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Taiwaniaquinoids are a unique family of diterpenoids predominantly isolated from Taiwania cryptomerioides Hayata. Previously, we evaluated the antiproliferative effect of several synthetic taiwaniaquinoids against human lung (A-549), colon (T-84), and breast (MCF-7) tumor cell lines. Herein, we report the in vitro and in vivo antitumor activity of the most potent compounds. Their cytotoxic activity against healthy peripheral blood mononuclear cells (PBMCs) has also been examined. We underscore the limited toxicity of compound C36 in PBMCs and demonstrate that it exerts its antitumor effect in MCF-7 cells (IC 50 = 1.8 µM) by triggering an increase in reactive oxygen species, increasing the cell population in the sub-G 1 phase of the cell cycle (90 %), and ultimately activating apoptotic (49.6 %) rather than autophagic processes. Western blot results suggested that the underlying mechanism of the C36 apoptotic effects was linked to caspase 9 activation and a rise in the Bax/Bcl-2 ratio. In vivo analyses showed normal behavior and hematological parameters in C57BL/6 mice post C36 treatment. Moreover, no significant impact was observed on the biochemical parameters of these animals, indicating that C36 did not induce liver toxicity. Furthermore, C36 demonstrated a significant reduction in tumor growth in immune-competent C57BL/6 mice implanted with E0771 mouse mammary tumor cells, effectively improving survival rates. These findings position taiwaniaquinoids, particularly compound C36, as promising therapeutic candidates for human breast cancer., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier Masson SAS.. All rights reserved.)

Background: Trastuzumab is a drug used in HER2-positive breast cancer that increases patient survival. Due to cardiotoxicity is the most important side effect of trastuzumab treatment, cardiac monitoring should be a priority. The purpose of this study is to evaluate plasma NT-proBNP level and major cardiovascular risk factors as possible early predictors of trastuzumab-induced cardiotoxicity in HER2-positive breast cancer patients., Methods: We conducted a retrospective observational study involving 66 patients with HER2-positive breast cancer treated with trastuzumab. Left ventricle ejection fraction (LVEF), NT-proBNP values, and the history of cardiovascular risk factors were collected. Cardiotoxicity was diagnosed considering a decrease of the LVEF from baseline or clinical manifestation of congestive heart failure. NT-proBNP cut-off points were considered to establish normal or abnormal values according to patient age., Results: 27.3% of the patients suffered cardiotoxicity during trastuzumab treatment. Most cases were diagnosed due to the appearance of cardiac symptomatology (66.7%). Logistic regression analysis showed a significant association of diabetes mellitus (OR 5.9, 95% CI 1.2-28.5, p = 0.028) and high NT-proBNP levels (OR 22.0, 95% CI 5.7-85.4, p < 0.0001) with the development of trastuzumab-induced cardiotoxicity., Conclusion: NT-proBNP levels above the upper limit of the normal range adjusted to age or diabetes mellitus seem to be associated with a higher risk of developing cardiotoxicity. However, some limitations of the present study make necessary further studies aimed to clarify whether NT-proBNP and diabetes-associated markers determinations can be useful in the monitoring of cardiotoxicity risk in breast cancer patients undergoing trastuzumab therapy., Competing Interests: Declaration of competing interest The authors have stated that they have no conflict of interest., (Copyright © 2020 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

The synthesis of podocarpanes, including 12,19-dihydroxy-13-acetyl-8,11,13-podocarpatriene (23), isolated from Gaultheria yunnanensis and not previously synthesized, and totarane-type terpenoids, starting from the natural labdane trans-communic acid (15), is described. Their antiproliferative activities against MCF-7, T-84 and A-549 human tumoural cell lines are studied. An antiproliferative effect was induced by compounds 23, 27 and 28, with IC 50  < 10 μM in two (27) or three cell lines (23 and 28). No correlation with log P values was observed. The totarane o-quinone 27, and especially the catechol 28, which is readily oxidisable to compound 27, were the most active compounds, highlighting the functional groups present in C11 and C12. Compound 28 showed limited toxicity in normal peripheral blood mononuclear cells (78.5% cell viability versus non-treated control cultures at 10 μM), and appeared to exert an antiproliferative effect in A-549 cells (IC 50 0.6 μM) through a mechanism that involves the induction of apoptosis mediated by an increased Bax/Bcl-2 ratio. The results of the present study indicate that compound 28, at least, might be useful as an antitumoral agent. Further studies are required to elucidate the cellular and molecular elements involved in its effect, and the activity/toxicity in preclinical models., (Copyright © 2018 Elsevier Masson SAS. All rights reserved.)

