Ku70 predicts response and primary tumor recurrence after therapy in locally advanced head and neck cancer

Nonhomologous end joining repair pathway molecules as predictive biomarkers for patients with oral squamous cell carcinoma

Purpose

Nonhomologous end-joining (NHEJ) is critical for the repair of either pathologic double-strand breaks (DSBs) and/or for the repair of physiologic DSBs created during radiotherapy to kill the tumor cell. Therefore, patients with higher expression of NHEJ repair proteins might develop resistance to ionizing radiation, allowing the disease to recur. As cancer of the oral cavity is a serious health problem globally, the present study aimed to examine the expression of Ku70/80, X-ray repair cross-complementing protein 4 (XRCC4) and DNA ligase IV-core molecules of the NHEJ pathway in patients with oral cancer.

Materials and Methods

Protein expression of Ku70/80, XRCC4, and DNA ligase IV were studied by Immunohistochemistry and mRNA expression of Ku70 and Ku80 were studied using reverse transcription polymerase chain reaction. Data were analyzed statistically using SPSS.

Results

A univariate survival analysis revealed an association of Ku70 mRNA with shorter overall survival (OS). While protein expression of XRCC4 showed an association with reduced relapse-free survival and shorter OS. Multivariate survival analysis demonstrated that XRCC4 and DNA ligase IV are independent prognosticators for predicting adverse disease outcomes.

Conclusion

Strong expression of repair proteins - XRCC4 and DNA ligase IV is associated with unfavorable disease outcome in patients with oral squamous cell carcinoma.

Targeting DNA Damage Response and Repair to Enhance Therapeutic Index in Cisplatin-Based Cancer Treatment

Platinum-based chemotherapies, such as cisplatin, play a large role in cancer treatment. The development of resistance and treatment toxicity creates substantial barriers to disease control, yet. To enhance the therapeutic index of cisplatin-based chemotherapy, it is imperative to circumvent resistance and toxicity while optimizing tumor sensitization. One of the primary mechanisms by which cancer cells develop resistance to cisplatin is through upregulation of DNA repair pathways. In this review, we discuss the DNA damage response in the context of cisplatin-induced DNA damage. We describe the proteins involved in the pathways and their roles in resistance development. Common biomarkers for cisplatin resistance and their utilization to improve patient risk stratification and treatment personalization are addressed. Finally, we discuss some of the current treatments and future strategies to circumvent the development of cisplatin resistance.

DNA Damage Response during Replication Correlates with CIN70 Score and Determines Survival in HNSCC Patients

Aneuploidy is a consequence of chromosomal instability (CIN) that affects prognosis. Gene expression levels associated with aneuploidy provide insight into the molecular mechanisms underlying CIN. Based on the gene signature whose expression was consistent with functional aneuploidy, the CIN70 score was established. We observed an association of CIN70 score and survival in 519 HNSCC patients in the TCGA dataset; the 15% patients with the lowest CIN70 score showed better survival (p = 0.11), but association was statistically non-significant. This correlated with the expression of 39 proteins of the major repair complexes. A positive association with survival was observed for MSH2, XRCC1, MRE11A, BRCA1, BRCA2, LIG1, DNA2, POLD1, MCM2, RAD54B, claspin, a negative for ERCC1, all related with replication. We hypothesized that expression of these factors leads to protection of replication through efficient repair and determines survival and resistance to therapy. Protein expression differences in HNSCC cell lines did not correlate with cellular sensitivity after treatment. Rather, it was observed that the stability of the DNA replication fork determined resistance, which was dependent on the ATR/CHK1-mediated S-phase signaling cascade. This suggests that it is not the expression of individual DNA repair proteins that causes therapy resistance, but rather a balanced expression and coordinated activation of corresponding signaling cascades.

