Cisplatin restores p53 function and enhances the radiosensitivity in HPV16 E6 containing SiHa cells

Targeted Therapy as a Potential De-Escalation Strategy in Locally Advanced HPV-Associated Oropharyngeal Cancer: A Literature Review

The treatment landscape of locally advanced HPV-oropharyngeal squamous cell carcinoma (OPSCC) is undergoing transformation. This is because the high cures rates observed in OPSCC are paired with severe treatment-related, long-term toxicities. These significant adverse effects have led some to conclude that the current standard of care is over-treating patients, and that de-intensifying the regimens may achieve comparable survival outcomes with lower toxicities. Consequently, several de-escalation approaches involving locally advanced OPSCC are underway. These include the reduction of dosage and volume of intensive cytotoxic regimens, as well as elimination of invasive surgical procedures. Such de-intensifying treatments have the potential to achieve efficacy and concurrently alleviate morbidity. Targeted therapies, given their overall safer toxicity profiles, also make excellent candidates for de-escalation, either alone or alongside standard treatments. However, their role in these endeavors is currently limited, because few targeted therapies are currently in clinical use for head and neck cancers. Unfortunately, cetuximab, the only FDA-approved targeted therapy, has shown inferior outcomes when paired with radiation as compared to cisplatin, the standard radio-sensitizer, in recent de-escalation trials. These findings indicate the need for a better understanding of OPSCC biology in the design of rational therapeutic strategies and the development of novel, OPSCC-targeted therapies that are safe and can improve the therapeutic index of standard therapies. In this review, we summarize ongoing research on mechanism-based inhibitors in OPSCC, beginning with the salient molecular features that modulate tumorigenic processes and response, then exploring pharmacological inhibition and pre-clinical validation studies of candidate targeted agents, and finally, summarizing the progression of those candidates in the clinic.

Lack of CD44 overexpression and application of concurrent chemoradiotherapy with cisplatin independently indicate excellent prognosis in patients with HPV-positive oropharyngeal cancer

BACKGROUND

HPV-16 positivity in patients with squamous cell carcinoma of oropharynx (OPSCC) is associated with better prognosis. However, in more than 40% of HPV infected patients progression of cancer disease is observed, which indicates the presence of cancer cells resistant to therapy. Some studies suggest that there may be a subpopulation of cancer stem cells (CSCs), which simultaneously exhibit unlimited ability to self-renew and differentiate towards neoplastic cells. The relation between HPV16 infection and biomarkers of CSCs is unclear.

OBJECTIVE

The aim of the study was to compare the expression of CD44, CD98, ALDH1/2 and P16 in oropharyngeal cancer patients with or without HPV16 infection, as well as to analyze the prognostic potential of selected CSCs biomarkers in these two subgroups.

METHODS

The study was performed in a group of 63 patients. HPV16 infection status was analyzed by quantitative polymerase chain reaction, while CD44, CD98, ALDH1/2 and P16 expression by immunohistochemistry. In survival analysis, two endpoints were applied: overall survival (OS) and disease-free survival (DFS).

RESULTS

Among 63 cancers, HPV16 infection was found in 25 tumors (39.7%), overexpression of CD44, CD98, ALDH1/2 and P16 in 43 (68.2%), 30 (47.6%), 33 (52.4%) and 27 (42.9%) cancers, respectively. In the HPV16-positive subgroup, DFS rate of 100% was observed in patients with tumors characterized by lack of CD44 overexpression and those treated with concurrent chemoradiotherapy with cisplatin (CisPt-CRT). In the HPV16-negative subgroup 100% of DFS was noticed for patients (n = 6) with P16 immunopositive tumors. In this subgroup none of the CSCs biomarkers evaluated in the study had any impact on OS or DFS. In patients with HPV16-positive oropharyngeal cancer, lack of CD44 overexpression and application of CisPt-CRT were found to be positive prognostic factors.

