This work is dedicated to analysis of the thermal sensitivity and efficiency of thermosensitization to γ-radiation of three cell lines of breast cancer of different molecular subtypes. It has been established that the cells of the studied lines differ in sensitivity to hyperthermia and, as a result, in the effectiveness of thermoradiosensitization, which raises the question of finding criteria for assessing the rationale of using hyperthermia in each specific case. It has been shown that the level of heat-responsive expression of the HSP70 gene and also the level of cell genomic instability can serve as such criteria. It was found that the efficiency of thermoradiosensitization is significantly higher in MDA-MB-231 cells compared to the cells of other lines studied. The data obtained suggest that the use of hyperthermia as a radiotherapy-sensitizing cotreatment may be particularly promising toward triple negative breast cancer.

The possibility of using hyperthermia for the efficient radiosensitization of tumor cells with radio- and chemoresistant phenotype was tested in an in vitro model. The work was carried out on MCF-7/MDR1 line cells derived from a human breast carcinoma and demonstrating the phenomenon of multidrug resistance due to overexpression of the MDR1 gene. The tumor cells of the maternal MCF-7 line were used in the comparative experiments. The cell cultures were exposed to heat stress (42–44°С, 30–90 min), then to the action of γ-radiation in doses of 2–8 Gy. Cytotoxic effects were estimated in the MTT test, as well as by the intensity of apoptosis and necrosis or a decrease in clonogenicity. The transcriptional stress response of heated cells was studied using real-time PCR, determining the accumulation of mRNA encoding inducible heat shock proteins HSP70 and HSP27. It was established that MCF-7/MDR1 radio- and chemoresistant cells do not have increased thermoresistance, and their responses to heat stress are comparable to those for MCF-7 cells. At the same time, it was demonstrated that hyperthermal pretreatment allows a significant enhancement of the cytotoxic effect of γ-radiation on MCF-7/MDR1 cells, which proves the possibility of the efficient use of hyperthermia to increase the sensitivity to radiation of radioresistant tumors that have multidrug resistance and are unsusceptible to chemotherapeutic radiosensitizers. The molecular mechanisms of thermo-radiosensitization of tumor cells are considered.

The high frequency of breast cancer worldwide and the high mortality among women with this malignancy are a serious challenge for modern medicine. A deeper understanding of the mechanisms of carcinogenesis and emergence of metastatic, therapy-resistant breast cancers would help development of novel approaches to better treatment of this disease. The review is dedicated to the role of members of the heat shock protein 70 subfamily (HSP70s or HSPA), mainly inducible HSP70, glucose-regulated protein 78 (GRP78 or HSPA5) and GRP75 (HSPA9 or mortalin), in the development and pathogenesis of breast cancer. Various HSP70-mediated cellular mechanisms and pathways which contribute to the oncogenic transformation of mammary gland epithelium are reviewed, as well as their role in the development of human breast carcinomas with invasive, metastatic traits along with the resistance to host immunity and conventional therapeutics. Additionally, intracellular and cell surface HSP70s are considered as potential targets for therapy or sensitization of breast cancer. We also discuss a clinical implication of Hsp70s and approaches to targeting breast cancer with gene vectors or nanoparticles downregulating HSP70s, natural or synthetic (small molecule) inhibitors of HSP70s, HSP70-binding antibodies, HSP70-derived peptides, and HSP70-based vaccines.

Within aggressive malignancies, there usually are the “hypoxic zones”—poorly vascularized regions where tumor cells undergo oxygen deficiency through inadequate blood supply. Besides, hypoxia may arise in tumors as a result of antiangiogenic therapy or transarterial embolization. Adapting to hypoxia, tumor cells acquire a hypoxia-resistant phenotype with the characteristic alterations in signaling, gene expression and metabolism. Both the lack of oxygen by itself and the hypoxia-responsive phenotypic modulations render tumor cells more radioresistant, so that hypoxic tumors are a serious challenge for radiotherapy. An understanding of causes of the radioresistance of hypoxic tumors would help to develop novel ways for overcoming this challenge. Molecular targets for and various approaches to radiosensitizing hypoxic tumors are considered in the present review. It is here analyzed how the hypoxia-induced cellular responses involving hypoxia-inducible factor-1, heat shock transcription factor 1, heat shock proteins, glucose-regulated proteins, epigenetic regulators, autophagy, energy metabolism reprogramming, epithelial–mesenchymal transition and exosome generation contribute to the radioresistance of hypoxic tumors or may be inhibited for attenuating this radioresistance. The pretreatments with a multitarget inhibition of the cancer cell adaptation to hypoxia seem to be a promising approach to sensitizing hypoxic carcinomas, gliomas, lymphomas, sarcomas to radiotherapy and, also, liver tumors to radioembolization.

Hyperthermia is used in combination with radiation therapy to enhance the radiation response of the target tumor. However, many tumors are thermoresistant, which makes the thermo-radiosensitization ineffective. In this work, we studied a possibility of enhancing the radiosensitiz-ing effect of hyperthermia on cancer cells in the case of combining heating and treatments with inhibitors of proteasomal protein degradation. The objects of the study were HeLa, MCF-7, and PC-3 cell lines derived from human carcinomas of various localization. Before irradiation (2-6 Gy), cell cultures were subjected to heat stress (42-44 °C for 20-60 min) without or in the pres-ence of proteasome inhibitors (MG132, bortezomib). The death and survival of the treated cells was evaluated by the level of apoptosis/necrosis, by clonogenicity, and in the MTT test. The pro-teotoxicity of the exposures and the subcellular redistribution of heat shock proteins were ana-lyzed using cell fractionation, electrophoresis, and immunoblotting. The results show that, com-pared with hyperthermia, the combined effect (hyperthermia + proteasome inhibitor) significantly increased the radiosensitization of cancer cells, which was manifested in the intensification of their postradiation death and significant suppression of clonogenicity. Thus, the combination of hyperthermia with proteasome inhibitors (for example, with bortezomib, which is clinically ap-proved) can help sensitize radioresistant tumors to radiation therapy.

