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Adriana Haimovitz-Friedman

Publications and source records attributed to Adriana Haimovitz-Friedman.

9 recordsLinked to original sources
PubMed2005

ATM regulates target switching to escalating doses of radiation in the intestines.

Although stem cells succumbing to reproductive death are assumed to be the single relevant targets in radiation tissue damage, recent studies showed intestinal stem cell damage is conditionally linked to crypt endothelial apoptosis, defining a two-target model. Here we report that when mouse intestines were protected against microvascular apoptosis, radiation switched as the dose escalated to a previously unrecognized crypt stem cell target, activating ceramide synthase-mediated apoptosis to initiate intestinal damage. Whereas ataxia telangiectasia-mutated (ATM) kinase normally represses ceramide synthase, its derepression in Atm(-/-) mice increased crypt stem cell radiosensitivity 3.7-fold without sensitizing the microvascular response. Discovery of this intestinal radiosensitivity mechanism allowed design of an antisense Atm oligonucleotide treatment which phenocopied the Atm(-/-) mouse, reordering ceramide synthase-mediated stem cell death to become the first-line gastrointestinal response of wild-type littermates. These experiments indicate that tissues operate multiple potential targets activated consecutively according to their inherent radiosensitivities that may be reordered therapeutically to control radiation tissue responses.

Animals↗
PubMed2005

Down-regulation of ATM protein sensitizes human prostate cancer cells to radiation-induced apoptosis.

Treatment with the protein kinase C activator 12-O-tetradecanoylphorbol 12-acetate (TPA) enables radiation-resistant LNCaP human prostate cancer cells to undergo radiation-induced apoptosis, mediated via activation of the enzyme ceramide synthase (CS) and de novo synthesis of the sphingolipid ceramide (Garzotto, M., Haimovitz-Friedman, A., Liao, W. C., White-Jones, M., Huryk, R., Heston, D. W. W., Cardon-Cardo, C., Kolesnick, R., and Fuks, Z. (1999) Cancer Res. 59, 5194-5201). Here, we show that TPA functions to decrease the cellular level of the ATM (ataxia telangiectasia mutated) protein, known to repress CS activation (Liao, W.-C., Haimovitz-Friedman, A., Persaud, R., McLoughlin, M., Ehleiter, D., Zhang, N., Gatei, M., Lavin, M., Kolesnick, R., and Fuks, Z. (1999) J. Biol. Chem. 274, 17908-17917). Gel shift analysis in LNCaP and CWR22-Rv1 cells demonstrated a significant reduction in DNA binding of the Sp1 transcription factor to the ATM promoter, and quantitative reverse transcription-PCR showed a 50% reduction of ATM mRNA between 8 and 16 h of TPA treatment, indicating that TPA inhibits ATM transcription. Furthermore, treatment of LNCaP, CWR22-Rv1, PC-3, and DU-145 human prostate cells with antisense-ATM oligonucleotides, which markedly reduced cellular ATM levels, significantly enhanced radiation-induced CS activation and apoptosis, leading to apoptosis at doses as a low as 1 gray. These data suggest that the CS pathway initiates a generic mode of radiation-induced apoptosis in human prostate cancer cells, regulated by a suppressive function of ATM, and that ATM might represent a potential target for pharmacologic inactivation with potential clinical applications in human prostate cancer.

Apoptosis↗
PubMed2004

Host acid sphingomyelinase regulates microvascular function not tumor immunity.

Previous studies provided evidence that MCA/129 fibrosarcomas and B16 melanomas grow 2- to 4-fold faster in acid sphingomyelinase (asmase)-deficient mice than in asmase(+/+) littermates and are resistant to single-dose irradiation due to inability to mount an apoptotic response in tumor microvascular endothelium. However, others postulated the differences might be associated with a host antitumor immune response in asmase(+/+) mice that is not expressed in asmase(-/-) mice due to phenotypic deficiency in antitumor immunity. The present studies demonstrate that none of the tumor-host combinations displayed the classic criteria of an immunogenic tumor because they lacked endotumoral or peritumoral infiltrates almost entirely. Furthermore, neither MCA/129 fibrosarcoma nor B16 melanoma tumors showed differences in growth or radioresponsiveness when implanted into mutant mouse models (Rag(-/-) and MEF(-/-)) lacking functional immune cell [natural killer (NK), NK-T, T, and B cells] populations. Additionally, development and function of B-, T-, and NK-cell populations in asmase(-/-) mice were normal, indistinguishable from their wild-type littermates. These data provide definitive evidence that MCA/129 fibrosarcomas and B16F1 melanomas do not elicit a host immune response in wild-type mice and that the asmase(-/-) phenotype is not deficient in antitumor immunity, supporting the notion that the patterns of tumors growth and radiation response are conditionally linked to the ability of the tumor endothelium to undergo ASMase-mediated apoptosis.