Correlative analyses between tissue-based hypoxia biomarkers and hypoxia PET imaging in head and neck cancer patients during radiochemotherapy-results from a prospective trial

PURPOSE

Tumor hypoxia impairs the response of head-and-neck cancer (HNSCC) patients to radiotherapy and can be detected both by tissue biomarkers and PET imaging. However, the value of hypoxia biomarkers and imaging for predicting HNSCC patient outcomes are incompletely understood, and potential correlations between tissue and PET data remain to be elucidated. Here, we performed exploratory analyses of potential correlations between tissue-based hypoxia biomarkers and longitudinal hypoxia imaging in a prospective trial of HNSCC patients.

METHODS

Forty-nine patients undergoing chemoradiation for locally advanced HNSCCs were enrolled in this prospective trial. They underwent baseline biopsies and [¹⁸F]FDG PET imaging and [¹⁸F]FMISO PET at weeks 0, 2, and 5 during treatment. Immunohistochemical analyses for p16, Ki67, CD34, HIF1α, CAIX, Ku80, and CD44 were performed, and HPV status was assessed. Biomarker expression was correlated with biological imaging information and patient outcome data.

RESULTS

High HIF1α tumor levels significantly correlated with increased tumor hypoxia at week 2 as assessed by the difference in the [¹⁸F]FMISO tumor-to-background ratios, and high HIF1α and CAIX expressions were both associated with a deferred decrease in hypoxia between weeks 2 and 5. Loco-regional recurrence rates after radiotherapy were significantly higher in patients with high CAIX expression and also increased for high levels of the DNA repair factor Ku80. HPV status did not correlate with any of the tested hypoxia biomarkers, and HPV-positive patients showed higher loco-regional control rates and progression-free survival independent of their hypoxia dynamics.

CONCLUSION

In this exploratory trial, high expression of the tissue-based hypoxia biomarkers HIF1α and CAIX correlated with adverse hypoxia dynamics in HNSCCs during chemoradiation as assessed by PET imaging, and high CAIX levels were associated with increased loco-regional recurrence rates. Hence, hypoxia biomarkers warrant further investigations as potential predictors of hypoxia dynamics and hypoxia-associated radiation resistance.

Effect of Ku80 on the radiosensitization of cisplatin in the cervical carcinoma cell line HeLa

Cisplatin chemotherapy in combination with radiotherapy is the primary therapeutic strategy for the treatment of cervical cancer; however, the underlying molecular mechanism for cisplatin radiosensitization remains unknown. The aim of the present study was to investigate the effect of Ku80, a DNA double-strand break (DSB) repair protein, on cisplatin radiosensitization in cervical cancer. The pre-established Ku80 suppression cervical cancer cell line HeLa/Ku80-siRNA and the normal HeLa cell line underwent 6 MV X-ray irradiation (6 Gy) individually or in combination with 5 µg/ml cisplatin treatment. Alterations in apoptosis, the cell cycle and γH2AX expression were detected. Following irradiation individually and combined with cisplatin, compared with normal HeLa cells, HeLa/Ku80-siRNAexhibited an increased rate of apoptosis (P<0.05). It was identified that the earlier cisplatin was administered following irradiation, the higher the rate of apoptosis. Cell cycle analysis indicated that, following irradiation combined with cisplatin, the cells were arrested in G₁ and S phase rather than in G₂/M phase following irradiation alone. Microscopic imaging of immunofluorescence staining and western blotting identified that HeLa/Ku80-siRNA cells exhibited more γH2AX foci remaining following treatment with irradiation and cisplatin, particularly in the group treated with 6 Gy irradiation for 1 h together with 23 h of exposure to cisplatin. Irradiation in combination with cisplatin promoted the apoptosis of HeLa cells in association with the inhibition of Ku80, and it was identified that the earlier cisplatin was administered following irradiation, the more apoptosis was induced. This maybe because irradiation combined with cisplatin is able to arrest cells in G₁ and S phase to rapidly repair damaged DNA, and the lack of Ku80 induces the inability to repair DSB, resulting in increased apoptosis. The results of the present study suggest that Ku80 may be a potent molecular target in cisplatin radiosensitization.

