Chang W. Song

Enhancement of tumor thermal therapy using gold nanoparticle–assisted tumor necrosis factor-α delivery

Tumor necrosis factor-α (TNF-α) is a potent cytokine with anticancer efficacy that can significantly enhance hyperthermic injury. However, TNF-α is systemically toxic, thereby creating a need for its selective tumor delivery. We used a newly developed nanoparticle delivery system consisting of 33-nm polyethylene glycol–coated colloidal gold nanoparticles (PT-cAu-TNF-α) with incorporated TNF-α payload (several hundred TNF-α molecules per nanoparticle) to maximize tumor damage and minimize systemic exposure to TNF-α. SCK mammary carcinomas grown in A/J mice were treated with 125 or 250 μg/kg PT-cAu-TNF-α alone or followed by local heating at 42.5°C using a water bath for 60 minutes, 4 hours after nanoparticle injection. Increases in tumor growth delay were observed for both PT-cAu-TNF-α alone and heat alone, although the most dramatic effect was found in the combination treatment. Tumor blood flow was significantly suppressed 4 hours after an i.v. injection of free TNF-α or PT-cAu-TNF-α. Tumor perfusion, imaged by contrast enhanced ultrasonography, on days 1 and 5 after treatment revealed perfusion defects after the injection of PT-cAu-TNF-α alone and, in many regions, complete flow inhibition in tumors treated with combination treatment. The combination treatment of SCK tumors in vivo reduced the in vivo/in vitro tumor cell survival to 0.05% immediately following heating and to 0.005% at 18 hours after heating, suggesting vascular damage–mediated tumor cell killing. Thermally induced tumor growth delay was enhanced by pretreatment with TNF-α-coated gold nanoparticles when given i.v. at the proper dosage and timing. [Mol Cancer Ther 2006;5(4):1014–20]

Radiation-induced vascular damage in tumors: implications of vascular damage in ablative hypofractionated radiotherapy (SBRT and SRS).

We have reviewed the studies on radiation-induced vascular changes in human and experimental tumors reported in the last several decades. Although the reported results are inconsistent, they can be generalized as follows. In the human tumors treated with conventional fractionated radiotherapy, the morphological and functional status of the vasculature is preserved, if not improved, during the early part of a treatment course and then decreases toward the end of treatment. Irradiation of human tumor xenografts or rodent tumors with 5–10 Gy in a single dose causes relatively mild vascular damages, but increasing the radiation dose to higher than 10 Gy/fraction induces severe vascular damage resulting in reduced blood perfusion. Little is known about the vascular changes in human tumors treated with high-dose hypofractionated radiation such as stereotactic body radiotherapy (SBRT) or stereotactic radiosurgery (SRS). However, the results for experimental tumors strongly indicate that SBRT or SRS of human tumors with doses higher than about 10 Gy/fraction is likely to induce considerable vascular damages and thereby damages the intratumor microenvironment, leading to indirect tumor cell death. Vascular damage may play an important role in the response of human tumors to high-dose hypofractionated SBRT or SRS.

Metformin kills and radiosensitizes cancer cells and preferentially kills cancer stem cells

The anti-cancer effects of metformin, the most widely used drug for type 2 diabetes, alone or in combination with ionizing radiation were studied with MCF-7 human breast cancer cells and FSaII mouse fibrosarcoma cells. Clinically achievable concentrations of metformin caused significant clonogenic death in cancer cells. Importantly, metformin was preferentially cytotoxic to cancer stem cells relative to non-cancer stem cells. Metformin increased the radiosensitivity of cancer cells in vitro, and significantly enhanced the radiation-induced growth delay of FSaII tumors (s.c.) in the legs of C3H mice. Both metformin and ionizing radiation activated AMPK leading to inactivation of mTOR and suppression of its downstream effectors such as S6K1 and 4EBP1, a crucial signaling pathway for proliferation and survival of cancer cells, in vitro as well as in the in vivo tumors. Conclusion: Metformin kills and radiosensitizes cancer cells and eradicates radioresistant cancer stem cells by activating AMPK and suppressing mTOR.

