The p53 gene as a modifier of intrinsic radiosensitivity: implications for radiotherapy

Raman spectroscopy and supervised learning as a potential tool to identify high-dose-rate-brachytherapy induced biochemical profiles of prostate cancer

High-dose-rate-brachytherapy (HDR-BT) is an increasingly attractive alternative to external beam radiation-therapy for patients with intermediate risk prostate cancer. Despite this, no bio-marker based method currently exists to monitor treatment response, and the changes which take place at the biochemical level in hypo-fractionated HDR-BT remain poorly understood. The aim of this pilot study is to assess the capability of Raman spectroscopy (RS) combined with principal component analysis (PCA) and random-forest classification (RF) to identify radiation response profiles after a single dose of 13.5 Gy in a cohort of nine patients. We here demonstrate, as a proof-of-concept, how RS-PCA-RF could be utilised as an effective tool in radiation response monitoring, specifically assessing the importance of low variance PCs in complex sample sets. As RS provides information on the biochemical composition of tissue samples, this technique could provide insight into the changes which take place on the biochemical level, as result of HDR-BT treatment.

Current Indications for Transoral Robotic Surgery in Oropharyngeal Cancer

The incidence of oropharyngeal squamous cell carcinoma (OPSCC) is increasing dramatically and is conclusively linked to increasing rates of human papillomavirus (HPV) infection. HPV-related oropharyngeal cancers have been shown to occur in a unique demographic group and show favorable oncologic outcomes compared with HPV-negative OPSCC. There has been a paradigm shift in the treatment of early-stage OPSCC, with most patients now undergoing primary surgery in the United States. Transoral robotic surgery is associated with excellent oncologic and functional outcomes in the treatment of OPSCC and is increasingly being used for a broader range of oropharyngeal indications.

Impact of accumulated alterations in driver and passenger genes on response to radiation therapy

OBJECTIVE

Although various single genetic factors have been shown to affect radiosensitivity, high-throughput DNA sequencing analyses have revealed complex genomic landscapes in many cancer types. The aim of this study is to elucidate the association between accumulated alterations in driver and passenger genes and radiation therapy response.

METHODS

We used 59 human solid cancer cell lines derived from 11 organ sites. Radiation-induced cell death was measured using a standard colony-forming assay delivered as a single dose ranging from 0 to 12 Gy. Comprehensive genomic data for the cell lines were acquired from the Catalogue Of Somatic Mutations In Cancer v. 80. Random forest classifiers were constructed to predict radioresistant phenotypes using genomic features. The Cancer Genome Atlas data sets were used to evaluate the clinical impact of the genomic feature following radiotherapy.

RESULTS

The 59 cancer cell lines harbored either nucleotide variations or copy number variations in a median of 157 genes per cell. Radiosensitivity of the cancer cells was correlated with neither the number of driver gene mutations nor the number of passenger gene mutations. However, the proportion of driver gene alterations to total gene alterations in gene sets selected from the Kyoto Encyclopedia Genes and Genomes predicted radioresistant cells with sensitivity of 85% and specificity of 73%. High probability of radioresistance predicted by the model was associated with worse overall survival following definitive radiotherapy in patients of The Cancer Genome Atlas data sets.

CONCLUSION

Cellular radiosensitivity was associated with the proportion of driver to total gene alterations in the selected oncogenic pathways, which may be a biomarker candidate for response to radiation therapy.

ADVANCES IN KNOWLEDGE

These findings suggest that accumulated alterations in not only driver genes but also passenger genes affect radiosensitivity.

A Review of HPV-Related Head and Neck Cancer

Head and neck squamous cell carcinomas (HNSCCs) arise in the mucosal lining of the upper aerodigestive tract. Tobacco and alcohol use have been reported to be associated with HNSCC. Infection with high-risk human papillomaviruses (HPVs) has recently been implicated in the pathogenesis of HNSCCs. It is now widely accepted that high-risk HPV is a cause of almost all cervical cancers as well as some forms of HNSCCs. HPV-related HNSCCs are increasing. HPV-related HNSCCs and HPV-unrelated HNSCCs differ with respect to the molecular mechanisms underlying their oncogenic processes. HPV-related HNSCCs are known to have a better prognosis response to treatment as compared with HPV-unrelated HNSCCs. Therefore, in recent years, it has been required to accurately discriminate between HPV-related and HPV-unrelated HNSCCs. To diagnose the HPV-related HNSCCs, various methods including P16 immunohistochemistry, FISH, and genetic analyses of the HPV gene from histopathological and liquid biopsy specimens have been employed. Based on the results of the differential diagnosis, various treatments employing EGFR TKI and low-dose radiation have been employed. Here, we review the involvement of the HPV virus in HNSCCs as well as the molecular mechanism of carcinogenesis, classification, prognosis, diagnostic procedures, and therapy of the disease.

p16 as a prognostic factor for the response to induction chemotherapy in advanced hypopharyngeal squamous cell carcinoma

The present study was conducted to investigate the prognostic significance of p16 (also known as cyclin-dependent kinase inhibitor 2A) in the treatment of induction chemoradiotherapy for advanced hypopharyngeal squamous cell carcinoma (HPSCC). Patients who were treated with at least two cycles of induction chemotherapy followed by concurrent chemoradiotherapy for locally advanced HPSCC were reviewed in the study. The staining results were analyzed to examine the association between the chemotherapy response and the survival outcome. A total of 45 patients were enrolled for the present study; the majority had received induction chemotherapy with docetaxel, cisplatin, and 5-FU. Following induction chemotherapy, 17 patients (37.8%) exhibited a complete response and 28 patients (62.2%) exhibited a partial response. There were 11 patients (24.4%) with p16-positive immunohistochemical stains and 30 patients (66.7%) with p53-positive immunohistochemical stains. There was no significant difference in chemotherapy response, overall survival, or progression-free survival time between groups with p16-positive and p16-negative stains. Low p53 expression and chemotherapy response were not associated with each other. High p16 expression did not correlate with low p53 expression. In this study, p16 was not determined to predict the chemotherapy response for HPSCC. High p16 expression did not correlate with survival incidence for patients with HPSCC.

p16 as a prognostic factor for the response to induction chemotherapy in advanced hypopharyngeal squamous cell carcinoma

The present study was conducted to investigate the prognostic significance of p16 (also known as cyclin-dependent kinase inhibitor 2A) in the treatment of induction chemoradiotherapy for advanced hypopharyngeal squamous cell carcinoma (HPSCC). Patients who were treated with at least two cycles of induction chemotherapy followed by concurrent chemoradiotherapy for locally advanced HPSCC were reviewed in the study. The staining results were analyzed to examine the association between the chemotherapy response and the survival outcome. A total of 45 patients were enrolled for the present study; the majority had received induction chemotherapy with docetaxel, cisplatin, and 5-FU. Following induction chemotherapy, 17 patients (37.8%) exhibited a complete response and 28 patients (62.2%) exhibited a partial response. There were 11 patients (24.4%) with p16-positive immunohistochemical stains and 30 patients (66.7%) with p53-positive immunohistochemical stains. There was no significant difference in chemotherapy response, overall survival, or progression-free survival time between groups with p16-positive and p16-negative stains. Low p53 expression and chemotherapy response were not associated with each other. High p16 expression did not correlate with low p53 expression. In this study, p16 was not determined to predict the chemotherapy response for HPSCC. High p16 expression did not correlate with survival incidence for patients with HPSCC.

