Drug resistance in ovarian cancer - the role of p53

TP53 Alterations in Myelodysplastic Syndromes and Acute Myeloid Leukemia

TP53 mutations are less frequent in myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML) than in solid tumors, except in secondary and therapy-related MDS/AMLs, and in cases with complex monosomal karyotype. As in solid tumors, missense mutations predominate, with the same hotspot mutated codons (particularly codons 175, 248, 273). As TP53-mutated MDS/AMLs are generally associated with complex chromosomal abnormalities, it is not always clear when TP53 mutations occur in the pathophysiological process. It is also uncertain in these MDS/AML cases, which often have inactivation of both TP53 alleles, if the missense mutation is only deleterious through the absence of a functional p53 protein, or through a potential dominant-negative effect, or finally a gain-of-function effect of mutant p53, as demonstrated in some solid tumors. Understanding when TP53 mutations occur in the disease course and how they are deleterious would help to design new treatments for those patients who generally show poor response to all therapeutic approaches.

Expression of p53 in epithelial ovarian tumors

Background

Ovarian cancers remain the most lethal of all gynecological malignancies despite major developments in their treatment.

Objectives

To study the rate of expression and staining patterns of p53 in various histological types and grades of epithelial ovarian tumors (EOT).

Materials and Methods

Sixty EOTs received in a tertiary care center were studied for gross, microscopy, and p53 immunohistochemistry (IHC) expression patterns. Parameters such as age, laterality of tumor, ascites, capsule rupture, tumor size, stage at presentation, metastasis, tumor grade, and number of mitosis were correlated.

Results

Of the sixty cases studied, 23 (38.3%) were malignant. Serous carcinomas were the largest group with 17 cases (74%) followed by mucinous with 4 cases (17%) and 2 clear cell carcinomas (9%). All benign and borderline EOT were p53 negative. 65.2% of the malignancies were p53 positive and all of them were serous malignancies. 15 out of 16 high-grade serous carcinomas were p53 positive (94%), while one case was negative (6%). 10 cases (63%) showed intense diffuse positivity of more than 60% of the nucleus, while 5 cases (31%) showed aberrant null staining <5% staining of the nucleus. All mucinous, clear cell carcinomas, and the only low-grade serous carcinoma in the study were p53 negative. P53 staining had positive correlations with variables like capsule rupture, ascites, laterality, and CA 125.

Conclusions

The study highlights the different rates of expression and staining patterns of p53 and the need for correct interpretation of p53 IHC for the diagnosis of various EOT.

pathCHEMO, a generalizable computational framework uncovers molecular pathways of chemoresistance in lung adenocarcinoma

Despite recent advances in discovering a wide array of novel chemotherapy agents, identification of patients with poor and favorable chemotherapy response prior to treatment administration remains a major challenge in clinical oncology. To tackle this challenge, we present a generalizable genome-wide computational framework pathCHEMO that uncovers interplay between transcriptomic and epigenomic mechanisms altered in biological pathways that govern chemotherapy response in cancer patients. Our approach is tested on patients with lung adenocarcinoma who received adjuvant standard-of-care doublet chemotherapy (i.e., carboplatin-paclitaxel), identifying seven molecular pathway markers of primary treatment response and demonstrating their ability to predict patients at risk of carboplatin-paclitaxel resistance in an independent patient cohort (log-rank p-value = 0.008, HR = 10). Furthermore, we extend our method to additional chemotherapy-regimens and cancer types to demonstrate its accuracy and generalizability. We propose that our model can be utilized to prioritize patients for specific chemotherapy-regimens as a part of treatment planning.

Nusrat Epsi et al. present pathCHEMO, a computational framework for uncovering transcriptomic and epigenomic pathways of chemoresistance in cancer that has the potential to improve clinical decision-making. They apply pathCHEMO to lung adenocarcinoma data from public databases, and identify seven molecular pathways implicated in carboplatin-paclitaxel resistance.

Gliotoxin Enhances Autophagic Cell Death via the DAPK1-TAp63 Signaling Pathway in Paclitaxel-Resistant Ovarian Cancer Cells