Chemopotentiating effects of low-dose fractionated radiation on cisplatin and paclitaxel in cervix cancer cell lines and normal fibroblasts from patients with cervix cancer

The aim of the present study was to compare the effects (assessed by clonogenic survival and γH2AX foci assays) of low-dose fractionated radiation LDFR (4 × 0.125 Gy, 4 × 0.25 Gy and 4 × 0.5 Gy) versus single radiation doses (0.5 Gy, 1 Gy and 2 Gy) on cisplatin and paclitaxel in HRS-negative cervix cancer cell lines SiHa and CaSki to see if the effects of LDFR can emerge in cells that not present low-dose hyper-radiosensitivity (HRS) phenomenon. Additionally, we report the effects in normal fibroblasts (HRS-negative and HRS-positive) from two patients with cervix cancer to see if the chemopotentiating effects of LDFR also apply to normal cells. LDFR (4 × 0.125 Gy, 4 × 0.25 Gy and 4 × 0.5 Gy) as well as single doses (0.5 Gy, 1 Gy and 2 Gy) enhanced cytotoxicity of cisplatin and paclitaxel in all the cell lines. Cisplatin-potentiating effects were maximum with LDFR 4 × 0.5 Gy, and were two-fold greater than those with a single dose of 2 Gy in SiHa, CaSki and HFIB2 cells. Paclitaxel-enhancing effects were also maximum with LDFR 4 × 0.5 Gy, however only in HRS-positive HFIB2 fibroblasts were significantly greater than those with a single dose of 2 Gy. The results demonstrate that LDFR may enhance the effects of cisplatin and paclitaxel in SiHa and CaSki cells, although they lack HRS phenomenon, and show that the magnitude of the potentiating effects of LDFR depends on cytostatic type and the size of low doses. In normal fibroblasts the chemopotentiating effects of LDFR seem to depend on HRS status. In conclusion, the unique enhancing effects of LDFR on cisplatin in cervical cancer cell lines, even when HRS negative, suggest that all patients with cervical cancer may benefit from the addition of LDFR to adjuvant cisplatin-based chemotherapy.

In Vitro and In Vivo Synergistic Therapeutic Effect of Cisplatin with Human Papillomavirus16 E6/E7 CRISPR/Cas9 on Cervical Cancer Cell Line

PURPOSE: Human papillomavirus (HPV) type 16 is one of the major etiologic factors of cervical cancer. Our study aims to investigate the potentiality of the antiviral clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated Cas9 system (CRISPR/Cas9) targeting the E6 and E7 oncogenes of HPV16 as a potential chemosensitizer of cisplatin (cis-diaminedichloroplatinum II; CDDP) for cervical cancer. METHODS: Specifically, the therapeutic efficacy of combination of CDDP and HPV16 E6 + E7-CRISPR/Cas9 was assessed in cervical cancer cells and cervical cancer xenograft models. RESULTS: In vitro experiments showed that long-term exposure of SiHa cells to the HPV16 E6 + E7-CRISPR/Cas9 induced apoptosis, and its pro-apoptosis effect became more obvious when combined with CDDP. In vivo study found the efficacy of the combination of HPV16 E6 + E7-CRISPR/Cas9 and CDDP were superior to either of the treatments in term of apoptosis induction and metastasis inhibition. CONCLUSION: Collectively, our results suggested that HPV16 E6 + E7-CRISPR/Cas9 could be an effective sensitizer of CDDP chemotherapy in cervical cancer.

Inhibition of antiviral drug cidofovir on proliferation of human papillomavirus-infected cervical cancer cells

In order to evaluate the potential application value of cidofovir (CDV) in the prevention of human papillomavirus (HPV) infection and treatment of cervical cancer, the inhibitory effect of CDV on the proliferation of HPV 18-positive HeLa cells in cervical cancer was preliminarily investigated, using cisplatin (DDP) as a positive control. An MTT assay was used to analyze the effects of CDV and DDP on HeLa cell proliferation. In addition, clone formation assay and Giemsa staining were used to examine the extent of HeLa cell apoptosis caused by CDV and DDP. Flow cytometry was also used to detect the shape and size of apoptotic cells following propidium iodide staining, while western blot analysis identified the expression levels of of E6 and p53 proteins in HeLa cells. A cell climbing immunofluorescence technique was used to locate the subcellular position of p53 in HeLa cells. The results demonstrated that CDV and DDP inhibited the proliferation of HeLa cells in a concentration- and time-dependent manner. Flow cytometry showed that CDV and DDP treatments resulted in cell arrest in the S-phase, and triggered programmed cell death. Furthermore, western blot analysis revealed that CDV and DDP inhibited E6 protein expression and activated p53 expression in HeLa cells. Finally, the immunofluorescence results indicated that CDV and DDP inhibited the nuclear export of p53 by E6 protein, which is required for degradation of endogenous p53 by MDM2 and human papilloma virus E6. In conclusion, CDV and DDP inhibited HeLa cell proliferation in a concentration- and time-dependent manner, reduced the expression of E6 protein, and reinstated p53 protein activity. Thus, CDV regulates cell cycle arrest and apoptosis, and may be a potential cervical cancer therapeutic strategy.

