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A Eastman

Publications and source records attributed to A Eastman.

At least 37 records · Page 2Linked to original sources
PubMed1997

Zinc inhibits apoptosis upstream of ICE/CED-3 proteases rather than at the level of an endonuclease.

Apoptosis is commonly associated with DNA digestion, but it remains controversial as to which endonuclease is involved. The ability of zinc to inhibit DNA digestion in intact cells, and inhibit a Ca2+/Mg2+-dependent endonuclease in cell lysates, has been used frequently to suggest this is the endonuclease involved. However, zinc has many other effects on cells, and here it is shown that zinc also prevents many upstream events in apoptosis. These studies were performed in human ML-1 cells following incubation with etoposide. During apoptosis, these cells undergo intracellular acidification, increased accumulation of Hoechst 33342, DNA digestion and chromatin condensation. Zinc inhibited all of these events. An upstream event in apoptosis is activation of ICE/CED-3 proteases which is commonly observed as proteolysis of a substrate protein, poly(ADP-ribose) polymerase (PARP). The ICE/CED-3 proteases are themselves activated by proteolysis, and this was detected here by cleavage of one family member CPP32. Zinc prevented cleavage of both CPP32 and PARP. We recently demonstrated that dephosphorylation of the retinoblastoma susceptibility protein Rb was a marker of an event even further upstream in apoptosis; zinc was also found to inhibit Rb dephosphorylation. Therefore, zinc must protect cells at a very early step in the apoptotic pathway, and not as a direct inhibitor of an endonuclease.

Journal Article↗
PubMed1997

7-Hydroxystaurosporine (UCN-01) causes redistribution of proliferating cell nuclear antigen and abrogates cisplatin-induced S-phase arrest in Chinese hamster ovary cells.

A variety of agents, such as caffeine, have been shown to abrogate the DNA damage-dependent G2 checkpoint and enhance cytotoxicity. However, these agents are too toxic for clinical use. We have reported that the potent protein kinase inhibitor 7-hydroxystaurosporine (UCN-01) at nontoxic doses abrogates the G2 arrest caused by the DNA-damaging agent cisplatin. Here, using Chinese hamster ovary cells, we show that cisplatin causes predominantly an S-phase arrest; UCN-01 abrogates this S-phase arrest, causing progression of cells to G2 and, subsequently, apoptotic cell death. In searching for an explanation for this accelerate DNA synthesis, we discovered that UCN-01 caused translocation of proliferating cell nuclear antigen (PCNA) to the detergent-insoluble, DNA-bound fraction. PCNA acts as a sliding clamp for DNA polymerase delta. Sequestering of PCNA by p21waf1/cip1 is required for p53-dependent G1 arrest in damaged cells. However, the S-phase arrest occurs independently of p53 and p21waf1/cip1. Our results suggest that PCNA is also a component of this S-phase checkpoint, despite the fact that CHO cells are defective for p53, and no increase in p21waf1/cip1 was observed. The mechanism by which PCNA is sequestered in the absence of p21waf1/cip1 and the mechanism by which UCN-01 disrupts this sequestration remain to be elucidated.

Alkaloids↗
PubMed1996

Detection of apoptosis by flow cytometry of cells simultaneously stained for intracellular pH (carboxy SNARF-1) and membrane permeability (Hoechst 33342).

Intracellular acidification appears to be a frequent and possibly universal occurrence during apoptosis. We have used carboxy SNARF-1 to measure intracellular pH by flow cytometry. We report here that the addition of Hoechst 33342 concurrently with carboxy SNARF-1 provides a clearer discrimination of the apoptotic population. Apoptotic cells accumulate Hoechst 33342 more rapidly than do viable nonapoptotic cells. The cells with greater Hoechst 33342 fluorescence are the same cells as those with decreased intracellular pH; these cells also have decreased volume. The different parameters in this analysis are presented for three models of apoptosis: human myeloblastoid ML-1 cells incubated with etoposide, murine cytotoxic T cells following withdrawal of interleukin-2, and Chinese hamster ovary cells incubated with staurosporine. In most circumstances, carboxy SNARF-1 provides excellent resolution of viable and apoptotic cells. However, the addition of Hoechst 33342 is particularly valuable when carboxy SNARF-1 alone can not fully discriminate the two cell populations. This situation occurs in Chinese hamster ovary cells, which undergo a smaller degree of acidification than do the other cell models. This situation also occurs when the extracellular pH is experimentally reduced to investigate the mechanism of pH dysregulation; the apoptotic cells appear to retain the ability to regulate intracellular pH at low pH, although they are defective in proton export at neutral pH.