Death-associated protein kinase 1 (DAPK1) expression induced by diverse death stimuli mediates apoptotic activity in various cancers, including ovarian cancer. In addition, mutual interaction between the tumor suppressor p53 and DAPK1 influences survival and death in several cancer cell lines. However, the exact role and connection of DAPK1 and p53 family proteins (p53, p63, and p73) in drug-resistant ovarian cancer cells have not been studied previously. In this study, we investigated whether DAPK1 induction by gliotoxin derived from marine fungus regulates the level of transcriptionally active p63 (TAp63) to promote apoptosis in an autophagy-dependent manner. Pre-exposure of paclitaxel-resistant ovarian cancer cells to gliotoxin inhibited the expression of multidrug resistant-associated proteins (MDR1 and MRP1-3), disrupted the mitochondrial membrane potential, and induced caspase-dependent apoptosis through autophagy induction after subsequent treatment with paclitaxel. Gene silencing of DAPK1 prevented TAp63-mediated downregulation of MDR1 and MRP1-3 and autophagic cell death after sequential treatment with gliotoxin and then paclitaxel. However, pretreatment with 3-methyladenine (3-MA), an autophagy inhibitor, had no effect on the levels of DAPK1 and TAp63 or on the inhibition of MDR1 and MRP1-3. These results suggest that DAPK1-mediated TAp63 upregulation is one of the critical pathways that induce apoptosis in chemoresistant cancer cells.

Palmatine from Unexplored Rutidea parviflora Showed Cytotoxicity and Induction of Apoptosis in Human Ovarian Cancer Cells

Ovarian cancer ranks amongst the deadliest cancers in the gynaecological category of cancers. This research work aims to evaluate in vitro anti-ovarian cancer activities and identify phytochemical constituents of a rarely explored plant species—Rutidea parviflora DC. The aqueous and organic extracts of the plant were evaluated for cytotoxicity using sulforhodamine B assay in four ovarian cancer cell lines and an immortalized human ovarian epithelial (HOE) cell line. The bioactive compounds were isolated and characterized by gas/liquid chromatography mass spectrometry and nuclear magnetic resonance spectroscopy. Caspase 3/7 activity assay, western blotting and flow cytometry were carried out to assess apoptotic effects of active compounds. The extracts/fractions of R. parviflora showed promising anti-ovarian cancer activities in ovarian cancer cell lines. A principal cytotoxic alkaloid was identified as palmatine whose IC₅₀ was determined as 5.5–7.9 µM. Palmatine was relatively selective towards cancer cells as it was less cytotoxic toward HOE cells, also demonstrating interestingly absence of cross-resistance in cisplatin-resistant A2780 cells. Palmatine further induced apoptosis by increasing caspase 3/7 activity, poly-ADP-ribose polymerase cleavage, and annexin V and propidium iodide staining in OVCAR-4 cancer cells. Our studies warranted further investigation of palmatine and R. parviflora extracts in preclinical models of ovarian cancer.

DoE to improve supercoiled p53-pDNA purification by O-phospho-l-tyrosine chromatography

P53 is implicated in various cellular functions and several studies have shown that transfection of cancer cells with wild-type p53-expressing plasmids could directly drive cells into growth arrest and/or apoptosis. In the present work, the 6.07 kbp pcDNA3-FLAG-p53 plasmid, which encodes the p53 tumor suppressor, was produced and recovered from a recombinant cell culture of Escherichia coli DH5α. Following plasmid biosynthesis, the O-phospho-l-tyrosine chromatographic matrix was explored to purify the supercoiled p53-encoding plasmid. In order to quickly determine the optimal chromatographic performance and to obtain the required purity degree, maximizing the recovery yield of the supercoiled plasmid DNA, the Composite Central Face design was applied. The model revealed to be statistically significant (p-value < 0.05), with coefficient of determination of 0.9434 for the recovery yield and 0.9581 for purity and the central point was successfully validated. After the chromatographic process optimization by using the design of experiments tool, 49.7% of the supercoiled p53-encoding plasmid was recovered with 98.2% of purity, when a decreasing ammonium sulphate gradient was applied. The dynamic binding capacity of the O-phospho-l-tyrosine agarose column was 0.35 ± 0.02 mg pDNA/mL matrix at 50% of the breakthrough. Finally, the purified sample was analysed to assess the content of endotoxins, proteins and genomic DNA, showing that all these impurity levels were below the recommendations of the regulatory agencies.

Tumor Microenvironment Activated Membrane Fusogenic Liposome with Speedy Antibody and Doxorubicin Delivery for Synergistic Treatment of Metastatic Tumors

Metastasis is the principal event leading to breast cancer death. Discovery of novel therapeutic approaches that are specific in targeting tumor metastasis factors while at the same time are an effective treatment of the tumor is urgently required. S100A4 protein is a key player in promoting metastasis and sequestrating the effect of tumor-suppressor protein p53. Here, a tumor microenvironment activated membrane fusogenic liposome was prepared to deliver rapidly anti-S100A4 antibody and doxorubicin into the cytoplasm directly in a fusion-dependent manner in order to bypass the cellular endocytosis to avoid the inefficient escape and degradation in the acidic endosome. After intracellular S100A4 blockage with anti-S100A4 antibody, the cytoskeleton of breast cancer 4T1 cells was rearranged and cell motility was suppressed. In the meantime, the antitumor effect of doxorubicin was enormously enhanced by reversing the effect of S100A4 on the sequestration of tumor-suppressor protein p53. Importantly, both local growth and metastasis of 4T1 cells were inhibited in a xenograft mouse model. Together, the speedy delivery of antibody and doxorubicin into cytoplasm based on a new membrane fusogenic liposome was an innovative approach for metastatic breast cancer treatment.

