The sensitivity to hyperthermia of human granulocyte/macrophage progenitor cells (CFU-GM) derived from blood or marrow of normal subjects and patients with chronic granulocytic leukaemia

Gold Coated Superparamagnetic Iron Oxide Nanoparticles as Effective Nanoparticles to Eradicate Breast Cancer Cells via Photothermal Therapy

Purpose: Unique physiochemical properties of Fe₂O₃ nanoparticles make them great agents to serve as therapeutic and diagnostic nanoparticles (NPs). In this study, we developed gold coated Fe₂O₃ nanoparticles for photothermal therapy of breast cancer cells.

Methods: Fe₂O₃ nanoparticles was prepared via microemulsion method and their surface was modified via gold. Differential light scattering (DLS) and transmission electron microscopy (TEM) methods were applied to evaluate physicochemical properties of NPs. Gold coated NP was further modified with MUC-1 aptamer as a targeting agent to increase drug delivery into the desired tissue. To evaluate cytotoxicity of prepared cells, MTT assay was employed. Targeting ability of aptamer modified NPs was assessed through confocal microscopy and flow cytometry method. Subsequently, MCF-7 and CHO cells were treated with aptamer modified NPs and were then irradiated via near infrared light (NIR) to produce heat.

Results: The morphology of NPs was spherical and monodisperse with the size of 16 nm, which was confirmed via DLS and TEM. Confocal microscopy and flow cytometry results indicated that aptamer modified NPs had higher uptake compared to bare NPs. Finally, NIR exposure results revealed that higher uptake of NPs and application of NIR led to significant death of MCF-7 cells compared to CHO cells.

Conclusion: To sum up, aptamer modified Fe₂O₃ nanoparticles showed higher uptake by cancerous cells and led to eradication of cancerous cells after exposure to NIR light.

Theranostic MUC-1 aptamer targeted gold coated superparamagnetic iron oxide nanoparticles for magnetic resonance imaging and photothermal therapy of colon cancer

Favorable physiochemical properties and the capability to accommodate targeting moieties make superparamegnetic iron oxide nanoparticles (SPIONs) popular theranostic agents. In this study, we engineered SPIONs for magnetic resonance imaging (MRI) and photothermal therapy of colon cancer cells. SPIONs were synthesized by microemulsion method and were then coated with gold to reduce their cytotoxicity and to confer photothermal capabilities. Subsequently, the NPs were conjugated with thiol modified MUC-1 aptamers. The resulting NPs were spherical, monodisperse and about 19nm in size, as shown by differential light scattering (DLS) and transmission electron microscopy (TEM). UV and X-ray photoelectron spectroscopy (XPS) confirmed the successful gold coating. MTT results showed that Au@SPIONs have insignificant cytotoxicity at the concentration range of 10-100μg/ml (P>0.05) and that NPs covered with protein corona exerted lower cytotoxicity than bare NPs. Furthermore, confocal microscopy confirmed the higher uptake of aptamer-Au@SPIONs in comparison with non-targeted SPIONs. MR imaging revealed that SPIONs produced significant contrast enhancement in vitro and they could be exploited as contrast agents. Finally, cells treated with aptamer-Au@SPIONs exhibited a higher death rate compared to control cells upon exposure to near infrared light (NIR). In conclusion, MUC1-aptamer targeted Au@SPIONs could serve as promising theranostic agents for simultaneous MR imaging and photothermal therapy of cancer cells.

The development and magnitude of thermotolerance during chronic hyperthermia in murine granulocyte-macrophage progenitors: II