Identification of biomarker microRNAs for predicting the response of colorectal cancer to neoadjuvant chemoradiotherapy based on microRNA regulatory network

Preoperative radiotherapy or chemoradiotherapy has become a standard procedure for treatment of patients with locally advanced colorectal cancer (CRC). However, patients’ responses to treatment are different and personalized. MicroRNAs (miRNAs) are promising biomarkers for predicting personalized responses. In this study, we collected 30 publicly reported miRNAs associated with chemoradiotherapy of CRC. We extracted 46 differentially expressed miRNAs from samples of responders and non-responders to preoperative radiotherapy from the Gene Expression Omnibus dataset (Student's t test, p-value < 0.05 and |fold-change| > 2). We performed a systematic and integrative bioinformatics analysis to identify biomarker miRNAs for prediction of CRC responses to chemoradiotherapy. Using the bioinformatics model, miR-198, miR-765, miR-671-5p, miR-630, miR-371-5p, miR-575, miR-202, miR-483-5p and miR-513a-5p were screened as putative biomarkers for treatment response. Literature validation and functional enrichment analysis were exploited to confirm the reliability of the predicted miRNAs. Quantitative polymerase chain reaction showed that seven of the candidates were significantly differentially expressed between radiosensitive and insensitive CRC cell lines. The unique target genes of miR-198 and miR-765 were altered significantly upon transfection of specific miRNA mimics in the radiosensitive cell line. These results demonstrated the predictive power of our model and suggested that miR-198, miR-765, miR-630, miR-371-5p, miR-575, miR-202 and miR-513a-5p could be used for predicting the response of CRC to preoperative chemoradiotherapy.

Inorganic polyphosphate enhances radio-sensitivity in a human non-small cell lung cancer cell line, H1299

Inorganic polyphosphate is a linear polymer containing tens to hundreds of orthophosphate residues linked by high-energy phosphoanhydride bonds. Polyphosphate has been recognized as a potent anti-metastasis reagent. However, the molecular mechanism underlying polyphosphate action on cancer cells is poorly understood. In this study, we investigated the involvement of polyphosphate in radio-sensitivity using a human non-small cell lung cancer cell line, H1299. We found that polyphosphate treatment decreases cellular adenosine triphosphate levels, suggesting a disruption of energy metabolism. We also found that the induction of DNA double-strand breaks was enhanced in polyphosphate-treated cells after X-ray irradiation and colony formation assay revealed that cell survival decreased compared with that of the control groups. These findings suggest that polyphosphate is a promising radio-sensitizer for cancer cells. Therefore, we hypothesized that polyphosphate treatment disrupts adenosine triphosphate-mediated energy transfer for cellular survival and DNA repair, thereby reducing the cellular capability to resist X-ray irradiation.

WNT activation by lithium abrogates TP53 mutation associated radiation resistance in medulloblastoma

TP53 mutations confer subgroup specific poor survival for children with medulloblastoma. We hypothesized that WNT activation which is associated with improved survival for such children abrogates TP53 related radioresistance and can be used to sensitize TP53 mutant tumors for radiation. We examined the subgroup-specific role of TP53 mutations in a cohort of 314 patients treated with radiation. TP53 wild-type or mutant human medulloblastoma cell-lines and normal neural stem cells were used to test radioresistance of TP53 mutations and the radiosensitizing effect of WNT activation on tumors and the developing brain. Children with WNT/TP53 mutant medulloblastoma had higher 5-year survival than those with SHH/TP53 mutant tumours (100% and 36.6% ± 8.7%, respectively (p < 0.001)). Introduction of TP53 mutation into medulloblastoma cells induced radioresistance (survival fractions at 2Gy (SF2) of 89% ± 2% vs. 57.4% ± 1.8% (p < 0.01)). In contrast, β-catenin mutation sensitized TP53 mutant cells to radiation (p < 0.05). Lithium, an activator of the WNT pathway, sensitized TP53 mutant medulloblastoma to radiation (SF2 of 43.5% ± 1.5% in lithium treated cells vs. 56.6 ± 3% (p < 0.01)) accompanied by increased number of γH2AX foci. Normal neural stem cells were protected from lithium induced radiation damage (SF2 of 33% ± 8% for lithium treated cells vs. 27% ± 3% for untreated controls (p = 0.05). Poor survival of patients with TP53 mutant medulloblastoma may be related to radiation resistance. Since constitutive activation of the WNT pathway by lithium sensitizes TP53 mutant medulloblastoma cells and protect normal neural stem cells from radiation, this oral drug may represent an attractive novel therapy for high-risk medulloblastomas.

Different protein expression associated with chemotherapy response in oropharyngeal cancer according to HPV status

BACKGOUND

Oropharyngeal cancer (OPC) associated with human papilloma virus (HPV OPC) shows better treatment outcomes than non-HPV OPC. We investigated the expression of p53, β-tubulin, bcl-2 and ERCC 1, which are well-known biomarkers to predict the chemotherapy response, according to HPV status in OPC patients.

METHODS

Patients who treated with at least 2 cycles of induction chemotherapy followed by concurrent chemoradiotherapy for locally advanced oropharyngeal cancer were reviewed. HPV PCR and immunohistochemical stain was done in paraffin embedded tumor tissue and evaluated the relation with the chemotherapy response and survival outcomes according to HPV status.

RESULTS

Seventy-four patients were enrolled for this study and all patients received induction chemotherapy with docetaxel, 5-FU and cisplatin. After induction chemotherapy, complete response (CR) was shown in 22 patients (30%) and partial response (PR) in 46 patients (62%). HPV + was detected in 21 patients (28%), while 35 patients (47%) showed p16+ expression by IHC analysis. p16 positive patients showed better overall response, PFS and OS than p16 negative patients. p53 and class III beta-tubulin expression were significantly higher in HPV- and p16- than HPV + and p16+ patients. Conversely, bcl-2 expression was greater in HPV + or p16+ than HPV- or p16- patients. ERCC1 expression did not differ significantly according to HPV status. In multivariate analyses, early T stage (p = 0.036) and good PS (PS 0) (p = 0.029) showed a better 3Y-PFS rate, and low p53 expression (p = 0.012) and complete response after induction chemotherapy (p = 0.026) were highly associated with 3Y-OS rate. Low expression of p53 and p16 positive patients showed significantly prolonged OS than others (p = 0.010).

CONCLUSION

P53, class III beta-tubulin and bcl-2 were differently expressed in OPC according to HPV status and present study suggested the underlying mechanism of better response to chemotherapy in case of HPV OPC than non-HPV OPC. Among these biomarkers, p53 is the strongest prognostic marker in OPC and p53 in addition to p16 support the rationale to study of de-escalation strategy for OPC.