A functional perspective of nitazoxanide as a potential anticancer drug

Cancer is a group of diseases characterized by uncontrolled cell proliferation, evasion of cell death and the ability to invade and disrupt vital tissue function. The classic model of carcinogenesis describes successive clonal expansion driven by the accumulation of mutations that eliminate restraints on proliferation and cell survival. It has been proposed that during cancer's development, the loose-knit colonies of only partially differentiated cells display some unicellular/prokaryotic behavior reminiscent of robust ancient life forms. The seeming "regression" of cancer cells involves changes within metabolic machinery and survival strategies. This atavist change in physiology enables cancer cells to behave as selfish "neo-endo-parasites" that exploit the tumor stromal cells in order to extract nutrients from the surrounding microenvironment. In this framework, it is conceivable that anti-parasitic compounds might serve as promising anticancer drugs. Nitazoxanide (NTZ), a thiazolide compound, has shown antimicrobial properties against anaerobic bacteria, as well as against helminths and protozoa. NTZ has also been successfully used to promote Hepatitis C virus (HCV) elimination by improving interferon signaling and promoting autophagy. More compelling however are the potential anti-cancer properties that have been observed. NTZ seems to be able to interfere with crucial metabolic and pro-death signaling such as drug detoxification, unfolded protein response (UPR), autophagy, anti-cytokine activities and c-Myc inhibition. In this article, we review the ability of NTZ to interfere with integrated survival mechanisms of cancer cells and propose that this compound might be a potent addition to the current chemotherapeutic strategy against cancer.

The consequence of oncomorphic TP53 mutations in ovarian cancer

Ovarian cancer is the most lethal gynecological malignancy, with an alarmingly poor prognosis attributed to late detection and chemoresistance. Initially, most tumors respond to chemotherapy but eventually relapse due to the development of drug resistance. Currently, there are no biological markers that can be used to predict patient response to chemotherapy. However, it is clear that mutations in the tumor suppressor gene TP53, which occur in 96% of serous ovarian tumors, alter the core molecular pathways involved in drug response. One subtype of TP53 mutations, widely termed gain-of-function (GOF) mutations, surprisingly converts this protein from a tumor suppressor to an oncogene. We term the resulting change an oncomorphism. In this review, we discuss particular TP53 mutations, including known oncomorphic properties of the resulting mutant p53 proteins. For example, several different oncomorphic mutations have been reported, but each mutation acts in a distinct manner and has a different effect on tumor progression and chemoresistance. An understanding of the pathological pathways altered by each mutation is necessary in order to design appropriate drug interventions for patients suffering from this deadly disease.

Research perspective: potential role of nitazoxanide in ovarian cancer treatment. Old drug, new purpose?

Among gynecological malignancies epithelial ovarian cancer (EOC) is the leading cause of death. Despite improvements in conventional chemotherapy combinations, the overall cure rate has remained mostly stable over the years, and only 10%–15% of patients maintain a complete response following first-line therapy. To improve the efficacy of ovarian cancer chemotherapy it is essential to develop drugs with new mechanisms of action. Compared to normal tissues, protein disulfide isomerase (PDI) is overexpressed in ovarian tumors. PDI is a cellular enzyme in the lumen of the endoplasmic reticulum (ER) of eukaryotes or the periplasmic region of prokaryotes. This protein catalyzes the formation and breakage of disulphide bonds between cysteine residues in proteins, which affects protein folding. Selective inhibition of PDI activity has been exhibited both in vitro and in vivo anticancer activity in human ovarian cancer models. PDI inhibition caused accumulation of unfolded or misfolded proteins, which led to ER stress and the unfolded protein response (UPR), and in turn resulted in cell death. Nitazoxanide [NTZ: 2-acetyloxy-N-(5-nitro-2-thiazolyl)benzamide] is a thiazolide antiparasitic agent with excellent activity against a wide variety of protozoa and helminths. In this article, we propose that NTZ, acting as PDI inhibitor, may be a new and potent addition to the chemotherapeutic strategy against ovarian cancer.

