The oncolytic peptide LTX-315 kills cancer cells through Bax/Bak-regulated mitochondrial membrane permeabilization

Differential scanning calorimetry in drug-membrane interactions

Differential Scanning Calorimetry (DSC) is a central technique in investigating drug - membrane interactions, a critical component of pharmaceutical research. DSC measures the heat difference between a sample of interest and a reference as a function of temperature or time, contributing essential knowledge on the thermally induced phase changes in lipid membranes and how these changes are affected by incorporating pharmacological substances. The manuscript discusses the use of phospholipid bilayers, which can form structures like unilamellar and multilamellar vesicles, providing a simplified yet representative membrane model to investigate the complex dynamics of how drugs interact with and penetrate cellular barriers. The manuscript consolidates data from various studies, providing a comprehensive understanding of the mechanisms underlying drug - membrane interactions, the determinants that influence these interactions, and the crucial role of DSC in elucidating these components. It further explores the interactions of specific classes of drugs with phospholipid membranes, including non-steroidal anti-inflammatory drugs, anticancer agents, natural products with antioxidant properties, and Alzheimer's disease therapeutics. The manuscript underscores the critical importance of DSC in this field and the need for continued research to improve our understanding of these interactions, acting as a valuable resource for researchers.

Chemokine-derived oncolytic peptide induces immunogenic cancer cell death and significantly suppresses tumor growth

Chemokinostatin-1 (CKS1) is a 24-mer peptide originally discovered as an anti-angiogenic peptide derived from the CXCL1 chemokine. Here, we demonstrate that CKS1 acts not only as an anti-angiogenic peptide but also as an oncolytic peptide due to its structural and physical properties. CKS1 induced both necrotic and apoptotic cell death specifically in cancer cells while showing minimal toxicity in non-cancerous cells. Mechanistically, CKS1 disrupted the cell membrane of cancer cells quickly after treatment and activated the apoptotic pathway at later time points. Furthermore, immunogenic molecules were released from CKS1-treated cells, indicating that CKS1 induces immunogenic cell death. CKS1 effectively suppressed tumor growth in vivo. Collectively, these data demonstrate that CKS1 functions as an oncolytic peptide and has a therapeutic potential to treat cancer.

LTX-315 triggers anticancer immunity by inducing MyD88-dependent maturation of dendritic cells

LTX-315 is a synthetic cationic oncolytic peptide with potent anticancer activity but limited toxicity for non-malignant cells. LTX-315 induces both immunogenic tumor cell death and generation of tumor-specific immune responses in multiple experimental tumor models. Given the central role of dendritic cell (DC) maturation in the induction of antigen-specific immunity, we investigated the effect of LTX-315 treatment on the maturation of tumor-infiltrating DCs (TiDCs) and the generation of anti-melanoma immunity. We found that LTX-315 treatment induces the maturation of DCs, both indirectly through the release of cancer cell-derived damage-associated molecular patterns (DAMPs)/alarmins and nucleic acids (DNA and RNA) capable of triggering distinct Toll-like receptor (TLR) signaling, and, directly by activating TLR7. The latter results in the ignition of multiple intracellular signaling pathways that promotes DC maturation, including NF-κB, mitogen activated protein kinases (MAPKs), and inflammasome signaling, as well as increased type 1 interferon production. Critically, the effects of LTX-315 on DCs the consequent promotion of anti-melanoma immunity depend on the cytosolic signal transducer myeloid differentiation response gene 88 (MyD88). These results cast light on the mechanisms by which LTX-315 induces DC maturation and hence elicits anticancer immunity, with important implications for the use of LTX-315 as an anticancer immunotherapeutic.

Chemokine-derived oncolytic peptide induces immunogenic cancer cell death and significantly suppresses tumor growth

Chemokinostatin-1 (CKS1) is a 24-mer peptide originally discovered as an anti-angiogenic peptide derived from the CXCL1 chemokine. Here, we demonstrate that CKS1 acts not only as an anti-angiogenic peptide but also as an oncolytic peptide due to its structural and physical properties. CKS1 induced both necrotic and apoptotic cell death specifically in cancer cells while showing minimal toxicity in non-cancerous cells. Mechanistically, CKS1 disrupted the cell membrane of cancer cells quickly after treatment and activated the apoptotic pathway at later time points. Furthermore, immunogenic molecules were released from CKS1 treated cells, indicating that CKS1 induces immunogenic cell death. CKS1 effectively suppressed tumor growth in vivo. Collectively, these data demonstrate that CKS1 is a unique peptide that functions both as an anti-angiogenic peptide and as an oncolytic peptide and has a therapeutic potential to treat cancer.

ΔM4: Membrane-Active Peptide with Antitumoral Potential against Human Skin Cancer Cells

Peptides have become attractive potential agents due to their affinity to cancer cells. In this work, the biological activity of the peptide ΔM4 against melanoma cancer cell line A375, epidermoid carcinoma cell line A431, and non-tumoral HaCaT cells was evaluated. The cytotoxic MTT assay demonstrates that ΔM4 show five times more activity against cancer than non-cancer cells. The potential membrane effect of ΔM4 was evaluated through lactate dehydrogenase release and Sytox uptake experiments. The results show a higher membrane activity of ΔM4 against A431 in comparison with the A375 cell line at a level of 12.5 µM. The Sytox experiments show that ΔM4 has a direct effect on the permeability of cancer cells in comparison with control cells. Infrared spectroscopy was used to study the affinity of the peptide to membranes resembling the composition of tumoral and non-tumoral cells. The results show that ΔM4 induces a fluidization effect on the tumoral lipid system over 5% molar concentration. Finally, to determine the appearance of phosphatidylserine on the surface of the cell, flow cytometry analyses were performed employing an annexin V-PE conjugate. The results suggest that 12.5 µM of ΔM4 induces phosphatidylserine translocation in A375 and A431 cancer cells. The findings of this study support the potential of ΔM4 as a selective agent for targeting cancer cells. Its mechanism of action demonstrated selectivity, membrane-disrupting effects, and induction of phosphatidylserine translocation.

