Ceramide-Enriched Membrane Domains Contribute to Targeted and Nontargeted Effects of Radiation through Modulation of PI3K/AKT Signaling in HNSCC Cells

Statins as anti-tumor agents: A paradigm for repurposed drugs

BACKGROUND

Statins, frequently prescribed medications, work by inhibiting the rate-limiting enzyme HMG-CoA reductase (HMGCR) in the mevalonate pathway to reduce cholesterol levels. Due to their multifaceted benefits, statins are being adapted for use as cost-efficient, safe and effective anti-cancer treatments. Several studies have shown that specific types of cancer are responsive to statin medications since they rely on the mevalonate pathway for their growth and survival.

RECENT FINDINGS

Statin are a class of drugs known for their potent inhibition of cholesterol production and are typically prescribed to treat high cholesterol levels. Nevertheless, there is growing interest in repurposing statins for the treatment of malignant neoplastic diseases, often in conjunction with chemotherapy and radiotherapy. The mechanism behind statin treatment includes targeting apoptosis through the BCL2 signaling pathway, regulating the cell cycle via the p53-YAP axis, and imparting epigenetic modulations by altering methylation patterns on CpG islands and histone acetylation by downregulating DNMTs and HDACs respectively. Notably, some studies have suggested a potential chemo-preventive effect, as decreased occurrence of tumor relapse and enhanced survival rate were reported in patients undergoing long-term statin therapy. However, the definitive endorsement of statin usage in cancer therapy hinges on population based clinical studies with larger patient cohorts and extended follow-up periods.

CONCLUSIONS

The potential of anti-cancer properties of statins seems to reach beyond their influence on cholesterol production. Further investigations are necessary to uncover their effects on cancer promoting signaling pathways. Given their distinct attributes, statins might emerge as promising contenders in the fight against tumorigenesis, as they appear to enhance the efficacy and address the limitations of conventional cancer treatments.

Differential Formation of Stress Granules in Radiosensitive and Radioresistant Head and Neck Squamous Cell Carcinoma Cells

PURPOSE

Stress granules (SGs) are cytoplasmic aggregates in which mRNAs and specific proteins are trapped in response to a variety of damaging agents. They participate in the cellular defense mechanisms. Currently, their mechanism of formation in response to ionizing radiation and their role in tumor-cell radiosensitivity remain elusive.

METHODS AND MATERIALS

The kinetics of SG formation was investigated after the delivery of photon irradiation at different doses to head and neck squamous cell carcinoma cell lines with different radiosensitivities and the HeLa cervical cancer cell line (used as reference). In parallel, the response to a canonical inducer of SGs, sodium arsenite, was also studied. Immunolabeling of SG-specific proteins and mRNA fluorescence in situ hybridization enabled SG detection and quantification. Furthermore, a ribopuromycylation assay was used to assess the cell translational status. To determine whether reactive oxygen species were involved in SG formation, their scavenging or production was induced by pharmacologic pretreatment in both SCC61 and SQ20B cells.

RESULTS

Photon irradiation at different doses led to the formation of cytoplasmic foci that were positive for different SG markers. The presence of SGs gradually increased from 30 minutes to 2 hours postexposure in HeLa, SCC61, and Cal60 radiosensitive cells. In turn, the SQ20B and FaDu radioresistant cells did not form SGs. These results indicated a correlation between sensitivity to photon irradiation and SG formation. Moreover, SG formation was significantly reduced by reactive oxygen species scavenging using dimethyl sulfoxide in SCC61 cells, which supported their role in SG formation. However, a reciprocal experiment in SQ20B cells that depleted glutathione using buthionine sulfoximide did not restore SG formation in these cells.

CONCLUSIONS

SGs are formed in response to irradiation in radiosensitive, but not in radioresistant, head and neck squamous cell carcinoma cells. Interestingly, compared with sodium arsenite-induced SGs, photon-induced SGs exhibited a different morphology and cellular localization. Moreover, photon-induced SGs were not associated with the inhibition of translation; rather, they depended on oxidative stress.

The 'stealth-bomber' paradigm for deciphering the tumour response to carbon-ion irradiation

Numerous studies have demonstrated the higher biological efficacy of carbon-ion irradiation (C-ions) and their ballistic precision compared with photons. At the nanometre scale, the reactive oxygen species (ROS) produced by radiation and responsible for the indirect effects are differentially distributed according to the type of radiation. Photon irradiation induces a homogeneous ROS distribution, whereas ROS remain condensed in clusters in the C-ions tracks. Based on this linear energy transfer-dependent differential nanometric ROS distribution, we propose that the higher biological efficacy and specificities of the molecular response to C-ions rely on a 'stealth-bomber' effect. When biological targets are on the trajectories of the particles, the clustered radicals in the tracks are responsible for a 'bomber' effect. Furthermore, the low proportion of ROS outside the tracks is not able to trigger the cellular mechanisms of defence and proliferation. The ability of C-ions to deceive the cellular defence of the cancer cells is then categorised as a 'stealth' effect. This review aims to classify the biological arguments supporting the paradigm of the 'stealth-bomber' as responsible for the biological superiority of C-ions compared with photons. It also explains how and why C-ions will always be more efficient for treating patients with radioresistant cancers than conventional radiotherapy.

