Depending on the initiating stimulus, cancer cell death can be immunogenic or non-immunogenic. Inducers of immunogenic cell death (ICD) rely on endoplasmic reticulum (ER) stress for the trafficking of danger signals such as calreticulin (CRT) and ATP. We found that nanosecond pulsed electric fields (nsPEF), an emerging new modality for tumor ablation, cause the activation of the ER-resident stress sensor PERK in both CT-26 colon carcinoma and EL-4 lymphoma cells. PERK activation correlates with sustained CRT exposure on the cell plasma membrane and apoptosis induction in both nsPEF-treated cell lines. Our results show that, in CT-26 cells, the activity of caspase-3/7 was increased fourteen-fold as compared with four-fold in EL-4 cells. Moreover, while nsPEF treatments induced the release of the ICD hallmark HMGB1 in both cell lines, extracellular ATP was detected only in CT-26. Finally, in vaccination assays, CT-26 cells treated with nsPEF or doxorubicin equally impaired the growth of tumors at challenge sites eliciting a protective anticancer immune response in 78% and 80% of the animals, respectively. As compared to CT-26, both nsPEF- and mitoxantrone-treated EL-4 cells had a less pronounced effect and protected 50% and 20% of the animals, respectively. These results support our conclusion that nsPEF induce ER stress, accompanied by bona fide ICD.

Accumulating data indicates that some cancer treatments can restore anticancer immunosurveillance through the induction of tumor immunogenic cell death (ICD). Nanosecond pulsed electric fields (nsPEF) have been shown to efficiently ablate melanoma tumors. In this study we investigated the mechanisms and immunogenicity of nsPEF-induced cell death in B16F10 melanoma tumors. Our data show that in vitro nsPEF (20–200, 200-ns pulses, 7 kV/cm, 2 Hz) caused a rapid dose-dependent cell death which was not accompanied by caspase activation or PARP cleavage. The lack of nsPEF-induced apoptosis was confirmed in vivo in B16F10 tumors. NsPEF also failed to trigger ICD-linked responses such as necroptosis and autophagy. Our results point at necrosis as the primary mechanism of cell death induced by nsPEF in B16F10 cells. We finally compared the antitumor immunity in animals treated with nsPEF (750, 200-ns, 25 kV/cm, 2 Hz) with animals were tumors were surgically removed. Compared to the naïve group where all animals developed tumors, nsPEF and surgery protected 33% (6/18) and 28.6% (4/14) of the animals, respectively. Our data suggest that, under our experimental conditions, the local ablation by nsPEF restored but did not boost the natural antitumor immunity which stays dormant in the tumor-bearing host.

Persistent infection with high risk genotypes of human papillomavirus (HPV) is the cause of cervical cancer, one of most common cancer among woman worldwide, and represents an important risk factor associated with other anogenital and oropharyngeal cancers in men and women. Here, we designed a therapeutic vaccine based on integrase defective lentiviral vector (IDLV) to deliver a mutated nononcogenic form of HPV16 E7 protein, considered as a tumor specific antigen for immunotherapy of HPV‐associated cervical cancer, fused to calreticulin (CRT), a protein able to enhance major histocompatibility complex class I antigen presentation (IDLV‐CRT/E7). Vaccination with IDLV‐CRT/E7 induced a potent and persistent E7‐specific T cell response up to 1 year after a single immunization. Importantly, a single immunization with IDLV‐CRT/E7 was able to prevent growth of E7‐expressing TC‐1 tumor cells and to eradicate established tumors in mice. The strong therapeutic effect induced by the IDLV‐based vaccine in this preclinical model suggests that this strategy may be further exploited as a safe and attractive anticancer immunotherapeutic vaccine in humans.

Gold nanoparticles (AuNPs) have been extensively used in biological applications because of their high biocompatibility, ease of characterization and the extensive knowledge of their surface chemistry. These features make AuNPs readily exploitable for drug delivery and novel diagnostic and therapeutic approaches. In a previous work, we showed that small size (5–10 nm) AuNPs functionalized by sodium 3-mercapto-1-propanesulfonate (3MPS) can be efficiently loaded with the glucocorticoid drug dexamethasone (DXM) and are stable in water and PBS. In the present study, we further analysed the stability and the drug release kinetics of DXM-loaded AuNPs functionalized by sodium 3-mercaptopropane sulfonate (AuNP-3MPS/DXM) and their unconjugated counterparts (AuNP-3MPS) in different biological media. Moreover, we evaluated AuNP-3MPS cyto-compatibility on two mammalian cell lines and tested their specific activity as drug carriers on DXM-sensitive murine and human tumor cells. The colloidal stability of AuNP-3MPS/DXM was significantly increased in all tested culture media, compared with the unconjugated AuNP-3MPS and both AuNP-3MPS formulations which proved non-toxic to biological systems in vitro. Most importantly, we showed that AuNP-3MPS/DXM continuously release bioactive DXM molecules that efficiently induce cell proliferation arrest and apoptotic cell death on a human lymphoma cell line and upregulation of the DXM-inducible programmed cell death-1 (PD-1) molecule on activated mouse T lymphocytes. These data confirm that the AuNP-3MPS/DXM conjugate is a promising system for drug delivery and open interesting perspectives for future in vivo applications.