Regulation of p53 expression and apoptosis by vault RNA2-1-5p in cervical cancer cells

nc886 or VRNA2-1 has recently been identified as a noncoding RNA instead of a vault RNA or a pre-microRNA. Several studies have reported that pre-miR-886 plays a tumor-suppressive role in a wide range of cancer cells through its activity as a cellular protein kinase RNA-activated (PKR) ligand and repressor. However, by sequencing stem-PCR products, we found that a microRNA originating from this precursor, vault RNA2-1-5p (VTRNA2-1-5p), occurs in cervical cancer cells. The expression levels of the predicted targets of VTRNA2-1-5p are negatively correlated with VTRNA2-1-5p levels by quantitative reversion transcription PCR (qRT-PCR). Previous results have shown that VTRNA2-1-5p is overexpressed in human cervical squamous cell carcinomas (CSCCs) compared with adjacent healthy tissues. Inhibition of VTRNA2-1-5p increases Bax protein expression and apoptotic cell death in cervical cancer cells. Our findings suggest that VTRNA2-1-5p has oncogenic activity related to the progression of cervical cancer. Here, we report that VTRNA2-1-5p directly targeted p53 expression and functioned as an oncomir in cervical cancer. VTRNA2-1-5p inhibition decreased cervical cancer cell invasion, proliferation, and tumorigenicity while increasing apoptosis and p53 expression. Interestingly, VTRNA2-1-5p inhibition also increased cisplatin-induced apoptosis of HeLa and SiHa cells. In human clinical cervical cancer specimens, low p53 expression and high VTRNA2-1-5p expression were positively associated. In addition, VTRNA2-1-5p was found to directly target the 5′ and 3′ untranslated regions (UTRs) of p53. We propose that VTRNA2-1-5p is a direct regulator of p53 and suggest that it plays an essential role in the apoptosis and proliferation of cervical cancer cells.

Human Papillomavirus E6/E7-Specific siRNA Potentiates the Effect of Radiotherapy for Cervical Cancer in Vitro and in Vivo

The functional inactivation of TP53 and Rb tumor suppressor proteins by the HPV-derived E6 and E7 oncoproteins is likely an important step in cervical carcinogenesis. We have previously shown siRNA technology to selectively silence both E6/E7 oncogenes and demonstrated that the synthetic siRNAs could specifically block its expression in HPV-positive cervical cancer cells. Herein, we investigated the potentiality of E6/E7 siRNA candidates as radiosensitizers of radiotherapy for the human cervical carcinomas. HeLa and SiHa cells were transfected with HPV E6/E7 siRNA; the combined cytotoxic effect of E6/E7 siRNA and radiation was assessed by using the cell viability assay, flow cytometric analysis and the senescence-associated β-galactosidase (SA-β-Gal) assay. In addition, we also investigated the effect of combined therapy with irradiation and E6/E7 siRNA intravenous injection in an in vivo xenograft model. Combination therapy with siRNA and irradiation efficiently retarded tumor growth in established tumors of human cervical cancer cell xenografted mice. In addition, the chemically-modified HPV16 and 18 E6/E7 pooled siRNA in combination with irradiation strongly inhibited the growth of cervical cancer cells. Our results indicated that simultaneous inhibition of HPV E6/E7 oncogene expression with radiotherapy can promote potent antitumor activity and radiosensitizing activity in human cervical carcinomas.

