Modulation of cisplatinum cytotoxicity by p53: effect of p53-mediated apoptosis and DNA repair

Triptolide enhances carboplatin-induced apoptosis by inhibiting nucleotide excision repair (NER) activity in melanoma

Introduction: Carboplatin (CBP) is a DNA damaging drug used to treat various cancers, including advanced melanoma. Yet we still face low response rates and short survival due to resistance. Triptolide (TPL) is considered to have multifunctional antitumor effects and has been confirmed to enhance the cytotoxic effects of chemotherapeutic drugs. Herein, we aimed to investigate the knowledge about the effects and mechanisms for the combined application of TPL and CBP against melanoma. Methods: Melanoma cell lines and xenograft mouse model were used to uncover the antitumor effects and the underlying molecular mechanisms of the alone or combined treatment of TPL and CBP in melanoma. Cell viability, migration, invasion, apoptosis, and DNA damage were detected by conventional methods. The rate-limiting proteins of the NER pathway were quantitated using PCR and Western blot. Fluorescent reporter plasmids were used to test the NER repair capacity. Results: Our results showed that the presence of TPL in CBP treatment could selectively inhibit NER pathway activity, and TPL exerts a synergistic effect with CBP to inhibit viability, migration, invasion, and induce apoptosis of A375 and B16 cells. Moreover, combined treatment with TPL and CBP significantly inhibited tumor progression in nude mice by suppressing cell proliferation and inducing apoptosis. Discussion: This study reveals the NER inhibitor TPL which has great potential in treating melanoma, either alone or in combination with CBP.

p53 inhibits CTR1-mediated cisplatin absorption by suppressing SP1 nuclear translocation in osteosarcoma

Background

Osteosarcoma (OS) is a malignant bone tumor mainly affecting children and young adolescents. Cisplatin is a first-line chemotherapy drug for OS, however, drug resistance severely limits the survival of OS. Nevertheless, cellular factors in cisplatin resistance for OS remain obscure. In this study, the function and potential mechanism of p53 in cisplatin absorption were explored in OS cells.

Methods

The CRISPR-Cas9 gene editing technology was performed to obtain p53 gene knock-out U2OS cells. The p53 over-expression 143B cell line was established by lentivirus-mediated virus infection. Moreover, the functions of p53 and CTR1 in cisplatin absorption were assessed by inductively coupled plasma mass spectrometry (ICP-MS) through CTR1 over-expression and knock-down. Further, the DNA binding activity of SP1 on CTR1 gene promoter was determined by dual-luciferase assay and chromatin immunoprecipitation (ChIP) assay. The functional regulation of p53 on SP1 was studied by nucleocytoplasmic separation assay and electrophoretic mobility shift assay (EMSA). The interaction between p53 and SP1 was verified by Co-Immunoprecipitation assay.

Results

Under cisplatin treatment, p53 knock-out promoted CTR1 expression and cisplatin uptake, while p53 overexpression inhibited CTR1 expression and cisplatin uptake. Moreover, p53 regulated CTR1 level not by binding to CTR1 promoter directly but by suppressing the nuclear translocation of transcription factor specificity protein 1 (SP1). It was verified that SP1 is directly bound with CTR1 promoter. SP1 overexpression stimulated CTR1 expression, and SP1 knock-down attenuated CTR1 expression.

Conclusion

The p53 might function as a negative regulator in CTR1 mediated cisplatin absorption, and the p53-SP1-CTR1 axis is a target for cisplatin resistance.

Mechanisms of Resistance to Conventional Therapies for Osteosarcoma

Osteosarcoma (OS) is the most common primary bone tumor, mainly occurring in children and adolescents. Current standard therapy includes tumor resection associated with multidrug chemotherapy. However, patient survival has not evolved for the past decades. Since the 1970s, the 5-year survival rate is around 75% for patients with localized OS but dramatically drops to 20% for bad responders to chemotherapy or patients with metastases. Resistance is one of the biological processes at the origin of therapeutic failure. Therefore, it is necessary to better understand and decipher molecular mechanisms of resistance to conventional chemotherapy in order to develop new strategies and to adapt treatments for patients, thus improving the survival rate. This review will describe most of the molecular mechanisms involved in OS chemoresistance, such as a decrease in intracellular accumulation of drugs, inactivation of drugs, improved DNA repair, modulations of signaling pathways, resistance linked to autophagy, disruption in genes expression linked to the cell cycle, or even implication of the micro-environment. We will also give an overview of potential therapeutic strategies to circumvent resistance development.