Animals↗
PubMed1996

Intracellular calcium stores are not required for Bcl-2-mediated protection from apoptosis.

The ability of Bcl-2 to inhibit cell death is well documented but its mechanism of action remains elusive. Recent reports have suggested that Bcl-2 prevents apoptosis by inhibiting the release of Ca2+ from the thapsigargin-sensitive Ca2+ store. The mobilization of Ca2+ from this store has been implicated as a signal regulating apoptotic cell death induced by glucocorticoids and by interleukin-3 withdrawal. The present study was designed to determine if Bcl-2 would still inhibit apoptosis after depletion of intracellular Ca2+ stores. We compared the response of two Chinese hamster ovary cell lines (5AHSmyc and 5A300bcl-2.2) following incubation with the calcium ionophore ionomycin to deplete intracellular Ca2+ stores. Continued incubation of 5AHSmyc cells in calcium-free media induced substantial apoptotic DNA fragmentation within 4 h and >95% loss of viability within 48 h. However, 5A300bcl-2.2 cells showed no evidence of DNA fragmentation or loss of viability over the same time period. Intracellular Ca2+ was analyzed with the Ca2+-sensitive fluorescent dye INDO-1 and confirmed that ionomycin was capable of releasing Ca2+ from intracellular stores in both cell lines. These results show that depletion of intracellular Ca2+ stores induces apoptosis and that these Ca2+ stores are not required for the protection afforded by Bcl-2.

Animals↗
PubMed1996

Phorbol ester augments butyrate-induced apoptosis of colon cancer cells.

Butyrate is a potentially selective therapeutic agent for many adenocarcinomas. Butyrate causes reversible growth arrest as well as some death of VACO 5 colon cancer cells. Combined treatment with butyrate and the phorbol ester TPA leads instead only to cell death, while TPA causes little death on its own. Cells dying during treatment with TPA and butyrate, as well as those dying in the presence of butyrate alone, exhibit features typical of apoptosis, including detachment, shrinkage and internucleosomal DNA cleavage. Pre-treating VACO 5 cell cultures with TPA for as little as 6 hr prior to butyrate addition led to a markedly diminished enhancement of butyrate-induced apoptosis. Treatment with a distinct PKC activator, bryostatin 1, was ineffective in enhancing butyrate-induced death and, furthermore, counteracted the death-enhancing actions of TPA. Such antagonism was apparent when bryostatin was added after 12 hr of TPA/butyrate treatment but was much less effective thereafter. The duration of TPA/butyrate treatment required for depressing cell survival by >95% was thereby estimated to be 24 hr. Other colon cancer cell lines were examined for the extent of cell death following treatment with TPA/butyrate. In each of these lines, butyrate inhibited cell replication in a reversible manner, similar to that seen in VACO 5. However, the combination of butyrate and TPA led to high levels of cell death in only a subset of these lines. TPA/butyrate-treated cultures of COLO 201 exhibited extensive apoptosis, similar in timing and magnitude to the response by VACO 5, whereas HCT 116 was reversibly growth-arrested. Our findings indicate that the PKC system plays a critical role in maintaining cell survival during butyrate-induced growth arrest.

Adenocarcinoma↗
PubMed1996

The involvement of protein phosphatases in the activation of ICE/CED-3 protease, intracellular acidification, DNA digestion, and apoptosis.