Improvement of Tumor Oxygenation by Mild Hyperthermia

Abstract Song, C. W., Park, H. and Griffin, R. J. Improvement of Tumor Oxygenation by Mild Hyperthermia. There is now abundant evidence that oxygenation in rodent, canine and human tumors is improved during and for up to 1–2 days after heating at mild temperatures. An increase in tumor blood perfusion along with a decline in the oxygen consumption rate appears to account for the improvement of tumor oxygenation by mild hyperthermia. The magnitude of the increase in tumor pO2, determined with oxygen-sensitive microelectrodes, caused by mild hyperthermia is less than that caused by carbogen breathing. However, mild hyperthermia is far more effective than carbogen breathing in increasing the radiation response of experimental tumors, probably because mild hyperthermia oxygenates both (diffusion-limited) chronically hypoxic and (perfusion-limited) acutely hypoxic cells, whereas carbogen breathing oxygenates only the chronically hypoxic cells. Mild hyperthermia is also more effective than nicotinamide, which is known to oxygenate acutely hypoxic cells, in enhancing the radiation response of experimental tumors. The combination of mild hyperthermia with carbogen or nicotinamide is highly effective in reducing the hypoxic cell fraction in tumors and increasing the radiation response of experimental tumors. A primary rationale for the use of hyperthermia in combination with radiotherapy has been that hyperthermia is equally cytotoxic toward fully oxygenated and hypoxic cells and that it directly sensitizes both fully oxygenated and hypoxic cells to radiation. Such cytotoxicity and such a radiosensitizing effect may be expected to be significant when the tumor temperature is elevated to at least 42–43°C. Unfortunately, it is often impossible to uniformly raise the temperature of human tumors to this level using the hyperthermia devices currently available. However, it is relatively easy to raise the temperature of human tumors into the range of 39–42°C, which is a temperature that can improve tumor oxygenation for up to 1–2 days. The potential usefulness of mild hyperthermia to enhance the response of human tumors to radiotherapy by improving tumor oxygenation merits continued investigation.

Physiological mechanisms in hyperthermia: A review

In experimental animal systems, hyperthermia at therapeutic temperature (43-45 degrees C) causes a profound increase in blood flow in normal tissues while it induces only meager and temporal increases in blood flow in tumors. A severe vascular occlusion and hemorrhage usually follows the increase in blood flow in the tumors at the above temperatures. Another pronounced physiological change in tumors by heat is a prompt decrease in intratumor pH. The decrease in intratumor pH would accentuate the thermokilling of tumor cells and also possibly inhibit repair of thermodamage and development of thermotolerance in tumors. The temperature in tumors may rise higher than that in normal tissues during heating because of inefficient heat dissipation from the tumor as a result of decrease blood flow or vascular occlusion. Thus, the differential effects of heat on vascular function and pH in tumors and normal tissues may result in a greater damage in tumors than in surrounding normal tissues. Further investigation is urgently needed to find out whether similar physiological changes occur in human tumors and normal tissues by hyperthermia.

Radiobiology of stereotactic body radiation therapy/stereotactic radiosurgery and the linear-quadratic model