High-resolution mass spectrometry assay for quantifying ceramides and dihydroceramides in the cerebrospinal fluid from patients who experienced intracranial infection after craniotomy

Ceramides (CERs) and dihydroceramides (dhCERs) are biologically active lipids involved in cell proliferation, differentiation, and apoptosis, as well as associated with infectious diseases. The concentration of CERs and dhCERs in the cerebrospinal fluid (CSF) could potentially allow the distinction of patients with intracranial infection (ICI) after craniotomy from controls, but the quantification is limited by their ultralow concentrations. Therefore, a novel high performance liquid chromatography-triple-quadrupole/time-of-flight mass spectrometry (HPLC-QTOF-MS) with Sequential Window Acquisition of All Theoretical Fragment Ion Spectra (SWATH) was applied to measure CERs and dhCERs in CSF, since it possesses a higher sensitivity (LLOQ = 0.1 pmol/mL) than the multiple reaction monitoring (MRM) acquisition carried on triple quadrupole (QqQ) MS. This method was validated and applied to CSF samples from patients who experienced postoperative ICI (63 patients) and controls who did not experience it after surgery (62 patients). This assay was linear over the measuring range 0.1-100 pmol/mL for these CER and dhCER species with good accuracy and precision. Elevated CERs and dhCERs were observed in CSF from patients who experienced postoperative ICI. CER 16:0 was found with a clinical sensitivity of 93.65 % and specificity of 87.1 % in distinguishing the 63 patients with ICI from the 62 controls. Therefore, this method could be applied in the detection of CERs and dhCERs in CSF, which were correlated with the presence of ICI.

The Chaperone Protein GRP78 Promotes Survival and Migration of Head and Neck Cancer After Direct Radiation Exposure and Extracellular Vesicle-Transfer

Background and Purpose

Increased levels of the chaperone protein GRP78 have been implicated in poorer outcomes of cancer therapy. We have therefore explored the functional connection between the expression of GRP78 and the development of radioresistance and metastatic behavior in HNSCC.

Material and Methods

The association between gene expression of GRP78 and survival in HNSCC patients was examined using the TCGA database. The influence of ionizing radiation on the GRP78 levels in HNSCC cell lines, their secreted extracellular vesicles (EV) and non-irradiated EV-recipient cells was investigated by Western Blot and FACS. The consequences of chemical inhibition or experimental overexpression of GRP78 on radioresistance and migration of HNSCC cells were analyzed by clonogenic survival and gap closure assays.

Results

Elevated levels of GRP78 RNA in HNSCC correlated with poorer overall survival. Radiation increased GRP78 protein expression on the surface of HNSCC cell lines. Experimental overexpression of GRP78 increased both radioresistance and migratory potential. Chemical inhibition of GRP78 impaired cell migration. EVs were identified as a potential source of increased GRP78 content as elevated levels of surface GRP78 were found in EVs released by irradiated cells. These vesicles transferred GRP78 to non-irradiated recipient cells during co-cultivation.

Conclusions

We have identified the chaperone protein GRP78 as a potential driver of increased radioresistance and motility in HNSCC. The uptake of GRP78-rich EVs originating from irradiated cells may contribute to a poorer prognosis through bystander effects mediated by the transfer of GRP78 to non-irradiated cells. Therefore, we consider the chaperone protein GRP78 to be an attractive target for improving radiotherapy strategies.

Plasma Ceramides Pathophysiology, Measurements, Challenges, and Opportunities

Ceramides are a family of lipid molecules, composed of sphingosine and a fatty acid, and transported by lipoproteins (primarily by low-density lipoproteins) in the bloodstream. They are not only structural lipids, but multifunctional and bioactive molecules with key roles in many important cellular pathways, such as inflammatory processes and apoptosis, representing potential biomarkers of cardiometabolic diseases as well as pharmacological targets. Recent data reported ceramide modulation by diet and aerobic exercise, suggesting nutrients and exercise-targeting sphingolipid pathways as a countermeasure, also in combination with other therapies, for risk and progression of chronic disease prevention and health maintenance. In this review, we focus on the available data regarding remarks on ceramide structure and metabolism, their pathophysiologic roles, and the effect of dietary habit and aerobic exercise on ceramide levels. Moreover, advancements and limitations of lipidomic techniques and simplification attempts to overcome difficulties of interpretation and to facilitate practical applications, such as the proposal of scores, are also discussed.