Discovery of an orally active small-molecule irreversible inhibitor of protein disulfide isomerase for ovarian cancer treatment

Protein disulfide isomerase (PDI), an endoplasmic reticulum chaperone protein, catalyzes disulfide bond breakage, formation, and rearrangement. The effect of PDI inhibition on ovarian cancer progression is not yet clear, and there is a need for potent, selective, and safe small-molecule inhibitors of PDI. Here, we report a class of propynoic acid carbamoyl methyl amides (PACMAs) that are active against a panel of human ovarian cancer cell lines. Using fluorescent derivatives, 2D gel electrophoresis, and MS, we established that PACMA 31, one of the most active analogs, acts as an irreversible small-molecule inhibitor of PDI, forming a covalent bond with the active site cysteines of PDI. We also showed that PDI activity is essential for the survival and proliferation of human ovarian cancer cells. In vivo, PACMA 31 showed tumor targeting ability and significantly suppressed ovarian tumor growth without causing toxicity to normal tissues. These irreversible small-molecule PDI inhibitors represent an important approach for the development of targeted anticancer agents for ovarian cancer therapy, and they can also serve as useful probes for investigating the biology of PDI-implicated pathways.

TLR4 signaling induced by lipopolysaccharide or paclitaxel regulates tumor survival and chemoresistance in ovarian cancer

Toll-like receptors (TLRs) expressed on immune cells trigger inflammatory responses. TLRs are also expressed on ovarian cancer (OvCa) cells, but the consequences of signaling by the TLR4/MyD88 pathway in these cells are unclear. Here, TLR4 and MyD88 expression in OvCa tissues (n=20) and cell lines (OVCAR3, SKOV3, AD10, A2780 and CP70) was evaluated by reverse transcriptase-PCR, western blots and immunohistochemistry. Cell growth, apoptosis, nuclear factor-kappaB (NF-kappaB) translocation, IRAK4 and TRIF expression and cJun phosphorylation were measured following tumor cell exposure to the TLR4 ligands, lipopolysaccharide (LPS) or paclitaxel (PTX). Culture supernatants were tested for cytokine levels. TLR4 was expressed in all tumors, tumor cell lines and normal epithelium. MyD88 was detectable in tumor tissues and in 3/5 OvCa lines but not in normal cells. In MyD88(+) SCOV3 cells, LPS or PTX binding to TLR4 induced IRAK4 activation and cJun phosphorylation, activated the NF-kappaB pathway and promoted interleukin (IL)-8, IL-6, vascular endothelial growth factor and monocyte chemotactic protein-1 production and resistance to drug-induced apoptosis. Silencing of TLR4 in SCOV3 cells with small interference RNA resulted in phosphorylated-cJun (p-cJun) downregulation and a loss of PTX resistance. In PTX-sensitive, MyD88(neg) A2780 cells, TLR4 stimulation upregulated TRIF, and TLR4 silencing eliminated this effect. Thus, TLR4/MyD88 signaling supports OvCa progression and chemoresistance, promoting immune escape.

Akt promotes cisplatin resistance in human ovarian cancer cells through inhibition of p53 phosphorylation and nuclear function

Resistance to cisplatin-based chemotherapy is a major cause of treatment failure in human ovarian cancer. Wild-type TP53 status is often, but not always, associated with cisplatin sensitivity, suggesting that additional factors may be involved. Overexpression/activation of the phosphatidylinositol-3-kinase/Akt pathway is commonly observed in ovarian cancer, and Akt activation is a determinant of chemoresistance in ovarian cancer cells, an effect that may be due, in part, to its inhibitory actions on p53-dependent apoptosis. To that end, we examined the role and regulation of p53 in chemosensitive ovarian cancer cells, as well as in their chemoresistant counterparts, and investigated if and how Akt influences this pathway. Cisplatin induced apoptosis in chemosensitive, but not chemoresistant cells, and this was inhibited by downregulation of p53. Cisplatin upregulated PUMA in a p53-dependent manner, and the presence of PUMA was necessary, but not sufficient for cisplatin-induced apoptosis. p53 was phosphorylated on numerous N-terminal residues, including Ser15, Ser20, in response to cisplatin in chemosensitive, but not chemoresistant cells. Furthermore, activation of Akt inhibited the cisplatin-induced upregulation of PUMA, and suppressed cisplatin-induced p53 phosphorylation, while inhibition of Akt increased total and phospho-p53 contents and sensitized p53 wild-type, chemoresistant cells to cisplatin-induced apoptosis. Finally, mutation of Ser15 and/or Ser20, but not of Ser37, to alanine significantly attenuated the ability of p53 to facilitate CDDP-induced apoptosis, and this was independent of PUMA expression. These results support the hypothesis that p53 is a determinant of CDDP sensitivity, and suggest that Akt contributes to chemoresistance, in part, by attenuating p53-mediated PUMA upregulation and phosphorylation of p53, which are essential, but independent determinants of sensitivity to CDDP-induced apoptosis.