Human Papillomavirus: Current and Future RNAi Therapeutic Strategies for Cervical Cancer

Human papillomaviruses (HPVs) are small DNA viruses; some oncogenic ones can cause different types of cancer, in particular cervical cancer. HPV-associated carcinogenesis provides a classical model system for RNA interference (RNAi) based cancer therapies, because the viral oncogenes E6 and E7 that cause cervical cancer are expressed only in cancerous cells. Previous studies on the development of therapeutic RNAi facilitated the advancement of therapeutic siRNAs and demonstrated its versatility by siRNA-mediated depletion of single or multiple cellular/viral targets. Sequence-specific gene silencing using RNAi shows promise as a novel therapeutic approach for the treatment of a variety of diseases that currently lack effective treatments. However, siRNA-based targeting requires further validation of its efficacy in vitro and in vivo, for its potential off-target effects, and of the design of conventional therapies to be used in combination with siRNAs and their drug delivery vehicles. In this review we discuss what is currently known about HPV-associated carcinogenesis and the potential for combining siRNA with other treatment strategies for the development of future therapies. Finally, we present our assessment of the most promising path to the development of RNAi therapeutic strategies for clinical settings.

Human papillomavirus confers radiosensitivity in cancer cervix: a hypothesis toward a possible restoration of apoptotic pathways based on clinical outcomes

ABSTRACT 

Aim: To evaluate if high baseline local human papillomavirus (HPV) titer confers radiosensitivity in cancer cervix. A hypothesis is proposed to explain the clinical outcomes. Materials & methods: 121 serial HPV titers from cervical smears of 21 patients were estimated during radiotherapy (RT) and correlated with RT dose–response curves, local response and local disease-free survival (LDFS). Results: Local response (p = 0.04) and LDFS (p = 0.06) were better in high HPV than low HPV baseline group. On multivariate analysis, RT doses for 50% tumor regression and baseline HPV titer were the only predictors for LDFS. Conclusion: Serial reductions of HPV titers following RT could restore the HPV induced temporarily downregulated p53 and pRb apoptotic pathways resulting in radiosensitivity of these tumors.

Targeted silencing of MLL5β inhibits tumor growth and promotes gamma-irradiation sensitization in HPV16/18-associated cervical cancers

We previously identified a novel MLL5 isoform, MLL5β, which was essential for E6 and E7 transcriptional activation in HPV16/18-associated cervical cancers. In this report, we investigated the potential of RNAi-mediated silencing of MLL5β through the use of MLL5β-siRNA as a novel therapeutic strategy for HPV16/18-positive cervical cancer. We observed concurrent downregulation of E6 and E7 after MLL5β silencing, leading to growth inhibition via the activation of apoptosis and senescence in the HeLa cell model. This corresponded with the enhanced antitumor effects of MLL5β-siRNA compared with E6- or E7-siRNA single treatments. Significant reduction in tumor size after MLLβ-siRNA treatment in the HeLa xenograft tumor model further emphasized the importance of MLL5β in HPV16/18-associated tumor growth and the potential of RNAi therapeutics that target MLL5β. We also identified MLL5β as a modulator of gamma-irradiation (IR) sensitization properties of cisplatin. We observed that while MLL5β silencing alone was enough to evoke cisplatin-like IR sensitization in tumor cells in vitro, overexpression of MLL5β inhibited the ability of cisplatin to sensitize HeLa cells to IR-induced cytotoxicity. MLL5β-siRNA-IR cotreatment was also observed to enhance tumor growth inhibition in vivo. Taken together, our findings highlight the potential of targeted silencing of MLL5β via the use of MLL5β-siRNA as a novel therapeutic strategy and propose that MLL5β-siRNA could be a viable alternative for cisplatin in the current cisplatin-based chemotherapeutics for HPV16/18-associated cervical cancers.

