuromuscular disorders, it is acted as anticancerogenic effect through excessive mitochondria reactive oxygen species (ROS) production, apoptosis, and caspase activations. The TRPM2 cation channel is activated by ROS and ADP-ribose and it is inhibited by 2-aminoethyl diphenylborinate (2-APB) and N-(p-amylcinnamoyl) anthranilic acid (ACA). The aim of this study was an investigation of involvement BTX-induced TRPM2 activation on the mitochondria ROS production and apoptosis levels in the DBTRG glioblastoma and SH-SY5Y neuroblastoma tumor cells.

MATERIAL AND METHODS

The DBTRG and SH-SY5Y cells were divided into four groups as control, BTX (5 IU for 24 h), BTX + ACA (25 µM for 30 min), and BTX + 2-APB (100 µM for 30 min).

RESULTS

BTX treatment increased mitochondrial membrane depolarization (JC-1), mitochondrial (MitROS), and cytosolic (DHR123 and DCFH-DA) ROS levels, neuronal death (propidium iodide/Hoechst) rate, caspase -3, and -9 levels in the BTX group, although their levels were diminished in the BTX + ACA and BTX + 2-APB groups. The ACA and 2-APB treatments also decreased BTX-induced increase of TRPM2 cytosolic free Ca²⁺ concentration in the glioblastoma and neuroblastoma cell death.

CONCLUSIONS

BTX caused neuroblastoma and glioblastoma tumor cell death by activating the mitochondria ROS production via stimulating TRPM2 signaling pathways. BTX may serve as a potential therapeutic target via activation of TRPM2 for treating glioblastoma and neuroblastoma cells.

Botulinum Neurotoxins and Cancer-A Review of the Literature

Botulinum neurotoxins (BoNT) possess an analgesic effect through several mechanisms including an inhibition of acetylcholine release from the neuromuscular junction as well as an inhibition of specific pain transmitters and mediators. Animal studies have shown that a peripheral injection of BoNTs impairs the release of major pain transmitters such as substance P, calcitonin gene related peptide (CGRP) and glutamate from peripheral nerve endings as well as peripheral and central neurons (dorsal root ganglia and spinal cord). These effects lead to pain relief via the reduction of peripheral and central sensitization both of which reflect important mechanisms of pain chronicity. This review provides updated information about the effect of botulinum toxin injection on local pain caused by cancer, painful muscle spasms from a remote cancer, and pain at the site of cancer surgery and radiation. The data from the literature suggests that the local injection of BoNTs improves muscle spasms caused by cancerous mass lesions and alleviates the post-operative neuropathic pain at the site of surgery and radiation. It also helps repair the parotid damage (fistula, sialocele) caused by facial surgery and radiation and improves post-parotidectomy gustatory hyperhidrosis. The limited literature that suggests adding botulinum toxins to cell culture slows/halts the growth of certain cancer cells is also reviewed and discussed.

Anti-cancer Potential of Captopril and Botulinum Toxin Type-A and Associated p53 Gene Apototic Stimulating Activity

Mutational inactivation of p53 is a key player in the development of human cancer. Thus, retrieving the tumor suppressor activity of p53 gene is considered a novel strategy in cancer therapy. Current study aimed to investigate the anti-cancer potentials of botulinum toxin type-A (BTX-A) and captopril as a trial to shed light on effective anti-cancer therapy with lower side effects. Cytotoxic effect of captopril and BTX-A was determined using MTT assay against colon (HCT116) and prostate cancer (DU145) cells compared to their effect on normal vero cells. Anti-proliferation assay and anti-metastatic effect were carried out using trypan blue exclusion method and wound scratch migration test, respectively. The ability of test drugs to induce apoptosis in cancer cells was examined using real time PCR. Recorded data revealed that captopril exhibited a statistically significant cytotoxicity (P < 0.05) to cancer cells (IC50 values of 1.5 and 1.2 mg/mL) with much lower toxicity to normal cells. At the same time, IC50 values post BTX-A treatment were 7.2 and 6.4 U/mL for HCT116 and DU145 cells, respectively without any toxicity to vero cells. Both drugs showed inhibitory potentials on cellular proliferation and the ability of cancer cells to migrate in scratched monolayers was obviously inhibited along with increasing their concentrations. P53 expression levels in captopril and BTX-A treated DU145 cells were elevated by 4 and 2.5 folds, respectively, while lower level of apoptosis induction in HCT116 cells was observed. Accordingly, BTX-A and captopril could present potential anti-cancer candidates through triggering cancer cells towards self-destruction.

Anticancer Activity of Bacterial Proteins and Peptides

Despite much progress in the diagnosis and treatment of cancer, tumour diseases constitute one of the main reasons of deaths worldwide. The side effects of chemotherapy and drug resistance of some cancer types belong to the significant current therapeutic problems. Hence, searching for new anticancer substances and medicines are very important. Among them, bacterial proteins and peptides are a promising group of bioactive compounds and potential anticancer drugs. Some of them, including anticancer antibiotics (actinomycin D, bleomycin, doxorubicin, mitomycin C) and diphtheria toxin, are already used in the cancer treatment, while other substances are in clinical trials (e.g., p28, arginine deiminase ADI) or tested in in vitro research. This review shows the current literature data regarding the anticancer activity of proteins and peptides originated from bacteria: antibiotics, bacteriocins, enzymes, nonribosomal peptides (NRPs), toxins and others such as azurin, p28, Entap and Pep27anal2. The special attention was paid to the still poorly understood active substances obtained from the marine sediment bacteria. In total, 37 chemical compounds or groups of compounds with antitumor properties have been described in the present article.