Many events in apoptosis have been identified but their temporal relationships remain obscure. Apoptosis in human ML-1 cells induced by etoposide is characterized by intracellular acidification, enhanced Hoechst 33342 fluorescence, DNA digestion, chromatin condensation, and proteolysis of poly(ADP-ribose) polymerase. This proteolysis is a marker for the action of ICE/CED-3 proteases, which are critical activators of apoptosis. We observed that three serine/threonine protein phosphatase inhibitors, okadaic acid, calyculin A, and cantharidin, prevented all of these apoptotic characteristics. To determine which protein phosphatase was involved, we investigated the dephosphorylation of the retinoblastoma susceptibility protein Rb, a substrate for protein phosphatase 1 but not protein phosphatase 2A. Rb was dephosphorylated during apoptosis, and each inhibitor prevented this dephosphorylation at the same concentrations that prevented apoptosis. No increase in protein phosphatase 1 activity was observed in apoptotic cells suggesting that dephosphorylation of Rb may result from loss of Rb kinase activity in the presence of a constant level of protein phosphatase activity. Long term inhibition of protein phosphatase 1 (>8 h) also led to the appearance of dephosphorylated Rb, cleavage of poly(ADP-ribose) polymerase and apoptosis, suggesting these events are not solely dependent upon protein phosphatase 1. Rb dephosphorylation was also observed in several other models of apoptosis. Hence, an imbalance between protein phosphatase 1 and Rb kinase may be a common means to activate ICE/CED-3 proteases resulting in the subsequent events of apoptosis.

Acids↗
PubMed1996

UCN-01: a potent abrogator of G2 checkpoint function in cancer cells with disrupted p53.

BACKGROUND: Arrest of the cell cycle in G2 phase following DNA damage helps protect cell viability by allowing time for DNA repair before entry into mitosis (M phase). Abrogation of G2 arrest sensitizes cells to the effects of DNA-damaging agents. UCN-01 (7-hydroxystaurosporine), a protein kinase C inhibitor that may block G2 checkpoint regulation, has been reported to enhance the cytotoxicity of mitomycin C, a known DNA-damaging agent. PURPOSE: We studied the effect of UCN-01 on G2 checkpoint control in human lymphoma CA46 cells, whose sensitivity to various DNA-damaging agents and G2 response to DNA damage have been characterized. We also assessed the ability of UCN-01 to enhance the cytotoxicity of gamma irradiation in CA46 cells and human colon carcinoma HT-29 cells, both of which are mutant for p53 function. The influence of p53 function on UCN-01-mediated abrogation of the G2 checkpoint and enhancement of DNA-damaging agent cytotoxicity was studied in transfected human breast carcinoma MCF-7 cells that either expressed or did not express the human papillomavirus type-16 E6 protein. MCF-7 cells have normal p53 function, and the E6 protein binds p53 protein and promotes its destruction. METHODS: The effect of UCN-01 on cell cycle arrest induced by gamma irradiation was studied in CA46 cells and in transfected MCF-7 cells by use of flow cytometry. A histone H1 phosphorylation assay was employed to measure cyclin B1/Cdc2 kinase activity in extracts derived from irradiated and nonirradiated CA46 cells that had been either treated or not treated with UCN-01; the phosphorylation status of Cdc2 kinase protein in the same extracts was determined by use of western blotting. The effect of UCN-01 on the cytotoxicity of gamma irradiation in CA46 and HT-29 cells was determined by use of MTT (thiazolyl blue) and clonogenic (colony-forming) assays, respectively; a clonogenic assay was also used to measure the effect of UCN-01 on the cytotoxicity of cisplatin in transfected and nontransfected MCF-7 cells. RESULTS: G2 arrest induced in CA46 cells by gamma irradiation was minibited by treatment with UCN-01 in a dose-dependent manner; arrest in G2 was completely abrogated by exposure to 300 nM UCN-01. Biochemical markers indicative of the G2/M transition, including the activation of cyclin B1/Cdc2 kinase and the suppression of Cdc2 threonine-14 and tyrosine-15 phosphorylation, were detected in irradiated cells treated with UCN-01. UCN-01 enhanced the cytotoxicity of gamma irradiation in CA46 and HT-29 cells. MCF-7 cells with functional p53 protein were more resistant to G2 checkpoint abrogation by UCN-01 than MCF-7 cells with disrupted p53 function. UCN-01 markedly enhanced the cell-killing activity of cisplatin in MCF-7 cells defective for p53 function. CONCLUSIONS AND IMPLICATIONS: UCN-01 is a potent abrogator of G2 checkpoint control in cancer cells with disrupted p53 function. UCN-01 might be capable of enhancing the effectiveness of DNA-damaging agents in the treatment of tumors with cells lacking normal p53 function.

Alkaloids↗
PubMed1996

BCL-2 and MCL-1 expression in Chinese hamster ovary cells inhibits intracellular acidification and apoptosis induced by staurosporine.