The in vitro antiproliferative activities of some taiwaniaquinoids and related compounds with functionalized A, B, or C rings against human breast (MCF-7), colon (T-84), and lung (A-549) tumor cell lines were assayed. The most potent compounds, 16, 27, and 36, were more effective than the naturally occurring taiwaniaquinones A (4) and F (5) in all three cell lines. The structure-activity relationship study of these new taiwaniaquinoids highlighted the correlation between the bromo substituent and the antiproliferative activity, especially in MCF-7 cells. These findings indicate that some of the taiwaniaquinoids might be useful as cytostatic agents against breast, colon, and lung cancer cell lines.

Background: Around 20%-30% of breast cancers overexpress the proto-oncogene human epidermal growth receptor 2 (HER2), and they are characterized by being very invasive. Therefore, many current studies are focused on testing new therapies against tumors that overexpress this receptor. In particular, there exists major interest in new strategies to fight breast cancer resistant to trastuzumab (Tmab), a humanized antibody that binds specifically to HER2 interfering with its mitogenic signaling. Our team has previously developed immunostimulating complexes (ISCOMs) as nanocapsules functionalized with lipid vinyl sulfones, which can incorporate protein A and bind to G immunoglobulins that makes them very flexible nanocarriers., Methods and Results: The aim of this in vitro study was to synthesize and evaluate a drug delivery system based on protein A-functionalized ISCOMs to target HER2-overexpressing cells. We describe the preparation of ISCOMs, the loading with the drugs doxorubicin and paclitaxel, the binding of ISCOMs to alkyl vinyl sulfone-protein A, the coupling of Tmab, and the evaluation in both HER2-overexpressing breast cancer cells (HCC1954) and non-overexpressing cells (MCF-7) by flow cytometry and fluorescence microscopy. Results show that the uptake is dependent on the level of overexpression of HER2, and the analysis of the cell viability reveals that targeted drugs are selective toward HCC1954, whereas MCF-7 cells remain unaffected., Conclusion: Protein A-functionalized ISCOMs are versatile carriers that can be coupled to antibodies that act as targeting agents to deliver drugs. When coupling to Tmab and loading with paclitaxel or doxorubicin, they become efficient vehicles for the selective delivery of the drug to Tmab-resistant HER2-overexpressing breast cancer cells. These nanoparticles may pave the way for the development of novel therapies for poor prognosis resistant patients.

Background: Monitoring renal function is important in imatinib-treated patients with chronic myeloid leukemia because serum creatinine may increase during the course of therapy. The mechanism of this increase and its reversibility on treatment cessation have never been investigated., Patients and Methods: We retrospectively analyzed data from imatinib-treated patients explored in our renal physiology unit with measurement of glomerular filtration rate (urinary clearance of (51)CrEDTA) and of urinary clearance and tubular secretion of creatinine. Results were compared with those of controls matched for measured glomerular filtration rate, age, gender, and ethnicity. We also analyzed variations of serum creatinine before and during imatinib cessation and after imatinib resumption in patients enrolled in imatinib discontinuation studies., Results: In 4 imatinib-treated patients who underwent thorough renal exploration, the part of creatinine clearance due to tubular secretion was negligible (2.4, 3.1, -1.3, and 2.8 mL/min) and significantly lower than that measured in their respective controls (17.7 ± 5.6, 43.0 ± 18.0, 23.1 ± 6.7, and 18.6 ± 5.6 mL/min, P < .001). In 1 patient, exploration was repeated after imatinib discontinuation and evidenced a recovery of creatinine tubular secretion (20.3 vs. 17.9 ± 5.2 mL/min in the control population, P = .2). In 15 patients of imatinib discontinuation studies, a median decrease in serum creatinine of 17.9% was observed after imatinib cessation. Resumption of treatment in 6 patients led to a median increase in serum creatinine of 18.8%., Conclusions: Imatinib completely blunts tubular secretion of creatinine, a previously unreported pharmacologic property. This inhibition increases serum creatinine independently of any glomerular dysfunction and is fully reversible on imatinib cessation., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Xenografts are a popular model for the study of the action of new antitumor drugs. However, xenografts are highly heterogeneous structures, and therefore it is sometimes difficult to evaluate the effects of the compounds on tumor metabolism. In this context, imaging mass spectrometry (IMS) may yield the required information, due to its inherent characteristics of sensitivity and spatial resolution. To the best of our knowledge, there is still no clear analysis protocol to properly evaluate the changes between samples due to the treatment. Here we present a protocol for the evaluation of the effect of 2-hydroxyoleic acid (2-OHOA), an antitumor compound, on xenografts lipidome based on IMS. Direct treated/control comparison did not show conclusive results. As we will demonstrate, a more sophisticated protocol was required to evaluate these changes including the following: (1) identification of different areas in the xenograft, (2) classification of these areas (necrotic/viable) to compare similar types of tissues, (3) suppression of the effect of the variation of adduct formation between samples, and (4) normalization of the variables using the standard deviation to eliminate the excessive impact of the stronger peaks in the statistical analysis. In this way, the 36 lipid species that experienced the largest changes between treated and control were identified. Furthermore, incorporation of 2-hydroxyoleic acid to a sphinganine base was also confirmed by MS/MS. Comparison of the changes observed here with previous results obtained with different techniques demonstrates the validity of the protocol.