Received Feb 26, 2013, and in revised form Mar 11, 2013. Accepted for publication Mar 12, 2013The validity of the linear-quadratic (LQ) model for calculatingisoeffect doses in radiation therapy has been intensivelydebated in recent issues of the International Journal of Radi-ation Oncology, Biology, Physics (1-3).TheLQmodelissimple and convenient, and by far it has been the most usefulmeans for isodose calculation in treating tumors with conven-tional fractionated radiation therapy (2-4). The LQ modelsolely depends on the expected incidence of direct interactionsof radiation with specific cellular targets (ie, DNA strands).Because the LQ survival curve continuously bends downwardwith increasing radiation dose, many assume that the LQcalculation will inherently overestimate cell death caused byhigh-dose-per-fraction radiation therapy. Interestingly, however,clinical results have shown that the LQ model actually under-estimates tumor control by stereotactic body radiation therapy(SBRT) or stereotactic radiosurgery (SRS) (5), indicating thatmechanism(s) in addition to DNA strand breaks and/or chro-mosome aberrations may be involved in response of tumors toSBRT or SRS. Therefore, it has been hypothesized that SBRTor SRS may cause significant vascular damage in tumors,leading to indirect cell death (5, 6). We have recently reviewedprevious studies on the radiation-induced vascular damage intumors and pointed out the potentially important role of indi-rect/necrotic cell death due to the vascular damage in tumorcontrol with SBRT and SRS (7). We further discussed theradiobiological principles of SBRT and SRS in relation toradiation-induced vascular damage and resultant indirect celldeath (8). Interestingly, some 35 years ago we (C.W.S. andS.H.L.) realized that irradiation of rodent tumors with 10-20Gy in a single dose caused severe vascular injury, leading tonecrotic cell death in significant fractions of tumor cells 2 to 3days after the treatment (9, 10). Figure 1 summarizes theobservations we made on the effects of 10 Gy (1000 rads) ofx-rays in a single dose on the clonogenic surviving cells inWalker 256 rat tumors (10). The surviving cell fraction, asmeasured with an in vivoein vitro excision method, wasapproximately 2.6 10

Radiobiological basis of total body irradiation with different dose rate and fractionation: Repair capacity of hemopoietic cells

Abstract Total body irradiation (TBI) followed by bone marrow transplantation is being used in the treatment of malignant or non-malignant hemopoietic disorders. It has been believed that the ability of hemopoietic cells to repair sublethal radiation damage is negligible. Therefore, several school of investigators suggested that TBI in a single exposure at extremely low dose rate (5 rad/min) over several hours, or in several fractions in 2–3 days, should yield a higher therapeutic gain, as compared with a single exposure at a high dose rate (26 rad/min). We reviewed the existing data in the literature, in particular, the response of hemopoietic cells to fractionated doses of irradiation and found that the repair capacity of both malignant and non-malignant hemopoietic cells might be greather than has been thought. It is concluded that we should not underestimate the ability of hemopoietic cells to repair sublethal radiation damage in using TBI.

Anginex synergizes with radiation therapy to inhibit tumor growth by radiosensitizing endothelial cells

We have demonstrated that the designed peptide anginex displays potent antiangiogenic activity. The aim of our study was to investigate the effect of anginex on established tumor vasculature as an adjuvant to radiation therapy of solid tumors. In the MA148 human ovarian carcinoma athymic mouse model, anginex (10 mg/kg) in combination with a suboptimal dose of radiation (5 Gy once weekly for 4 weeks) caused tumors to regress to an impalpable state. In the more aggressive SCK murine mammary carcinoma model, combination of anginex and a single radiation dose of 25 Gy synergistically increased the delay in tumor growth compared to the tumor growth delay caused by either treatment alone. Immunohistochemical analysis also demonstrated significantly enhanced effects of combined treatment on tumor microvessel density and tumor or endothelial cell proliferation and viability. In assessing physiologic effects of anginex, we observed a reduction in tumor perfusion and tumor oxygenation in SCK tumors after 5–7 daily treatments with anginex with no reduction in blood pressure. To test anginex as a radiosensitizer, additional studies using SCK tumors were performed. Three daily i.p. injections of anginex were able to enhance the effect of 2 radiation doses of 10 Gy, resulting in 50% complete responses, whereas the known antiangiogenic agent angiostatin did not enhance the radiation response of SCK tumors. Mechanistically, it appears that anginex functions as an endothelial cell‐specific radiosensitizer because anginex showed no effect on in vitro radiosensitivity of SCK or MA148 tumor cells, whereas anginex significantly enhanced the in vitro radiosensitivity of 2 endothelial cell types. This work supports the idea that the combination of the antiangiogenic agent anginex and radiation may lead to improved clinical outcome in treating cancer patients.