Salvage proton beam therapy in local recurrent uveal melanoma

PURPOSE

To evaluate survival and ocular outcome in recurrent uveal melanoma treated with proton beam therapy as salvage therapy.

DESIGN

Retrospective, interventional case series.

METHODS

We evaluated 48 patients with local recurrence of uveal melanoma after primary treatment with brachytherapy, transpupillary thermotherapy, proton beam therapy, laser photocoagulation, CyberKnife radiation, or photodynamic therapy. All patients received proton beam therapy as a salvage therapy at the Helmholtz Zentrum Berlin between July 2000 and December 2010. Kaplan-Meier analysis was used to obtain survival rates.

RESULTS

The Kaplan-Meier estimator for local tumor control was 92.1% at 10 years after secondary treatment with proton beam therapy. Local recurrence developed in 3 patients; 1 of them underwent enucleation. During follow-up, 20.8% of the patients died (16.7% of metastasis, 4.1% of other causes or not specified). The most frequent surgical interventions were phacoemulsification (20.8%) and pars plana vitrectomy (10.4%). The Kaplan-Meier estimators were 77.4% for survival and 70.1% for the absence of metastasis 10 years after the primary treatment.

CONCLUSIONS

Proton beam therapy as a salvage treatment resulted in high local tumor control rates in recurrent uveal melanoma, especially if the primary therapy was transpupillary thermotherapy or plaque brachytherapy. Preservation of the globe was possible in most patients. Enucleations were indicated only in case of re-recurrences of uveal melanoma, but not because of secondary complications like intractable pain or secondary glaucoma. Retreatment was associated with vision deterioration, but loss of vision remained exceptional. Further larger prospective studies are needed to confirm the presented results of our retrospective analysis.

Human papilloma virus and survival of oropharyngeal cancer patients treated with surgery and adjuvant radiotherapy

Impact of p16 protein, a surrogate marker for human papilloma virus induced cancer, p53 and EGFR as well as clinical factors on survival in a patient cohort with oropharyngeal squamous cell carcinoma (OPSCC) treated by surgical resection and adjuvant radiotherapy (RT) ± concomitant chemotherapy (CT). This is a retrospective analysis of patient's charts and tumor tissue. 57 patients were consecutively included and their tumor tissue assembled on a tissue microarray following immunohistochemical analysis. Survival times were estimated by means of Kaplan-Meier analysis. The importance of clinical and immunohistochemical factors for outcome was estimated by cox proportional hazard models. With 88% 5-year overall survival, 91% 5-year disease-specific survival and 91% 5-year disease-free survival, respectively, we found excellent survival rates in this surgically treated patient cohort of mainly advanced OPSCC (93% AJCC stage III or IV). The only factors positively influencing survival were p16 overexpression as well as p53 negativity and even more pronounced the combination of those biomarkers. Survival analysis of patients classified into three risk categories according to an algorithm based on p16, smoking, T- and N-category revealed a low, intermediate and high-risk group with significant survival differences between the low and the high-risk group. Patients with OPSCC can be successfully treated by surgery and adjuvant RT ± CT with a clear survival benefit of p16 positive, p53 negative patients. We recommend considering a combination of immunohistochemical (p16, p53) and clinical factors (smoking, T- and N-category) for risk stratification.

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.

Berberine inhibited radioresistant effects and enhanced anti-tumor effects in the irradiated-human prostate cancer cells

The purpose of this study was to elucidate the mechanism underlying enhanced radiosensitivity to ⁶⁰Co γ-irradiation in human prostate PC-3 cells pretreated with berberine. The cytotoxic effect of the combination of berberine and irradiation was superior to that of berberine or irradiation alone. Cell death and Apoptosis increased significantly with the combination of berberine and irradiation. Additionally, ROS generation was elevated by berberine with or without irradiation. The antioxidant NAC inhibited berberine and radiation-induced cell death. Bax, caspase-3, p53, p38, and JNK activation increased, but activation of Bcl-2, ERK, and HO-1 decreased with berberine treatment with or without irradiation. Berberine inhibited the anti-apoptotic signal pathway involving the activation of the HO-1/NF-κB-mediated survival pathway, which prevents radiation-induced cell death. Our data demonstrate that berberine inhibited the radioresistant effects and enhanced the radiosensitivity effects in human prostate cancer cells via the MAPK/caspase-3 and ROS pathways.

Human papillomavirus-associated head and neck squamous cell carcinoma survival: a comparison by tumor site and initial treatment

Recent evidence suggests that human papillomavirus (HPV)-positive head and neck squamous cell carcinoma (HNSCC) patients have better survival than HPV-negative patients. However, it is unclear if similar patterns for survival exist across different tumor sites, and whether HPV-associated prognosis is modified by type of treatment. We prospectively tested 222 histologically confirmed HNSCC primary tumors for HPV DNA by PCR and HPV E6/E7 RNA by RT-PCR prior to treatment at a large urban health center. Cox proportional hazard ratio models were constructed to assess HPV-associated differences in overall and disease-specific survival adjusting for clinical and demographic covariates. HPV detection varied significantly by primary HNSCC tumor site, from 35 % for oropharynx, to 25 % for hypopharynx, 5 % for larynx, and 3 % for oral cavity (p < 0.0001), with HPV16 accounting for the majority (95 %) of HPV-positive tumors. The hazard-risk of overall and disease-specific death comparing HPV16-positive versus negative oropharyngeal HNSCC was reduced by 74 and 89 %, respectively (p values < 0.05), and was independent of other prognostic indicators; no statistically significant changes in outcomes were observed for non-oropharyngeal HNSCC sites. Prediction of overall survival was better with combined DNA and RNA HPV16 positive PCR detection. There was no difference in HPV16-associated survival whether patients received either surgery or (chemo)radiotherapy as their initial treatment modality. Improved HPV-associated HNSCC survival is limited to patients with oropharyngeal primaries. No selective treatment advantage is observed for HPV-positive tumors, although clinical trials are needed to evaluate which treatment modalities provide the most benefit for HPV-positive HNSCC.

Molecular targets and mechanisms of radiosensitization using DNA damage response pathways

The cellular reaction to genomic instability includes a network of signal transduction pathways collectively referred to as the DNA damage response (DDR). Activated by a variety of DNA lesions, the DDR orchestrates cell cycle arrest and DNA repair, and initiates apoptosis in instances where damage cannot be repaired. As such, disruption of the DDR increases the prevalence of DNA damage secondary to incomplete repair, and in doing so, enhances radiation-induced cytotoxicity. This article describes the molecular agents and their targets within DDR pathways that sensitize cells to radiation. Moreover, it reviews the therapeutic implications of these compounds, provides an overview of relevant clinical trials and offers a viewpoint on the evolution of the field in the years to come.