Membrane lipid therapy is a novel approach to rationally design or discover therapeutic molecules that target membrane lipids. This strategy has been used to design synthetic fatty acid analogs that are currently under study in clinical trials for the treatment of cancer. In this context, and with the aim of controlling tumor cell growth, we have designed and synthesized a hydroxylated analog of triolein, hydroxytriolein (HTO). Both triolein and HTO regulate the biophysical properties of model membranes, and they inhibit the growth of non-small-cell lung cancer (NSCLC) cell lines in vitro. The molecular mechanism underlying the antiproliferative effect of HTO involves regulation of the lipid membrane structure, protein kinase C-α and extracellular signal-regulated kinase activation, the production of reactive oxygen species, and autophagy. In vivo studies on a mouse model of NSCLC showed that HTO, but not triolein, impairs tumor growth, which could be associated with the relative resistance of HTO to enzymatic degradation. The data presented explain in part why olive oil (whose main component is the triacylglycerol triolein) is preventive but not therapeutic, and they demonstrate a potent effect of HTO against cancer. HTO shows a good safety profile, it can be administered orally, and it does not induce nontumor cell (fibroblast) death in vitro or side effects in mice, reflecting its specificity for cancer cells. For these reasons, HTO is a good candidate as a drug to combat cancer that acts by regulating lipid structure and function in the cancer cell membrane., (Copyright © 2015 by The American Society for Pharmacology and Experimental Therapeutics.)

The first enantiospecific syntheses of neopetrosiquinones A (6) and B (7), two merosesquiterpenes isolated from the deep-water sponge Neopetrosia cf. proxima, from the labdane diterpene trans-communic acid (10) have been achieved. A key step of the synthetic sequence is the simultaneous aromatization of the C ring and the benzylic oxidation on C-7 of an advanced intermediate, mediated by the oxygen-DDQ system. The in vitro antiproliferative activities of neopetrosiquinone B (7) and of the synthetic intermediates 8 and 9 against human breast (MCF-7), lung (A-549), and colon (T-84) tumor cell lines have been assayed. The most potent was compound 9 (IC50 = 4.1 μM), which was twice as active as natural compound 7 (IC50 = 8.3 μM) against A-549 cells. In addition, the treatment with these compounds resulted in an induction of apoptosis. These findings indicate that the terpene benzoquinones reported here might be potentially useful as anticancer agents.