The effect of catalase on migration and invasion of lung cancer cells by regulating the activities of cathepsin S, L, and K

Abundant clinical evidences indicate that up-regulation of several cathepsins in many human cancers is correlated with malignant progression and poor patient prognosis. In addition, a decrease in catalase activity or accumulation of hydrogen peroxide correlates with cancer metastasis. Recent studies indicate that cathepsin activation and expression can be modulated via H2O2 treatment. However, the actual relationship between catalase and cathepsins is not yet fully understood. In the present study, we found that catalase expression (or activity) was higher, while intracellular and extracellular Cat S, Cat L, and Cat K activities were lower in the non-invasive CL1-0 cells compared to the highly invasive CL1-5 cells. After CL1-0 cells were transfected with catalase-shRNA, the corresponding ROS (H2O2) level and Cat S, Cat L, or Cat K expression (or activity) was up-regulated, accompanied by an increase in cell migration and invasion. On the other hand, ROS (H2O2) level, cathepsin S, L, and K activities, cell migration and invasion were decreased in catalase-overexpressed CL1-5 cells. It is suggested that catalase may regulate cathepsin activity by controlling the production of ROS (H2O2), leading to variation in migration and invasion ability of lung cancer cells.

Role of proteomics in translational research in cervical cancer

Cervical cancer is one of the leading causes of cancer morbidity and mortality in women worldwide. More than 98% of cases are related to a human papillomavirus (HPV) infection. Infection with specific subtypes of HPV has been strongly implicated in cervical carcinogenesis. The identification and functional verification of host proteins associated with HPV E6 and E7 oncoproteins may provide useful information for understanding cervical carcinogenesis and the development of cervical cancer-specific markers. In addition, proteomic profiling of altered proteins by anticancer drugs on cervical cancer cells may contribute to providing the fundamental resources for investigation of disease-specific target proteins, elucidation of the novel mechanisms of action and development of new drugs. The advent of proteomics has provided the hope of discovering novel biological markers for use in the screening, early diagnosis and prediction of response to therapy. This review describes the studies where profiles of protein expression in cervical cancer have been generated.

Effects of novel human cathepsin S inhibitors on cell migration in human cancer cells

Elevated cathepsin S (Cat S) level is correlated with higher migration ability in tumor cells. This study investigates the inhibitory effect of novel synthetic α-ketoamide compounds on cathepsin activity and cancer cell migration. The effect of several α-ketoamide compounds on the activity of recombinant cathepsins (Cat S, Cat L and Cat K) was examined. Two highly metastatic cancer cell lines were incubated with three Cat S-specific compounds (6n, 6 w and 6r) to analyze their effect on cellular Cat S activity and cell migration. At a 100 nM concentration, compounds 6n, 6r and 6 w effectively inhibited Cat S activity. Cat S activity and cell migration were significantly reduced in CL1-3 cells after treatment with either 6n or 6 w at 5 μM. Similar results were also obtained when A2058 cells were treated with 6n. These results highlight the therapeutic potential of α-ketoamide compounds, especially 6n and 6 w, to prevent or delay cancer metastasis.

p53 negatively regulates Aurora A via both transcriptional and posttranslational regulation

p53 plays an important role in mitotic checkpoint, but what its role is remains enigmatic. Aurora A is a Ser/Thr kinase involved in correcting progression of mitosis. Here, we show that p53 is a negative regulator for Aurora A. We found that p53 deficiency leads to Aurora A elevation. Ectopic expression of p53 or DNA damage-induced expression of p53 can suppress the expression of Aurora A. Mechanistic studies show that p53 is a negative regulator for Aurora A expression through both transcriptional and posttranslational regulation. p53 knockdown in cancer cells reduces the level of p21, which, in turn, increases the activity of CDK2 followed by induction of Rb1 hyperphosphorylation and its dissociation with transcriptional factor E2F3. E2F3 can bind to Aurora A gene promoter, potentiating Aurora A gene expression and p53 deficiency, enhancing the binding of E2F3 on Aurora A promoter. Also, p53 deficiency leads to decelerating Aurora A's turnover rate, due to the fact that p53 deficiency causes the downregulation of Fbw7α, a component of E3 ligase of Aurora A. Consistently, p53 knockdown-mediated Aurora A elevation is mitigated when Fbw7α is ectopically expressed. Thus, p53-mediated Aurora A degradation requires Fbw7α expression. Significantly, inverse correlation between p53 and Aurora A elevation is translated into the deregulation of centrosome amplification. p53 knockdown leads to high percentages of cells with abnormal amplification of centrosome. These data suggest that p53 is an important negative regulator of Aurora A, and that loss of p53 in many types of cancer could lead to abnormal elevation of Aurora A and dysregulated mitosis, which provides a growth advantage for cancer cells.