The Role of the Core Non-Homologous End Joining Factors in Carcinogenesis and Cancer

DNA double-strand breaks (DSBs) are deleterious DNA lesions that if left unrepaired or are misrepaired, potentially result in chromosomal aberrations, known drivers of carcinogenesis. Pathways that direct the repair of DSBs are traditionally believed to be guardians of the genome as they protect cells from genomic instability. The prominent DSB repair pathway in human cells is the non-homologous end joining (NHEJ) pathway, which mediates template-independent re-ligation of the broken DNA molecule and is active in all phases of the cell cycle. Its role as a guardian of the genome is supported by the fact that defects in NHEJ lead to increased sensitivity to agents that induce DSBs and an increased frequency of chromosomal aberrations. Conversely, evidence from tumors and tumor cell lines has emerged that NHEJ also promotes chromosomal aberrations and genomic instability, particularly in cells that have a defect in one of the other DSB repair pathways. Collectively, the data present a conundrum: how can a single pathway both suppress and promote carcinogenesis? In this review, we will examine NHEJ's role as both a guardian and a disruptor of the genome and explain how underlying genetic context not only dictates whether NHEJ promotes or suppresses carcinogenesis, but also how it alters the response of tumors to conventional therapeutics.

Clinicopathological and molecular characteristics of Ku 70/80 expression in Nigerian breast cancer and its potential therapeutic implications

Ku 70/80 is a regulator of the Non-Homologous End Joining (NHEJ) roles in clinicopathological features, and has prognostic significance in breast cancer (BC) in Caucasian populations. However, its significance in the Nigerian BC population, which is characterized by a higher rate of the triple-negative and basal phenotype, p53 mutation rate and BRCA1 deficiency, still needs to be investigated. We hypothesize that Ku70/80 expression shows adverse expression in Nigerian BC and, furthermore, that it is likely to have a therapeutic implication for Black BC management. This study investigated the biological, clinicopathological and prognostic significance of Ku 70/80 expression in a BC cohort from a Nigerian population. Ku 70/80 expression was determined in 188 well-characterized formalin-fixed, paraffin-embedded (FFPE) BC samples using tissue microarray and immunohistochemistry. Ku 70/80 expression was correlated with clinicopathological, molecular and prognostic characteristics of patients. Ku 70/80 was expressed in 113 (60.1%) tumors, and was positively associated with metastatic disease, triple-negative and basal phenotype, BRCA1 down regulators (MTA-1 and ID4), p-cadherin, PI3KCA and p53 expression. It inversely correlated with BRCA1, BRCA2, BARD1 and p27. Ku 70/80 was predictive of breast cancer-specific survival in multivariate analysis, but not of disease-free interval. This study demonstrated that Ku 70/80 expression is associated with triple negativity and down-regulation of the homologous recombination pathway of DNA repair. Therefore, the development of novel drugs to target KU70/80 may improve the patients' outcome in the treatment of Black BC.

Enhanced cell migration and apoptosis resistance may underlie the association between high SERPINE1 expression and poor outcome in head and neck carcinoma patients

High SERPINE1 expression is a common event in head and neck squamous cell carcinoma (HNSCC); however, whether it plays a role in determining clinical outcome remains still unknown. We studied SERPINE1 as a prognostic marker in two HNSCC patient cohorts. In a retrospective study (n = 80), high expression of SERPINE1 was associated with poor progression-free (p = 0.022) and cancer-specific (p = 0.040) survival. In a prospective study (n = 190), high SERPINE1 expression was associated with poor local recurrence-free (p = 0.022), progression-free (p = 0.002) and cancer-specific (p = 0.006) survival. SERPINE1 expression was identified as an independent risk factor for progression-free survival in patients treated with chemo-radiotherapy or radiotherapy (p = 0.043). In both patient cohorts, high SERPINE1 expression increased the risk of metastasis spread (p = 0.045; p = 0.029). The association between SERPINE1 expression and survival was confirmed using the HNSCC cohort included in The Cancer Genome Atlas project (n = 507). Once again, patients showing high expression had a poorer survival (p < 0.001). SERPINE1 over-expression in HNSCC cells reduced cell proliferation and enhanced migration. It also protected cells from cisplatin-induced apoptosis, which was accompanied by PI3K/AKT pathway activation. Downregulation of SERPINE1 expression had the opposite effect. We propose SERPINE1 expression as a prognostic marker that could be used to stratify HNSCC patients according to their risk of recurrence.