This article describes the antitumor properties of a new family of merosesquiterpenes, which were synthesized by Diels-Alder cycloaddition of the labdane diene trans-communic acid, highly abundant in Cupressus sempervirens, or its methyl ester, with the appropriate dienophile. These compounds demonstrated potent cytotoxic activity in vitro against human breast, colon, and lung tumor cells. We highlight the elevated activity (IC50: 0.35 ± 0.10 μM) and specificity (TI: 9) of compound 13 against the MCF-7 line, which corresponds to the most prevalent breast cancer cell subtype, luminal A. It was found that compound 13 exerts its anti-tumor action by inducing oxidative stress, arresting the cell cycle in stages G0-G1, and activating apoptosis, which are all associated with low cyclin D1 regulation, pRb hypophosphorylation, increased expression of p27 and p53, and poly (ADP-ribose) polymerase (PARP) fractioning. Epithelial-mesenchymal transition, a phenomenon associated with metastasis promotion and a worsened prognosis also appeared to be inhibited by compound 13. In addition, it markedly reduced tumor development in immunocompetent C57BL/6 mice with allografts of E0771 mouse breast tumor cells (luminal A subtype). According to these findings, this new family of compounds, especially compound 13, may be highly useful in the treatment of human breast cancer., (Copyright © 2014 Elsevier Masson SAS. All rights reserved.)

The number of patients with colorectal cancer, the third most frequently diagnosed malignancy in the world, has increased markedly over the past 20 years and will continue to increase in the future. Despite recent advances in chemotherapy, currently used anticancer molecules are unable to improve the prognosis of advanced or recurrent colorectal cancer, which remains incurable. The transport of classical drugs by nanoparticles has shown great promise in terms of improving drug distribution and bioavailability, increasing tissue half-life and concentrating anticancer molecules in the tumor mass, providing optimal drug delivery to tumor tissue, and minimizing drug toxicity, including those effects associated with pharmaceutical excipients. In addition, colon cancer targeting may be improved by incorporating ligands for tumor-specific surface receptors. Similarly, nanoparticles may interact with key drug-resistance molecules to prevent a reduction in intracellular drug levels drug. Recently published data have provided convincing pre-clinical evidence regarding the potential of active-targeted nanotherapeutics in colon cancer therapy, although, unfortunately, only a few of these therapies have been translated into early-phase clinical trials. As nanotechnology promises to be a new strategy for improving the prognosis of colon cancer patients, it would be very useful to analyze recent progress in this field of research. This review discusses the current status of nanoparticle-mediated cancer-drug delivery, the challenges restricting its application, and the potential implications of its use in colon cancer therapy.

The potential use of gene therapy to improve the response of patients with advanced cancer is being intensively analyzed. We evaluated the cytotoxic impact of the gef gene, a suicide gene, which has a demonstrated antiproliferative activity in tumor cells, in colon carcinoma cells in order to improve the antitumour effect of chemotherapeutic drugs used as first line treatment in the management of advanced colon cancer. We found that the gef gene induced a marked decrease in cell viability (50% in 24h) in T-84 cells through cell death by apoptosis. Interestingly, when gef gene expression was combined with drugs of choice in the clinical treatment of colon cancer (5-fluorouracil, oxaliplatin and irinotecan), a strong synergistic effect was observed with approximately a 15-20% enhancement of the antiproliferative effect. Our data demonstrate, for the first time, that gef gene expression induces significant growth arrest in colon cancer cells and that it is able to enhance the effect of some cytotoxic drugs compared with a single therapeutic approach. These results indicate the potential therapeutic value of the gef gene in colon cancer combination therapy., (Copyright © 2012 Elsevier Masson SAS. All rights reserved.)

Advance in the knowledge of molecular biology has thrown light on many aspects of apoptosis regulation mechanisms. This has allowed a change in anti-cancer therapy trends, from classic cytotoxic strategies to the development of new non-harmful therapies which target the apoptosis response selectively only in tumour cells. We have selected an anthranilic alcohol-derived acyclic 5-fluorouracil O,N-acetal (5) to carry out the anti-cancer studies. This compound shows activity as a potent growth inhibitor of the tumour cell line MCF-7 at a very low concentration. Moreover, when this compound was administered to the non-neoplastic cell line, MCF-10A displayed less toxicity resulting in lower rates of apoptosis. Further studies by microarray hybridization, real-time PCR and western blot showed that when administered to human breast cancer cells, MCF-7, 5 had no activity against classic pro-apoptotic genes such as p53, and even induced the down-regulation of anti-apoptotic genes such as Bcl-2. In contrast, several pro-apoptotic genes related with the endoplasmic reticulum (ER)-stress-induced apoptosis, such as BBC3 and Noxa, appeared up-regulated. These results seem to show that the mechanism of action and selectivity of 5 was via the activation of the ER stress-induced apoptosis. The selective activity of this compound against tumour cells via the ER stress-induced apoptosis supposes a great advantage for future therapeutic use., (Copyright © 2012 Elsevier Masson SAS. All rights reserved.)