The non-neuronal and nonmuscular effects of botulinum toxin: an opportunity for a deadly molecule to treat disease in the skin and beyond

There is growing evidence that botulinum neurotoxins (BoNTs) exhibit biological effects on various human cell types with a host of associated clinical implications. This review aims to provide an update on the non-neuronal and nonmuscular effects of botulinum toxin. We critically analysed recent reports on the structure and function of cellular signalling systems subserving biological effects of BoNTs. The BoNT receptors and intracellular targets are not unique for neurotransmission. They have been found in both neuronal and non-neuronal cells, but there are differences in how BoNT binds to, and acts on, neuronal vs. non-neuronal cells. The non-neuronal cells that express one or more BoNT/A-binding proteins, and/or cleavage target synaptosomal-associated protein 25, include: epidermal keratinocytes; mesenchymal stem cells from subcutaneous adipose; nasal mucosal cells; urothelial cells; intestinal, prostate and alveolar epithelial cells; breast cell lines; neutrophils; and macrophages. Serotype BoNT/A can also elicit specific biological effects in dermal fibroblasts, sebocytes and vascular endothelial cells. Nontraditional applications of BoNT have been reported for the treatment of the following dermatological conditions: hyperhidrosis, Hailey-Hailey disease, Darier disease, inversed psoriasis, aquagenic palmoplantar keratoderma, pachyonychia congenita, multiple eccrine hydrocystomas, eccrine angiomatous hamartoma, eccrine sweat gland naevi, congenital eccrine naevus, Raynaud phenomenon and cutaneous leiomyomas. Experimental studies have demonstrated the ability of BoNT/A to protect skin flaps, facilitate wound healing, decrease thickness of hypertrophic scars, produce an anti-ageing effect, improve a mouse model of psoriasiform dermatitis, and have also revealed extracutaneous effects of BoNT arising from its anti-inflammatory and anticancer properties. BoNTs have a much wider range of applications than originally understood, and the individual cellular responses to the cholinergic impacts of BoNTs could provide fertile ground for future studies.

Botulinum toxin type A affects the transcriptome of cell cultures derived from muscle biopsies of controls and spastic patients

Botulin toxin (BTX) is widely used for treating skeletal muscle spasticity. Experimental reports on BTX treatment were mainly focused on the neuromuscular junction, while relatively little is known about toxin effects on the muscle cell itself. We investigated possible impact of BTX type A on skeletal muscle cell transcriptome by microarray analysis in muscle-derived cell cultures (fibroblasts, myoblasts and myotubes) from controls and spastic patients, and results were then validated at transcript and protein level. BTX-A treatment of control cells induced major changes in the myogenic component of the transcriptome, whereas the same treatment had a negligible effect in the fibrogenic component. BTX-A treatment of cell cultures from spastic patients induced an increased number of genes differentially expressed both in the fibrogenic and myogenic components. Specifically, BTX-A had a major effect on cell cycle-related genes in myoblasts, on muscle contraction-related genes in myotubes, and on extracellular matrix-related genes in fibroblasts from spastic patients. Our findings show that in vitro BTX-A treatment differentially affects transcript expression in muscle cells from spastic patients compared to those from controls suggesting a direct effect of BTX-A on muscle-specific functional pathways.

Botulinum neurotoxin type A: Actions beyond SNAP-25?

Botulinum neurotoxin type A (BoNT/A), the most potent toxin known in nature which causes botulism, is a commonly used therapeutic protein. It prevents synaptic vesicle neuroexocytosis by proteolytic cleavage of synaptosomal-associated protein of 25 kDa (SNAP-25). It is widely believed that BoNT/A therapeutic or toxic actions are exclusively mediated by SNAP-25 cleavage. On the other hand, in vitro and in vivo findings suggest that several BoNT/A actions related to neuroexocytosis, cell cycle and apoptosis, neuritogenesis and gene expression are not necessarily mediated by this widely accepted mechanism of action. In present review we summarize the literature evidence which point to the existence of unknown BoNT/A molecular target(s) and modulation of unknown signaling pathways. The effects of BoNT/A apparently independent of SNAP-25 occur at similar doses/concentrations known to induce SNAP-25 cleavage and prevention of neurotransmitter release. Accordingly, these effects might be pharmacologically significant. Potentially the most interesting are observations of antimitotic and antitumor activity of BoNT/A. However, the exact mechanisms require further studies.

Botulinum toxin A, brain and pain

Botulinum neurotoxin type A (BoNT/A) is one of the most potent toxins known and a potential biological threat. At the same time, it is among the most widely used therapeutic proteins used yearly by millions of people, especially for cosmetic purposes. Currently, its clinical use in certain types of pain is increasing, and its long-term duration of effects represents a special clinical value. Efficacy of BoNT/A in different types of pain has been found in numerous clinical trials and case reports, as well as in animal pain models. However, sites and mechanisms of BoNT/A actions involved in nociception are a matter of controversy. In analogy with well known neuroparalytic effects in peripheral cholinergic synapses, presently dominant opinion is that BoNT/A exerts pain reduction by inhibiting peripheral neurotransmitter/inflammatory mediator release from sensory nerves. On the other hand, growing number of behavioral and immunohistochemical studies demonstrated the requirement of axonal transport for BoNT/A's antinociceptive action. In addition, toxin's enzymatic activity in central sensory regions was clearly identified after its peripheral application. Apart from general pharmacology, this review summarizes the clinical and experimental evidence for BoNT/A antinociceptive activity and compares the data in favor of peripheral vs. central site and mechanism of action. Based on literature review and published results from our laboratory we propose that the hypothesis of peripheral site of BoNT/A action is not sufficient to explain the experimental data collected up to now.