[Thermosensitization of tumor cells with inhibitors of chaperone activity and expression].

Effects of inhibitors of the heat shock protein 90 (HSP90) chaperone activity and inhibitors of the heat shock protein (HSP) expression on sensitivity of HeLa tumor cells to hyperthermia were studied. It was found that nanomolar concentrations of inhibitors of the HSP90 activity (17AAG or radicicol) slowed down chaperone-dependent reactivation of a thermo-labile reporter (luciferase) in heat-stressed HeLa cells and slightly enhanced their death following incubation for 60 min at 43 degrees C. Herein, the inhibitors of HSP90 activity stimulated de novo induction of additional chaperones (HSP70 and HSP27) that significantly increased the intracellular HSP levels.

[Inhibitors of the heat shock protein 90 activity: a novel class of tumor radiosensitizers].

The 90 kDa heat shock protein (HSP90) is one of major chaperones of eukaryotes which catalyzes maturation and activation of its client proteins. Among the identified client proteins there are oncogene products, hormone or growth factor receptors and key components of signaling pathways responsible for the malignant growth of tumors or their resistance to chemotherapy and radiotherapy. In the case of inhibition of the HSP90 chaperone function, such proteins are inactivated and degraded soon that leads to simultaneous blocking several pathways essential for proliferation and survival of malignant cells; therefore, pharmacological inhibitors of the HSP90 chaperone activity could be used in anticancer therapy.

[Increased plasma membrane permeability for Ca2+ in radiation-induced thymocyte apoptosis].

Parameters of the Ca2+ permeability (the 45Ca influx rate in the presence of orthovanadate blocking the Ca(2+)-ATPhase, and the initial rate of the 45Ca uptake) and the DNA fragmentation were determined in rat thymocytes after gamma-irradiation-induced (with a dose of 5 Gy) apoptosis. Within the first 30-90 min after irradiation, the 45Ca influx rate that is characteristic of the membrane passive permeability remained unchanged. The initial rate of the 45Ca uptake that is characteristic of the Ca2+ exchange almost doubled.

[Specificity of morphological changes and DNA degradation in the Ehrlich ascite carcinoma cells exposed to various damaging agents].

Using the Ehrlich ascite carcinoma cells, exposed to oxidative stress, heat shock, cytochalasin B, vinblastine, Triton X-100 and energy starvation, morphological changes, DNA degradation, and form of cell death were investigated. A rather clear specificity of cell morphology, characteristic of apoptosis, was revealed for the most of treatments, including membrane blebs, chromatin condensation and apoptotic body formation. Karyorhexis was not common for the examined cells.

[Lack of serum causes apoptosis of thymocytes not requiring protein synthesis and ATP generation].

Incubation of rat thymocytes in serum-free media was found to result in their apoptotic death characterized by internucleosomal DNA fragmentation, nuclear pyknosis and subsequent irreversible plasma membrane damage. As in the case of glucocorticoid (hydrocortisone)-induced apoptosis, DNA fragmentation under serum withdrawal was suppressed by endonuclease inhibitors (Zn2+ and spermine). At the same time, protein synthesis inhibitors (cycloheximide and puromycin) failed to block the apoptosis induced by serum withdrawal but inhibited the hydrocortisone-induced apoptosis.

[Fragmentation of Ehrlich ascites carcinoma DNA during influences causing aggregation of cytoskeletal proteins].

Upon exposures of Ehrlich ascites carcinoma cells to heat shock (44 degrees, 1 hr), oxidative stress or energy deprivation, their DNA undergoes fragmentation (35-45% after 5 hrs of incubation) which is considered as a hallmark of apoptosis. Prior to DNA fragmentation the cells exhibited blebbing (55-90% after 1 hr), thus being suggestive of cytoskeletal damage and a 1.5-2-fold increase in the Triton-insoluble protein concentration (protein aggregation) after 3 hrs.

[Damage to and interphase death of Ehrlich ascites carcinoma tumor cells at different growth stages during energy starvation and heat shock].

The reaction of the Ehrlich ascite carcinoma cells, being at different phases of their growth, to the energy deprivation (rotenone in glucose-free medium) and heat shock (HS) was investigated. The criteria of this reaction were interphase death (according to Trypan blue staining) and structural changes (appearance of big blebs). It was found that proliferating cells (from log phase), judging from the two criteria, were more sensitive to a separate action of both energy deprivation and HS, than the resting ones (from stationary phase).

[The relationship of damage to and death of ascitic tumor cells during starvation to the ATP and free calcium content in the cells].

Ascite tumor cells EL-4 were incubated in conditions of energy starvation (Hanks salt solution with rothenone and without glucose) at 37 degrees C for 3 hours. Under these conditions, some structural cell damages appeared within the first hours: enlarging and flattening of the cells, blebbing, vacuolization of the cytoplasm, nuclear chromatin condensation. Later on, a share of cells with obvious damage decreased, whereas that of the cells stained with trypan blue (dead cells) much increased (up to 90% after a 3 hour incubation).