Targeting Molecular Mechanisms Underlying Treatment Efficacy and Resistance in Osteosarcoma: A Review of Current and Future Strategies

Osteosarcoma is the most common primary malignant bone tumour in children and adolescents. Due to micrometastatic spread, radical surgery alone rarely results in cure. Introduction of combination chemotherapy in the 1970s, however, dramatically increased overall survival rates from 20% to approximately 70%. Unfortunately, large clinical trials aiming to intensify treatment in the past decades have failed to achieve higher cure rates. In this review, we revisit how the heterogenous nature of osteosarcoma as well as acquired and intrinsic resistance to chemotherapy can account for stagnation in therapy improvement. We summarise current osteosarcoma treatment strategies focusing on molecular determinants of treatment susceptibility and resistance. Understanding therapy susceptibility and resistance provides a basis for rational therapy betterment for both identifying patients that might be cured with less toxic interventions and targeting resistance mechanisms to sensitise resistant osteosarcoma to conventional therapies.

Hybrid of niosomes and bio-synthesized selenium nanoparticles as a novel approach in drug delivery for cancer treatment

The current study intends to investigate a novel drug delivery system (DDS) based on niosomes structure (NISM) and bovine serum albumin (BSA) which was formulated to BSA coated NISM (NISM-B). Also, selenium nanoparticles (SeNPs) have been prepared by BSA mediated biosynthesis. Finally, the NISM-B was hybridized with SeNPs and was formulated as NISM-B@SeNPs for drug delivery applications. Physicochemical properties of all samples were characterized by UV-Vis spectroscopy, FT-IR, DLS, FESEM, and EDX techniques. The cytotoxicity of all samples against A549 cell line was assessed by cell viability analysis and flow cytometry for apoptotic cells as well as RT-PCR for the expression of MDR-1, Bax, and Bcl-2 genes. Besides, in vivo biocompatibility was performed by LD₅₀ assay to evaluate the acute toxicity. The proposed formulation has a regular spherical shape and approximately narrow size distribution with proper zeta-potential values; the proposed DDS revealed a good biocompatibility. The compound showed a significant cytotoxic effect against A549 cell line. Although the Bax/Bcl-2 expression ratio was significantly in NISM-B@SeNPs- treated cancer cells, the expression of MDR-1 was non-significantly lower in NISM-B@SeNPs-treated cancer cells. The obtained results suggest that the proposed DDS presents a promising approach for drug delivery, co-delivery and multifunctional biomedicine applications.

TP53 in bone and soft tissue sarcomas

Genomic and functional study of existing and emerging sarcoma targets, such as fusion proteins, chromosomal aberrations, reduced tumor suppressor activity, and oncogenic drivers, is broadening our understanding of sarcomagenesis. Among these mechanisms, the tumor suppressor p53 (TP53) plays significant roles in the suppression of bone and soft tissue sarcoma progression. Although mutations in TP53 were thought to be relatively low in sarcomas, modern techniques including whole-genome sequencing have recently illuminated unappreciated alterations in TP53 in osteosarcoma. In addition, oncogenic gain-of-function activities of missense mutant p53 (mutp53) have been reported in sarcomas. Moreover, new targeting strategies for TP53 have been discovered: restoration of wild-type p53 (wtp53) activity through inhibition of TP53 negative regulators, reactivation of the wtp53 activity from mutp53, depletion of mutp53, and targeting of vulnerabilities in cells with TP53 deletions or mutations. These discoveries enable development of novel therapeutic strategies for therapy-resistant sarcomas. We have outlined nine bone and soft tissue sarcomas for which TP53 plays a crucial tumor suppressive role. These include osteosarcoma, Ewing sarcoma, chondrosarcoma, rhabdomyosarcoma (RMS), leiomyosarcoma (LMS), synovial sarcoma, liposarcoma (LPS), angiosarcoma, and undifferentiated pleomorphic sarcoma (UPS).

Anti-proliferative activity of biochanin A in human osteosarcoma cells via mitochondrial-involved apoptosis

Biochanin A is a major isoflavone in red clover and a potent chemopreventive agent against cancer. However, the effects of biochanin A on human osteosarcoma cells have never been clarified. This study investigated the anti-proliferative potential of biochanin A in osteosarcoma cells. The results indicate that biochanin A inhibited cell growth and colony formation in a dose-dependent manner with a minimal toxicity to normal cells. The combination of doxorubicin and biochanin A could synergistically inhibit osteosarcoma cell growth. The cytotoxic effect of biochanin A via the induction of apoptosis as evidenced by formation of apoptotic bodies, externalization of phosphatidylserine, accumulation of sub-G₁ phase cells, caspase 3 activation, and cleavage of PARP. Apoptosis was associated with loss of the mitochondrial membrane potential, release of cytochrome c, caspase 9 activation, increased Bax expression, and reduced Bcl-2 and Bcl-X_L expression. Pre-treatment with a caspase-9 specific inhibitor (Z-LEHD-FMK) partially attenuated cell death, suggesting involvement of the intrinsic mitochondrial apoptotic cascade. However, pre-treatment with the JNK inhibitor SP600125, the MEK inhibitor PD-98059, and the p38 MAPK inhibitor SB203580 or the antioxidants vitamin E, N-acetylcysteine, and glutathione failed to prevent biochanin A-induced cell death. Our results suggest that biochanin A inhibits cell growth and induces apoptosis in osteosarcoma cells by triggering activation of the intrinsic mitochondrial pathway and caspase-9 and -3 and increasing the Bax: Bcl-2/Bcl-X_L ratio.