Immunogenic Cell Death in Hematological Malignancy Therapy

Although the curative effect of hematological malignancies has been improved in recent years, relapse or drug resistance of hematological malignancies will eventually recur. Furthermore, the microenvironment disorder is an important mechanism in the pathogenesis of hematological malignancies. Immunogenic cell death (ICD) is a unique mechanism of regulated cell death (RCD) that triggers an intact antigen-specific adaptive immune response by firing a set of danger signals or damage-associated molecular patterns (DAMPs), which is an immunotherapeutic modality with the potential for the treatment of hematological malignancies. This review summarizes the existing knowledge about the induction of ICD in hematological malignancies and the current research on combining ICD inducers with other treatment strategies for hematological malignancies.

Immunogenic cell death inducer peptides: A new approach for cancer therapy, current status and future perspectives

Immunogenic Cell Death (ICD) is a type of cell death that kills tumor cells by stimulating the adaptive immune response against other tumor cells. ICD depends on the endoplasmic reticulum (ER) stress and the secretion of Damage-Associated Molecular Patterns (DAMP) by the dying tumor cell. DAMPs recruit innate immune cells such as Dendritic Cells (DC), triggering a cancer-specific immune response such as cytotoxic T lymphocytes (CTLs) to eliminate remaining cancer cells. ICD is accompanied by several hallmarks in dying cells, such as surface translocation of ER chaperones, calreticulin (CALR), and extracellular secretion of DAMPs such as high mobility group protein B1 (HMGB1) and adenosine triphosphate (ATP). Therapeutic peptides can kill bacteria and tumor cells thus affecting the immune system. They have high specificity and affinity for their targets, small size, appropriate cell membrane penetration, short half-life, and simple production processes. Peptides are interesting agents for immunomodulation since they may overcome the limitations of other therapeutics. Thus, the development of peptides affecting the TME and active antitumoral immunity has been actively pursued. On the other hand, several peptides have been recently identified to trigger ICD and anti-cancer responses. In the present review, we review previous studies on peptide-induced ICD, their mechanism, their targets, and markers. They include anti-microbial peptides (AMPs), cationic or mitochondrial targeting, checkpoint inhibitors, antiapoptotic inhibitors, and "don't eat me" inhibitor peptides. Also, peptides will be investigated potentially inducing ICD that is divided into ER stressors, ATPase inhibitors, and anti-microbial peptides.

Natural peptides for immunological regulation in cancer therapy: Mechanism, facts and perspectives

Cancer incidence and mortality rates are increasing annually. Treatment with surgery, chemotherapy and radiation therapy (RT) is unsatisfactory because many patients have advanced disease at the initial diagnosis. However, the emergence of immunotherapy promises to be an effective strategy to improve the outcome of advanced tumors. Immune checkpoint antibodies, which are at the forefront of immunotherapy, have had significant success but still leave some cancer patients without benefit. For more cancer patients to benefit from immunotherapy, it is necessary to find new drugs and combination therapeutic strategies to improve the outcome of advanced cancer patients and achieve long-term tumor control or even eradication. Peptides are promising choices for tumor immunotherapy drugs because they have the advantages of low production cost, high sequence selectivity, high tissue permeability, low toxicity and low immunogenicity etc., and the adjuvant matching and technologies like nanotechnology can further optimize the effects of peptides. In this review, we present the current status and mechanisms of research on peptides targeting multiple immune cells (T cells, natural killer (NK) cells, dendritic cells (DCs), tumor-associated macrophages (TAMs), regulatory T cells (Tregs)) and immune checkpoints in tumor immunotherapy; and we summarize the current status of research on peptide-based tumor immunotherapy in combination with other therapies including RT, chemotherapy, surgery, targeted therapy, cytokine therapy, adoptive cell therapy (ACT) and cancer vaccines. Finally, we discuss the current status of peptide applications in mRNA vaccine delivery.

Antimicrobial Peptides Mediate Apoptosis by Changing Mitochondrial Membrane Permeability

Changes in mitochondrial membrane permeability are closely associated with mitochondria-mediated apoptosis. Antimicrobial peptides (AMPs), which have been found to enter cells to exert physiological effects, cause damage to the mitochondria. This paper reviews the molecular mechanisms of AMP-mediated apoptosis by changing the permeability of the mitochondrial membrane through three pathways: the outer mitochondrial membrane (OMM), inner mitochondrial membrane (IMM), and mitochondrial permeability transition pore (MPTP). The roles of AMPs in inducing changes in membrane permeability and apoptosis are also discussed. Combined with recent research results, the possible application prospects of AMPs are proposed to provide a theoretical reference for the development of AMPs as therapeutic agents for human diseases.

Biophysical Characterization of LTX-315 Anticancer Peptide Interactions with Model Membrane Platforms: Effect of Membrane Surface Charge

LTX-315 is a clinical-stage, anticancer peptide therapeutic that disrupts cancer cell membranes. Existing mechanistic knowledge about LTX-315 has been obtained from cell-based biological assays, and there is an outstanding need to directly characterize the corresponding membrane-peptide interactions from a biophysical perspective. Herein, we investigated the membrane-disruptive properties of the LTX-315 peptide using three cell-membrane-mimicking membrane platforms on solid supports, namely the supported lipid bilayer, intact vesicle adlayer, and tethered lipid bilayer, in combination with quartz crystal microbalance-dissipation (QCM-D) and electrochemical impedance spectroscopy (EIS) measurements. The results showed that the cationic LTX-315 peptide selectively disrupted negatively charged phospholipid membranes to a greater extent than zwitterionic or positively charged phospholipid membranes, whereby electrostatic interactions were the main factor to influence peptide attachment and membrane curvature was a secondary factor. Of note, the EIS measurements showed that the LTX-315 peptide extensively and irreversibly permeabilized negatively charged, tethered lipid bilayers that contained high phosphatidylserine lipid levels representative of the outer leaflet of cancer cell membranes, while circular dichroism (CD) spectroscopy experiments indicated that the LTX-315 peptide was structureless and the corresponding membrane-disruptive interactions did not involve peptide conformational changes. Dynamic light scattering (DLS) measurements further verified that the LTX-315 peptide selectively caused irreversible disruption of negatively charged lipid vesicles. Together, our findings demonstrate that the LTX-315 peptide preferentially disrupts negatively charged phospholipid membranes in an irreversible manner, which reinforces its potential as an emerging cancer immunotherapy and offers a biophysical framework to guide future peptide engineering efforts.