Multiple physiological and pharmacological stimuli induce cells to die by apoptosis. In many cases, this apoptosis is inhibited by BCL-2, suggesting the involvement of a common regulatory pathway. One frequent characteristic of apoptosis is the digestion of DNA into oligonucleosome-length fragments. Intracellular acidification and increased intracellular calcium have been variously implicated in activating the endonuclease responsible for this DNA digestion. To explore the involvement of these potential signals in endonuclease activation, we have analyzed three Chinese hamster ovary cell lines: a parental line, one expressing a cDNA encoding BCL-2, and the third expressing the BCL-2 family member MCL-1. Apoptosis was induced with the protein kinase inhibitor staurosporine and intracellular pH and calcium were measured by flow cytometry. We found that both MCL-1 and BCL-2 inhibited DNA digestion compared to the parent cell line, although BCL-2 was more potent in this regard. Concurrent with DNA digestion, we observed intracellular acidification; MCL-1 and BCL-2 inhibited intracellular acidification to an extent commensurate with their ability to inhibit DNA digestion. In contrast, staurosporine caused a dose-dependent increase in intracellular calcium in all three cell lines, demonstrating that intracellular free calcium levels did not correlate with the induction of apoptosis. These results suggest that BCL-2 and MCL-1 may regulate a pathway for intracellular pH homeostasis during apoptotic cell death.

Acids↗
PubMed1996

The expression of proopiomelanocortin (POMC) and of corticotropin releasing hormone receptor (CRH-R) genes in mouse skin.

The proopiomelanocortin (POMC) and the corticotropin releasing hormone receptor (CRH-R) genes are expressed in the skin of the C57BL/6 mouse throughout the entire hair cycle, and CRH immunoreactivity is present in the pilosebaceous unit of the hair follicle and the epidermis. These findings suggest that some components of hypothalamo-pituitary axis are operating in mouse skin.

Animals↗
PubMed1996

Enhancement of cisplatin-induced cytotoxicity by 7-hydroxystaurosporine (UCN-01), a new G2-checkpoint inhibitor.

DNA-damaging agents arrest cell cycle progression at either G1 or G2. A variety of agents such as caffeine have been shown to abrogate the DNA damage-dependent G2 checkpoint and enhance cytotoxicity. Unfortunately, this strategy has not enhanced therapeutic activity because adequate concentrations of these modulators are not tolerated in vivo. Here, using Chinese hamster ovary cell lines, we show that the potent protein kinase inhibitor 7-hydroxy-staurosporine (UCN-01) abrogates the G2 arrest induced by the DNA-damaging agent cisplatin. UCN-01 not only was effective at inducing mitosis when added to G2-arrested cells but also prevented cells from arresting in G2 when added to S-phase cells. Furthermore, UCN-01 did not cause premature mitosis of S-phase cells; rather, the cells progressed to G2 before undergoing mitosis. These effects were observed at noncytotoxic concentrations of UCN-01 that alone had no effect on cell cycle passage. Furthermore, the same concentrations of UCN-01 that resulted in abrogation of the cisplatin-induced G2 arrest also enhanced cisplatin-induced cytotoxicity, as determined by a colony formation assay. UCN-01 enhanced cisplatin cytotoxicity up to 60-fold and reduced by 3-fold the concentration of cisplatin required to kill 90% of the cells. The concentrations of UCN-01 required for this enhancement have been shown to be well tolerated in animal models, suggesting that this combination may represent an effective strategy for enhancing cisplatin-based chemotherapeutic regimens.

Alkaloids↗
PubMed1995

Apoptosis in an interleukin-2-dependent cytotoxic T lymphocyte cell line is associated with intracellular acidification. Role of the Na(+)/H(+)-antiport.