The chemosensitivity of testicular germ cell tumors

Although rare cancers overall, testicular germ cell tumors (TGCTs) are the most common type of cancer in young males below 40 years of age. Both subtypes of TGCTs, i.e., seminomas and non-seminomas, are highly curable and the majority of even metastatic patients may expect to be cured. These high cure rates are not due to the indolent nature of these cancers, but rather to their sensitivity to chemotherapy (and for seminomas to radiotherapy). The delineation of the cause of chemosensitivity at the molecular level is of paramount importance, because it may provide insights into the minority of TGCTs that are chemo-resistant and, thereby, provide opportunities for specific therapeutic interventions aimed at reverting them to chemosensitivity. In addition, delineation of the molecular basis of TGCT chemo-sensitivity may be informative for the cause of chemo-resistance of other more common types of cancer and, thus, may create new therapeutic leads. p53, a frequently mutated tumor suppressor in cancers in general, is not mutated in TGCTs, a fact that has implications for their chemo-sensitivity. Oct4, an embryonic transcription factor, is uniformly expressed in the seminoma and embryonic carcinoma components of non-seminomas, and its interplay with p53 may be important in the chemotherapy response of these tumors. This interplay, together with other features of TGCTs such as the gain of genetic material from the short arm of chromosome 12 and the association with disorders of testicular development, will be discussed in this paper and integrated in a unifying hypothesis that may explain their chemo-sensitivity.

Molecular mechanisms of chemoresistance in osteosarcoma (Review)

Due to the emergence of adjuvant and neoadjuvant chemotherapy, the survival rate has been greatly improved in osteosarcoma (OS) patients with localized disease. However, this survival rate has remained unchanged over the past 30 years, and the long-term survival rate for OS patients with metastatic or recurrent disease remains poor. To a certain extent, the reason behind this may be ascribed to the chemoresistance to anti-OS therapy. Chemoresistance in OS appears to be mediated by numerous mechanisms, which include decreased intracellular drug accumulation, drug inactivation, enhanced DNA repair, perturbations in signal transduction pathways, apoptosis- and autophagy-related chemoresistance, microRNA (miRNA) dysregulation and cancer stem cell (CSC)-mediated drug resistance. In addition, methods employed to circumvent these resistance mechanism have been shown to be effective in the treatment of OS. However, almost all the current studies on the mechanisms of chemoresistance in OS are in their infancy. Further studies are required to focus on the following aspects: i) Improving the delivery of efficacy through novel delivery patterns; ii) improving the understanding of the signal transduction pathways that regulate the proliferation and growth of OS cells; iii) elucidating the signaling pathways of autophagy and its association with apoptosis in OS cells; iv) utilizing high-throughput miRNA expression analysis to identify miRNAs associated with chemoresistance in OS; and v) identifying the role that CSCs play in tumor metastasis and in-depth study of the mechanism of chemoresistance in the CSCs of OS.

Mutant p53 and the response to chemotherapy and radiation

In addition to playing roles in the genesis and progression of cancer, mutant p53 also appears to play a significant role in the response to cancer therapy. In response to chemotherapy and radiation, two mainstays of cancer treatment, most cancer cells harboring p53 mutations show a reduced sensitivity compared to cells lacking p53 or those with wild type p53. However, there are also many instances where mutant p53 has shown no effect or enhances cellular sensitivity to chemotherapy and radiation. Similar to the in vitro cellular studies, the majority of clinical studies show a correlation between the presence of mutant p53 in patient tumors and adverse outcomes following treatment with chemotherapy agents or radiation in comparison to tumors with wild-type p53. However, it still remains unclear whether the presence of mutant p53 in tumors can serve as a reliable prognostic factor and aid in treatment planning. Thus, as genomic analysis of patient tumors becomes more cost effective, the role of mutant p53 in tumor responses from cancer therapy ultimately needs to be addressed. This chapter will discuss current mechanisms of how p53 mutations affect cellular responses to chemotherapy and radiation and discuss patient outcomes based on p53 status.

Inhaled gene therapy in lung cancer: proof-of-concept for nano-oncology and nanobiotechnology in the management of lung cancer

Lung cancer still remains one of the leading causes of death among cancer patients. Although novel targeted therapies have been established in everyday treatment practice, and conventional platinum-based doublets have demonstrated effective results regarding overall and progression-free survival, we have still failed to achieve long-term survival. Therefore, several strategies of applying locoregional therapy are under investigation. Aerosol chemotherapy is already under investigation and, taking this a step further, aerosol gene therapies with multiple delivery systems are being developed. Several efforts have demonstrated its efficiency and effectiveness, but there are still multiple factors that have to be considered and combined to achieve an overall more effective multifunctional treatment. In the current review, we present data regarding aerosol delivery systems, transporters, carriers, vectors, genes, toxicity, efficiency, specificity, lung microenvironment and delivery gene therapy systems. Finally, we present current studies and future perspectives.

p53-dependent radiobiological responses to internalised indium-111 in human cells

INTRODUCTION

The p53 tumour suppressor protein plays a pivotal role in the response of mammalian cells to DNA damage. It regulates cell cycle progression, apoptosis and DNA repair mechanisms and is therefore likely to influence response to targeted radionuclide therapy. This study investigated the role of p53 in the cellular response to the Auger-emitting radionuclide indium-111.