Peptide Aggregation Induced Immunogenic Rupture (PAIIR)

Immunogenic cell death (ICD) arises when cells are under stress, and their membranes are damaged. They release damage-associated molecular patterns (DAMPs) that stimulate and drive the type and magnitude of the immune response. In the presence of an antigen, DAMPs ride the longevity and efficacy of antigen-specific immunity. Yet, no tool can induce the controlled ICD with predictable results. A peptide-based tool, [II], is designed that aggregates in the cell and causes cell membrane damage, generates ICD and DAMPs release on various cell types, and hence can act as an adjuvant. An influenza vaccine is prepared by combining [II] with influenza hemagglutinin (HA) subunit antigens. The results show that [II] induced significantly higher HA-specific immunoglobulin G1 (IgG1) and IgG2a antibodies than HA-only immunized mice, while the peptide itself did not elicit antibodies. This paper demonstrates the first peptide-aggregation induced immunogenic rupture (PAIIR) approach as a vaccine adjuvant. PAIIR is a promising adjuvant with a high potential to promote universal protection upon influenza HA vaccination.

Intratumoural administration and tumour tissue targeting of cancer immunotherapies

Immune-checkpoint inhibitors and chimeric antigen receptor (CAR) T cells are revolutionizing oncology and haematology practice. With these and other immunotherapies, however, systemic biodistribution raises safety issues, potentially requiring the use of suboptimal doses or even precluding their clinical development. Delivering or attracting immune cells or immunomodulatory factors directly to the tumour and/or draining lymph nodes might overcome these problems. Hence, intratumoural delivery and tumour tissue-targeted compounds are attractive options to increase the in situ bioavailability and, thus, the efficacy of immunotherapies. In mouse models, intratumoural administration of immunostimulatory monoclonal antibodies, pattern recognition receptor agonists, genetically engineered viruses, bacteria, cytokines or immune cells can exert powerful effects not only against the injected tumours but also often against uninjected lesions (abscopal or anenestic effects). Alternatively, or additionally, biotechnology strategies are being used to achieve higher functional concentrations of immune mediators in tumour tissues, either by targeting locally overexpressed moieties or engineering 'unmaskable' agents to be activated by elements enriched within tumour tissues. Clinical trials evaluating these strategies are ongoing, but their development faces issues relating to the administration methodology, pharmacokinetic parameters, pharmacodynamic end points, and immunobiological and clinical response assessments. Herein, we discuss these approaches in the context of their historical development and describe the current landscape of intratumoural or tumour tissue-targeted immunotherapies.

Polypeptide LTX-315 reverses the cisplatin chemoresistance of ovarian cancer cells via regulating Beclin-1/PI3K/mTOR signaling pathway

OBJECTIVE

Polypeptide LTX-315 induces immunogenic cell death, thus having the potential to improve the effect of anticancer treatment. However, the function of LTX-315 in reversing chemoresistance in ovarian cancer (OC) still remains elusive. Our study aims to decipher the effect of LTX-315 on reversing the chemoresistance of OC cells and explore its mechanism.

METHODS

SKOV3, A2780, SKOV3/DDP, and A2780/DDP cells (cisplatin [DDP]-resistant cells] were treated with different concentrations of LTX-315 (10 and 20 µmol/L), respectively. Cell counting kit-8 assay, Transwell assay, and flow cytometry were used to assess cell viability, migration, invasion, apoptosis rate, and cell cycle of the cells. Western blot was performed to examine the expression of cleaved caspase 3, caspase 3, cleaved Poly (ADP-ribose) polymerase (PARP), PARP, Bax, Bcl-2, Beclin-1, p-Akt, Akt, p-mammalian target of rapamycin (mTOR), and mTOR. Furthermore, OC cells were treated with autophagy inhibitor 3-methyladenine (3-MA), and "rescue experiments" were performed.

RESULTS

DDP-resistant OC cell models were established, and LTX-315 treatment resulted in lower IC₅₀ of DDP. In OC cells treated with LTX-315, the viability, migration, invasion and the expression of Bcl-2 of were repressed, but the apoptotic rate and the expression of cleaved caspase 3, cleaved PARP and Bax were increased, and the cell cycle was arrested. Moreover, LTX-315 promoted Beclin-1 expression level and inhibited p-Akt and p-mTOR expression levels, whereas 3-MA could partially reverse the biological effects of LTX-315 on OC cells.

CONCLUSION

LTX-315 can inhibit the resistance of OC cells to DDP in vitro and plays a role by regulating Beclin-1/phosphatidylinositol-3-kinase/mTOR signaling pathway.

Safety, Antitumor Activity, and T-cell Responses in a Dose-Ranging Phase I Trial of the Oncolytic Peptide LTX-315 in Patients with Solid Tumors

PURPOSE

LTX-315 is a first-in-class, 9-mer membranolytic peptide that has shown potent immunomodulatory properties in preclinical models. We conducted a phase I dose-escalating study of intratumoral LTX-315 administration in patients with advanced solid tumors.

PATIENTS AND METHODS

Thirty-nine patients were enrolled, receiving LTX-315 injections into accessible tumors. The primary objective was to assess the safety and tolerability of this approach, with antitumor and immunomodulatory activity as secondary objectives. Tumor biopsies were collected at baseline and posttreatment for analysis of immunologic parameters.