S100A4 mRNA expression level is a predictor of radioresistance of pancreatic cancer cells

Improving poor outcomes in patients with pancreatic cancer requires a greater understanding of the biological mechanisms contributing to radioresistance. We, therefore, sought to identify genes involved in the radioresistance of pancreatic cancer cells. Two pancreatic cancer cell lines, CFPAC-1 and Capan-1, were repeatedly exposed to radiation, establishing two radioresistant cell lines. Gene expression profiling using cDNA microarrays was performed to identify genes responsible for radioresistance. The levels of expression of mRNAs encoded by selected genes and their correlation with radiation dose resulting in 50% survival rate were analyzed in pancreatic cancer cell lines. The radiation dose resulting in a 50% survival rate was significantly higher in irradiated (IR) compared to parental CFPAC-1 cells (8.31 ± 0.85 Gy vs. 2.14 ± 0.04 Gy, P<0.0001), but was lower in IR compared with parental Capan-1 cells (2.66 ± 0.24 Gy vs. 2.25 ± 0.03 Gy, P=0.04). cDNA microarray analysis identified 4 genes, including S100 calcium binding protein A4 (S100A4), overexpressed and 23 genes underexpressed in the IR compared with the parental cell lines. The levels of S100A4 mRNA expression were correlated with radiation dose resulting in a 50% survival rate (Pearson's test, R2=0.81, P=0.0025). S100A4 mRNA expression may predict radioresistance of pancreatic cancer cells and may play an important role in the poor response of pancreatic cancer cells to radiation therapy.

Radiosensitivity of human prostate cancer cells can be modulated by inhibition of 12-lipoxygenase

Nearly 30% of prostate cancer (PCa) patients treated with potentially curative doses relapse at the sites of irradiation. How some tumor cells acquire radioresistance is poorly understood. The platelet-type 12-lipoxygenases (12-LOX)-mediated arachidonic acid metabolism is important in PCa progression. Here we show that 12-LOX confers radioresistance upon PCa cells. Treatment with 12-LOX inhibitors baicalein or BMD122 sensitizes PCa cells to radiation, without radiosensitizing normal cells. 12-LOX inhibitors and radiation, when combined, have super additive or synergistic inhibitory effects on the colony formation of both androgen-dependent LNCaP and androgen-independent PC-3 PCa cells. In vivo, the combination therapy significantly reduced tumor growth.

p53 Stabilization induces cell growth inhibition and affects IGF2 pathway in response to radiotherapy in adrenocortical cancer cells

Adrenocortical carcinoma (ACC) is a very rare endocrine tumour, with variable prognosis, depending on tumour stage and time of diagnosis. However, it is generally fatal, with an overall survival of 5 years from detection. Radiotherapy usefulness for ACC treatment has been widely debated and seems to be dependent on molecular alterations, which in turn lead to increased radio-resistance. Many studies have shown that p53 loss is an important risk factor for malignant adrenocortical tumour onset and it has been reported that somatic mutations in TP53 gene occur in 27 to 70% of adult sporadic ACCs. In this study, we investigated the role of somatic mutations of the TP53 gene in response to ionizing radiation (IR). We studied the status of p53 in two adrenocortical cell lines, H295R and SW-13, harbouring non-functioning forms of this protein, owing to the lack of exons 8 and 9 and a point mutation in exon 6, respectively. Moreover, these cell lines show high levels of p-Akt and IGF2, especially H295R. We noticed that restoration of p53 activity led to inhibition of growth after transient transfection of cells with wild type p53. Evaluation of their response to IR in terms of cell proliferation and viability was determined by means of cell count and TUNEL assay.(wt)p53 over-expression also increased cell death by apoptosis following radiation in both cell lines. Moreover, RT-PCR and Western blotting analysis of some p53 target genes, such as BCL2, IGF2 and Akt demonstrated that p53 activation following IR led to a decrease in IGF2 expression. This was associated with a reduction in the active form of Akt. Taken together, these results highlight the role of p53 in response to radiation of ACC cell lines, suggesting its importance as a predictive factor for radiotherapy in malignant adrenocortical tumours cases.

Identification of the proteins related to p53-mediated radioresponse in nasopharyngeal carcinoma by proteomic analysis

Radiotherapy is the primary treatment for nasopharyngeal cancer (NPC), and p53 is closely associated with the radiosensitivity of cancer, but the molecular mechanisms of p53-mediated radioresponse in NPC remains unclear. We previously established NPC CNE2sip53 cell line with p53 knockdown and paired control cell line CNE2/pSUPER, which provides a cell model system to investigate mechanisms of p53-mediated radioresponse in NPC. In this study, we first compared the radiosensitivity of CNE2sip53 and CNE2/pSUPER by a clonogenic survival assay, cell growth assay, and Hoechst 33258 staining and flow cytometry analysis of apoptotic cells. The results showed that the radiosensitivity of CNE2sip53 was significantly lower than that of CNE2/pSUPER, indicating that p53 plays a role in mediating NPC radiosensitivity. To search for the proteins associated with the p53-mediated radioresponse in NPC, a proteomic approach was performed to identify the radioresponsive proteins in CNE2sip53 and CNE2p/SUPER, respectively, and then the difference of radioresponsive proteins in CNE2sip53 and CNE2p/SUPER was compared. As a result, 14 differential radioresponsive proteins were identified in the two cell lines, 4 proteins of which were conformed by Western blot. Among them, 9 and 5 proteins were identified solely from CNE2p/SUPER and CNE2sip53, respectively. Furthermore, protein-protein interaction analysis showed that 7 differential radioresponsive proteins identified only in CNE2p/SUPER were related to p53 protein. Our results suggest that the differential radioresponsive proteins unique to CNE2p/SUPER may be involved in p53-mediated radioresponse in NPC, which will be helpful for elucidating the mechanisms of p53-mediated NPC cellular response to radiotherapy.

Sublethal radiation injury uncovers a functional transition during erythroid maturation

OBJECTIVE

Clastogenic injury of the erythroid lineage results in anemia, reticulocytopenia, and transient appearance of micronucleated reticulocytes. However, the micronucleated reticulocyte dose-response in murine models is only linear to 2 Gy total body irradiation and paradoxically decreases at higher exposures, suggesting complex radiation effects on erythroid intermediates. To better understand this phenomenon, we investigated the kinetics and apoptotic response of the erythron to sublethal radiation injury.

MATERIALS AND METHODS

We analyzed the response to 1 and 4 Gy total body irradiation of erythroid progenitors and precursors using colony assays and imaging flow cytometry, respectively. We also investigated cell cycling and apoptotic gene expression of the steady-state erythron.

RESULTS

After 1 Gy total body irradiation, erythroid progenitors and precursors were partially depleted. In contrast, essentially all bone marrow erythroid progenitors and precursors were lost within 2 days after 4 Gy irradiation. Imaging flow cytometry analysis revealed preferential loss of phenotypic erythroid colony-forming units and proerythroblasts immediately after sublethal irradiation. Furthermore, these populations underwent radiation-induced apoptosis, without changes in steady-state cellular proliferation, at much higher frequencies than later-stage erythroid precursors. Primary erythroid precursor maturation is associated with marked Bcl-xL upregulation and Bax and Bid downregulation.