METHODS

Two stable clones of a HT1080 fibrosarcoma cell line, differing only in p53 status due to RNAi-mediated knockdown of p53 expression, were incubated for 1 h with [¹¹¹In]-oxinate (0-10 MBq/ml). Radiopharmaceutical uptake into HT1080 cells was measured in situ using a non-contact phosphorimager method. Cellular sensitivity and DNA damage were measured by, respectively, clonogenic survival analysis and the single cell gel electrophoresis (Comet) assay.

RESULTS

Mean uptake of [¹¹¹In]-oxinate in HT1080 cells was unaffected by p53 status, reaching a maximum of 9Bq/cell. [¹¹¹In]-oxinate-induced cytotoxicity was also identical in both clones, as measured by IC50 (0.68 MBq/ml). However the formation of DNA damage, measured immediately after treatment with [¹¹¹In]-oxinate, was found to be up to 2.5-fold higher in the p53-deficient HT1080 clone.

CONCLUSIONS

The increased DNA damage induced in p53-deficient HT1080 cells suggests an early deficiency in the repair of DNA damage during the treatment period. However, the similarity in cellular sensitivity, irrespective of p53 status, suggests that reduced p53 leads to a concomitant reduction in p53-dependent cytotoxicity despite the persistence of DNA damage. The results may provide insight into how tumours that differ in p53 status respond to therapeutic radionuclides.

Overcoming cisplatin resistance using gold(III) mimics: anticancer activity of novel gold(III) polypyridyl complexes

Gold(III) compounds have been recognized as anticancer agents due to their structural and electronic similarities with currently employed platinum(II) species. An added benefit to gold(III) agents is the ability to overcome cisplatin resistance. This work identified four gold(III) compounds, [Au(Phen)Cl(2)]PF(6), [Au(DPQ)Cl(2)]PF(6), [Au(DPPZ)Cl(2)]PF(6), and [Au(DPQC)Cl(2)]PF(6), (Phen = 1,10-phenanthroline, DPQ = dipyrido[3,2-d:2',3'-f]quinoxaline, DPPZ = dipyrido[3,2-a:2',3'-c] phenazine, DPQC = dipyrido[3,2-d:2',3'-f] cyclohexyl quinoxaline) that exhibited anticancer activity in both cisplatin sensitive and cisplatin resistant ovarian cancer cells. Two of these compounds, [Au(DPQ)Cl(2)]PF(6) (AQ) and [Au(DPPZ)Cl(2)]PF(6) (AZ), displayed exceptional anticancer activity and were the focus of more intensive mechanistic study. At the molecular level, AQ and AZ formed DNA adducts, generated free radicals, and upregulated pro-apoptotic signaling molecules (p53, caspases, PARP, death effectors). Taken together, these two novel gold(III) polypyridyl complexes exhibit potent antitumor activity in cisplatin resistant cancer cells. These activities may be mediated, in part, by the activation of apoptotic signaling.

Base excision DNA repair defect in Gadd45a-deficient cells

As one of a number of p53-regulated genes, Gadd45a (growth arrest and DNA damage inducible gene) has been shown to delay carcinogenesis and decrease mutation frequency. Gadd45a is known to regulate nucleotide excision DNA repair (NER) in response to UV radiation. Here, we report an emerging role for Gadd45a in base excision repair (BER). Gadd45a-null mouse embryo fibroblasts MEF and gadd45a-deficient human colon cancer cells exhibited slow BER after treatment with methyl methanesulfonate (MMS) a pure base-damaging agent. In addition, removal of AP sites by apurinic/apyrimidinic endonuclease 1/redox factor 1 (APE1/Ref1) was significantly delayed in gadd45a-null cells. Moreover, the localization of APE1/Ref1 within the nucleus was observed in gadd45a wild-type cells, whereas APE1 become mainly distributed in the cytoplasm, and there is a reduced interaction with proliferating cell nuclear antigen (PCNA) in Gadd45a-deficient cells. Inasmuch as p53 has been shown to regulate BER in addition to the NER pathway, our data suggest that p53-regulated gene Gadd45a contributes to the BER response by affecting the interaction of cellular APE1/Ref1 with PCNA. Gadd45a might be a key component gene of the p53 pathway involved in protection from carcinogenic base damage and maintenance of genomic stability, although the downstream mechanism including APE1/Ref1 will need further study.