RESULTS

The most common treatment-related grade 1-2 adverse events were vascular disorders including transient hypotension (18 patients, 46%), flushing (11 patients, 28%), and injection site reactions in 38% of patients. The most common grade 3 LTX-315-related toxicities were hypersensitivity or anaphylaxis (4 patients, 10%). Analysis of immune endpoints in serial biopsies indicated that LTX-315 induces necrosis and CD8⁺ T-cell infiltration into the tumor microenvironment. Sequencing of the T-cell receptor repertoire in peripheral blood identified significant expansion of T-cell clones after treatment, of which 49% were present in available tumor biopsies after treatment, suggesting that they were tumor associated. Substantial volume reduction (≥30%) of injected tumors occurred in 29% of the patients, and 86% (12/14 biopsies) had an increase in intralesional CD8⁺ T cells posttreatment. No partial responses by immune-related response criteria were seen, but evidence of abscopal effect was demonstrated following treatment with LTX-315.

CONCLUSIONS

LTX-315 has an acceptable safety profile, is clinically active, induces changes in the tumor microenvironment and contributes to immune-mediated anticancer activity.

Targeting Cancer Heterogeneity with Immune Responses Driven by Oncolytic Peptides

Accumulating preclinical and clinical evidence indicates that high degrees of heterogeneity among malignant cells constitute a considerable obstacle to the success of cancer therapy. This calls for the development of approaches that operate - or enable established treatments to operate - despite such intratumoral heterogeneity (ITH). In this context, oncolytic peptides stand out as promising therapeutic tools based on their ability to drive immunogenic cell death associated with robust anticancer immune responses independently of ITH. We review the main molecular and immunological pathways engaged by oncolytic peptides, and discuss potential approaches to combine these agents with modern immunotherapeutics in support of superior tumor-targeting immunity and efficacy in patients with cancer.

Peptides that immunoactivate the tumor microenvironment

Cancer immunotherapy has achieved positive clinical outcomes and is revolutionizing cancer treatment. However, cancer immunotherapy has thus far failed to improve outcomes for most "cold tumors", which are characterized by low infiltration of immune cells and immunosuppressive tumor microenvironment. Enhancing the responsiveness of cold tumors to cancer immunotherapy by stimulating the components of the tumor microenvironment is a strategy pursued in the last decade. Currently, most of the agents used to modify the tumor microenvironment are small molecules or antibodies. Small molecules exhibit low affinity and specificity towards the target and antibodies have shortcomings such as poor tissue penetration and high production cost. Peptides may overcome these drawbacks and therefore are promising materials for immunomodulating agents. Here we systematically summarize the currently developed immunoactivating peptides and discuss the potential of peptide therapeutics in cancer immunology.

Synthetic Peptide ΔM4-Induced Cell Death Associated with Cytoplasmic Membrane Disruption, Mitochondrial Dysfunction and Cell Cycle Arrest in Human Melanoma Cells

Melanoma is the most dangerous and lethal form of skin cancer, due to its ability to spread to different organs if it is not treated at an early stage. Conventional chemotherapeutics are failing as a result of drug resistance and weak tumor selectivity. Therefore, efforts to evaluate novel molecules for the treatment of skin cancer are necessary. Antimicrobial peptides have become attractive anticancer agents because they execute their biological activity with features such as a high potency of action, a wide range of targets, and high target specificity and selectivity. In the present study, the antiproliferative activity of the synthetic peptide ΔM4 on A375 human melanoma cells and spontaneously immortalized HaCaT human keratinocytes was investigated. The cytotoxic effect of ΔM4 treatment was evaluated through propidium iodide uptake by flow cytometry. The results indicated selective toxicity in A375 cells and, in order to further investigate the mode of action, assays were carried out to evaluate morphological changes, mitochondrial function, and cell cycle progression. The findings indicated that ΔM4 exerts its antitumoral effects by multitarget action, causing cell membrane disruption, a change in the mitochondrial transmembrane potential, an increase of reactive oxygen species, and cell cycle accumulation in S-phase. Further exploration of the peptide may be helpful in the design of novel anticancer peptides.

Lactoferrin, a multi-functional glycoprotein: Active therapeutic, drug nanocarrier & targeting ligand

Recent progress in protein-based nanomedicine, inspired by the success of Abraxane® albumin-paclitaxel nanoparticles, have resulted in novel therapeutics used for treatment of challenging diseases like cancer and viral infections. However, absence of specific drug targeting, poor pharmacokinetics, premature drug release, and off-target toxicity are still formidable challenges in the clinic. Therefore, alternative protein-based nanomedicines were developed to overcome those challenges. In this regard, lactoferrin (Lf), a glycoprotein of transferrin family, offers a promising biodegradable well tolerated material that could be exploited both as an active therapeutic and drug nanocarrier. This review highlights the major pharmacological actions of Lf including anti-cancer, antiviral, and immunomodulatory actions. Delivery technologies of Lf to improve its pries and enhance its efficacy were also reviewed. Moreover, different nano-engineering strategies used for fabrication of drug-loaded Lf nanocarriers were discussed. In addition, the use of Lf for functionalization of drug nanocarriers with emphasis on tumor-targeted drug delivery was illustrated. Besides its wide application in oncology nano-therapeutics, we discussed the recent advances of Lf-based nanocarriers as efficient platforms for delivery of anti-parkinsonian, anti-Alzheimer, anti-viral drugs, immunomodulatory and bone engineering applications.

Antimicrobial Peptide TP4 Targets Mitochondrial Adenine Nucleotide Translocator 2

Tilapia piscidin (TP) 4 is an antimicrobial peptide derived from Nile tilapia (Oreochromis niloticus), which shows broad-spectrum antibacterial activity and excellent cancer-killing ability in vitro and in vivo. Like many other antimicrobial peptides, TP4 treatment causes mitochondrial toxicity in cancer cells. However, the molecular mechanisms underlying TP4 targeting of mitochondria remain unclear. In this study, we used a pull-down assay on A549 cell lysates combined with LC-MS/MS to discover that TP4 targets adenine nucleotide translocator (ANT) 2, a protein essential for adenine nucleotide exchange across the inner membrane. We further showed that TP4 accumulates in mitochondria and colocalizes with ANT2. Moreover, molecular docking studies showed that the interaction requires Phe1, Ile2, His3, His4, Ser11, Lys14, His17, Arg21, Arg24 and Arg25 residues in TP4 and key residues within the cavity of ANT2. These findings suggest a mechanism by which TP4 may induce mitochondrial dysfunction to disrupt cellular energy metabolism.

