Kinase-dead PKB gene therapy combined with hyperthermia for human breast cancer

Association between integrin-linked kinase and hyperthermia in oral squamous cell carcinoma

The present study aimed to observe the effect of the biological functions of integrin-linked kinase (ILK) silencing combined with hyperthermia on Tca8113 cells. Lentivirus-mediated short hairpin RNA (shRNA)-targeting ILK was transfected into oral squamous cell carcinoma (OSCC) Tca8113 cells and, combined with hyperthermia, several experimental methods were used to detect their biological behavior in vitro. On the basis of in vitro experiments, Tca8113 cells were transplanted into nude mice models, and ILK-shRNA-lentivirus was injected into the nude mice transplanted tumor and combined with hyperthermia. Tumor morphology and the associated protein expression changes were determined. Subsequent to ILK silencing combined with hyperthermia, the growth, migration and proliferation of Tca8113 cells were significantly inhibited. Flow cytometry revealed that the cells were blocked in the S phase, and western blot analysis demonstrated that ILK, phosphorylated (p)-RAC-alpha serine/threonine-protein kinase (Akt), p-glycogen synthase kinase-3β and p-heat shock factor 1 protein expression levels were significantly decreased, while apoptosis-associated protein B-cell lymphoma-2-associated X protein expression and the efficacy of hypothermia were significantly increased. By ILK silencing combined with hyperthermia, a significant therapeutic effect on transplanted tumors was observed in nude mice. Immunohistochemistry revealed the same results as the in vitro experiments. ILK silencing combined with hyperthermia can inhibit the growth, proliferation and migration of Tca8113 cells, promote Tca8113 cell apoptosis, inhibit the phosphatidylinositol-3-kinase/Akt signaling pathway and increase hyperthermia sensitivity; the combination therapy exhibits a synergistic sensitizing effect. Therefore, ILK silencing combined with hypothermia may serve as a novel combination therapy strategy against OSCC.

Inhibition of mTOR promotes hyperthermia sensitivity in SMMC-7721 human hepatocellular carcinoma cell line

The mammalian target of rapamycin (mTOR) is a critical mediator of the phosphoinositide 3-kinase/protein kinase B/mTOR signaling pathway, and mTOR activity is induced following heat shock. Thermotherapy is used to treat hepatocellular carcinoma (HCC). However, the role of mTOR in modulating thermosensitivity in HCC has yet to be elucidated. In the present study, the antisense plasmid pEGFP-C1-mTOR was transfected into SMMC-7721 cells, and the expression levels of mTOR were analyzed by reverse transcription-polymerase chain reaction and western blot analysis. The thermal responses of the transfected cells were also examined. The results revealed that SMMC-7721 cells were sensitive to heat treatment, and cell viability was significantly inhibited following hyperthermia treatment (P<0.01). The mRNA and protein expression levels of mTOR decreased post-transfection. Cell proliferation, colony-forming ability and motility were all significantly decreased following hyperthermia treatment in the transfected cells. Flow cytometry analysis demonstrated that apoptosis was significantly increased following treatment (P<0.01). The number of cells in S phase was increased, and the cell cycle was arrested in S phase. In conclusion, inhibition of mTOR increased the thermosensitivity of SMMC-7721 cells by increasing cellular apoptosis and inducing S phase arrest.

Correlation between the expression of Id-1 and hyperthermia-associated molecules in oral squamous cell carcinoma

OBJECTIVE

To investigate the expression of inhibitor of differentiation/DNA binding (Id-1), phosphatidylinositol-3-kinase/protein kinase B pathway proteins and hyperthermia-associated protein and their association with various clinicopathological factors in oral squamous cell cancer (OSCC), and explore the relationship among them in OSCC.

METHODS

Id-1, phosphorylated protein kinase B (p-Akt), phosphorylated glycogen synthase kinase 3β (p-GSK3β) and phosphorylated heat shock factor 1 (p-HSF1) expression were assessed immunohistochemically in 76 OSCC.