Growth inhibition and sensitization to cisplatin by zoledronic acid in osteosarcoma cells

Since osteosarcoma is a drug-resistant disease, the aim of the present study was to explore the possible interest of therapeutic approaches including nitrogen-containing biphosphonate zoledronic acid using osteosarcoma cell lines with different genetic backgrounds. Parental p53+/pRb+ U2-OS, p53-mutant U2-OS (U2-OS/175) and p53-/pRb- SAOS were sensitive to zoledronic acid with no significant differences in IC50 values. Analysis of cell cycle distribution revealed a time-dependent shifting of U2-OS cells towards G2 phase with cell cycle arrest in G2 phase at 96 h of exposure to the compound. Conversely, U2-OS/175 and SAOS cells responded to treatment with transient cell accumulation in S phase up to 48-72 h, respectively. Cell lines were exposed to increasing concentrations of cisplatin alone or combined with sub-toxic doses of zoledronic acid. A growth inhibitory effect was seen after combined treatment in U2-OS, otherwise resistant to cisplatin up to 100 ng/ml. Zoledronic acid did not efficiently sensitized U2-OS/175 and SAOS to cisplatin, thereby suggesting that different behavior may depend on p53 mutation. This data was confirmed in U2-OS cells where p53 expression was downregulated by RNA interference. Present findings indicate occurrence of sensitization to cisplatin by zoledronic acid in wild-type p53 osteosarcoma cells but not in p53-null cells nor in cells expressing a dominant-negative form of p53, supporting that wild-type p53 is required for synergistic interaction of cisplatin and zoledronic acid.

Activation of membrane androgen receptors potentiates the antiproliferative effects of paclitaxel on human prostate cancer cells

Genomic signaling mechanisms require a relatively long time to get into action and represent the main way through which steroid hormones affect target cells. In addition, steroids may rapidly activate cellular functions by non-genomic signaling mechanisms involving membrane sites. Understanding in depth the molecular mechanisms of the non-genomic action represents an important frontier for developing new and more selective pharmacologic tools for endocrine therapies. In the present study, we report that membrane-impermeable testosterone-bovine serum albumin (BSA) acts synergistically with paclitaxel in modifying actin and tubulin cytoskeleton dynamics in LNCaP (androgen sensitive) and DU-145 (androgen insensitive) human prostate cancer cell lines. In addition, coincubation of either cell line with testosterone-BSA and paclitaxel induced inhibition of cell proliferation and apoptosis. Finally, in vivo experiments in LNCaP and DU-145 tumor xenografts in nude mice showed that both agents decrease tumor mass, whereas testosterone-BSA enhances the effect of paclitaxel. Our findings suggest that chronic activation of membrane androgen receptors in vitro and in vivo facilitates and sustains for a longer time the antitumoral action of cytoskeletal acting agents.

DNA mismatch repair and p53 function are major determinants of the rate of development of cisplatin resistance

As opposed to factors that control sensitivity to the acute cytotoxic effect of cisplatin, little is known about the factors that determine the rate at which resistance develops. This study examined how loss of p53 or DNA mismatch repair (MMR) function affected the rate of development of resistance to cisplatin in human colon carcinoma cells during sequential cycles of cisplatin exposure that mimic the way the drug is used in the clinic. We used a panel of sublines molecularly engineered to express either the MMR- and p53-proficient phenotype or singly or doubly deficient phenotypes. Loss of either MMR or p53 alone increased the rate of development of resistance to cisplatin by 1.8- and 2.4-fold, respectively; however, loss of both MMR and p53 increased the rate by 4.8-fold. Inhibition of DNA polymerase zeta by suppression of the expression of its REV3 subunit eliminated the increased rate of development of resistance observed in the MMR-deficient cells. Loss of p53 or MMR increased the steady-state level of REV3 and of REV1 mRNA; loss of both functions increased these levels much further by a factor of 20.2-fold for REV3 and 10.3-fold for REV1. The basal level of homologous recombination measured using a reporter vector was 1.3- to 1.7-fold higher in cells that had lost either p53 or MMR function, and 2.6-fold higher in cells that had lost both. In the p53- and MMR-proficient cells, cisplatin induced a 17-fold increase in homologous recombination even when the recombining sequences that did not contain cisplatin adducts; the magnitude of induction was even greater in cells that had lost either one or both functions. We conclude that separate from effects on sensitivity to the acute cytotoxic effect of cisplatin, loss of MMR, especially when combined with loss of p53, results in rapid evolution of cisplatin resistance during sequential rounds of drug exposure that is likely mediated by enhanced mutagenic translesion synthesis. The DNA damage response activated by cisplatin is accompanied by a p53- and MMR-dependent increase in homologous recombination even between adduct-free sequences.