Cell cycle progression data on human skin cancer cells with anticancer synthetic peptide LTX-315 treatment

Skin cancer, including melanoma and non-melanoma (NMSC), represents the most common type of malignancy in the white population [1]. The incidence rate of melanoma is increasing worldwide, while the associated mortality remains stable. On the other hand, the incidence of NMSC varies widely [1,2]. Camilio and collaborators recently described the anticancer properties of LTX-315, a novel synthetic anticancer peptide, commercialized as Oncopore™ [3,4]. Despite various studies demonstrating the efficiency of LTX-315 therapy in inducing cancer cell death, the effects on cell cycle progression of this antitumoral peptide are poorly understood. In this research, we present data about the effect of LTX-315 on the cell cycle of two skin cancer cell lines: epidermoid carcinoma cells (A431) and melanoma cells (A375); as well as on an immortalized normal keratinocyte cell line, HaCaT. Additionally, its cytotoxicity on the cells was determined by measuring the uptake of propidium iodide, in order to establish its relationship with cell cycle progression. The analysed data obtained by flow cytometry show different cell cycle distributions in non-tumoral and skin cancer-derived cell lines in response to LTX-315 treatment. Non-tumoral cells showed a sub-G1 peak, while for tumoral cells there was a shift in the G1peak without producing an obvious distant and distinct sub-G1 peak. This data is in accordance with a major decrease in cell viability in non-cancer cells.

LTX-315 sequentially promotes lymphocyte-independent and lymphocyte-dependent antitumor effects

LTX-315 is an oncolytic peptide that has antitumor efficacy in mice grafted with various tumor cell lines and is currently being tested in phase II clinical trials. Here we aimed to further evaluate LTX-315 in conditional genetic mouse models of cancer that typically resist current treatment options and to better understand the drug's mode of action in vivo. We report LTX-315 mediates profound antitumor effects against Braf- and Pten-driven melanoma and delays the progression of Kras- and P53-driven soft tissue sarcoma in mice. Additionally, we show in melanoma that LTX-315 triggers two sequential phases of antitumor response. The first phase of response, which begins within minutes of drug delivery into tumors, is defined by disrupted tumor vasculature and decreased tumor burden and occurs independently of lymphocytes. The second phase of response, which continues over weeks, is defined by long-term alteration of the tumor microenvironment; the changes induced by LTX-315 are most notably characterized by CD8+ T cell infiltration. We further show that these CD8+ T cells are involved in suppressing melanoma outgrowth in mice and report similar CD8+ T cell infiltration following LTX-315 treatment in melanoma and sarcoma patients. Taken together, these findings reveal LTX-315's multiple antitumor effects, including disrupting the tumor vasculature and promoting the conversion of poorly immunogenic tumors into ones that display antitumor T cell immunity.

Tumor lysis with LTX-401 creates anticancer immunity

Local immunotherapies such as the intratumoral injection of oncolytic compounds aim at reinstating and enhancing systemic anticancer immune responses. LTX-315 is a first-in-class, clinically evaluated oncolytic peptide-based local immunotherapy that meets these criteria. Here, we show that LTX-401, yet another oncolytic compound designed for local immunotherapy, depicts a similar safety profile and that sequential local inoculation of LTX-401 was able to cure immunocompetent host from subcutaneous MCA205 and TC-1 cancers. Cured animals exhibited long-term immune memory effects that rendered them resistant to rechallenge with syngeneic tumors. Nevertheless, the local treatment with LTX-401 alone had only limited abscopal effects on secondary contralateral lesions. Anticancer effects resulting from single as well as sequential injections of LTX-401 were boosted in combination with PD-1 and CTLA-4 immune checkpoint blockade (ICB), and sequential LTX-401 treatment combined with double ICB exhibited strong abscopal antineoplastic effects on contralateral tumors underlining the potency of this combination therapy.

Combining the oncolytic peptide LTX-315 with doxorubicin demonstrates therapeutic potential in a triple-negative breast cancer model

Background

Immunochemotherapy, the combined use of immunotherapy and chemotherapy, has demonstrated great promise in several cancers. LTX-315 is an oncolytic peptide with potent immunomodulatory properties designed for the local treatment of solid tumors. By inducing rapid immunogenic cell death through the release of danger-associated molecular pattern molecules (DAMPs), LTX-315 is capable of reshaping the tumor microenvironment, turning “cold” tumors “hot” through a significant increase in tumor-infiltrating lymphocytes.

Methods

We investigated the potential of LTX-315 to be used in combination with standard-of-care chemotherapy (doxorubicin, brand name CAELYX®) against triple-negative breast cancer in an orthotopic 4 T1 mammary fat pad model. Tumor growth curves were compared using one-way ANOVA analysis of variance and Tukey’s multiple comparisons test, and animal survival curves were compared using the log-rank (Mantel-Cox) test. We considered p values ≤0.05 to indicate statistical significance.

Results

We found that LTX-315 displayed a strong additive antitumoral effect when used in combination with CAELYX®, and induced immune-mediated changes in the tumor microenvironment, followed by complete regression in the majority of animals treated. Furthermore, imaging techniques and histological examination showed that the combination induced strong local necrosis, followed by an increase in the infiltration of CD4+ and CD8+ immune cells into the tumor parenchymal tissue.

Conclusions

Our data demonstrate that LTX-315 is a promising combination partner with CAELYX® for the treatment of triple-negative breast cancer.

Autres immunothérapies

ALTERNATIVE IMMUNOTHERAPIES

Monoclonal antibodies targeted at immune checkpoint molecules such as PD-1, PD-L1, and CTLA-4 have revolutionized the field of oncology in a few years. This success is explained by the large spectrum of activity of these therapies (more than 30 different cancer types), and the durability of tumor responses which provide benefits in overall survival for patients. However, a majority of patients do not respond to these treatments and novel immune strategies are needed to overcome resistance to monotherapies. A compelling effort is ongoing with numerous novel immunotherapies being in clinical development. Beyond immunomodulatory antibodies, other immunotherapies (small inhibitory molecules, vaccines, cytokines, viruses, cells) are in clinical trials or have been already approved, not only targeting T-cells but also other immune cells, including innate immune cells. This review summarizes the recent advances obtained with these new therapies.