DNA ligase4 as a prognostic marker in nasopharyngeal cancer patients treated with radiotherapy

BACKGROUND

The capability for DNA double-strand breaks (DSBs) repair is crucial for inherent radiosensitivity of tumor and normal cells. We have investigated the clinicopathologic significance of DNA repair gene expression in nasopharyngeal (NP) carcinoma.

MATERIALS AND METHODS

A total of 65 NP cancer patients who received radiotherapy were included. The immunopositivity to Ku 70, DNA-PKcs, MRN, RAD50, XRCC4, and LIG4 were examined in all tumor tissues.

RESULTS

The patients comprised 42 males and 23 females, with a median age of 56 years (range, 18-84). The expression levels of RAD50 (0,+1,+2,+3) were 27.7%, 32.3%, 21.5%, and 18.5%. LIG4 (±) were 43.1% and 56.9% respectively. The 5-year OS rate of patients with LIG4 (±) were 90% and 67.9%, respectively (p=0.035). The 5-year TTP rate of patients with LIG4 (±) were 75.9%, 55.5%, respectively (P=0.039).

CONCLUSIONS

Our results suggest the possibility of predicting the radiosensitivity of NP cancer by performing immunohistochemical analysis of LIG4.

New biological markers in the decision of treatment of head and neck cancer patients

Head and neck squamous cell carcinoma is the sixth most common cancer type worldwide. Also the 5-year survival rate of less than 50 % seems to be lower than other cancer types. There are some reasons behind this high mortality rate; one of them is the lack of knowledge about the biology and genomic instability behind the carcinogenic processes. These biological features could condition the failure of frontline treatment, in which case rescue treatment should be used, representing an overtreatment for the patients. For years many biological factors have been tested as prognostic and predictive factors in relation to treatment with a modest success. To find appropriate tests which could be used in the context of the individualized treatment decision, we have reviewed new biological markers, not only in tumor tissue, but also in normal tissue from head and neck carcinoma patients.

Investigation of radiosensitivity gene signatures in cancer cell lines

Intrinsic radiosensitivity is an important factor underlying radiotherapy response, but there is no method for its routine assessment in human tumours. Gene signatures are currently being derived and some were previously generated by expression profiling the NCI-60 cell line panel. It was hypothesised that focusing on more homogeneous tumour types would be a better approach. Two cell line cohorts were used derived from cervix [n = 16] and head and neck [n = 11] cancers. Radiosensitivity was measured as surviving fraction following irradiation with 2 Gy (SF2) by clonogenic assay. Differential gene expression between radiosensitive and radioresistant cell lines (SF2 median) was investigated using Affymetrix GeneChip Exon 1.0ST (cervix) or U133A Plus2 (head and neck) arrays. There were differences within cell line cohorts relating to tissue of origin reflected by expression of the stratified epithelial marker p63. Of 138 genes identified as being associated with SF2, only 2 (1.4%) were congruent between the cervix and head and neck carcinoma cell lines (MGST1 and TFPI), and these did not partition the published NCI-60 cell lines based on SF2. There was variable success in applying three published radiosensitivity signatures to our cohorts. One gene signature, originally trained on the NCI-60 cell lines, did partially separate sensitive and resistant cell lines in all three cell line datasets. The findings do not confirm our hypothesis but suggest that a common transcriptional signature can reflect the radiosensitivity of tumours of heterogeneous origins.