We have previously reported that murine granulocyte-macrophage progenitors (CFU-GM) are capable of developing thermotolerance during chronic hyperthermia at temperatures of 40 to 42 degrees C. However, a differential profile of intrinsic thermal response and, in particular, the capability of developing thermotolerance during chronic heating was identified between CFU-GM and macrophage colony-forming units (CFU-M) stimulated respectively, by lung conditioned medium (LCM) and L929 cell conditioned medium (CCM). Nucleated marrow cells treated in vitro were cultured in McCoy's 5A medium plus 15% fetal bovine serum (FBS) in semisolid agar with 10% of CCM. Two different treatment protocols were used in this study to determine the kinetics of thermotolerance in CFU-M: (1) nucleated marrow from mouse tibia and femur were chronically heated in vitro at temperatures of 40, 41 and 42 degrees C (up to 480 min) or (2) nucleated marrow cells were heated over a period of 90 min stepwise from 37 to 42 degrees C, at a heating rate of 0.056 degrees C/min, before exposure to 42 degrees C. The amount of thermotolerance developed was analysed at various times after chronic incubation at 40-42 degrees C by a challenge with 15 min at 44 degrees C. In contrast to CFU-GM, the surviving fraction of CFU-M heated with 15 min at 44 degrees C did not increase during chronic hyperthermia at 40 degrees C for up to 480 min indicating failure to develop thermotolerance. However, CFU-M were able to develop thermotolerance during prolonged incubation at 41 and 42 degrees C, although to a much less extent than observed in CFU-GM. In other words, there was much less development of thermotolerance in murine CFU-M compared to that in CFU-GM. Furthermore, a slow temperature transit from 37 to 42 degrees C over 90 min before exposure to 42 degrees C induced CFU-M to develop thermotolerance. The thermotolerance ratio (TTR, the ratio of the surviving fraction at maximum tolerance versus normotolerance) increased from a maximum of 3.5 after 180 min at 42 degrees C (no warm-up) to a maximum of 4.1 after 60 min at 42 degrees C when the cells received a slow warm-up to 42 degrees C. This implies that in the murine bone marrow granulocyte/macrophage lineage, CFU-M does not normally develop thermotolerance during hyperthermia and that the colony forming unit-granulocyte (CFU-G) and CFU-GM play a more critical role than CFU-M in the initiation and promotion of thermotolerance during chronic hyperthermia. However, in a situation that simulates the slow heat-up used clinically in wholebody hyperthermia, e.g., the 90 min slow warm-up from 37 to 42 degrees C, stimulated CFU-M to develop greater thermotolerance more rapidly than during rapid heating.

The development and magnitude of thermotolerance during chronic hyperthermia in murine bone marrow granulocyte-macrophage progenitors: I

Murine bone marrow granulocyte-macrophage progenitors (CFU-GM) are capable of developing thermotolerance during exposure to temperatures < 42.5 degrees C. Bone marrow from the tibia and femora was heated to 40-42 degrees C (i.e. chronic hyperthermia), and challenged immediately with 15 min at 44 degrees C at regular intervals during treatment (step-up heating). CFU-GM were heated and cultured in McCoy's 5A medium + 15% FBS (fetal bovine serum) and lung-conditioned medium (source of colony stimulating factor) in semisolid agar. The kinetics of thermotolerance development and decay, and the magnitude of the thermotolerance during chronic heating with temperatures of 40-41.5 degrees C were similar. Survival increased rapidly to a maxima by approximately 120 min of hyperthermia (temperatures of 40-41.5 degrees C) and thereafter decreased with a slope similar to the controls. Normalization for cell killing by chronic hyperthermia that occurred during "step-up' heating permitted analysis of thermotolerance in the surviving cells. The surviving fraction after 15 min at 44 degrees C, during incubation at 40, 41 and 41.5 degrees C increased from 0.13 to maxima of 0.56 +/- 0.04, 0.71 +/- 0.03 and 0.82 +/- 0.03 respectively, by 150 min and did not decrease for up to 480 min during chronic hyperthermia. The surviving fraction after 15 min at 44 degrees C during incubation at 42 degrees C increased more slowly than during incubations at 40-41.5 degrees C. The survival of thermotolerant cells after exposure to 15 min at 44 degrees C during 42 degrees C chronic hyperthermia was maximal at 0.87 +/- 0.08 by 120 min and then decreased after approximately 150 min of exposure to 42 degrees C. The thermotolerance ratios (TTR's) were 4.0, 5.4, 6.7 and 6.9 for temperatures of 40, 41, 41.5 and 42 degrees C respectively. The results suggest that chronic hyperthermia temperatures (i.e. 40-42 degrees C) induce rapid thermotolerance development in CFU-GM during the thermal exposure and protect this normal marrow progenitor during whole body hyperthermia or ex vivo purging of leukaemic cells.