CONCLUSIONS

Micronucleated reticulocyte loss after higher sublethal radiation exposures results from rapid depletion of erythroid progenitors and precursors. This injury reveals that erythroid colony-forming units and proerythroblasts constitute a particularly proapoptotic compartment within the erythron. We conclude that the functional transition of primary proerythroblasts to later-stage erythroid precursors is characterized by a shift from a proapoptotic to an antiapoptotic phenotype.

Ototoxicity from combined Cisplatin and radiation treatment: an in vitro study

Objective. Combined cisplatin (CDDP) and radiotherapy is increasingly being used to treat advanced head and neck cancers. As both CDDP and radiation can cause hearing loss, it is important to have a better understanding of the cellular and molecular ototoxic mechanisms involved in combined therapy. Procedure. The effects of CDDP, radiation, and combined CDDP-radiation on the OC-k3 cochlear cell line were studied using MTS assay, flow cytometry, Western blotting, and microarray analysis. Results. Compared to using CDDP or radiation alone, its combined use resulted in enhanced apoptotic cell death and apoptotic-related gene expression, including that of FAS. Phosphorylation of p53 at Ser15 (a marker for p53 pathway activation in response to DNA damage) was observed after treatment with either CDDP or radiation. However, posttreatment activation of p53 occurred earlier in radiation than in CDDP which corresponded to the timings of MDM2 and TP53INP1 expression. Conclusion. Enhanced apoptotic-related gene expressions leading to increased apoptotic cell deaths could explain the synergistic ototoxicity seen clinically in combined CDDP-radiation therapy. CDDP and radiation led to differential temporal activation of p53 which suggests that their activation is the result of different upstream processes. These have implications in future antiapoptotic treatments for ototoxicity.

HPV-associated head and neck cancer: a virus-related cancer epidemic

A rise in incidence of oropharyngeal squamous cell cancer--specifically of the lingual and palatine tonsils--in white men younger than age 50 years who have no history of alcohol or tobacco use has been recorded over the past decade. This malignant disease is associated with human papillomavirus (HPV) 16 infection. The biology of HPV-positive oropharyngeal cancer is distinct with P53 degradation, retinoblastoma RB pathway inactivation, and P16 upregulation. By contrast, tobacco-related oropharyngeal cancer is characterised by TP53 mutation and downregulation of CDKN2A (encoding P16). The best method to detect virus in tumour is controversial, and both in-situ hybridisation and PCR are commonly used; P16 immunohistochemistry could serve as a potential surrogate marker. HPV-positive oropharyngeal cancer seems to be more responsive to chemotherapy and radiation than HPV-negative disease. HPV 16 is a prognostic marker for enhanced overall and disease-free survival, but its use as a predictive marker has not yet been proven. Many questions about the natural history of oral HPV infection remain under investigation. For example, why does the increase in HPV-related oropharyngeal cancer dominate in men? What is the potential of HPV vaccines for primary prevention? Could an accurate method to detect HPV in tumour be developed? Which treatment strategies reduce toxic effects without compromising survival? Our aim with this review is to highlight current understanding of the epidemiology, biology, detection, and management of HPV-related oropharyngeal head and neck squamous cell carcinoma, and to describe unresolved issues.

Head and neck cancer radiosensitization by the novel poly(ADP-ribose) polymerase inhibitor GPI-15427

BACKGROUND

In this study, we tested the ability of a novel poly(adenosine diphosphate ribose) polymerase (PARP) inhibitor, 10-(4-methyl-piperazin-1-ylmethyl)-2H-7-oxa-1,2-diaza-benzo[de]-anthracen-3-one (GPI-15427), to enhance the effect of radiotherapy in a xenograft model of human head and neck squamous cell carcinoma (HNSCC).

METHODS

Human xenograft HNSCC tumors were established in female nude mice: animals were treated with orally administered GPI-15427 at varied doses prior to tumor irradiation. In vitro and in vivo apoptosis analyses and neutral single-cell gel electrophoresis (comet) assay were performed, with the "tail moment" calculated to evaluate DNA double-strand break damage.

RESULTS

Orally administered GPI-15427 given before radiation therapy significantly reduced tumor volume, and cells demonstrated significantly elevated mean tail moments (indicative of DNA damage) and enhanced apoptosis both in vitro and in vivo, compared with radiation-alone and control groups.

CONCLUSIONS

Use of the PARP-1 inhibitor GPI-15427 induced significant sensitization to radiotherapy, representing a promising new treatment in the management of HNSCC.

[Relation between epidermal growth factor receptor (EGFR) and p53 expression and radiocurability of laryngeal squamous cell cancer]

Radiotherapy and surgery are the most important treatment modalities for the majority of laryngeal cancers. Because of high efficacy and better organ preservation radiotherapy is generally preferred for early and intermediate stage of the disease. Some of patients with more locally advanced cancers can still be cured by means of radiotherapy, but we have not got reliable prognostics factors for predicting radiocurability. THE AIM OF MY STUDY: was to investigate the value of p53 and EGFR expression for predicting clinical outcomes of laryngeal cancer patients treated with radiotherapy.

METHODS AND MATERIALS

The study included 50 patients with laryngeal cancer treated in Department of Radiotherapy of Silesian Oncology Center between the years 1998 and 2003. Paraffin sections from archival material were studied immunohistochemically for detection p53 and EGFR and correlated with clinical parameters and local tumor control and patient survival.

RESULTS

Accumulation of p53 and EGFR were detected in 65% and 50% of tumor respectively. No relationship was observed between immunostaining for investigated proteins and clinicopathologic factors. The TNM tumor stage was the most significant prognostic factor for local control and overall survival. p53 was favorable prognostic factor with 5-years disease free survival rate 82% for patients p53-positive and 75% for p53-negative patients (p = 0.04).

CONCLUSION

The TNM tumor stage is the most important prognostic factor for laryngeal cancer. Tumors accumulating p53 have better prognosis what indicates possibly role for p53 immunohistochemical analysis for predicting outcomes of radiotherapy in patients with laryngeal cancer.

Prevalence, Morphology, and Prognosis of Human Papillomavirus in Tonsillar Cancer

Objectives:

We sought to identify the prevalence of human papillomavirus (HPV) in tonsillar squamous cell carcinoma, and to examine the relationship of HPV to prognosis and tumor morphology.

Methods:

We performed in situ hybridization for HPV and retrospective clinical outcome analysis.

Results:

Of the 48 patients with tonsillar carcinoma, in situ hybridization identified 35% as HPV-positive tumors. Age-matched controls had no evidence of HPV. There was no significant difference between HPV-positive and HPV-negative patients regarding age (p = 0.34), tobacco consumption (p = 0.59), alcohol consumption (p = 0.91), or treatment method (p = 0.39). Forty-four patients were eligible for outcome analysis. The overall rate of recurrence in this population was 25%, and the disease-specific survival rate was 84%. There was no significant difference between the two groups either in the incidence of recurrence (p = 0.14) or in the disease-specific survival rate (p = 0.19). HPV-associated tumors developed from the tonsillar crypts significantly more frequently than did HPV-negative tumors (p = 0.01).