Despite advances in cancer treatment, a large number of patients eventually develop metastatic disease that is generally incurable. Systemic chemotherapy remains the standard treatment for these patients. Several chemotherapeutic combinations have proven effective in the management of cancer. Paradoxically, although the purpose of polychemotherapy is to improve the prognosis and prolong the survival of patients, it often carries considerable toxicity that causes substantial adverse symptoms. For this reason, a major goal of cancer research is to improve the effectiveness of these cytotoxic agents and reduce their adverse effects. Gene transfer has been proposed as a new strategy to enhance the efficacy of anti-tumor drugs in the treatment of intractable or metastatic cancers. In fact, the association of gene therapy and drugs (combined therapy) has been reported to increase the anti-proliferative effect of classical treatments in lung, bladder, pancreatic, colorectal and breast cancers, among others. Various especially promising therapies have been proposed in this context, including the use of suicide genes, antisense oligonucleotides, ribozymes and RNA interference. In this chapter, we review recent progress in the development of novel anti-cancer strategies that associate cytotoxic agents with gene transfer to enhance their antitumor effect.

Completing a SAR study, a series of (RS)-6-substituted-7- or 9-(1,2,3,5-tetrahydro-4,1-benzoxazepine-3-yl)-7H or 9H-purines was previously prepared. The most potent antiproliferative agent against the MCF-7 adenocarcinoma cell line that belongs to the benzoxazepine O,N-acetalic family is (RS)-9-[1-(9H-fluorenyl-9-methoxycarbonyl)-1,2,3,5-tetrahydro-4,1-benzoxazepine-3-yl]-6-chloro-9H-purine (16, IC(50) = 0.67 ± 0.18 μM), whilst (RS)-7-{2-(N-hydroxymethylphenyl)-2-nitrobenzenesulfonamido]-1-methoxyethyl}-6-chloro-7H-purine (37) shows the lowest IC(50) value between the family of acyclic O,N-acetals (IC(50) = 3.25 ± 0.23 μM). Moreover, 16 showed the better in vitro Therapeutic Index in breast cell lines (3.19), whilst 37 was found to be 3.69-fold more active against HT-29 human colon cancer cell line than versus IEC-6 normal rat intestinal epithelial cell line. The global apoptotic cells caused by 16 and 37 against MCF-7 were 80.08% and 54.85% of cell population after 48 h, respectively. cDNA microarray technology reveals potential drug targets, which are mainly centred on positive apoptosis regulatory pathway genes, and the repression of genes involved in carcinogenesis, proliferation and tumour invasion., (Copyright © 2011 Elsevier Masson SAS. All rights reserved.)

Completing an SAR study, a series of (RS)-6-substituted-7- or 9-(1,2,3,5-tetrahydro-4,1-benzoxazepine-3-yl)-7H or 9H-purines has been prepared under microwave-assisted conditions. Their antiproliferative activities on MCF-7 and MDA-MB-231 cancerous cell lines are presented, being the majority of the IC(50) values below 1μM. The most active compound (RS)-2,6-dichloro-9-[1-(p-nitrobenzenesulfonyl)-1,2,3,5-tetrahydro-4,1-benzoxazepin-3-yl]-9H-purine (14) presents an IC(50) of 0.166μM against the human cancerous cell line MDA-MB-231. Compound 14 was the most selective against the human breast adenocarcinoma MCF-7 and MDA-MB-231 cancer cell lines (Therapeutic Indexes, TIs=5.1 and 11.0, respectively) in relation to the normal one MCF-10A. (RS)-14 was resolved into its enantiomers. Both enantiomers are equally potent, but more potent than the corresponding racemic mixture. (R)-14 induces apoptosis against MCF-7 up to 52.50% of cell population after 48h, being more potent than the clinical-used drug paclitaxel (43%). (RS)-14 induces no acute toxicity in mice after two weeks of treatment., (Copyright © 2010 Elsevier Masson SAS. All rights reserved.)