Comparative heat sensitivity of murine and human hemopoietic progenitors and clonogenic leukemia cells

The aim of this study was to compare the thermal sensitivity of normal murine and human hemopoietic progenitors to that of leukemic murine and human clonogenic cells in order to assess the clinical relevance of experimental data. Colony forming units-granulocyte-macrophage (CFU-GM) from normal human bone marrow and from bone marrow of patients with acute lymphocytic leukemia (ALL), acute myelogenous leukemia (AML), and Hodgkin's disease in complete remission proved to be less sensitive to 42.5 degrees C in vitro hyperthermia (D0: 93.9 min) than murine bone marrow CFU-GM (D0: 49.6 min). Leukemic colony forming cells (CFU-L) from HL-60 suspension culture--when compared to human CFU-GM--showed significantly increased thermal sensitivity (D0: 22.8 min). While the thermal sensitivity of CFU-L from a murine leukemia cell line (WEHI 3-B) was not statistically significant when compared to that of CFU-L from HL-60 (D0 values 17.0 versus 22.8 min), the vertical difference between the parallel regression lines suggested an approximately three-fold greater survival for human CFU-L. Although carefully controlled hyperthermia is an easy purging technique, the relevance of murine data to human clinical practice must be considered critically.

Radiation and heat sensitivity of human T-lineage acute lymphoblastic leukemia (ALL) and acute myeloblastic leukemia (AML) clones displaying multiple drug resistance (MDR)

The hyperthermia as well as radiation responses of multidrug resistant (CEM/VLB100 with classical MDR and CEM/VM-1 with atypical MDR), methotrexate resistant (CEM/MTX) subclones of CCRF-CEM T-lineage ALL cell line were compared with those of a drug sensitive (CEM-1-3) subclone from the same parent cell line. Also analyzed were the hyperthermia as well as radiation responses of multidrug resistant (HL60/AR) and drug sensitive subclones of the HL60 AML cell line. Notably, the drug resistant subclones of CEM and HL60 were as sensitive to hyperthermia as were the drug sensitive subclones. Importantly, no thermotolerant plateau was observed in the hyperthermia survival curves of the drug resistant subclones, indicating that drug/multidrug resistance is not associated with a greater likelihood of thermal tolerance development during hyperthermia. Similarly, the drug resistant CEM and HL60 subclones were not more radiation resistant than the drug sensitive subclones. Thus, the classical or atypical forms of multidrug resistance or methotrexate resistance of the analyzed leukemic cell lines were not associated with radiation resistance. Furthermore, the radiation survival curves of the drug resistant subclones lacked a distinct initial shoulder and their n values were not greater than those of the drug sensitive subclones, suggesting that multidrug resistance is not associated with an increased ability to repair or accumulate sublethal radiation damage. Our findings provide evidence that there is no apparent association between drug/multidrug resistance and heat or radiation sensitivity of CEM T-lineage ALL or HL60 AML leukemia cells. The results of this study indicate that acquired resistance to methotrexate, vinblastine, vincristine, etoposide, actinomycin-D, adriamycin, or daunomycin, or pleiotropic multidrug resistance do not necessarily confer radiation resistance for human leukemic cells.

Survival and characteristics of murine leukaemic and normal stem cells after hyperthermia: a murine model for human bone marrow purging

The effect of hyperthermia in vitro on the survival and leukaemogenic effectiveness of WEHI 3-B cells and on the survival and transplantation efficiency of bone marrow cells was compared in a murine model system. Normal murine clonogenic haemopoietic cells (day 9 CFU-S and CFU-GM) proved to be significantly less sensitive to 42.5 degrees C hyperthermia (Do values: 54.3 and 41.1 min, respectively) than leukaemic clonogenic cells (CFU-L) derived from suspension culture or from bone marrow of leukaemic mice (Do: 17.8 min). Exposure for 120 min to 42.5 degrees C reduced the surviving fraction of CFU-L to 0.002 and that of CFU-S to 0.2. If comparable graft sizes were transplanted from normal or heat exposed bone marrow, 60-day survival of supralethally irradiated mice was similar. Surviving WEHI 3-B cells were capable of inducing leukaemia in vivo. The two log difference in the surviving fraction of CFU-L and CFU-S after 120 min exposure to 42.5 degrees C suggests that hyperthermia ex vivo may be a suitable purging method for autologous bone marrow transplantation.