High RAB25 expression is associated with good clinical outcome in patients with locally advanced head and neck squamous cell carcinoma

Currently there are no molecular markers able to predict clinical outcome in locally advanced head and neck squamous cell carcinoma (HNSCC). In a previous microarray study, RAB25 was identified as a potential prognostic marker. The aim of this study was to analyze the association between RAB25 expression and clinical outcome in patients with locally advanced HNSCC treated with standard therapy. In a retrospective immunohistochemical study (n = 97), we observed that RAB25-negative tumors had lower survival (log-rank, P = 0.01) than patients bearing positive tumors. In an independent prospective mRNA study (n = 117), low RAB25 mRNA expression was associated with poor prognosis. Using classification and regression tree analysis (CART) we established two groups of patients according to their RAB25 mRNA level and their risk of death. Low mRNA level was associated with poor local recurrence-free (log-rank, P = 0.005), progression-free (log-rank, P = 0.002) and cancer-specific (log-rank, P < 0.001) survival. Multivariate Cox model analysis showed that low expression of RAB25 was an independent poor prognostic factor for survival (hazard ratio: 3.84, 95% confidence interval: 1.93-7.62, P < 0.001). Patients whose tumors showed high RAB25 expression had a low probability of death after treatment. We also found lower RAB25 expression in tumors than in normal tissue (Mann-Whitney U, P < 0.001). Moreover, overexpression of RAB25 in the UM-SCC-74B HNSCC cell line increased cisplatin sensitivity, and reduced cell migration and invasion. Our findings support a tumor suppressor role for RAB25 in HNSCC and its potential use to identify locally advanced patients with a high probability of survival after genotoxic treatment.

Genome stability pathways in head and neck cancers

Genomic instability underlies the transformation of host cells toward malignancy, promotes development of invasion and metastasis and shapes the response of established cancer to treatment. In this review, we discuss recent advances in our understanding of genomic stability in squamous cell carcinoma of the head and neck (HNSCC), with an emphasis on DNA repair pathways. HNSCC is characterized by distinct profiles in genome stability between similarly staged cancers that are reflected in risk, treatment response and outcomes. Defective DNA repair generates chromosomal derangement that can cause subsequent alterations in gene expression, and is a hallmark of progression toward carcinoma. Variable functionality of an increasing spectrum of repair gene polymorphisms is associated with increased cancer risk, while aetiological factors such as human papillomavirus, tobacco and alcohol induce significantly different behaviour in induced malignancy, underpinned by differences in genomic stability. Targeted inhibition of signalling receptors has proven to be a clinically-validated therapy, and protein expression of other DNA repair and signalling molecules associated with cancer behaviour could potentially provide a more refined clinical model for prognosis and treatment prediction. Development and expansion of current genomic stability models is furthering our understanding of HNSCC pathophysiology and uncovering new, promising treatment strategies.

Comprehensive assessment of prognostic markers for sinonasal squamous cell carcinoma

BACKGROUND

Little is known about the molecular signature of the rare tumor sinonasal squamous cell carcinoma (SNSCC). The purpose of this study was to comprehensively assess various molecular biomarkers in SNSCC.

METHODS

We chose 13 markers for this study, which have been known as prognostic markers in head and neck squamous cell carcinoma. Expression of these markers was examined by either in situ hybridization or immunohistochemical methods on tissue microarrays made from 70 SNSCC specimens and 28 matched-pair normal tissues from patients who underwent surgical resection at our institution. Expression data were correlated with patient clinicopathologic parameters and survival.

RESULTS

Of the 13 markers, only epidermal growth factor receptor (EGFR) protein expression was associated with significantly shorter disease-free survival (DFS; p = .01307). EGFR expression was also associated with shorter overall survival (OS), but the difference was not statistically significant.

CONCLUSION

Targeted inhibition of tumor EGFR expression may be a new approach to treating SNSCC.