Conclusions:

As previously described, HPV is significantly associated with squamous cell carcinoma of the tonsil; however, HPV status in our series did not correlate with clinical outcome. Morphologically, we found that HPV-positive tumors had their origin in the tonsillar crypts, whereas HPV-negative tumors arose from the surface epithelium.

Glucose deprivation increases nuclear DNA repair protein Ku and resistance to radiation induced oxidative stress in human cancer cells

Recent studies have indicated that nutrient deprivation particularly glucose may play a major role in tumor cell tolerance to a generally oxidative stress environment in solid tumors. Here, we studied the impact of glucose deprivation on the response of human colon (HT29) and prostate (DU145) cancer cells to gamma radiation. A significant decrease in intracellular glucose level was observed in glucose deprived cells as measured by bioreductive assay. The survival of HT29 and DU145 were increased by 30 and 100% respectively when these cells were exposed to gamma radiation in the absence of glucose compared to that in the presence of glucose. In glucose depleted medium, glutathione (GSH), a free radical scavenger, content remained the same, and showed no correlation with the radiation resistance induced by glucose deprivation. Glucose regulated protein78 (GRP78), a stress response survival protein, was not significantly increased in cells deprived of glucose for 4 h compared to those cells in glucose. DNA repair protein Ku, which is known to play a major role in cellular resistance to radiation, was significantly increased in glucose deprived cancer cells that showed enhanced radiation resistance. These results have demonstrated, for the first time, that glucose deprivation mediated stress increased the expression of nuclear Ku and resistance to radiation induced oxidative stress in human cancer cells. The additional resistance caused by glucose deprivation in cancer cells has clinical significance since solid tumors are known to have low level of glucose due to diffusion limited blood supply and higher metabolic activity.

Overview of radiosensitivity of human tumor cells to low-dose-rate irradiation

PURPOSE

We compared clonogenic survival in 27 human tumor cell lines that vary in genotype after low-dose-rate (LDR) or high-dose rate (HDR) irradiation. We measured susceptibility to LDR-induced redistribution in the cell cycle in eight of these cell lines.

METHODS AND MATERIALS

We measured clonogenic survival after up to 96 hours of LDR (0.25 Gy/h) irradiation. We compared these with clonogenic survival after HDR irradiation (50 Gy/h). Using flow cytometry, we measured LDR-induced redistribution as a function of time during LDR irradiation in eight of these cell lines.

RESULTS

Coefficients that describe clonogenic survival after both LDR and HDR irradiation segregate into four radiosensitivity groups that associate with cell genotype: mutant (mut)ATM, wild-type TP53, mutTP53, and an unidentified gene in radioresistant glioma cells. The LDR and HDR radiosensitivity correlates at lower doses ( approximately 2 Gy HDR, approximately 6 Gy LDR), but not at higher doses (HDR > 4 Gy; LDR > 6 Gy). The rate of LDR-induced loss of clonogenic survival changes at approximately 24 hours; wild-type TP53 cells become more resistant and mutTP53 cells become more sensitive. Redistribution induced by LDR irradiation also changes at approximately 24 hours.

CONCLUSIONS

Radiosensitivity of human tumor cells to both LDR and HDR irradiation is genotype dependent. Analysis of coefficients that describe cellular radiosensitivity segregates 27 cell lines into four statistically distinct groups, each associating with specific genotypes. Changes in cellular radiosensitivity and redistribution in the cell cycle are strongly time dependent. Our data establish a genotype-dependent time-dependent model that predicts clonogenic survival, explains the inverse dose-rate effect, and suggests possible clinical applications.

A quantitative overview of radiosensitivity of human tumor cells across histological type and TP53 status

PURPOSE

We have previously shown in a limited number of tumor cell lines derived from only two histological types that clonogenic survival patterns fall into radiosensitivity groups, each group associating with a specific genotype. We now establish a global, quantitative description of human tumor cells based on genotype-dependent radiosensitivity across histological types.

METHODS

We measure clonogenic radiosensitivity in 39 human tumor cell lines that vary in histological type (colorectal, glioblastoma, prostate, bladder, teratoma, breast, melanoma and liver) and expression of several genes purported to influence radiosensitivity: ATM (ataxia telangiectasia mutated), TP53 (tumor protein 53), CDKN1A (cyclin-dependent kinase N1A), 14-3-3sigma (an isoform of the 14-3-3 gene) and DNA mismatch repair genes . For each survival curve we use the linear-quadratic model and a linear-linear model to extract multiple coefficients and seek correlation across histological types.

RESULTS

Under one-parameter analysis, survival rate at circa 2 Gy, cell lines segregate into two major, statistically-significant groups that correlate with TP53 status (wildtype versus mutant). Under two-parameter analysis, cell lines segregate into four radiosensitivity groups based on correlations between response at lower doses (ca. 2 Gy) and a component of response to higher doses (>4 Gy).

CONCLUSIONS

Intrinsic radiosensitivity of 39 human tumor cell lines segregate into distinct genotype-dependent radiosensitivity groups that associate with mutATM, wtTP53, mutTP53, and an unidentified factor in some glioblastoma cells. Genotype-dependent radiosensitivity underlies histology-dependent variation in radiosensitivity. Our analysis establishes a quantitative overview of radiosensitivity that can predict possible response of human tumors to radiotherapy protocols.

Irradiation leads to apoptosis of Kupffer cells by a Hsp27-dependant pathway followed by release of TNF-alpha

In a previous publication, we were able to show that irradiation of Kupffer cells, the liver resident macrophages, leads to an increased TNF-alpha concentration in the culture medium. The pathomechanisms underlying this phenomenon, however, remained to be elucidated. Here, we show that following irradiation of Kupffer cells, the apoptosis rate increased drastically within 48 h. At the same time, the total TNF-alpha concentration in cell lysates of Kupffer cells attached to the culture plate decreased. However, normalization of the TNF-alpha concentration with respect to cell number revealed that TNF-alpha concentration per attached cell remained constant during the observation period. Western blot analysis showed that heat shock protein 27 (Hsp27) is strongly downregulated and bax is upregulated in irradiated Kupffer cells as compared to sham-irradiated cells. Overexpression of Hsp27 in Kupffer cells was shown to prevent the effect of irradiation on bax expression, apoptosis and, at the same time, on increase of TNF-alpha concentration in the Kupffer cell medium. We conclude that irradiation of Kupffer cells leads to apoptosis because of downregulation of Hsp27 and consecutive upregulation of bax expression. Furthermore, we suggest that apoptosis of Kupffer cells leads to an increase of TNF-alpha concentration in the culture medium which may be due to cell death rather than active release or synthesis.

Genotype-dependent radiosensitivity: clonogenic survival, apoptosis and cell-cycle redistribution

PURPOSE

We describe variations of three radiation-induced endpoints on the basis of cell genotype: Clonogenic survival, expression of apoptosis and cell-cycle redistribution.