Clinical relevance of dominant-negative p73 isoforms for responsiveness to chemotherapy and survival in ovarian cancer: evidence for a crucial p53-p73 cross-talk in vivo

PURPOSE

We aimed to determine the clinical role of the p53 family members p53 and p73 in the responsiveness to platinum-based chemotherapy and survival in ovarian cancer, considering their cross-talk and the p53 polymorphism at codon 72.

EXPERIMENTAL DESIGN

A detailed analysis of p53 and p73 in a series of 122 ovarian cancers was done. We used a functional yeast-based assay to determine the p53 mutational status. Red yeast colonies, indicating mutant p53, were subsequently sequenced to determine the specific p53 alteration. p53 mutations were divided into two groups according to their previous characterization in the literature: those that efficiently inhibit transcriptionally active TAp73 function and those that do not. A p53 polymorphism at codon 72 was determined in corresponding normal tissue or blood of ovarian cancer patients. Isoform-specific p73 expression analysis using real-time reverse transcription-PCR has previously been done in the majority of ovarian cancers included in this study. In a retrospective chart review, responsiveness to chemotherapy was assessed, and survival data with long follow-up times were collected.

RESULTS

Eighty of 122 (65.6%) of ovarian cancers harbored p53 mutations. p53 mutational status was an important determinant of responsiveness to platinum-based chemotherapy in all patients with a residual tumor of <2 cm in diameter after initial surgery (wild-type versus mutant, P = 0.029). In addition, p53 mutational status was a strong prognosticator for recurrence-free and overall survival (P < 0.0001 and P = 0.003, respectively) in univariate analyses. High expression levels of dominant-negative p73 isoforms (DeltaNp73 and DeltaN'p73) significantly correlated with chemotherapeutic failure (P = 0.048) and with worse recurrence-free and overall survival in patients with p53 mutant cancers (P = 0.048 and P = 0.005, respectively). Eight p53 mutations, present in 19 cases, were found that efficiently inhibit TAp73 (i.e., 175H, 220C, 245S, 245D, 248W, 248Q, 266E, and 273H). Patients with p53 mutations that efficiently inhibit TAp73 function had a significantly shorter overall survival than patients with p53 mutations of unknown effect on TAp73 (P = 0.044). The p53 polymorphism at codon 72 had no influence on responsiveness to chemotherapy or survival.

CONCLUSION

We provide the first clinical evidence that dominant-negative p73 isoforms contribute to drug resistance in vivo, underscoring the importance of a p53-p73 cross-talk. NH2-terminally truncated p73 isoforms were of significant clinical effect by providing an additional unfavorable factor for response to platinum-based chemotherapy and survival in p53 mutant ovarian cancers.

[Isolation of mitochondrial DNA binding proteins which are specific for maize cox1 promoter]

We purified DNA binding proteins which interact with the promoter region of cox1 gene from maize mitochondria. Presence of poly[dIdC-dIdC] and KCl in concentrations up to 500 mM had no influence on binding efficiency demonstrating high specificity of complexes formed. Surprisingly, we did not detect DNA binding when probes containing promoter regions of other mitochondrial genes (cox3, rrn26) were used. Mobility shift competition studies also suggest that the protein posseses binding specificity towards cox1 promoter. The core motif AAGTA proved to be necessary for DNA binding. Using combination of EMSA and elution of proteins from PAG we showed that DNA-protein complex formed contains three polypeptides with molecular mass 60, 44 and 22 kD. We suggest that the isolated proteins may play an important role in the regulation of plant cox1 gene transcription.

Mechanisms of drug resistance in cancer chemotherapy

The management of cancer involves procedures, which include surgery, radiotherapy and chemotherapy. Development of chemoresistance is a persistent problem during the treatment of local and disseminated disease. A plethora of cytotoxic drugs that selectively, but not exclusively, target actively proliferating cells include such diverse groups as DNA alkylating agents, antimetabolites, intercalating agents and mitotic inhibitors. Resistance constitutes a lack of response to drug-induced tumour growth inhibition; it may be inherent in a subpopulation of heterogeneous cancer cells or be acquired as a cellular response to drug exposure. Resistance varies. Although regulatory approval may require efficacy in as few as 20% of trial cohorts, a drug may subsequently be used in unselected patients displaying resistance to the treatment. Principal mechanisms may include altered membrane transport involving the P-glycoprotein product of the multidrug resistance (MDR) gene as well as other associated proteins, altered target enzyme (e.g. mutated topoisomerase II), decreased drug activation, increased drug degradation due to altered expression of drug-metabolising enzymes, drug inactivation due to conjugation with increased glutathione, subcellular redistribution, drug interaction, enhanced DNA repair and failure to apoptose as a result of mutated cell cycle proteins such as p53. Attempts to overcome resistance mainly involve the use of combination drug therapy using different classes of drugs with minimally overlapping toxicities to allow maximal dosages and with narrowest cycle intervals, necessary for bone marrow recovery. Adjuvant therapy with P-glycoprotein inhibitors and, in specific instances, the use of growth factor and protein kinase C inhibitors are newer experimental approaches that may also prove effective in abrogating or delaying onset of resistance. Gene knockout using antisense molecules may be another effective way of blocking drug resistance genes. Conversely, drug resistance may also be used to good purpose by transplanting retrovirally transformed CD34 cells expressing the MDR gene to protect the bone marrow during high-dose chemotherapy.