Apoptosis is a form of cell death associated with DNA fragmentation and chromatin condensation. We recently established that intracellular acidification occurred during apoptosis following cytotoxic insult. The current studies were designed to determine whether intracellular acidification was more generally associated with apoptosis, specifically in a model of growth factor withdrawal. Upon withdrawal of interleukin-2, CTLL-2 cells accumulated in the G1 phase of the cell cycle and started to fragment their DNA around 12 h concurrent with both decreased pH and increased Ca2. Chelation of Ca2+ did not inhibit DNA digestion, whereas incubation with a calcium ionophore prevented both acidification and DNA digestion. Hence, acidification rather than increased Ca2+ was associated with apoptosis. The acidified cells represented a discrete population up to 0.7 pH units below normal. The extent of acidification depended upon the extracellular pH; above pH 6.3, intracellular pH was significantly below extracellular pH, whereas below pH 6.3, the cells still regulated their pH. Inhibition of the Na+/H(+)-antiport prevented the apoptotic cells from regulating their intracellular pH under these acidic conditions. These intracellular pH under these acidic conditions. These results demonstrate that apoptotic cells retain a functional antiport but that its set-point has changed. Many survival factors are known to phosphorylate and activate the antiport, hence apoptosis is likely to be associated with dephosphorylation. Although acidification always occurred during apoptosis, maintaining intracellular pH above 7.2 did not prevent apoptosis, suggesting that an acid pH is not essential for apoptosis. We hypothesize that other critical regulators of apoptosis must be subject to dephosphorylation.

Amiloride↗
PubMed1995

Fish oil, atherogenesis, and thrombogenesis.

Marine fish consumption is known to reduce mortality from ischemic heart disease. The use of fish oil as a dietary supplement, however, is not universally recommended. In large doses, fish oil reduces plasma cholesterol and triacylglycerol but increases low density lipoprotein (LDL) levels and the potential for free radical generation and bleeding. Moderate marine fish consumption is known to reduce mortality without altering commonly measured variables, i.e., plasma cholesterol levels, in vitro platelet aggregation, and bleeding times. In swine, we observed that monocyte adhesions and platelet clumps over the lesion surface of proximal left anterior descending (LAD) coronary arteries are markedly reduced when an atherogenic diet was supplemented with cod-liver oil, even when the cholesterol levels were equalized with the untreated group. These findings suggest that fish oil is hypothrombogenic. We developed an in vitro assay to delineate the mechanism whereby fish oil reduced monocyte-endothelial cell interactions in vivo. The effects of supplementing the culture medium with different fatty acids on adhesions between lipopolysaccharide (LPS) stimulated swine aortic endothelial cells (SAEC) and the human monocyte-like cell line, U937, was investigated in a 10 minute adhesion assay at 37 degrees C. Exposure of SAEC for 6 hours to media containing 50-200 microMs eicosapentaenoic (EPA), stearic, oleic, linoleic, and arachidonic acid, respectively, revealed that only EPA reduced U937-SAEC adhesion. Exposure of U937 to EPA also reduced adhesions. EPA was not effective when added to the SAEC more than 2 hours after they were stimulated with LPS. Exposure of human umbilical vein endothelial cells (HUVEC) to EPA reduced the expression of VCAM-1, ELAM-1, and ICAM-1 after 5 hours of stimulation with LPS. These results suggest that EPA may functionally impair the induction/expression of adhesion molecules.

Animals↗
PubMed1995

Survival factors, intracellular signal transduction, and the activation of endonucleases in apoptosis.

Cell survival is normally mediated by factors in the extracellular environment, whereas genetic changes that constitutively activate intracellular survival pathways often occur in cancer. It is suggested that a Ras/Raf/MAP kinase-dependent pathway is critical for cell survival. Apoptosis results from loss of these survival factors or deregulation of survival pathways. If protein kinase cascades mediate survival, then it is likely that phosphatases mediate apoptosis. Potential targets for dephosphorylation include regulators of ion homeostasis as these have been implicated in the regulation of endonucleases associated with apoptosis. Survival factors also modulate anticancer drug response and understanding these pathways may improve therapy.

Animals↗
PubMed1995

Assays for DNA fragmentation, endonucleases, and intracellular pH and Ca2+ associated with apoptosis.

The methods described here facilitate assessment of the DNA digestion that was once considered a hallmark of apoptosis, but is now recognized as a common overdigestion of genomic DNA; less frequent breaks also lead to the morphological appearance of an apoptotic nucleus. Whatever level of DNA digestion occurs, it may be brought about by activity of one of a number of endonucleases. Whether one endonuclease is responsible in all cases of apoptosis or whether different endonucleases are responsible in various systems and circumstances remains unknown. In attempting to identify changes in ion concentrations that might activate these endonucleases, we have observed intracellular acidification to correlate with apoptosis consistently. This observation may have other implications since the acidification could be responsible for activating other proteins, such as proteases, which are also associated with apoptosis. The importance of such events to the onset of apoptosis remains to be fully established.