RESULTS

Id-1 (73.8%), p-Akt (65.8%), p-GSK3β (60.5%) and p-HSF1 (75%) were found to be overexpressed in most of the oral cancer samples tested, and the expressions of them are correlated with advanced clinical stage, metastasis and recurrence (p<0.01), but there is no apparent relationship with gender, age, differentiation and habits (p>0.05). Survival curves show that the survival of patients with high Id-1, p-Akt, p-GSK3β and p-HSF1 expression was significantly worse than those with low Id-1, p-Akt, p-GSK3β and p-HSF1 expression (p=0.000). Id-1 expression was significantly higher in cases with high expression of p-Akt, p-GSK3β and p-HSF1 than in those with low expression (p=0.002, p=0.003, p=0.001).

CONCLUSIONS

This study revealed that there was a positive correlation between Id-1 expression and the expression of p-Akt, p-GSK3β and p-HSF1. The inhibition of Id-1 expression can improve the efficacy of hyperthermia in OSCC.

AKT inhibitor suppresses hyperthermia-induced Ndrg2 phosphorylation in gastric cancer cells

Hyperthermia is one of the most effective adjuvant treatments for various cancers with few side effects. However, the underlying molecular mechanisms still are not known. N-myc downstream-regulated gene 2 (NDRG2), a tumor suppressor, has been shown to be involved in diverse cellular stresses including hypoxia, lipotoxicity, etc. In addition, Ndrg2 has been reported to be related to progression of gastric cancer. In the current study, our data showed that the apoptosis rate of MKN28 cells increased relatively rapidly to 13.4% by 24 h after treatment with hyperthermia (42°C for 1 h) compared to 5.1% in control cells (P < 0.05). Nevertheless, there was no obvious change in the expression level of total Ndrg2 during this process. Further investigation demonstrated that the relative phosphorylation levels of Ndrg2 at Ser332, Thr348 increased up to 3.2- and 1.9-fold (hyperthermia group vs control group) at 3 h in MKN28 cells, respectively (P < 0.05). We also found that heat treatment significantly increased AKT phosphorylation. AKT inhibitor VIII (10 µM) decreased the phosphorylation level of Ndrg2 induced by hyperthermia. Accordingly, the apoptosis rate rose significantly in MKN28 cells (16.4%) treated with a combination of AKT inhibitor VIII and hyperthermia compared to that (6.8%) of cells treated with hyperthermia alone (P < 0.05). Taken together, these data demonstrated that Ndrg2 phosphorylation could be induced by hyperthermia in an AKT-dependent manner in gastric cancer cells. Furthermore, AKT inhibitor VIII suppressed Ndrg2 phosphorylation and rendered gastric cancer cells susceptible to apoptosis induced by hyperthermia.

Tumor cell kill by c-MYC depletion: role of MYC-regulated genes that control DNA double-strand break repair

MYC regulates a myriad of genes controlling cell proliferation, metabolism, differentiation, and apoptosis. MYC also controls the expression of DNA double-strand break (DSB) repair genes and therefore may be a potential target for anticancer therapy to sensitize cancer cells to DNA damage or prevent genetic instability. In this report, we studied whether MYC binds to DSB repair gene promoters and modulates cell survival in response to DNA-damaging agents. Chromatin immunoprecipitation studies showed that MYC associates with several DSB repair gene promoters including Rad51, Rad51B, Rad51C, XRCC2, Rad50, BRCA1, BRCA2, DNA-PKcs, XRCC4, Ku70, and DNA ligase IV. Endogenous MYC protein expression was associated with increased RAD51 and KU70 protein expression of a panel of cancer cell lines of varying histopathology. Induction of MYC in G(0)-G(1) and S-G(2)-M cells resulted in upregulation of Rad51 gene expression. MYC knockdown using small interfering RNA (siRNA) led to decreased RAD51 expression but minimal effects on homologous recombination based on a flow cytometry direct repeat green fluorescent protein assay. siRNA to MYC resulted in tumor cell kill in DU145 and H1299 cell lines in a manner independent of apoptosis. However, MYC-dependent changes in DSB repair protein expression were not sufficient to sensitize cells to mitomycin C or ionizing radiation, two agents selectively toxic to DSB repair-deficient cells. Our results suggest that anti-MYC agents may target cells to prevent genetic instability but would not lead to differential radiosensitization or chemosensitization.