Cancer stem cells (CSCs) are a great challenge in the fight against cancer because these self-renewing tumorigenic cell fractions are thought to be responsible for metastasis dissemination and cases of tumor recurrence. In comparison with non-stem cancer cells, CSCs are known to be more resistant to chemotherapy, radiotherapy, and immunotherapy. Elucidation of mechanisms and factors that promote the emergence and existence of CSCs and their high resistance to cytotoxic treatments would help to develop effective CSC-targeting therapeutics. The present review is dedicated to the implication of molecular chaperones (protein regulators of polypeptide chain folding) in both the formation/maintenance of the CSC phenotype and cytoprotective machinery allowing CSCs to survive after drug or radiation exposure and evade immune attack. The major cellular chaperones, namely heat shock proteins (HSP90, HSP70, HSP40, HSP27), glucose-regulated proteins (GRP94, GRP78, GRP75), tumor necrosis factor receptor-associated protein 1 (TRAP1), peptidyl-prolyl isomerases, protein disulfide isomerases, calreticulin, and also a transcription heat shock factor 1 (HSF1) initiating HSP gene expression are here considered as determinants of the cancer cell stemness and potential targets for a therapeutic attack on CSCs. Various approaches and agents are discussed that may be used for inhibiting the chaperone-dependent development/manifestations of cancer cell stemness.

The effects of coherent monochromatic 0.14 THz radiation on human dermal fibroblasts were experimentally investigated using a solid-state radiation source based on an IMPATT diode. The fibroblast cells were exposed for 20 minutes to a wave beam of different power (10, 30, 50, 70, and 100 mW) and such parameters as proliferative activity, wound closure percentage, and the level of nitric oxide production in irradiated cells were studied. No tangible changes in the examined parameters were revealed, thereby allowing us to conclude that the low-frequency THz radiation does not affect the functional activity of the human dermal fibroblasts.

We propose to combine small molecule inhibitors of the chaperone activity of heat shock proteins (Hsps) with inhibitors of the Hsp expression for better targeting tumors. Our approach is based on such known facts: (i) cancer cells are addicted to the chaperone activity of Hsp90 and Hsp70, and (ii) inhibition of the Hsp90/Hsp70 chaperone activity in cancer cells leads to the HSF1-mediated induction of additional Hsps that can impair antitumor effects of the chaperone inactivation.

Реакции нормальных и опухолевых клеток и тканей на гипертермию в сочетании с ионизирующей радиацией. ОбзорКабаков А.Е. 1 , Анохин Ю.Н. 2 , Лебедева Т.В. 1  1 МРНЦ им.А.Ф.Цыба -филиал ФГБУ «НМИЦ радиологии» Минздрава России, Обнинск; 2 ИАТЭ -филиал ФГАОУ ВО «Национальный исследовательский ядерный университет «МИФИ», Обнинск В обзоре представлен анализ литературы о модифицирующем действии гипертермии (ГТ) на радиационный ответ нормальных и опухолевых клеток и тканей, а также об использовании ГТ для повышения радиочувствительности опухолей.Проанализированные данные свидетельствуют о том, что радиосенсибилизирующие эффекты ГТ проявляются в аддитивном или синергетическом усилении цитотоксичности в облучённых био-объектах.Степень такого усиления зависит от уровня нагрева, дозы радиации, последовательности применения и интервала между воздействиями, типа ткани и пр.Радиосенсибилизирующие эффекты ГТ проявляются не только на опухолевых, но и на нормальных клетках и тканях.Это обстоятельство требует определения фактора терапевтического выигрыша в разных случаях применения термолучевой терапии опухолей.В клеточных реакциях на ГТ и радиационное воздействие активно участвуют белки теплового шока (БТШ), которые являются одним из факторов устойчивости опухолей к термо-, химио-и радиотерапии.Показано, что функционирование БТШ90 необходимо для пострадиационной репарации разрывов ядерной ДНК.Кроме того, БТШ90, БТШ70 и БТШ27 являются мощными супрессорами апоптоза и помогают стрессированной клетке реактивировать или деградировать денатурированные стрессом белки.В случае комбинации ГТ и облучения эти БТШ образуют комплексы с денатурированными внутриклеточными белками и уже не могут действовать как радиопротекторы и блокаторы апоптоза.Таким образом, рекрутирование БТШ для защиты от протеотоксических эффектов ГТ происходит в ущерб БТШ-опосредованной радиорезистентности раковых клеток и, следовательно, способствует их радиосенсибилизации.Однако, индукция и временное повышение уровней БТШ90, БТШ70 и БТШ27 в переживших ГТ клетках может сделать их на какой-то период термотолерантными и более радиорезистентными, что следует учитывать в случае последовательного комбинирования ГТ и лучевой терапии.

Апоптоз в опухолевых клетках, подвергнутых сочетанному действию гипертермии и облучения: исследование молекулярных механизмов и мишенейКабаков А.Е., Кудрявцев В.А