Chemotherapy resistance in osteosarcoma: current challenges and future directions

For patients with osteosarcoma, the use of chemotherapy has improved survival from 11% with surgical resection alone in the 1960s, to 70% by the mid-1980s. However, survival has since plateaued, despite advances in anticancer therapy. Elucidation of the mechanisms of chemoresistance and implementation of strategies to overcome chemoresistance will likely be pivotal to improving survival. In this review, the focus is on the current understanding of the mechanisms of resistance to the most commonly used agents in the treatment of osteosarcoma and the methods employed to overcome chemotherapy resistance.

Enhanced P53 and BAX gene expression and apoptosis in A549 cells by cis-Pt(II) complex of 3-aminoflavone in comparison with cis-DDP

Lung cancer remains one of the most common causes of cancer-related death worldwide. Approximately 80% is histologically non-small cell lung carcinoma (NSCLC) and in about 70% of patients it is an unresectable type. Clinical studies indicated that application of platinum derivatives caused good results and combinations of platinum with other agents could improve median survivals. In view of the central problem of sufficient efficiency of drugs in chemotherapy, efforts have focused on the development of alternative platinum-based analogues that can be more effective in cancer treatment. cis-bis(3-aminoflavone)dichloroplatinum(II) (cis-Pt(II) complex of 3-aminoflavone) represents a novel class of platinum-based potential antitumour agents. In order to evaluate the degree of apoptosis, acridine orange/ethidium bromide and Hoechst 33258/propidum iodide double staining as well as RT-PCR (P53 and BAX expression evaluation) were used in lung cancer cell line A549 after treatment with this compound in comparison with cis-diamminedichloroplatinum(II) (cis-DDP). Apoptotic cells at early and late stages and also necrotic ones were observed after usage of cis-Pt(II) complex of 3-aminoflavone and the percentage of these cells outnumbered the values obtained after cis-DDP application. The former compound induced a higher percentage of P53 and BAX expression in A549 cells in comparison with the latter one. Results indicate the beneficial properties of cis-Pt(II) complex of 3-aminoflavone as a potential antitumor drug.

Cellular processing of platinum anticancer drugs

Cisplatin, carboplatin and oxaliplatin are platinum-based drugs that are widely used in cancer chemotherapy. Platinum-DNA adducts, which are formed following uptake of the drug into the nucleus of cells, activate several cellular processes that mediate the cytotoxicity of these platinum drugs. This review focuses on recently discovered cellular pathways that are activated in response to cisplatin, including those involved in regulating drug uptake, the signalling of DNA damage, cell-cycle checkpoints and arrest, DNA repair and cell death. Such knowledge of the cellular processing of cisplatin adducts with DNA provides valuable clues for the rational design of more efficient platinum-based drugs as well as the development of new therapeutic strategies.

Kidney slices of human and rat to characterize cisplatin-induced injury on cellular pathways and morphology

Kidney slices represent an in vitro model that has the cellular complexity of in vivo tissue to provide insights into mechanisms of organ injury, as shown in this study with the model nephrotoxicant cisplatin. Cell pathways altered by cisplatin exposure are assessed by gene expression analysis, cell function, and morphology in human and rat kidney slices in comparison to rat kidney from an in vivo study. The acute nephrosis of the tubular epithelium induced by cisplatin in vivo was reproduced in both human and rat kidney slices, while the glomerulus appeared resistant even at high concentrations. Kidney gene expression changes of in vivo and in vitro samples were indicative of transcription, DNA damage, cell cycle, proliferation, and apoptosis that are in agreement with the mechanism of cisplatin causing DNA damage, growth arrest, and apoptosis; while genes indicative of protein damage, the disruption of transport and calcium homeostasis, cellular metabolism, and oxidative stress are pathways linked with cisplatin binding to various cellular proteins and macromolecules. Both concentration and time-dependent gene expression changes evident in the in vitro model preceded a change in tissue morphology. Functional assays confirming cell dysfunction and increased apoptosis revealed the rat kidney to be more sensitive to the effects of cisplatin than human kidney as demonstrated by significant decreases in slice ATP and GSH levels, significant increases in caspase 9 and 3 activity, p53 protein levels, and increased DNA laddering. The regional markers of proximal and distal tubular injury, alpha- and pi-glutathione S-transferases, were shown for the human kidney slices to be significantly increased by cisplatin. In this study, cisplatin-induced nephrotoxicity was demonstrated morphologically in rat and human kidney slices, and the associated gene expression and functional changes characterized the cellular pathways involved.