Hyperthermia induced NFkappaB mediated apoptosis in normal human monocytes

Conceptual approaches of heat-induced cytotoxic effects against tumor cells must address factors affecting therapeutic index, i.e., the relative toxicity for neoplastic versus normal tissues. Accordingly, we investigated the effect of hyperthermia treatment (HT) on the induction of DNA fragmentation, apoptosis, cell-cycle distribution, NFkappaB mRNA expression, DNA-binding activity, and phosphorylation of IkappaBalpha in the normal human Mono Mac 6 (MM6) cells. For HT, cells were exposed to 43 degrees C. FACS analysis showed a 48.5% increase in apoptosis, increased S-phase fraction, and reduced G2 phase fraction after 43 degrees C treatments. EMSA analysis showed a dose-dependent inhibition of NFkappaB DNA-binding activity after HT. This HT-mediated inhibition of NFkappaB was persistent even after 48 h. Immunoblotting analysis revealed dose-dependent inhibition of IkappaBalpha phosphorylation. Similarly, RPA analysis showed that HT persistently inhibits NFkappaB mRNA. These results demonstrate that apoptosis upon HT exposure of MM6 cells is regulated by IkappaBalpha phosphorylation mediated suppression of NFkappaB.

The effect of estradiol on in vivo tumorigenesis is modulated by the human epidermal growth factor receptor 2/phosphatidylinositol 3-kinase/Akt1 pathway

To determine whether the epidermal growth factor receptor 2 (ErbB2) and Akt1 can alter the in vivo growth of MCF-7 cells, parental cells or cells stably transfected with constitutively active Akt1 (myr-Akt1) or dominant-negative Akt1 mutants (K179M-Akt1 and R25C-Akt1) were implanted into athymic nude mice. Tumor growth was monitored in the presence or absence of the antiestrogen tamoxifen and the selective ErbB2 inhibitor, AG825. MCF-7 [parental or empty vector transfected, cytomegalovirus (CMV)] and myr-Akt1 cells formed tumors upon estradiol supplementation after 20-30 d (59-, 29-, and 17-fold increase in tumor volume, respectively). Tamoxifen and AG825 blocked the estradiol effect by 93 and 96% in MCF-7 xenografts, 88 and 81% in CMV xenografts, and 91% in myr-Akt1 xenografts. Furthermore, AG825 suppressed the growth of established tumors in CMV and myr-Akt1 inoculated animals by 68 and 75%, respectively, as compared with continued estrogen supplementation, suggesting a role for ErbB2. When K179M-Akt1 or R25C-Akt1 cells were injected into ovariectomized animals, tumor growth was reduced upon estradiol treatment by 95% and 98%, respectively, supporting a role for Akt1. In contrast to ovariectomized animals, in intact animals, myr-Akt1 cells could establish tumors without estradiol priming after 40-50 d (20-fold increase in tumor volume). Loss of Akt1 phosphorylation was associated with tumor growth inhibition. Immunohistochemical assays showed that in tumors from parental and CMV xenografts, estradiol decreased estrogen receptor-alpha expression and induced progesterone receptor expression and Akt phosphorylation, effects that were inhibited by tamoxifen, AG825, and R25C-Akt1 by 89, 82, and 77% for progesterone receptor expression and 48, 66, and 73% for pAkt expression, respectively. Cumulatively, our results suggest that Akt1 and ErbB2 are involved in in vivo tumorigenesis and modulation of estrogen receptor-alpha expression and activity.

Cellular mechanisms of neuronal damage from hyperthermia

Hyperthermia can cause brain damage and also exacerbate the brain damage produced by stroke and amphetamines. The developing brain is especially sensitive to hyperthermia. The severity of, and mechanisms underlying, hyperthermia-induced neuronal death depend on both temperature and duration of exposure. Severe hyperthermia can produce necrotic neuronal death. For a window of less severe heat stresses, cultured neurons exhibit a delayed death with apoptotic characteristics including cytochrome c release and caspase activation. Little is known about mechanisms of hyperthermia-induced damage upstream of these late apoptotic effects. This chapter considers several possible upstream mechanisms, drawing on both in vivo and in vitro studies of the nervous system and other tissues. Hyperthermia-induced damage in some non-neuronal cells includes endoplasmic reticular stress due to denaturing of nascent polypeptide chains, as well as nuclear and cytoskeletal damage. Evidence is presented that hyperthermia produces mitochondrial damage, including depolarization, in cultured mammalian neurons.