Oncolysis with DTT-205 and DTT-304 generates immunological memory in cured animals

Oncolytic peptides and peptidomimetics are being optimized for the treatment of cancer by selecting agents with high cytotoxic potential to kill a maximum of tumor cells as well as the capacity to trigger anticancer immune responses and hence to achieve long-term effects beyond therapeutic discontinuation. Here, we report on the characterization of two novel oncolytic peptides, DTT-205 and DTT-304 that both selectively enrich in the lysosomal compartment of cancer cells yet differ to some extent in their cytotoxic mode of action. While DTT-304 can trigger the aggregation of RIP3 in ripoptosomes, coupled to the phosphorylation of MLKL by RIP3, DTT-205 fails to activate RIP3. Accordingly, knockout of either RIP3 or MLKL caused partial resistance against cell killing by DTT-304 but not DTT-205. In contrast, both agents shared common features in other aspects of pro-death signaling in the sense that their cytotoxic effects were strongly inhibited by both serum and antioxidants, partially reduced by lysosomal inhibition with bafilomycin A1 or double knockout of Bax and Bak, yet totally refractory to caspase inhibition. Both DTT-304 and DTT-205 caused the exposure of calreticulin at the cell surface, as well as the release of HMGB1 from the cells. Mice bearing established subcutaneous cancers could be cured by local injection of DTT-205 or DTT-304, and this effect depended on T lymphocytes, as it led to the establishment of a long-term memory response against tumor-associated antigens. Thus, mice that had been cured from cancer by the administration of DTT compounds were refractory against rechallenge with the same cancer type several months after the disappearance of the primary lesion. In summary, DTT-205 and DTT-304 both have the capacity to induce immunotherapeutic oncolysis.

The anticancer peptide RT53 induces immunogenic cell death

In recent years, immunogenic cell death (ICD) has emerged as a revolutionary concept in the development of novel anticancer therapies. This particular form of cell death is able, through the spatiotemporally defined emission of danger signals by the dying cell, to induce an effective antitumor immune response, allowing the immune system to recognize and eradicate malignant cells. To date, only a restricted number of chemotherapeutics can trigger ICD of cancer cells. We previously reported that a peptide, called RT53, spanning the heptad leucine repeat region of the survival protein AAC-11 fused to a penetrating sequence, selectively induces cancer cell death in vitro and in vivo. Interestingly, B16F10 melanoma cells treated by RT53 were able to mediate anticancer effects in a tumor vaccination model. Stimulated by this observation, we investigated whether RT53 might mediate ICD of cancer cells. Here, we report that RT53 treatment induces all the hallmarks of immunogenic cell death, as defined by the plasma membrane exposure of calreticulin, release of ATP and the exodus of high-mobility group box 1 protein (HMGB1) from dying cancer cells, through a non-regulated, membranolytic mode of action. In a prophylactic mouse model, vaccination with RT53-treated fibrosarcomas prevented tumor growth at the challenge site. Finally, local intratumoral injection of RT53 into established cancers led to tumor regression together with T-cell infiltration and the mounting of an inflammatory response in the treated animals. Collectively, our results strongly suggest that RT53 can induce bona fide ICD of cancer cells and illustrate its potential use as a novel antitumor and immunotherapeutic strategy.

Synthesis of breast cancer targeting conjugate of temporin-SHa analog and its effect on pro- and anti-apoptotic protein expression in MCF-7 cells

The frog natural product temporin-SHa (FLSGIVGMLGKLF_amide) is a potent antimicrobial peptide, as is the analog [S3K]SHa. By solid-phase synthesis, we prepared temporin-SHa and several temporin-SHa analogs with one or more D-alanine residues incorporated. The natural product and the analog [G10a]SHa were found to be cytotoxic in mammalian cell lines and induce cell death. To achieve selectivity, we conjugated the analog [G10a]SHa with a breast cancer targeting peptide (BCTP). The resulting peptide temporin [G10a]SHa-BCTP conjugate was selectively active against the MCF-7 breast cancer cell line with no cytotoxicity in NIH-3T3 fibroblasts. Unlike the natural product or [G10a]SHa, the conjugated peptide induced apoptosis, downregulating the expression of Bcl-2 and survivin and upregulating Bax and caspase-3.

Antimicrobial peptides with selective antitumor mechanisms: prospect for anticancer applications

In the last several decades, there have been significant advances in anticancer therapy. However, the development of resistance to cancer drugs and the lack of specificity related to actively dividing cells leading to toxic side effects have undermined these achievements. As a result, there is considerable interest in alternative drugs with novel antitumor mechanisms. In addition to the recent approach using immunotherapy, an effective but much cheaper therapeutic option of pharmaceutical drugs would still provide the best choice for cancer patients as the first line treatment. Ribosomally synthesized cationic antimicrobial peptides (AMPs) or host defense peptides (HDP) display broad-spectrum activity against bacteria based on electrostatic interactions with negatively charged lipids on the bacterial surface. Because of increased proportions of phosphatidylserine (negatively charged) on the surface of cancer cells compared to normal cells, cationic amphipathic peptides could be an effective source of anticancer agents that are both selective and refractory to current resistance mechanisms. We reviewed herein the prospect for AMP application to cancer treatment, with a focus on modes of action of cationic AMPs.

LTX-315: a first-in-class oncolytic peptide that reprograms the tumor microenvironment

The oncolytic peptide LTX-315, which has been de novo designed based on structure–activity relationship studies of host defense peptides, has the ability to kill human cancer cells and induce specific anticancer immune response when injected locally into tumors established in immunocompetent mice. The oncolytic effect of LTX-315 involves perturbation of plasma membrane and the mitochondria with subsequent release of danger-associated molecular pattern molecules, which highlights the ability of LTX-315 to induce complete regression and protective immune responses. Treatment with LTX-315 reprograms the tumor microenvironment by decreasing the local abundance of immunosuppressive cells and by increasing the frequency of effector T cells.