METHODS

Clonogenic survival, apoptosis and cell-cycle redistribution are measured in multiple cell lines after exposure to radiation between 2 and 16 Gy. Cell lines varied in clonogenic radiosensitivity and expression of specific genes.

RESULTS

Clonal radiosensitivity is genotype-dependent, associating with four specific genes: A mutated form of Ataxia telangiectasia mutated (mutATM); with two forms of TP53, the gene that is template for tumor protein p53, wildtype TP53 (wtTP53) and mutated TP53 (mutTP53); and an unidentified gene in radioresistant glioblastoma cells. Apoptosis is also genotype-dependent showing elevated levels in cells that express mutATM and abrogated 14-3-3sigma (an isoform of the 14-3-3 gene) but less variation for different forms of TP53. Cell-cycle redistribution varied in mutATM cells. Kinetics of apoptosis are biphasic for both time and dose; cell lines did not express apoptosis at doses below 5 Gy or times before 24 hours. Kinetics of cell-cycle redistribution changed dynamically in the first 24 hours but showed little change after that time.

CONCLUSIONS

Clonogenic survival, radiation-induced apoptosis and radiation-induced redistribution in the cell-cycle vary with cell genotype, but not the same genotypes. There is temporal, not quantitative, correlation between apoptosis and clonal radiosensitivity with apoptosis suppressed by lower, less toxic doses of radiation (<5 Gy) but enabled after larger, more toxic doses. Kinetic patterns for apoptosis and redistribution show a common change at approximately 24 hours.

Low-dose local kidney irradiation inhibits progression of experimental crescentic nephritis by promoting apoptosis

BACKGROUND

Crescentic glomerulonephritis is a rapidly progressive form of nephritis and is usually resistant to therapeutic intervention. Apoptosis plays a role in the resolution of glomerulonephritis. We investigated the effects of local kidney irradiation on the progression of experimental crescentic glomerulonephritis.

METHODS

The following three experimental rat groups were generated: (1) Group I, sham-operated control (n = 12); (2) Group II, rats injected intravenously with rabbit anti-rat GBM antibody (nephrotoxic serum, NTS) (n = 23), and (3) Group III, a single low-dose irradiation of 0.5 Gy X-ray to both kidneys at days 6, 13, 20, and 27 after NTS injection (n = 55). Renal function and blood leukocyte count were examined in different groups of rats at various time points. Kidneys obtained at various time points were analyzed to determine the effects of radiation in experimental nephritis.

RESULTS

Radiation of the kidneys reduced the levels of blood urea nitrogen and serum creatinine compared with Group II nephritic rats of similar age (p < 0.05 or 0.001). No apparent changes in blood leukocyte counts were noted in various experimental groups. Glomerular hypercellularity, crescents, global sclerosis and tubulointerstitial damage developed gradually in Group II rats, but were decreased (p < 0.05 or 0.001) after radiation treatment. The extent of tubulointerstitial damage was also reduced, and radiation-associated histological improvements were accompanied by reduced infiltration of macrophages in the glomeruli and interstitium. The numbers of PCNA- and ED1-positive cells were reduced in the kidneys at 1 day post-irradiation, of rats irradiated at 6 and 13 days after NTS injection, compared with Group II at similar time intervals (p < 0.05). A larger numbers of TUNEL-positive cells were noted at 1 day post-irradiation in rats irradiated at 6 and 13 days after NTS injection, compared with Group II at similar time intervals (p < 0.05). Immunostaining for macrophages ED1 and TUNEL staining of serial sections of irradiated nephritic kidneys showed few ED1-positive macrophages stained for TUNEL. Overexpression of active caspases 3 and 7 was noted in irradiated kidneys, compared with the corresponding Group II rats at similar time intervals. Western blot analysis showed marked increase in active caspase 3 and active caspase 7 expression in irradiated kidneys compared with NTS injection only. A marked increase in the expression of p53 protein, which is closely related to radiation-induced apoptosis, was also observed in irradiated kidneys compared with NTS injection only.

CONCLUSION

Our study showed that renal radiation can alter acute glomerular inflammation by inducing apoptosis of intrinsic and infiltrating cells in the kidney in a rat model of crescentic glomerulonephritis. Low-dose kidney irradiation can inhibit the progression of experimental nephritis through inducing apoptosis.

Relative biological effectiveness of 6 MeV neutrons with respect to cell inactivation and disturbances of the G1 phase

The relative biological effectiveness (RBE) of neutrons and other types of densely ionizing radiation appears to be close to 1.0 for the induction of strand breaks, but considerably higher RBEs have been found for cellular end points such as colony-forming ability. This may be due to differences in the processing of strand breaks or to the involvement of other lesions whose yields are more dependent on radiation quality. Because cell cycle delays may be of great importance in the processing of DNA damage, we determined the RBE for disturbances of the G1 phase in four different cell types (Be11 melanoma, 4197 squamous cell carcinoma, EA14 glioma, GM6419 fibroblasts) and compared them with the RBE for cell inactivation. The method we used to determine the progress from G1 into S was as follows: Cells were serum-deprived for a number of days and then stimulated to grow with culture medium containing normal amounts of serum. Immediately before the change of medium, cells were exposed to graded doses of either 240 kV X rays or 6 MeV neutrons. At different times afterward, cells were labeled with BrdU and the numbers of active S-phase cells were assessed using two-parameter flow cytometry. For all four cell types, cells started to progress from G1 into S after a few hours. Radiation suppressed this process in all cases, but there were some interesting differences. For Be11 and 4197 cells, the most obvious effect was a delay in G1; the labeling index increased a few hours later in irradiated samples than in controls, and there was no significant effect on the maximum labeling index. For EA14 and GM6419 cells, although smaller doses were used because of greater radiosensitivity, a delay of the entry into S phase was again noticeable, but the most significant effect was a reduction in the maximum percentage of active S-phase cells after stimulation, indicating a permanent or long-term arrest in G1. The RBE for the G1 delay was the same for all four cell types, about 2.8, while the RBE for the G1 arrest varied between 3.2 for the most resistant Be11 cells and 1.7 for the most sensitive GM6419 cells. This trend was similar to that observed for the RBE for cell inactivation. If, as described above, the same number of strand breaks per dose is induced by neutrons and by X rays, the signal transduction cascade translates them into a greater G1 delay in the case of higher LET. This appears to be independent of repair capacity, because it is similar in all cell types we investigated. We therefore assume that a higher lesion density or the presence of other types of lesions is important for this relatively early effect. A G1 arrest, however, is more closely related to the later events leading to cell inactivation, where strand break repair does play a major role, influencing X-ray sensitivity more strongly than sensitivity to neutrons because of a lower repairability of lesions induced by higher-LET radiation.