The emerging era of personalized therapy in squamous cell carcinoma of the head and neck

Over the past three decades there has been a move toward organ preservation protocols in the management of locally advanced mucosal head and neck squamous cell carcinomas (LAHNSCC) with combinations of radiotherapy (RT), chemotherapy and, more recently, biological agents. Current standard chemoradiation strategies have reached the upper limits of toxicity. In addition, the traditional one size fits all approach of grouping patients according to traditional clinicopathological features fails to take into account the vast underlying biological heterogeneity of tumors and their host. A number of recent advances such as highly conformal RT, molecular profiling and targeted agents, and improvements in treatment response assessment have set the scene for a fundamental paradigm shift toward greater tailoring of therapy with the aim of improving outcomes and reducing the burden of survivorship. This review focuses on the recognition of the prognostic value of tumor human papillomavirus (HPV) status, the incorporation of biologically targeted therapies and the evolving role of molecular imaging in predicting tumor response and prognosis in the curative management of LAHNSCC.

The synergistic therapeutic effect of cisplatin with Human papillomavirus E6/E7 short interfering RNA on cervical cancer cell lines in vitro and in vivo

Human papillomavirus (HPV) types 16 and 18 are the major etiologic factors in the development of cervical epithelial neoplasia. Our study was designed to validate antiviral short interfering RNA (siRNA) targeting the E6 and E7 oncogenes as a potential chemosensitizer of cisplatin (cis-diaminedichloroplatinum II; CDDP) in cervical carcinoma. Specifically, the therapeutic efficacy of combination of CDDP and E6/E7-specific siRNA was assessed in an in vivo cervical cancer xenograft models. The combination of CDDP and E6/E7-specific siRNA had greater efficacy than the combination of CDDP and E6-specific siRNA especially in terms of inducing cellular senescence. Through in vitro and in vivo experiments, the mechanism of synergy between these two treatments was revealed, demonstrating that the combination of E6/E7-specific siRNA and CDDP therapy was significantly superior to either modality alone. In vitro, long-term exposure of HeLa cells to the combination of CDDP and E6/E7-specific siRNA induced apoptosis and cellular senescence. In vivo, E6/E7-specific siRNA potentiated the antitumor efficacy of CDDP via induction of apoptosis, senescence and antiangiogenesis. Our results suggest that E6/E7-specific siRNA may be an effective sensitizer of CDDP chemotherapy in cervical cancer.

Genomewide gene expression profiles of HPV-positive and HPV-negative oropharyngeal cancer: potential implications for treatment choices

OBJECTIVE

To study the difference in gene expression between human papillomavirus (HPV)-positive and HPV-negative oral cavity and oropharyngeal squamous cell carcinoma (OSCC).

DESIGN

We used Affymetrix U133 plus 2.0 arrays to examine gene expression profiles of OSCC and normal oral tissue. The HPV DNA was detected using polymerase chain reaction followed by the Roche LINEAR ARRAY HPV Genotyping Test, and the differentially expressed genes were analyzed to examine their potential biological roles using the Ingenuity Pathway Analysis Software, version 5.0.

SETTING

Three medical centers affiliated with the University of Washington.

PATIENTS

A total of 119 patients with primary OSCC and 35 patients without cancer, all of whom were treated at the setting institutions, provided tissues samples for the study.

RESULTS

Human papillomavirus DNA was found in 41 of 119 tumors (34.5%) and 2 of 35 normal tissue samples (5.7%); 39 of the 43 HPV specimens were HPV-16. A higher prevalence of HPV DNA was found in oropharyngeal cancer (23 of 31) than in oral cavity cancer (18 of 88). We found no significant difference in gene expression between HPV-positive and HPV-negative oral cavity cancer but found 446 probe sets (347 known genes) differentially expressed in HPV-positive oropharyngeal cancer than in HPV-negative oropharyngeal cancer. The most prominent functions of these genes are DNA replication, DNA repair, and cell cycling. Some genes differentially expressed between HPV-positive and HPV-negative oropharyngeal cancer (eg, TYMS, STMN1, CCND1, and RBBP4) are involved in chemotherapy or radiation sensitivity.