Oncolytic peptide LTX-315 induces an immune-mediated abscopal effect in a rat sarcoma model

LTX 315 is an oncolytic peptide with potent immunological properties. In the present study, we demonstrate that intratumoral treatment with LTX-315 resulted in a complete regression and systemic immune response in a rat fibrosarcoma model. The treatment was T-cell dependent, and also resulted in an abscopal effect as demonstrated by the regression of distal non-treated lesions. Significant infiltration of CD8⁺ T cells was observed in both treated and non-treated lesions, as shown by immunohistochemical and flow cytometric analysis. LTX-315 rapidly killed the cells in vitro with a lytic mode of action followed by the subsequent release of Danger-Associated Molecular Pattern (DAMP) molecules such as HMGB1, ATP and Cytochrome c. Together, our data demonstrate that LTX-315 represents a new approach to cancer immunotherapy, which has the potential as a novel immunotherapeutic agent.

Release of Cytochrome C from Bax Pores at the Mitochondrial Membrane

How cytochrome C is released from the mitochondria to the cytosol via Bax oligomeric pores, a process which is required for apoptosis, is still a mystery. Based on experimentally measured residue-residue distances, we recently solved the first atomic model for Bax oligomeric pores at the membranes using computational approaches. Here, we investigate the mechanism at the microsecond time- and nanometer space- scale using MD simulations. Our free energy landscape depicts a low barrier for the permeation of cytochrome C into the Bax C-terminal mouth, with the pathway proceeding to the inner cavity and exiting via the N-terminal mouth. Release is guided by organized charged/hydrophilic surfaces. The hydrophilicity and negative charge of the pore surface gradually increase along the release pathway from the pore entry to the exit opening. Rather than inert passing of the cytochrome C through a rigid pore, the flexible pore may selectively aid the cytochrome C passage. Once the Bax pore is formed in the membrane, with a low energy barrier, the release of cytochrome C may be readily achieved through energy fluctuations. Collectively, our work provides mechanistic insight in atomic detail into the release of cytochrome C through Bax oligomeric pores.

PINK1, Parkin, and Mitochondrial Quality Control: What can we Learn about Parkinson's Disease Pathobiology?

The first clinical description of Parkinson's disease (PD) will embrace its two century anniversary in 2017. For the past 30 years, mitochondrial dysfunction has been hypothesized to play a central role in the pathobiology of this devastating neurodegenerative disease. The identifications of mutations in genes encoding PINK1 (PTEN-induced kinase 1) and Parkin (E3 ubiquitin ligase) in familial PD and their functional association with mitochondrial quality control provided further support to this hypothesis. Recent research focused mainly on their key involvement in the clearance of damaged mitochondria, a process known as mitophagy. It has become evident that there are many other aspects of this complex regulated, multifaceted pathway that provides neuroprotection. As such, numerous additional factors that impact PINK1/Parkin have already been identified including genes involved in other forms of PD. A great pathogenic overlap amongst different forms of familial, environmental and even sporadic disease is emerging that potentially converges at the level of mitochondrial quality control. Tremendous efforts now seek to further detail the roles and exploit PINK1 and Parkin, their upstream regulators and downstream signaling pathways for future translation. This review summarizes the latest findings on PINK1/Parkin-directed mitochondrial quality control, its integration and cross-talk with other disease factors and pathways as well as the implications for idiopathic PD. In addition, we highlight novel avenues for the development of biomarkers and disease-modifying therapies that are based on a detailed understanding of the PINK1/Parkin pathway.

Iterative Design and in Vivo Evaluation of an Oncolytic Antilymphoma Peptide

Oncolytic peptides represent a promising new strategy within the field of cancer immunotherapy. Here we describe the systematic design and evaluation of short antilymphoma peptides within this paradigm. The peptides were tested in vitro and in vivo to identify a lead compound for further evaluation as novel oncolytic immunotherapeutic. In vitro tests revealed peptides with high activity against several lymphoma types and low cytotoxicity toward normal cells. Treated lymphoma cells exhibited a reduced mitochondrial membrane potential that resulted in an irreversible disintegration of their plasma membranes. No caspase activation or ultrastructural features of apoptotic cell death were observed. One of these peptides, 11, was shown to induce complete tumor regression and protective immunity following intralesional treatment of murine A20 B-lymphomas. Due to its selectivity for lymphoma cells and its ability to induce tumor-specific immune responses, 11 has the potential to be used in intralesional treatment of accessible lymphoma tumors.

The oncolytic compound LTX-401 targets the Golgi apparatus

LTX-401 is an oncolytic amino acid derivative with potential immunogenic properties. Here, we demonstrate that LTX-401 selectively destroys the structure of the Golgi apparatus, as determined by means of ultrastructural analyses and fluorescence microscopic observation of cells expressing Golgi-targeted GFP reporters. Subcellular fractionation followed by mass spectrometric detection revealed that LTX-401 selectively enriched in the Golgi rather than in mitochondria or in the cytosol. The Golgi-dissociating agent Brefeldin A (BFA) reduced cell killing by LTX-401 as it partially inhibited LTX-401-induced mitochondrial release of cytochrome c and the activation of BAX. The cytotoxic effect of LTX-401 was attenuated by the double knockout of BAX and BAK, as well as the mitophagy-enforced depletion of mitochondria, yet was refractory to caspase inhibition. LTX-401 induced all major hallmarks of immunogenic cell death detectable with biosensor cell lines including calreticulin exposure, ATP release, HMGB1 exodus and a type-1 interferon response. Moreover, LTX-401-treated tumors manifested a strong lymphoid infiltration. Altogether these results support the contention that LTX-401 can stimulate immunogenic cell death through a pathway in which Golgi-localized LTX-401 operates upstream of mitochondrial membrane permeabilization.