Bcl-2 Up-Regulation and P-p53 Down-Regulation Account for the Low Sensitivity of Murine L929 Fibrosarcoma Cells to Oridonin-Induced Apoptosis

Drug resistance has been a major limitation to chemotherapy. There are many mechanisms that contribute to such resistance. In our study, we subcloned oridonin-sensitive and low sensitive L929 cells and both types of cells grew at almost the same growth rate. The acquired low sensitivity to oridonin-induced apoptosis was associated with Bcl-2 up-regulation and down-regulation of p53 phosphorylation. The p38 inhibitor SB203580 decreased Bcl-2 expression in the low sensitive L929 cells and made the cells more sensitive to oridonin. Moreover, a higher dose of oridonin promoted p53 phosphorylation, increased Bax expression and subsequently induced death of low sensitive L929 cells, however, it had no effect on Bcl-2 expression. The increased Bcl-2/Bax ratio in oridonin low sensitive L929 cells did not inhibit caspase-9 or -3 activation, but suppressed the cleavage of poly (ADP-ribose) polymerase (PARP), indicating the existence of caspase-9 or -3 independent PARP activation. These results indicated that in L929 cells, there was a relationship among the low sensitivity to oridonin, down-regulation of p53 phosphorylation and Bcl-2 up-regulation.

A Randomized Study of Epithelial Ovarian Cancer: Is Chemotherapy Useful after Complete Remission?

Objective. The aim of this study is to verify whether consolidation chemotherapy with Cisplatin improves disease-free survival and/or overall survival in patients affected by epithelial ovarian cancer.Methods. A multicenter study examined 122 randomized patients in complete remission as judged by laparoscopy or laparotomy following first-line chemotherapy consisting of ACy (Adriamycin + Cyclophosphamide), PCy (Cisplatin + Cyclophosphamide), or Mitoxantrone + Carboplatin. Sixty-one of these patients were treated with 3 cycles of 5-Fluorouracil (FU) 500 mg/m2 for 5 days followed by Cisplatin at 100 mg/m2 on the 6th or 7th day every 28 days; the other 61 received no further treatment (nihil group).Results. Sixty patients in the Cisplatin arm were evaluable. There were 36 relapses in the FU+Cisplatin arm and 30 in the nihil arm. Peritoneal relapses were 25% for Cisplatin treatment vs. 16.4 % for nihil. There were 29 deaths in the Cisplatin arm vs. 27 for nihil. Median overall survival time (95 months with Cisplatin vs. 96 months in the nihil group) and median disease-free survival (66 months with Cisplatin vs. 73 in the nihil group) were similar in both arms (p=0.66 and p=0.41, respectively). There were no significant differences in tumor stage and grade between the two arms. Seven patients presented a second neoplasm during follow-up: six in the nihil arm, but only one patient in the Cisplatin arm. Death in these patients was due to the second neoplasm and not to progression of ovarian cancer.Conclusion. Three courses of additional platinum+FU treatment after five cycles of first-line chemotherapy without FU produced no increase in overall survival or disease-free survival.

Influence of surgery and postoperative therapy and tumor characteristics on patient prognosis in advanced ovarian carcinomas

OBJECTIVES

The prognosis in advanced ovarian cancer depends on clinical, morphological, biological and therapeutic variables. However, little is known about their real influences and interrelationships.

STUDY DESIGN

One hundred and nineteen long-term, follow-up patients with advanced ovarian carcinoma were analyzed. Overall survival was related to the extent of debulking surgery, response to chemotherapy and several clinicomorphological, histopathological, and immunohistochemical variables.

RESULTS

Among all variables, both radical surgery and response to chemotherapy exerted the greatest influence on patient prognosis as shown in both univariate and multifactorial analyses. Most established prognostic factors were of minor importance. Success of chemotherapy correlated with lower residual tumor volume, CA125 expression, FIGO-stage, and serous tumor type.