CONCLUSION

These results suggest that differences in the biology of HPV-positive and HPV-negative oropharyngeal cancer may have implications for the management of patients with these different tumors.

Hyperthermia, cisplatin and radiation trimodality treatment: a promising cancer treatment? A review from preclinical studies to clinical application

This review discusses available clinical and experimental data and the underlying mechanisms involved in trimodality treatment consisting of hyperthermia, cisplatin and radiotherapy. The results of phase I/II clinical trials show that trimodality treatment is effective and feasible in various cancer types and sites with tolerable toxicity. Based on these results, phase III trials have been launched to investigate whether significant differences in treatment outcome exist between trimodality and standard treatment. In view of the clinical interest, it is surprising to find so few preclinical studies on trimodality treatment. Although little information is available on the doses of the modalities and the treatment sequence resulting in the largest degree of synergistic interaction, the results from in vivo and in vitro preclinical studies support the use of trimodality treatment for cancer patients. Animal studies show an improvement in treatment outcome after trimodality treatment compared with mono- and bimodality treatment. Studies in different human tumour cell lines show that a synergistic interaction can be obtained between hyperthermia, cisplatin and radiation and that this interaction is more likely to occur in cell lines which are more sensitive to cisplatin.

Analysis of differential protein expression by cisplatin treatment in cervical carcinoma cells

Cisplatin (cis-diaminedichloroplatinum), a DNA-damaging agent, which readily induces apoptosis in vitro, is one of the widely used anticancer drug in the treatment of human malignancies. Cisplatin has played an important role in cervical cancer management for effective chemotherapeutic regimen, but the underlying mechanisms inducing cell death at protein level are unknown. Using proteome analysis, an investigation aimed at a better understanding of the antiproliferative mechanisms by cisplatin was carried out in HeLa cervical carcinoma cells. In total, 21 protein spots were found to be differentially expressed following cisplatin treatment, of which 12 were upregulated (eg, regulator of G-protein signaling, TRAF:TNF (tumor necrosis factor) receptor-associated factor-interacting protein [I-TRAF], and cyclin-dependent kinase inhibitor p27 [p27(kip1)]) and 9 were downregulated (eg, myc proto-oncoprotein [c-myc] and proliferating cell nuclear antigen). Interestingly, we found the upregulation of proliferating cell nuclear antigen, which used molecular marker in cervical cancer screening. On the basis of proteomic data, we showed that cisplatin induced TRAF2-mediated NF-kappaB downregulation. In addition, our study demonstrated that cisplatin induced membrane death receptor-mediated and mitochondria-mediated apoptosis pathway. Our findings may offer new insights into the antiproliferative mechanism by cisplatin and its mode of action in cervical carcinoma cells.

The inhibition of calcium carbonate crystal growth by the cysteine-rich Mdm2 peptide

The crystal growth of calcite, the most stable calcium carbonate polymorph, in the presence of the cysteine-rich Mdm2 peptide (containing 48 amino acids in the ring finger configuration), has been investigated by the constant composition technique. Crystallization took place exclusively on well-characterized calcite crystals in solutions supersaturated only with respect to this calcium carbonate salt. The kinetic results indicated a surface diffusion spiral growth mechanism. The presence of the Mdm2 peptide inhibited the crystal growth of calcite by 22-58% in the concentration range tested, through adsorption onto the active growth sites of the calcite crystal surface. The kinetic results favored a Langmuir-type adsorption model, and the value of the calculated affinity constant was k(aff)=147x10(4) dm(3)mol(-1), a(ads)=0.29.

Effects of cisplatin and gamma-irradiation on cell survival, the induction of chromosomal aberrations and apoptosis in SW-1573 cells

PURPOSE

Cisplatin was found to radiosensitize SW-1573 cells by inhibition of PLDR. Therefore, it was investigated whether cisplatin combined with gamma-radiation leads to an increase in the number of chromosomal aberrations or apoptotic cells compared with radiation alone.

METHODS

Confluent cultures of the human lung carcinoma cell line SW-1573 were treated with 1 microM cisplatin for 1 h, 4 Gy gamma-radiation, or a combination of both. Cell survival was studied by the clonogenic assay. Aberrations were analysed by FISH in prematurely condensed chromosomes (PCC) and the induction of apoptosis by counting fragmented nuclei.