Aberrant p53 alters DNA damage checkpoints in response to cisplatin: Downregulation of CDK expression and activity

The p53 tumor suppressor protein is a critical mediator of cell cycle arrest and apoptosis in response to genotoxic stress. Abrogation of p53 function is a major feature of tumor development and may result in a compromised DNA-damage response. In our study, we examined the effect of expressing a human p53 cDNA, encoding a histidine to leucine amino acid substitution at codon 179 (H179L), on the ability of wild-type p53-containing NIH3T3 cells to respond to treatment with the chemotherapeutic cisplatin. After 72 hr of cisplatin treatment control cells underwent apoptosis preceded by a combination of S- and G(2) arrest, as judged by flow cytometry of propidium iodide-stained cells, and TUNEL and caspase-3 assays. This correlated with increased expression of the pro-apoptotic protein Bax. In contrast, cells stably expressing H179L-p53 arrested in S-phase following cisplatin treatment, which correlated with a marked decrease in the expression of cdc2, cyclin B1 and cyclin A, and a decrease in CDK2 and cyclin A-associated kinase activity. Interestingly, H179L p53 expressing cells underwent apoptosis earlier than control cells, indicating that this aberrant p53 may enhance cisplatin chemosensitivity. These data suggest that dominant-negative p53 can influence the expression and activity of CDK complexes, thereby modifying cell behavior following cisplatin-induced genotoxicity.

Polyethyleneimine-based gene therapy by inhalation

The delivery of genes by inhalation holds promise for the treatment of a wide range of pulmonary and non-pulmonary disorders and offers numerous advantages over more invasive modes of delivery. Subsequent to the cloning of the cystic fibrosis gene, there was great interest in the delivery of genes directly to the lung surfaces by aerosol, and most early efforts focused on the use of non-viral vectors, particularly cationic lipids. Unfortunately, nebulisation shear forces, inefficient penetration of mucous barriers and inhibitory effects of surfactant and other lung-specific features have generally resulted in a lack of therapeutic effect, and much of this work has diminished in recent years as a consequence. Polyethyleneimine (PEI)-based formulations have proven stable during nebulisation and result in nearly 100% efficient transfection throughout the airways, as well as significant, although lower, levels of transfection throughout the lung parenchyma. Most importantly, therapeutic responses have been obtained in several animal lung tumour models when PEI-based complexes of p53 and IL-12 genes were delivered by aerosol. This approach may also prove useful as a means of localised genetic immunisation. In addition, this mode of delivery seems to be associated with surprisingly low toxicity, and results in little or no CpG immunostimulatory response, which has presented a challenge to repeated gene therapy via other modes of delivery.

Dickkopf 3 inhibits invasion and motility of Saos-2 osteosarcoma cells by modulating the Wnt-beta-catenin pathway

Osteosarcoma (OS) is a primary malignancy of bone with a tendency to metastasize early. Despite intensive chemotherapy and surgical resection, approximately 30% of patients still develop distant metastasis. Our previous work using clinical OS samples suggested that expression of the Wnt receptor LRP5 might be associated with tumor metastasis. In the present study, we used a Dickkopf (Dkk) family member and a dominant-negative LRP5 receptor construct to modulate Wnt signaling in OS cells. Saos-2 cells, which ectopically express Dkk-3, do not undergo apoptosis and exhibit enhanced resistance to serum starvation and chemotherapy-induced cytotoxicity. Transfection of Dkk-3 and dominant-negative LRP5 into Saos-2 cells significantly reduces invasion capacity and cell motility. This blockade is associated with changes in cell morphology consistent with a less invasive phenotype. In addition, Dkk-3 and dominant-negative LRP5 also induce changes in beta-catenin localization consistent with an increase in cell-cell adhesion. Taken together, these results support a possible role for Wnt signaling in the pathobiology and progression of human OS.

P53 mutation correlates with cisplatin sensitivity in head and neck squamous cell carcinoma lines

BACKGROUND

A critical factor for successful organ preservation treatment in head and neck cancer may be selecting tumors that respond to chemotherapy and radiation. Previous results in patients indicated that tumors that overexpressed p53 were more sensitive to chemotherapy than those that did not overexpress p53.

METHODS

To determine the relationship of p53 mutations to sensitivity to cisplatin in vitro, 23 head and neck squamous cell carcinoma (HNSCC) cell lines were analyzed for cisplatin sensitivity, p53 expression, and p53 mutation status.

RESULTS

Mutations of the p53 gene were identified in 13 of 23 of the cell lines tested. Mutation of the p53 gene was significantly associated with high levels of expression of the p53 protein. The average ID(50) (drug dose required to inhibit 50% of cell growth) for cell lines with mutant p53 was 6.8 microM, whereas the average ID(50) for cell lines with wild-type p53 was 13.7 microM.

CONCLUSIONS

These in vitro data support a role for mutation of the p53 tumor suppressor gene as a marker for response to cisplatin in HNSCC.