CONCLUSION

Prognosis and chemotherapeutic success in advanced ovarian cancer seem to be interrelated and may be influenced by the intensity of surgical interventions. This demands for greatest cytoreduction during initial surgery and correction for residual tumor volume and success of therapy in studies of prognostic factors.

Optimal sequencing in the treatment of recurrent ovarian cancer

Improvements in ovarian cancer management mean that it may now be a long-term disease for which treatment must be carefully considered. Optimal sequencing of chemotherapy may help to enhance patients' benefit of therapy and minimize toxicity. The response to retreatment with platinum or a platinum/taxane combination is strongly influenced by the treatment-free interval after initial therapy with a platinum combination. Response rates to platinum retreatment in platinum-resistant patients (relapse within 6 months) are lower than those in platinum-sensitive patients (relapse after 6 months). Increasing the platinum-free interval by using non-platinum-based chemotherapy for treatment after relapse appears to increase the likelihood of response to later rechallenge with platinum. Many alternative agents have been investigated for the treatment of patients with relapsed ovarian cancer, including single-agent topotecan, which has been shown to achieve favorable responses. Topotecan may cause myelosuppression, which is noncumulative but tends to increase in direct correlation with the number of prior chemotherapy courses. Therefore, the best use of topotecan may be early in the course of salvage therapy. The hematologic toxicities associated with topotecan can also be reduced by adjusting the dose and schedule. Prolonged use of topotecan may be feasible and potentially beneficial in some patients.

Human melanoma: drug resistance

Advanced malignant melanoma has a poor prognosis since chemotherapy is mostly ineffective because, in part, of the intrinsic and/or extrinsic resistance of melanoma cells to systemic treatment with antineoplastic agents. The reasons for the chemoresistant phenotype are currently unknown. The relevance of well-analyzed drug resistance mechanisms in melanoma such as intracellular and extracellular transport, drug resistance by induction of certain enzyme systems, and altered drug-target interaction is reviewed. It has been shown that most anticancer drugs kill susceptible cells through induction of apoptosis. Therefore, the significance of apoptotic deficiency caused by alteration in the apoptotic pathway is discussed in relation to specific molecules and apoptotic mechanisms like death-receptors, the Bcl-2 family, and the Hsp family of proteins. The complexity of the molecular variants involved in signal transduction along apoptotic pathways suggests that the cell may possess a variety of possibilities for regulating apoptosis and generating apoptosis deficiency. Thus apoptosis and apoptosis deficiency should be analyzed to understand the mechanisms of melanoma resistance.

Chemosensitivity testing in gynecologic oncology--dream or reality?

Cell culture and animal models have played an essential role in the research of new principles of therapy. Many methods for the individualized testing of therapy sensitivity and resistance have been developed, for example, the clonogenic assay. Presently, the ATP-TCA is commercially available as a testing kit. This review gives an overview of the tumor samples that were tested in the oncologic laboratory in the Department of Obstetrics and Gynecology, Munich Grosshadern between 1993 and 2001. All target parameters show a clear trend in favor of sequential, dose-intensified Epirubicin/Paclitaxel therapy. If this trend remains valid for the total number of patients, a significant impact of this new principle of therapy can be expected. By individualized planning of therapy with ATP-TCA testing, therapy in the individual patient could already be performed by the examination of sensitivity in the preoperative biopsy specimen.

Drug-resistance in human melanoma

Advanced malignant melanoma has a poor prognosis since chemotherapy is mostly ineffective due in part to the intrinsic and/or extrinsic resistance of melanoma cells to systemic treatment with anti-neoplastic agents. The reasons for the chemoresistant phenotype are unknown. The relevance of well-analyzed drug-resistance mechanisms, e.g., intracellular/extracellular transport and induction of certain enzyme systems, is reviewed. Most anti-cancer drugs kill susceptible cells through induction of apoptosis. Therefore, it appears that differences in the apoptotic pathways which lead to apoptotic deficiency may account for the ability of some tumor cells to resist drug therapy. Human melanomas, which are characteristically drug-resistant, are more likely to have altered apoptotic pathways and fewer pro-apoptotic molecules. Tumor cells with these characteristics are seldom sensitive to drugs. The complexity of the molecular variants involved in signal transduction along apoptotic pathways suggests that the cell may have a variety of possibilities for regulating apoptosis and generating apoptotic deficiency. Thus, apoptosis and apoptotic deficiency should be analyzed to better clarify the mechanisms of melanoma resistance.

Synergistic induction of apoptosis by the combination of trail and chemotherapy in chemoresistant ovarian cancer cells

OBJECTIVES

The aim of this study was to investigate whether TNF-related apoptosis-inducing ligand (TRAIL) alone or in combination with chemotherapy could induce apoptosis in ovarian cancer cells resistant to chemotherapy.