Novel treatment modalities, including gene therapy, are needed for patients with advanced melanoma. The E gene from the phage varphiX174 encodes a 91-aa protein which lyses Escherichia coli by formation of a transmembrane tunnel structure. To evaluate whether this E gene has a cytotoxic impact on melanoma cells in vitro and in vivo, and could therefore be used as a new therapeutic strategy for this tumor type, we selected the B16-F10 murine melanoma cell line as a model. We used a nonviral gene delivery approach (pcDNA3.1/E plasmid) to study the inhibition of melanoma cells' proliferation in vitro and direct intratumoral injection of pcDNA3.1/E complexed with jetPEI to deliver E cDNA to rapidly growing murine melanomas, and found that the E gene has both a strong antiproliferative effect in B16-F10 cells in vitro and induces an efficient decrease in melanoma tumor volume in vivo (90% in 15 days). Interestingly, the GFP-E fusion protein expressed in melanoma cells was located in the mitochondria. In vitro and in vivo analysis demonstrated significant functional and morphological mitochondrial alterations accompanied by a significant increase of cytochrome c and active caspase-3 and -9 in transfected cells, which suggests that tumoral cell death is mediated by the mitochondrial apoptotic pathway. These results show that E gene expression in melanoma cells has an extraordinary antitumor effect, which means it may be a new candidate for an effective strategy for melanoma treatment.

Extended studies on the synthesis and pharmacological evaluation of (RS)-6-substituted-7 or 9-(2,3-dihydro-5H-1,4-benzodioxepin-3-yl)-7H- or -9H-purines are presented. The microwave-assisted organic synthesis has provided faster access to the target compounds with the advantage of selective obtaining the N-7' or N-9' regioisomers simplifying their isolation. To test the behaviour of the products (including the purine bases) on cellular systems, cytotoxic activity against the MCF-7 human breast cancer cell line was determined, and the three most active compounds were used to study the cell cycle distribution and apoptosis in the MCF-7 cell line.

Completing a SAR study, a series of (RS)-1- or 3-(1,2,3,5-tetrahydro-4,1-benzoxazepine-3-yl)-pyrimidines and (RS)-6-substituted-7- or 9-(1,2,3,5-tetrahydro-4,1-benzoxazepine-3-yl)-7H- or 9H-purines have been prepared. Their antiproliferative activities on MCF-7 cells are here presented and discussed. (RS)-6-Chloro-9-[1-(9H-9-fluorenylmethoxycarbonyl)-1,2,3,5-tetrahydro-4,1-benzoxazepine-3-yl]-9H-purine (28) is the most active (IC(50)=0.67+/-0.18 microM) of the series so far described. cDNA microarray technology reveals potential drug targets, which are mainly centred on apoptosis regulatory pathway genes.

A series of eleven 2- and 6-substituted (R,S)-9-(2,3-dihydro-1,4-benzoxathiin-3-ylmethyl)-9H-purine derivatives was obtained by applying a standard Mitsunobu protocol that led to a six-membered ring contraction from (R,S)-3,4-dihydro-2H-1,5-benzoxathiepin-3-ol via an episulfonium intermediate. The signal approximately delta=151 ppm, which corresponds to the C4' carbon atom, is unequivocal proof of the N9' regioisomer. The potential of the target molecules as anticancer agents is reflected in their activity against the MCF-7 cancer cell line. The most active compounds have IC(50) values of (6.18+/-1.70) and (8.97+/-0.83) microM. The results indicate that the anticancer activity for the most active compounds is correlated with their capacity to induce apoptosis.

The anticarcinogenic potential of (RS)-1-(2,3-dihydro-5H-1,4-benzodioxepin-3-yl)uracil (DBDU), with the naturally occurring pyrimidine base uracil, is reported against the MCF-7 cancer cell line. The arrest in the G0/G1 and G2/M cell cycle phases was accounted for by decrease in the expression of the cyclin D1 and Cdk1 proteins, and increase in p21 and p27 proteins. Using a reverse transcription-polymerase chain reaction-based assay at a dose of 5 muM of DBDU cyclin D1 mRNA was decreased, suggesting that DBDU exerts its regulatory action on cyclin D1 at the level of transcription. DNA fragmentation was performed and demonstrated that apoptosis occurred in the tumor cell line treated with DBDU. The G0/G1 arrest is an irreversible process and the cells undergo apoptosis in a p53-independent manner. DBDU administered intravenously twice a week (50 mg/kg dose each time) induced neither toxicity nor death in mice for 5 weeks.