The oncolytic peptide LTX-315 triggers necrotic cell death

The oncolytic peptide LTX-315 has been designed for killing human cancer cells and turned out to stimulate anti-cancer immune responses when locally injected into tumors established in immunocompetent mice. Here, we investigated the question whether LTX-315 induces apoptosis or necrosis. Transmission electron microscopy or morphometric analysis of chromatin-stained tumor cells revealed that LTX-315 failed to induce apoptotic nuclear condensation and rather induced a necrotic phenotype. Accordingly, LTX-315 failed to stimulate the activation of caspase-3, and inhibition of caspases by means of Z-VAD-fmk was unable to reduce cell killing by LTX-315. In addition, 2 prominent inhibitors of regulated necrosis (necroptosis), namely, necrostatin-1 and cycosporin A, failed to reduce LTX-315-induced cell death. In conclusion, it appears that LTX-315 triggers unregulated necrosis, which may contribute to its pro-inflammatory and pro-immune effects.

The oncolytic peptide LTX-315 overcomes resistance of cancers to immunotherapy with CTLA4 checkpoint blockade

Intratumoral immunotherapies aim at reducing local immunosuppression, as well as reinstating and enhancing systemic anticancer T-cell functions, without inducing side effects. LTX-315 is a first-in-class oncolytic peptide-based local immunotherapy that meets these criteria by inducing a type of malignant cell death that elicits anticancer immune responses. Here, we show that LTX-315 rapidly reprograms the tumor microenvironment by decreasing the local abundance of immunosuppressive Tregs and myeloid-derived suppressor cells and by increasing the frequency of polyfunctional T helper type 1/type 1 cytotoxic T cells with a concomitant increase in cytotoxic T-lymphocyte antigen-4 (CTLA4) and drop in PD-1 expression levels. Logically, in tumors that were resistant to intratumoral or systemic CTLA4 blockade, subsequent local inoculation of LTX-315 cured the animals or caused tumor regressions with abscopal effects. This synergistic interaction between CTLA4 blockade and LTX-315 was reduced upon blockade of the β-chain of the interleukin-2 receptor (CD122). This preclinical study provides a strong rationale for administering the oncolytic peptide LTX-315 to patients who are receiving treatment with the CTLA4 blocking antibody ipilimumab.

Discovery of a 9-mer Cationic Peptide (LTX-315) as a Potential First in Class Oncolytic Peptide

Oncolytic immunotherapies represent a new promising strategy in the treatment of cancer. In our efforts to develop oncolytic peptides, we identified a series of chemically modified 9-mer cationic peptides that were highly effective against both drug-resistant and drug-sensitive cancer cells and with lower toxicity toward normal cells. Among these peptides, LTX-315 displayed superior anticancer activity and was selected as a lead candidate. This peptide showed relative high plasma protein binding abilities and a human plasma half-life of 160 min, resulting in formation of nontoxic metabolites. In addition, the lead candidate demonstrated relatively low ability to inhibit CYP450 enzymes. Collectively these data indicated that this peptide has potential to be developed as a new anticancer agent for intratumoral administration and is currently being evaluated in a phase I/IIa study.

The oncolytic peptide LTX-315 triggers immunogenic cell death

LTX-315 is a cationic amphilytic peptide that preferentially permeabilizes mitochondrial membranes, thereby causing partially BAX/BAK1-regulated, caspase-independent necrosis. Based on the observation that intratumorally injected LTX-315 stimulates a strong T lymphocyte-mediated anticancer immune response, we investigated whether LTX-315 may elicit the hallmarks of immunogenic cell death (ICD), namely (i) exposure of calreticulin on the plasma membrane surface, (ii) release of ATP into the extracellular space, (iii) exodus of HMGB1 from the nucleus, and (iv) induction of a type-1 interferon response. Using a panel of biosensor cell lines and robotized fluorescence microscopy coupled to automatic image analysis, we observed that LTX-315 induces all known ICD characteristics. This conclusion was validated by several independent methods including immunofluorescence stainings (for calreticulin), bioluminescence assays (for ATP), immunoassays (for HMGB1), and RT-PCRs (for type-1 interferon induction). When injected into established cancers, LTX-315 caused a transiently hemorrhagic focal necrosis that was accompanied by massive release of HMGB1 (from close-to-all cancer cells), as well as caspase-3 activation in a fraction of the cells. LTX-315 was at least as efficient as the positive control, the anthracycline mitoxantrone (MTX), in inducing local inflammation with infiltration by myeloid cells and T lymphocytes. Collectively, these results support the idea that LTX-315 can induce ICD, hence explaining its capacity to mediate immune-dependent therapeutic effects.

miR-27a regulates the sensitivity of breast cancer cells to cisplatin treatment via BAK-SMAC/DIABLO-XIAP axis

MicroRNA-27a (miR-27a) has been reported to be an onco-microRNA in multiple cancers promoting tumor growth and metastasis, but the role of miR-27a in regulating the cancer sensitivity to chemotherapy remains unknown. In this study, upregulation of miR-27a was validated by real-time PCR analysis in breast cancer (BC) cell lines and samples of BC patients. A negative correlation between miR-27a and bak was also observed in normal breast epithelial cell line MCF-10A and BC cell lines, suggesting that the bak is the potential target of miR-27a. miR-27a could modulate the growth and metastasis of BC cells. More importantly, we found that knockdown of miR-27a by the specific inhibitors significantly increased the sensitivity of T-47D cells to cisplatin (CDDP) treatment. After further investigation, we indicated that the knockdown of miR-27a promoted the apoptosis via mitochondrial pathway in T-47D cells treated with CDDP, depending on the BAK-second mitochondria-derived activator of caspase/direct IAP binding protein with low pI (SMAC/DIABLO)-X-linked inhibitor of apoptosis (XIAP) axis. Interestingly, we found that the sensitivity of T-47D cells to some other chemotherapeutic agents (5-fluorouracil, doxorubicin, and tumor necrosis factor-related apoptosis-inducing ligand) was also regulated by miR-27a. These findings improve our understanding of the role of miR-27a in breast cancer and might provide a novel strategy for cancer therapy.