Animals↗
PubMed1995

Enhanced radiation-induced cell killing by carboplatin in cells of repair-proficient and repair-deficient cell lines.

The objective of this study was to determine whether a deficiency for either one of two repair processes influences the phenomenon of enhancement of radiation-induced cell killing by carboplatin which has been reported previously in one cell line (V79) and which is presumably a result of an interaction between these two therapeutic modalities. Cell killing was enhanced in cells of four cell lines when the cells were exposed to carboplatin before and during irradiation in either air or hypoxia. In cell lines proficient in both excision repair and DNA double-strand break repair (K1 and AA8), and in a cell line deficient in nucleotide excision repair (UV41), the enhancement was characterized as both a reduction in the shoulder region of the survival curves indicated by a reduced Dq and a reduction in D0 in the terminal region of the survival curves determined for cells exposed in air and under hypoxic conditions. Only the latter effect was observed in a cell line deficient in DNA double-strand break repair (xrs-5). The survival curves were fitted to the data using the repair saturation model and a computer program developed by N. Albright (Radiat. Res. 118, 112-130, 1989). In hypoxia, the reductions in Dq were as great as from 7.0 Gy to 2.1 Gy, 3.3 Gy to 0 Gy and 1.7 Gy to 0 Gy for K1, AA8 and UV41 cells, respectively. Sensitizer enhancement ratios ranged from 1.3 to 1.7 and were similar for irradiation in air and under hypoxic conditions. This enhanced cell killing by carboplatin combined with radiation required levels of the drug sufficient to produce cytotoxicity by the drug alone as exemplified by the UV41 cell line, which is intrinsically sensitive to carboplatin and in which 1/30 of the drug concentration required for the other cell lines produced an enhanced cell killing at an equitoxic dose of only 5 microM.

Animals↗
PubMed1994

Mcl-1, a member of the Bcl-2 family, delays apoptosis induced by c-Myc overexpression in Chinese hamster ovary cells.

Mcl-1, a protein increased early in the differentiation of human myeloblastic ML-1 cells, has sequence similarity to Bcl-2. In the present study, we determined whether Mcl-1 has functional similarity to Bcl-2 by testing its ability to inhibit apoptosis induced by c-Myc overexpression. This was carried out using Chinese hamster ovary 5AHSmyc cells which contain the human c-myc proto-oncogene under the control of a heat shock promoter. Heat treatment induces c-Myc overexpression and thus apoptosis as determined by internucleosomal DNA fragmentation. We transfected 5AHSmyc cells with mcl-1 and found that clones expressing the introduced Mcl-1 protein exhibited reduced DNA fragmentation. Mcl-1 was also capable of delaying the onset of cell death as judged by loss of membrane integrity, although it could not provide complete protection from c-Myc overexpression. Thus, Mcl-1 has functional homology to Bcl-2 in that Mcl-1 can enhance cell viability under conditions that otherwise cause apoptosis.

Animals↗
PubMed1994

Cellular pharmacology of dichloro(ethylenediamine)platinum(II) in cisplatin-sensitive and resistant human ovarian carcinoma cells.

The cellular pharmacology of the tritium-labeled cisplatin analogue dichloro(ethylenediamine)platinum(II) ([3H]DEP) was compared in cisplatin-sensitive 2008 and resistant 2008/C13*5.25 human ovarian carcinoma cells. The cellular content of total [3H], ultrafiltrable [3H], and free native [3H]DEP was measured during and following incubation with 5 microM [3H]DEP. While the rate constant for [3H]DEP uptake in the resistant cells was reduced to 25% of that in the sensitive cells, DNA intrastrand adduct formation was reduced even further to 11%, indicating the presence of defects in both uptake and the ability of intracellular drug to access or react with DNA. The latter could not be accounted for by enhanced repair. Together, these defects were sufficient to account for the 11-fold level of resistance. At steady state, the intracellular to extracellular concentration ratio for native [3H]DEP was 7.7 in the sensitive cells and 11.7 in the resistant cells, suggesting the presence of a trapping or concentrative mechanism. Thus, despite the slower initial influx, the resistant cells eventually accumulated more free [3H]DEP than the sensitive cells. We conclude that the resistant phenotype in these cells is accounted for primarily by impaired uptake and decreased reaction of [3H]DEP with DNA rather than by changes in efflux or DNA repair.

Cisplatin↗