Animals↗
PubMed2003

The cyclin-dependent kinase inhibitor flavopiridol potentiates gamma-irradiation-induced apoptosis in colon and gastric cancer cells.

PURPOSE: Flavopiridol is a cyclin-dependent kinase inhibitor currently under development by the National Cancer Institute both as a single agent and in combination with chemotherapy. There have been numerous reports that flavopiridol potently enhances the induction of apoptosis by chemotherapy. However, the effect of flavopiridol on radiotherapy (RT)-induced apoptosis has been largely untested. RT has become the cornerstone of adjuvant treatment of colorectal and gastric cancer. In view of this, we elected to evaluate the effect of flavopiridol on potentiating RT-induced apoptosis in the human colon cancer cell line HCT-116 and the gastric cancer cell line MKN-74. EXPERIMENTAL DESIGN: The efficacy of combination of gamma-irradiation and flavopiridol was tested in vitro in MKN-74 and HCT-116 cells and correlated to changes in p21 expression. HCT-116 cells were also established as tumors in nude mice and treated with gamma-irradiation and flavopiridol either as single agents or in sequential combinations such that flavopiridol was either given 7 h before, concomitantly, or 3 and 7 h after gamma-irradiation. RESULTS: Flavopiridol significantly enhanced the induction of apoptosis by gamma-irradiation in both cell lines as measured by quantitative fluorescent microscopy, caspase-3 activation, poly(ADP-ribose) polymerase cleavage, and cytochrome c release. To achieve the best effect, it was important to expose the tumor cells to gamma-irradiation before the flavopiridol. This sequence dependence was confirmed in vivo. When gamma-irradiation was administered 7 h before flavopiridol, 42% of the tumor-bearing animals were rendered disease free, compared with no animals treated with either gamma-irradiation or flavopiridol alone. Examination of the p21 status of HCT-116 and MKN-74 cells, after treatment with sequential gamma-irradiation and flavopiridol, indicated a loss of p21 protein expression. Loss of p21 was mainly due to cleavage by caspases. HCT-116 cells that lack p21 (p21(-/-)) also exhibited sensitization to gamma-irradiation and showed an even greater enhancement of gamma-irradiation-induced apoptosis by flavopiridol when compared with the parental HCT-116 cells. CONCLUSIONS: These studies indicate that gamma-irradiation followed by flavopiridol enhances apoptosis and yields significantly increased tumor regressions and cures that are not achievable with radiation alone. These results indicate that flavopiridol can potently enhance the effect of gamma-radiation both in vitro and in vivo and may provide a new means to treat patients with locally advanced gastrointestinal cancers.

Animals↗
PubMed2003

Endothelial apoptosis initiates acute blood-brain barrier disruption after ionizing radiation.

Acute disruption of blood-brain barrier (BBB) is well recognized after radiation therapy to the central nervous system (CNS). We assessed the genetic regulation of acute BBB disruption and its relationship to vascular endothelial cell death in the CNS after irradiation. Adult rats were given graded single doses of X-ray to the cervical spinal cord. At different time intervals after irradiation, the irradiated spinal cord was processed for histological and immunohistochemical analysis. Disruption of blood-spinal cord barrier was assessed using albumin immunohistochemistry, i.v. injection of Evans blue dye, and (99m)Tc-diethylenetriamine pentaacetic acid. In the rat spinal cord, there was a dose-dependent apoptotic response during the first 24 h after irradiation, and apoptotic cells consisted of both endothelial and glial cells, as described previously (1, 2). A dose-dependent reduction in endothelial cell density was observed at 24 h after irradiation. This was associated with a similar dose-dependent disruption in blood-spinal cord barrier as demonstrated by albumin immunohistochemistry. Radiation-induced apoptosis in endothelial cells has been shown to be dependent on the acid sphingomyelinase (ASMase) pathway. After a single 50-Gy dose to the cervical spinal cord of ASMase +/+ mice, there was a 47.7% reduction in endothelial cell density at 24 h compared with nonirradiated controls. No decrease in endothelial cell density was observed in irradiated ASMase -/- mice. In the irradiated spinal cord of ASMase +/+ mice, there was evidence of albumin immunoreactivity and Evans blue dye staining around microvessels, and (99m)Tc-diethylenetriamine pentaacetic acid uptake increased at 24 h. Nonirradiated controls and the irradiated spinal cord of ASMase -/- mice demonstrated no evidence of leakage. We conclude that apoptosis of endothelial cells initiates acute BBB disruption in the CNS after irradiation and that acute BBB disruption after irradiation is mediated by the ASMase pathway.