Clinical and cellular pharmacology in relation to solid tumours of childhood

Our understanding of the clinical and cellular pharmacology of drugs commonly used in the treatment of childhood cancer have increased greatly over the past two decades. However, with the exception of childhood acute lymphoblastic leukaemia (ALL), our current knowledge of factors such as inter-patient pharmacokinetic variability and cellular determinants of chemosensitivity has not been utilized in the design of integrated clinical studies. Recent pre-clinical and clinical evaluation of the topoisomerase I inhibitors topotecan and irinotecan has highlighted the potential importance of pharmacological factors in their effectiveness as cytotoxics. In this review, the clinical and cellular pharmacology of vincristine, actinomycin D, doxorubicin, cyclophosphamide, ifosfamide, cisplatin, carboplatin and etoposide will be discussed in relation to the major paediatric solid tumours. For each disease type, knowledge of the clinical and cellular pharmacology of a candidate drug will be related to pharmacodynamic responses such as response, toxicity and prognosis. For diseases such as Wilms' tumour, osteogenic sarcoma and Ewing's tumour, histological response to initial induction chemotherapy is of prognostic significance, and the depth of response is increasingly recognised as an important determinant of prognosis for high-risk neuroblastoma. For several of these tumour types, the dose-intensity of chemotherapy may be an important variable in determining prognosis. However the relationship between pharmacokinetic variability, cellular pharmacology and the major determinants of chemosensitivity to those drugs employed in first line therapy is unknown. The study of these relationships, by means of up front window studies in children who present with high-risk disease, may be as important as the introduction of new agents. Indeed, the optimisation of current therapies may be required to allow a fully informed selection of those children for whom novel therapies are truly needed. Funding and international collaboration at the clinical and scientific level would be required to achieve these aims.

Sensitivity of p53-deficient cells to oxaliplatin and thio-TEPA (N, N', N" triethylenethiophosphoramide)

P53 is known as a determinant of cellular responses to DNA damage, including apoptosis, cell cycle arrest, and DNA repair. Its role is most easily understood in the context of Burkitt lymphoma and other apoptosis-prone cell types. A number of epithelial cancer cell types, by contrast, exhibit a higher threshold for apoptosis induction in response to DNA damage. In fact, p53 mediates DNA repair and protective responses in the latter cell types, in some cases p53-deficient cells being more sensitive to DNA damage, antithetical to the situation in Burkitt lymphoma and other apoptosis-prone cell types. Ultraviolet light, cisplatin, and nitrogen mustards produce damage that is repaired by a p53-regulated pathway. Here, we explore the sensitivity of the platinum compound oxaliplatin and thio-TEPA (N, N', N", triethylenethiophosphoramide), a cancer chemotherapeutic agent that produces largely base damage, in p53-defective cells. This work demonstrates that the contribution of p53 temporally correlates with DNA repair pathways to produce a resistant phenotype, while the p53-defective cells are more sensitive to certain DNA-damaging chemotherapeutic agents.

Growth suppression of established human osteosarcoma lung metastases in mice by aerosol gene therapy with PEI-p53 complexes

Lung metastases are a frequent complication of osteosarcoma and a treatment that would reduce the severity of this complication would be of great benefit to patients. We have used a formulation consisting of polyethyleneimine (PEI) and a p53 gene administered in aerosol to treat established lung micrometastases as a model of human osteosarcoma in nude mice. The SAOS-LM6 cell line, a metastatic derivative of the p53 null SAOS-2 line, expresses high levels of p53 protein after in vitro transfection with PEI-p53 complexes as determined by ELISA, and transfection with both p53wt and the p53 variant, p53-CD(1-366) in vitro, results in a marked inhibition of SAOS-LM6 cell proliferation. Aerosol delivery of plasmid DNA containing either the p53 gene or a p53-CD(1-366) variant gene formulated with PEI to mice resulted in highly significant reductions in the numbers and size of tumors (P<.001), the total number of tumor foci in the lungs (P<.001) and the size of individual tumor nodules in treated animals compared to untreated, PEI only-treated and PEI-CAT-treated control animals. The different tissues examined did not reveal any signs of toxicity or inflammation after repeated exposure to PEI-DNA. The aerosol delivery of PEI-based formulations of p53 or synthetic p53 variant genes represents a promising new strategy for the treatment of established human osteosarcoma lung metastases. The noninvasive nature of aerosol delivery coupled with low toxicity also make this therapeutic approach potentially appropriate for combination therapy with either radio- or chemotherapy.

Prolonged wild-type p53 protein accumulation and cisplatin resistance

The major limitation for the chemotherapeutic use of DNA-damaging agent cisplatin is the development of resistance in initially responsive tumors. One of the main pathways regulating cell survival following DNA damage is the p53 pathway. In this study we compared the cisplatin-induced response of p53 protein and its downstream targets p21WAF-1 and Mdm2 in the cisplatin-sensitive ovarian carcinoma cell line A2780 and its cisplatin-resistant derivative CP70. A higher dose of cisplatin and a longer exposure time was required to achieve the same level of p53, p21WAF-1, and Mdm2 protein accumulation in the cisplatin-resistant CP70 cells versus cisplatin-sensitive A2780 cells. A significant difference between the two cell lines was observed in cisplatin-induced stabilization of p53 protein. The p53 half-life increased 31-fold in CP70 cells compared to only 6-fold in A2780 cells. In contrast, there was no difference in p21WAF-1 half-life between the two cell lines. These results demonstrate that in A2780 and CP70 cells resistance to cisplatin correlates with prolonged p53 protein stabilization and accumulation.