METHODS

Twelve chemoresistant epithelial cancer cell lines were treated with each chemotherapeutic drug alone (cisplatin, doxorubicin, or paclitaxel), TRAIL alone, or the combination. Toxicity was assessed using the MTS assay. To assess whether growth inhibition was due to apoptosis, TUNEL assay, caspase activation (measured by caspase-3 and PARP cleavage), and the sub G0/G1 fraction of cells were measured. Synergism was confirmed by fractional inhibition and dose-effect analysis. Expression of death and decoy receptors was studied by immunoblotting and an RNase protection assay. Statistical comparison of means was performed using Student's t test.

RESULTS

The majority of the chemoresistant cells were also resistant to TRAIL alone. In contrast, the combination of TRAIL and chemotherapy resulted in a significant growth inhibition over a wide range of concentrations. This interaction was synergistic by dose-effect analysis. Flow cytometry demonstrated a significant increase in the fraction of apoptotic cells by the combination compared to each reagent alone. A significant enhancement in caspase and PARP cleavage was observed upon treatment with the combination. Finally, no correlation between induction of apoptosis and level of death receptors was found.

CONCLUSIONS

The data suggest that almost all the ovarian cancer cells, which are resistant to chemotherapy, are also resistant to TRAIL. The combination of TRAIL and chemotherapy overcomes this resistance in a synergistic fashion by triggering caspase-mediated apoptosis. The combination of TRAIL and chemotherapy could be useful as a therapy for chemoresistant ovarian cancers.

Relationship between expression of topoisomerase II isoforms and chemosensitivity in choroidal melanoma

Choroidal melanoma has a high mortality rate and responds poorly to existing chemotherapy, but unexpected ex vivo sensitivity of a subset of these tumours to topoisomerase II inhibitors has been noted. Since chemoresistance may be mediated by the molecular phenotype of tumours, immunohistochemistry has been used to study the expression of both isoforms of topoisomerase II (alpha and beta) in 29 choroidal melanomas for which chemosensitivity assay data for doxorubicin or mitoxantrone are also available. Of these, eight tumours were topoisomerase II beta-positive and 11 were topoisomerase II alpha-positive. Recent studies showing genetic abnormality (often monosomy of chromosome 3) in choroidal melanoma suggest that loss of immunostaining could be due to genomic loss rather than down-regulation of topoisomerase II beta in these tumours. There was no convincing excess of anthracycline resistance in the topoisomerase II beta-negative group. Addition of topoisomerase II alpha, MDR1 (11/17 positive), LRP (16/28 positive), and MRP (5/29 positive) data in multivariate analysis did not reliably predict sensitivity or resistance. Vincristine chemosensitivity showed no relation to MDR1, LRP or MRP in 18 tumours tested. While it is possible that some tumours which do express topoisomerase II beta may respond to anthracyclines, the molecular basis of resistance or sensitivity to anthracyclines or vincristine in uveal melanoma is complex and remains incompletely understood.

p53-dependent apoptosis in melanoma cells after treatment with camptothecin

Cutaneous malignant melanoma is a life-threatening cancer with poor prognosis due to a high metastasis potential. The main obstacle in treatment of metastatic melanoma is the resistance to chemotherapy. Recent studies indicated that apoptosis is a common mechanism of action for various cytotoxic agents. As p53 plays an important part in apoptosis, we investigated the role of p53 in chemosensitivity of melanoma cells. Previously, we found that melanoma cell lines containing wild-type p53 have significantly higher response rates to chemotherapy than cell lines with a mutant p53 gene. To confirm the role of p53 in melanoma chemosensitivity further, we transfected an expression vector, pED1, which carries a mutant p53 gene, into a wild-type p53 melanoma cell line, MMAN. We examined the effect of mutant p53 on camptothecin-induced apoptosis and the expression of genes which are known to be involved in apoptosis or drug resistance, such as bcl-2, bax, bak, p21waf1, and P-glycoprotein. Our results indicate that overexpression of the mutant p53 increased the growth rate of MMAN cells, reduced the sensitivity to camptothecin, and lowered drug-induced apoptosis by 2-3-fold. Flow cytometry indicated that the camptothecin-induced apoptosis is not associated with G1 arrest. Furthermore, camptothecin treatment reduced bcl-2 and P-glycoprotein expression in wild-type p53 MMAN cells, but not cells overexpressing mutant p53. These results demonstrate that p53 mutational status is a determinant of melanoma chemosensitivity. p53 may downregulate bcl-2 and P-glycoprotein to induce apoptosis in melanoma cells after chemotherapy.