Inhibition of Hsp90: a multitarget approach to radiosensitization

Hsp90, the 90 kDa heat shock protein, is a highly expressed molecular chaperone that modulates the stability and/or transport of a diverse set of critical cellular regulatory proteins. Among Hsp90 clients are a number of proteins, which in a cell type-dependent manner, contribute to tumor cell radioresistance. Exposure of a variety of solid tumor cell lines to clinically relevant Hsp90 inhibitors results in the simultaneous loss of these radioresponse-associated proteins, which is accompanied by an increase in radiosensitivity. This radiosensitization has been linked to a compromise in the DNA damage response to radiation including the inhibition of cell cycle checkpoint activation and DNA double-strand break repair. With respect to potential clinical application, the expression of ErbB3 seems to predict tumor cells that are resistant to the effects of Hsp90 inhibition on radiosensitivity. Moreover, whereas an increase in tumor cell radiosensitivity was consistently reported, the radiosensitivity of normal fibroblasts was not affected by Hsp90 inhibition, suggesting the potential for tumor-selective radiosensitization. This review summarizes the preclinical data available on Hsp90 inhibition and cellular radiosensitivity. Results generated to date suggest that Hsp90 inhibition can provide a multitarget approach to tumor radiosensitization.

Human tumor cells segregate into radiosensitivity groups that associate with ATM and TP53 status

We seek to determine whether cellular radiosensitivity in nineteen human colorectal tumor cell lines and three human glioblastoma tumor cell lines segregate into statistically distinct groups and whether such groups correlate with gene expression. We measure clonogenic survival in 22 cell lines that vary in radiosensitivity and in expression of selected genes: ATM, TP53, CDKN1A, 14-3-3sigma, Ki-ras and DNA mismatch repair genes. We describe and compare radiosensitivity in these cell lines by one-parameter or two parameter analysis. Radiosensitivity varies among and between colorectal tumor cell lines and glioblastoma cell lines. When compared directly using survival, or using two-parameter analysis of radiosensitivity, cell lines distribute into four statistically-significant radiosensitivity groups. These groups associate strongly with the status of two genes, ATM and TP53, but do not associate with CDKN1A, 14-3-3sigma, Ki-ras and DNA mismatch repair genes. Intrinsic cellular radiosensitivity of 22 colorectal and glioblastoma cell lines fall into four radiosensitivity groups that associate with expression of ATM and TP53. These analyses suggest multiple mechanisms underlay intrinsic cellular radiosensitivity.

Identification of proteins that regulate radiation-induced apoptosis in murine tumors with wild type p53

In this study, we investigated the molecular factors determining the induction of apoptosis by radiation. Two murine tumors syngeneic to C3H/HeJ mice were used: an ovarian carcinoma OCa-I, and a hepatocarcinoma HCa-I. Both have wild type p53, but display distinctly different radiosensitivity in terms of specific growth delay (12.7 d in OCa-I and 0.3 d in HCa-I) and tumor cure dose 50% (52.6 Gy in OCa-I and > 80 Gy in HCa-I). Eight-mm tumors on the thighs of mice were irradiated with 25 Gy and tumor samples were collected at regular time intervals after irradiation. The peak levels of apoptosis were 16.1 +/- 0.6% in OCa-I and 0.2 +/- 0.0% in HCa-I at 4 h after radiation, and this time point was used for subsequent proteomics analysis. Protein spots were identified by peptide mass fingerprinting with a focus on those related to apoptosis. In OCa-I tumors, radiation increased the expression of cytochrome c oxidase and Bcl2/adenovirus E1B-interacting 2 (Nip 2) protein higher than 3-fold. However in HCa-I, these two proteins showed no significant change. The results suggest that radiosensitivity in tumors with wild type p53 is regulated by a complex mechanism. Furthermore, these proteins could be molecular targets for a novel therapeutic strategy involving the regulation of radiosensitivity.

[The role of matrix metalloproteinases and tissue inhibitors of metalloproteinases in invasion of tumours of neuroepithelial tissue]

Tumour invasion requires degradation of extracellular matrix components and migration of cells through degraded structures into surrounding tissues. Matrix metalloproteinases (MMP) constitute a family of zinc and calcium-dependent endopeptidases that play a key role in the breakdown of extracellular matrix, and in processing of cytokines, growth factors, chemokines and cell surface receptors. Their activity is regulated at the levels of transcription, activation and inhibition by tissue inhibitors of metalloproteinases (TIMP). Changes in expression of MMP and TIMP are implicated in tumour invasion, because they may contribute to both migration of tumour cells and angiogenesis. Alterations of MMP expression observed in brain tumours arouse interest in the development and evaluation of synthetic matrix metalloproteinase inhibitors as antitumour agents.

Evidence that Individual Variations in TP53 and CDKN1A Protein Responsiveness are Related to Inherent Radiation Sensitivity

We tested the hypothesis that individual variations in the induction of the TP53 tumor suppressor protein by radiation are related to inherent radiosensitivity. Thirty-two fibroblast cell strains were examined. Radiosensitivity was measured by a clonogenic survival assay. The induction of TP53 and its transcriptionally activated CDKN1A (p21) protein were studied by Western blotting 3 h after a single dose of 5 Gy. The relative cell culture age, as determined by the colony size distribution, was studied as a confounding factor. Survival curves showed wide range of radiosensitivity. The surviving fraction at 2 Gy (SF2) ranged between 0.02 and 0.49 (mean = 0.29, SD = 0.13). TP53 induction ranged between 1.28 and 2.34 (mean = 1.80, SD = 0.31). CDKN1A showed a wider induction (1.09-4.05, mean = 2.33, SD = 0.78). Positive correlations were observed between SF2 and TP53 induction (R(2) = 0.62, P < 0.001) and CDKN1A (R(2) = 0.64, P < 0.001). No correlation with the colony size distribution was observed. In conclusion, these results suggest that the individual variations in radiosensitivity and in the level of induction of TP53 (and consequently CDKN1A) are congruent, irrespective of the genetic background of these nontransformed fibroblasts. It is postulated that underlying mechanisms culminating in a stronger TP53 induction lead to higher survival, presumably due to more efficient repair of radiation-induced damage.

Phenotypic features with p53 alterations related to human papillomavirus and prognostic evaluation in cervical cancer

Cervical cancer is one of the most common tumor affecting women worldwide. Human papillomavirus (HPV) was found to have a causal relationship with cervical cancer and its precursors. The interaction between HPV E6 protein and p53 was identified in in vitro studies. The aim of the study was to evaluate the prevalence of p53 alterations related to HPV infection and the prognostic significance of p53 alterations in cervical cancer. Studies were identified by a MEDLINE search, and all relevant articles were retrieved from 1991 to March 2004. The prevalence of p53 mutations is a rare event in cervical cancer. The correlation between p53 mutations and HPV or prognosis is controversial. Loss of heterozygosity (LOH) of p53 is more commonly found in cervical cancer and is related with the prognosis of this disease. There is no significant correlation between p53 polymorphism and development of cervical cancer. The p53 mutations were not commonly found in cervical cancer. LOH of p53 may contribute to the progression of this malignancy. p53 polymorphism failed to be an independent prognostic factor in predicting the outcome of patients with cervical cancer. Further, epidemiologic surveys should be undertaken in larger populations and in different geographical regions.