Heat-induced apoptosis via caspase-3 activation in tumour cells carrying mutant p53

Acute heat stress-indued apoptosis in mouse skeletal muscle is not associated with alteration of glutamine homeostasis

We previously demonstrated that exposing mice to heat causes functional and ultrastructural mitochondrial alterations and apoptosis in skeletal muscle. Emerging evidence indicates that glutamine (Gln) deprivation may increase cell susceptibility to apoptosis whereas Gln supplementation may protect cells against heat stress. In this study, we investigated the effect of short-term Gln treatment on heat-induced changes in mouse skeletal muscle. Male mice received vehicle, low-dose Gln (100 mg/kg/d) or high-dose Gln (300 mg/kg/d) through daily gavage for 10 days before a heat exposure test. During heat exposure, mice displayed a hyperthermic response and no significant differences in peak core body temperature were noted across the three groups. Neither heat exposure nor pretreatment with low-dose or high-dose Gln significantly affected Gln concentrations in plasma and gastrocnemius muscles. Heat-exposed mice had significantly higher caspase 3/7 levels in gastrocnemius muscle compared to unexposed controls. Heat exposure significantly increased ROS production and mitochondrial fragmentation and decreased mitochondrial membrane potential in flexor digitorum brevis muscle. These changes were not affected by low- or high-dose Gln pretreatment. Together, acute heat stress did not disrupt Gln homeostasis in mouse skeletal muscle and Gln supplementation did not protect mouse skeletal muscle against heat-induced injury. The results of this study do not support a role of Gln in heat-induced skeletal muscle apoptosis.

Hyperthermia induces therapeutic effectiveness and potentiates adjuvant therapy with non-targeted and targeted drugs in an in vitro model of human malignant melanoma

In the present study, we have aimed to characterize the intrinsic, extrinsic and ER-mediated apoptotic induction by hyperthermia in an in vitro model of human malignant melanoma and furthermore, to evaluate its therapeutic effectiveness in an adjuvant therapeutic setting characterized by combinational treatments with non-targeted (Dacarbazine & Temozolomide) and targeted (Dabrafenib & Vemurafenib) drugs. Overall, our data showed that both low (43 °C) and high (45 °C) hyperthermic exposures were capable of inducing cell death by activating all apoptotic pathways but in a rather distinct manner. More specifically, low hyperthermia induced extrinsic and intrinsic apoptotic pathways both of which activated caspase 6 only as opposed to high hyperthermia which was mediated by the combined effects of caspases 3, 7 and 6. Furthermore, significant involvement of the ER was evident (under both hyperthermic conditions) suggesting its role in regulating apoptosis via activation of CHOP. Our data revealed that while low hyperthermia activated IRE-1 and ATF6 only, high hyperthermia induced activation of PERK as well suggesting that ultimately these ER stress sensors can lead to the induction of CHOP via different pathways of transmitted signals. Finally, combinational treatment protocols revealed an effect of hyperthermia in potentiating the therapeutic effectiveness of non-targeted as well as targeted drugs utilized in the clinical setting. Overall, our findings support evidence into hyperthermia's therapeutic potential in treating human malignant melanoma by elucidating the underlying mechanisms of its complex apoptotic induction.

Design and Generation of Humanized Single-chain Fv Derived from Mouse Hybridoma for Potential Targeting Application

Single-chain variable antibody fragments (scFvs) are attractive candidates for targeted immunotherapy in several human diseases. In this study, a concise humanization strategy combined with an optimized production method for humanizing scFvs was successfully employed. Two antibody clones, one directed against the hemagglutinin of H5N1 influenza virus, the other against EpCAM, a cancer biomarker, were used to demonstrate the validity of the method. Heavy chain (VH) and light chain (VL) variable regions of immunoglobulin genes from mouse hybridoma cells were sequenced and subjected to the construction of mouse scFv 3-D structure. Based on in silico modeling, the humanized version of the scFv was designed via complementarity-determining region (CDR) grafting with the retention of mouse framework region (FR) residues identified by primary sequence analysis. Root-mean-square deviation (RMSD) value between mouse and humanized scFv structures was calculated to evaluate the preservation of CDR conformation. Mouse and humanized scFv genes were then constructed and expressed in Escherichia coli. Using this method, we successfully generated humanized scFvs that retained the targeting activity of their respective mouse scFv counterparts. In addition, the humanized scFvs were engineered with a C-terminal cysteine residue (hscFv-C) for site-directed conjugation for use in future targeting applications. The hscFv-C expression was extensively optimized to improve protein production yield. The protocol yielded a 20-fold increase in production of hscFv-Cs in E. coli periplasm. The strategy described in this study may be applicable in the humanization of other antibodies derived from mouse hybridoma.

Identification and functional analysis of the rat caspase-3 gene promoter

Caspase-3 is the major effector in apoptosis triggered by various stimuli. Previous studies demonstrated a significant increase in transcriptional activity of the caspase-3 gene during neuronal apoptosis. Recent findings suggest that differential expression of the caspase-3 gene may underlie the regulation of apoptotic susceptibility during brain development and after acute injury to the mature brain. We identified and cloned the rat caspase-3 gene promoter, determined its structure, and examined its regulation during a course of apoptosis in PC12 cells. Results demonstrate that this promoter lacks a TATA-box and contains a cluster of Sp1 elements and multiple transcription start sites. The first identified transcription start site is located 87-bp upstream from the first splicing site. A role of Sp1 elements in the regulation of caspase-3 promoter activity is demonstrated by the inhibition of Sp1 binding using mithramycin A. Results of deletion analysis show that an Ets-1-like element located between nucleotides -1646 and -1632 relative to the most extended transcription start site is necessary to achieve sustained transcriptional activity. Homology analysis revealed that the 5'-flanking region of the human caspase-3 gene exhibits significant similarity to a regulatory region of the rat gene.