Thermal sensitivity and thermal tolerance of human B-lineage acute lymphoblastic leukemia (ALL) cells

The thermal sensitivities of four B-cell precursor acute lymphoblastic (ALL) cell lines (REH and KM-3 = pre pre B-ALL; NALM-6 and HPB-NULL = pre B-ALL), and 1 B-cell ALL (NAMALWA) cell line were studied and compared to the thermal sensitivity of the T-lineage ALL cell line MOLT-3 using an in vitro clonogenic assay system by limiting dilution. B-lineage ALL cells were as sensitive to hyperthermia as were T-lineage ALL cells. D0 values at 42 degrees C ranged from 44.9 min (NALM-6) to 85.6 min (NAMALWA), D0 values at 43 degrees C ranged from 15.3 min (NALM-6) to 35.7 min (KM-3), and D0 values at 44 degrees C ranged from 11.1 min (NALM-6) to 23.8 min (HPB-NULL). By comparison, the D0 values of MOLT-3 cells were 95.1 min at 42 degrees C, 23.8 min at 43 degrees C, and 14.7 min at 44 degrees C. The maximum log kill values which were observed ranged from 0.8 log (KM-3 and HPB-NULL) to 1.3 logs (NALM-6) at 42 degrees C, from 1.4 logs (KM-3) to 4.2 logs (NALM-6) at 43 degrees C, and from 3.8 logs (HPB-NULL) to 4.8 logs (NALM-6) at 44 degrees C. A thermal tolerant plateau was observed in the hyperthermia survival curves of REH, NALM-6, and HPB-NULL cells, providing circumstantial evidence that thermal tolerance may develop in some B-cell precursor ALL cells after 90-120 min of continuous heating. In contrast, no thermal tolerant plateau was observed in the hyperthermia survival curves of pre-pre-B-ALL/KM-3 B-cell ALL/NAMALWA or T-lineage ALL/MOLT-3 cells. The kinetics of development and decay of thermotolerance was studied for NALM-6 cells. Thermotolerance after a priming heat exposure to 42 degrees C for 30 min was maximum at 8 hr with a maximum thermotolerance ratio of 2.0, and it decayed by 24 hr. These findings extend previous studies on the thermal sensitivity of human leukemia cells and provide new information on the thermal sensitivity and thermotolerance of B-lineage ALL cells.

Influence of limb restraint on the thermal response of bone marrow CFU-GM heated in situ

The method used to restrain anaesthetized (sodium pentobarbital) mice for in situ heating of tibial marrow affects the survival response of CFU-GM. Three methods of limb restraint, in addition to ischaemia induced by tourniquet, were examined for their relative effect on the thermal response of CFU-GM. The three methods of restraint were to secure only the toes with suture material to a submersion post in the water bath, to tape the foot, or to tape the leg. Temperatures in the lumen of the tibia were measured with a 100 micron (tip diameter) microthermocouple during representative experimental conditions. After heating in situ, bone marrow was extruded and CFU-GM cultured in standard soft agar conditions in lung-conditioned medium. The most restrictive restraining method, i.e. taping the leg, produced the greatest thermal response among the three restraining methods examined. The D0 (+/- 95% CI) of the 42 degrees C survival curve for CFU-GM was 22 +/- 4, 46 +/- 8, or 94 +/- 53 min for restraint of leg, foot, or toes, respectively. Survival reached a plateau by 100 min of heating indicative of the development of thermotolerance. The D0 of the 44 degrees C survival curve was 3 +/- 1, 6 +/- 2 and 16 +/- 6 min for restraint of leg, foot, or toes respectively. Ischaemia produced the most pronounced effect on the thermal response of tibial CFU-GM with D0 values of 2 +/- 1 or 3.6 +/- 1.5 min after exposure to 44 degrees C or 42 degrees C, respectively. The method of limb restraint affects the thermal sensitivity of CFU-GM most probably by blood flow obstruction and resultant pH decrease. Thus, precautions must be taken to ensure that limb restriction does not introduce artifacts in the hyperthermia response of normal tissues or tumours during heating in situ.