Effects of recombinant growth factors on radiation survival of human bone marrow progenitor cells

The purpose of this study was to evaluate the individual radioprotective effects of 4 distinct purified recombinant human hematopoietic growth factors, namely recombinant human granulocyte-macrophage colony stimulating factor (rGM-CSF), recombinant human granulocyte colony stimulating factor (rG-CSF), recombinant human interleukin 1 (rIL-1), and recombinant human interleukin 2 (rIL-2) on human myeloid (CFU-GM) and erythroid (BFU-E) bone marrow progenitor cells. We demonstrate that (a) preconditioning with rGM-CSF, rG-CSF, or rIL-1 enables CFU-GM to repair sublethal radiation damage and renders CFU-GM less radiosensitive, (b) preconditioning with rGM-CSF or rIL-1 enables BFU-E to repair sublethal radiation damage, and (c) preconditioning with rIL-2 does not increase the radiation survival of CFU-GM or BFU-E. The effects of recombinant growth factors, in particular rGM-CSF, on the radiation damage repair, radiosensitivity, and proliferative activity of bone marrow progenitor cells resulted in a substantial increase in the mean numbers of progenitor cell-derived hematopoietic colonies in irradiated marrow samples. The effects of rGM-CSF on the radiation response of CFU-GM and BFU-E, and the effects of rG-CSF as well as rIL-1 on the radiation response of CFU-GM did not appear to require the presence of T-cells/T-cell precursors, NK-cells, B-cells/B-cell precursors, monocytes, macrophages, MY8 antigen positive non-CFU-GM myeloblasts, promyelocytes, myelocytes, metamyelocytes, granulocytes, or glycophorin A positive erythroid cells since virtually identical results were obtained with unsorted marrow samples or highly purified fluorescence activated cell sorter (FACS) isolated progenitor cell suspensions. To our knowledge, this report represents the first study on recombinant human growth factor-induced modulation of the radiation responses of normal human bone marrow progenitor cells.

Blood flow and intravascular volume of mammary adenocarcinoma 13726a and normal tissues of rat during and following hyperthermia

The effects of hyperthermia on blood flow and intravascular volume were studied in mammary adenocarcinoma 13762A growing subcutaneously in the leg of Fischer F344 rats. The blood flow was determined using microspheres labelled with 125I, and the blood volume was determined using red blood cells labelled with 51Cr. At the end of heating with water bath at 43.5 degrees C for 1 hour, there was a marked elevation of 51Cr in tumor. The 125I content in tumor also was mildly elevated. Histologically there was a greater number of patent blood vessels per unit area, and they were dilated and hyperemic. In addition, widespread and diffuse hemorrhage could be seen. It appeared, therefore, that the increased 51Cr and 125I label in the tumors immediately after heating was, at least in part, a result of leakage of the labels to extravascular space in addition to possible vasodilation and increased blood flow. At 1 and 5 hours after heating, tumor blood flow was considerably reduced, and at 16 hours both tumor blood flow and blood volume were considerably reduced. Histological examination demonstrated that the tumor blood vessels remained dilated and hyperemic after heating. The effect of heat on blood flow and blood volume in the skin and muscle adjacent to the tumors was also investigated. Blood flow and blood volume in the surrounding normal tissues were significantly elevated at the end of heating. Blood flow was relatively unchanged at 1, 5, and 16 hours after heating, but blood volume was reduced to about one half. These findings indicate that hyperthermia may induce greater damage to vasculature of tumors than normal tissues, and that vascular damage in tumors may take some time to express itself following moderate hyperthermia.