Animals↗
PubMed2003

The epidermal growth factor receptor tyrosine kinase inhibitor ZD1839 selectively potentiates radiation response of human tumors in nude mice, with a marked improvement in therapeutic index.

PURPOSE: The epidermal growth factor receptor tyrosine kinase inhibitor ZD1839 (Iressa) markedly potentiates the efficacy of many cytotoxic agents against several human cancer xenografts, irrespective of tumor EGFR expression levels. We subsequently investigated the extent to which ZD1839 might improve radiation therapy (RT) in similar animal models of human cancer within the limits of tolerance at a relevant organ site. EXPERIMENTAL DESIGN: We carried out studies of ZD1839 in in vivo models of human non-small cell lung (A549 and SK-LC-16) and breast (MDA-MB468) cancers and human mesothelioma (JMN). The tumors were implanted s.c. over the rib cage or on the most proximate breast and RT given ventral dorsally to the chest only, with mediastinal protection. After the tumor reached a palpable size (0.4-0.6 mm), treatment was initiated with the maximum-tolerated dose (MTD) of ZD1839 (150 mg/kg once daily x 5 for 2 successive weeks), RT (a total of 40 Gy given fractionally at 4 Gy once daily x 5 for 2 successive weeks), or both ZD1839 and RT. RESULTS: This level of RT induced no untoward effects in the mice and was effective (18-72%) in bringing about regression of the tumors with a few complete regressions. ZD1839 alone, given p.o. on the same schedule at its MTD (150 mg/kg), was modestly inhibitory (35-40%) to tumor growth. RT and ZD1839 could be given together at the same doses on the same schedule, resulting in marked regression (50-99%) and a large number of complete regressions of each of the tumors studied. In these studies, the MTD of ZD1839 could be combined with the MTD of RT with no change in schedule or increase toxicity over ZD1839 or RT alone. CONCLUSIONS: ZD1839 significantly enhanced the antitumor action of RT against the test tumors without significant adverse effects, increasing the therapeutic selectively of ionizing radiation in these model systems. These results predict substantial benefits for this multimodality regimen of therapy in patients.

Animals↗
PubMed2003

Microvascular function regulates intestinal crypt response to radiation.

Recent evidence suggests that microvascular endothelial apoptosis represents the primary lesion in radiation damage to the gastrointestinal (GI) tract. Rescue of endothelium by depletion of acid sphingomyelinase or i.v. treatment with basic fibroblast growth factor (FGF) prevented the lethal GI syndrome in C(57)Bl/6 mice. Here we show that basic FGF increased crypt survival after irradiation by 2-3 fold, with a dose modification factor at D(10) of 1.15 (P < 0.01). Basic FGF inhibited initial crypt damage, assessed by crypt shrinkage at 18-24 h, but did not significantly affect the regeneration of surviving crypts at 3.5 days after irradiation. These data suggest that microvascular function regulates expression of radiation-induced crypt stem cell clonogen damage in the evolution of radiation injury to the GI mucosa.

Animals↗
PubMed2003

Tumor response to radiotherapy regulated by endothelial cell apoptosis.

About 50% of cancer patients receive radiation therapy. Here we investigated the hypothesis that tumor response to radiation is determined not only by tumor cell phenotype but also by microvascular sensitivity. MCA/129 fibrosarcomas and B16F1 melanomas grown in apoptosis-resistant acid sphingomyelinase (asmase)-deficient or Bax-deficient mice displayed markedly reduced baseline microvascular endothelial apoptosis and grew 200 to 400% faster than tumors on wild-type microvasculature. Thus, endothelial apoptosis is a homeostatic factor regulating angiogenesis-dependent tumor growth. Moreover, these tumors exhibited reduced endothelial apoptosis upon irradiation and, unlike tumors in wild-type mice, they were resistant to single-dose radiation up to 20 grays (Gy). These studies indicate that microvascular damage regulates tumor cell response to radiation at the clinically relevant dose range.

Animals↗