RESULTS

A radiosensitizing effect of cisplatin on cell survival was observed if time for PLDR was allowed. An increased number of chromosomal fragments were observed immediately after irradiation compared with 24 h after irradiation whereas color junctions are only formed 24 h after irradiation. No increase in chromosomal aberrations was found after combined treatment, but a significantly enhanced number of fragmented nuclei were observed when confluent cultures were replated after allowing PLDR.

CONCLUSION

The inhibition of PLDR by cisplatin in delayed plated SW-1573 cells did not increase chromosomal aberrations, but increased the induction of apoptosis.

C-Abl as a modulator of p53

P53 is renowned as a cellular tumor suppressor poised to instigate remedial responses to various stress insults that threaten DNA integrity. P53 levels and activities are kept under tight regulation involving a complex network of activators and inhibitors, which determine the type and extent of p53 growth inhibitory signaling. Within this complexity, the p53-Mdm2 negative auto-regulatory loop serves as a major route through which intra- and extra-cellular stress signals are channeled to appropriate p53 responses. Mdm2 inhibits p53 transcriptional activities and through its E3 ligase activity promotes p53 proteasomal degradation either within the nucleus or following nuclear export. Upon exposure to stress signals these actions of Mdm2 have to be moderated, or even interrupted, in order to allow sufficient p53 to accumulate in an active form. Multiple mechanisms involving a variety of factors have been demonstrated to mediate this interruption. C-Abl is a critical factor that under physiological conditions is required for the maximal and efficient accumulation of active p53 in response to DNA damage. C-Abl protects p53 by antagonizing the inhibitory effect of Mdm2, an action that requires a direct interplay between c-Abl and Mdm2. In addition, c-Abl protects p53 from other inhibitors of p53, such as the HPV-E6/E6AP complex, that inhibits and degrades p53 in HPV-infected cells. Surprisingly, the oncogenic form of c-Abl, the Bcr-Abl fusion protein in CML cells, also promotes the accumulation of wt p53. However, in contrast to the activation of p53 by c-Abl, its oncogenic form, Bcr-Abl, counteracts the growth inhibitory activities of p53 by modulating the p53-Mdm2 loop. Thus, it appears that by modulating the p53-Mdm2 loop, c-Abl and its oncogenic forms critically determine the type and extent of the cellular response to DNA damage.

Antiapoptotic effects of estrogen in normal and cancer human cervical epithelial cells

The present study investigated the antiapoptotic effects of estrogen in normal and cancer human cervical cells and the mechanisms involved. Baseline apoptosis in human cervical epithelial cells is mediated predominantly by P2X7-receptor-induced, Ca(2+)-dependent activation of the mitochondrial (caspase-9) pathway. Treatment with 10 nM 17beta-estradiol blocked apoptosis induced by the P2X7-receptor ligands ATP and 2',3'-0-(4-benzoylbenzoyl)-ATP in normal human cervical epithelial cells (hECEs) and attenuated the effect in hECEs immortalized with human papillomavirus-16 (ECE16-1) and the cancer cervical cells HT3 and CaSki. Diethylstilbestrol and to a lesser degree estrone could mimic the effects of 17beta-estradiol, whereas actinomycin-D and cycloheximide attenuated the response. The antiapoptotic effect of estrogen did not depend on cell cycle phase, and in both normal and cancer cervical cells, it involved attenuation of activation of caspase-9 and the terminal caspase-3. However, involvement of cascades upstream to the caspase-9 differed in normal vs. cancer cervical cells. In the normal hECEs estrogen blocked P2X7-receptor-induced calcium influx. In contrast, in the cancer CaSki cells, estrogen up-regulated expression of Bcl-2 and attenuated Ca(2+)-induced mitochondrial swelling (i.e. formation of mitochondrial permeability transition pores). Estrogen had no effect on P2X7-receptor-induced apoptosis in the anaplastic SiHa and Hela cells. These results point to a novel antiapoptotic effect of estrogen in the cervix that is independent of its mitogenic function. The results also suggest that cancer cervical cells evolved antiapoptotic mechanisms that enable the cells to evade apoptosis and could therefore promote tumor progression.