Clinicopathological significance of KU70/KU80, a key DNA damage repair protein in breast cancer

Although the role of BRCA1 and the homologous recombination (HR) pathway in breast cancer (BC) has been extensively studied, the alternative repair pathway for DNA double-strand breaks (DSBs), non-homologous end-joining (NHEJ) remains to be defined. Ku proteins bind to DNA DSB ends and play a key role in NHEJ. In this study we aimed to assess the expression and biological significance of the KU70/KU80 heterodimer in the different molecular classes of BC. The expression of KU70/KU80 was assessed immunohistochemically in a well-characterised and annotated series of 1302 unselected invasive BC cases with a long-term follow-up together with 25 cases with known BRCA1 mutations. The results were correlated with clinicopathological parameters, other DNA repair proteins and patient outcome. The expression of KU70/KU80 protein was further evaluated in various BC cell lines using western blotting and reverse-phase protein microarray (RPPA). Nuclear KU70/KU80 expression was correlated with features of poor prognosis including higher histological grade, lymphovascular invasion, negative oestrogen receptor expression, basal-like phenotype, P53 and CHK1 positivity. KU70/KU80 was expressed in all BRCA1-associated tumours and showed an inverse correlation with nuclear BRCA1 protein and aberrant cytoplasmic RAD51 expression. RPPA confirmed these results and showed higher expression of KU70/KU80 in BRCA1-deficient cell line compared to BRCA1-proficient cell line. KU70/KU80 expression showed an association with disease-free interval; however, it was not an independent predictor of outcome. As a conclusion, KU70/KU80 may play a role in DNA DSBs repair in HR-deficient tumours. Further study of other NHEJ markers in sporadic BC is warranted.

Prognostic role of MMP-9 expression in head and neck carcinoma patients treated with radiotherapy or chemoradiotherapy

OBJECTIVES

The purpose of this study was to evaluate the prognostic significance of the expression of metalloproteinases (MMPs)-2 and -9 at a transcriptional level in patients with head and neck squamous cell carcinoma (HNSCC).

PATIENTS AND METHODS

Real-time polymerase chain reaction was used to determine mRNA expression levels of MMP-2 and MMP-9 in 105 consecutive patients with HNSCC treated with radiotherapy or chemoradiotherapy. Continuous values of mRNA expression levels were analyzed using a classification and regression tree (CART) method.

RESULTS

Patients were grouped into two categories according to the results from CART analysis; high (n=71) and low (n=34) expression levels of MMP-9. MMP-2 expression was not included in the model. The 5-year adjusted survival rate was 92.9% for patients with low MMP-9 expression level and 61.0% for patients with a high expression level (P=0.006). Overexpression of MMP-9 was associated with a decrease in local control of the disease. In a multivariate analysis, MMP-9 expression was the only variable that was associated with adjusted survival. Considering patients with a low MMP-9 expression level as the reference group, patients with a high MMP-9 expression level had a 6.1 times higher risk of death from HNSCC (CI 95%: 1.4-26.4).

CONCLUSION

We found a significant relationship between the transcription of MMP-9 and adjusted survival in HNSCC patients treated with radiotherapy or chemoradiotherapy. These results suggest that MMP-9 transcription may serve as a marker of treatment response to radiotherapy or chemo-radiotherapy in patients with HNSCC.

Gene expression signatures and molecular markers associated with clinical outcome in locally advanced head and neck carcinoma

The purpose of this study was to identify molecular markers associated with tumor recurrence and survival in patients with locally advanced head and neck squamous cell carcinoma (HNSCC). We studied the expression profile of 63 pre-treatment tumor biopsies obtained from locally advanced HNSCCs treated with standard treatments. Cluster analysis identified three tumor subtypes associated with significant differences in local recurrence-free survival (LRFS) (P<0.001), progression free-survival (PFS) (P<0.009) and overall survival (OS) (P<0.004). Tumor subtype 1, associated with short LRFS, PFS and OS, showed features of epithelial-mesenchymal transition and undifferentiation. It also overexpressed genes involved in cell adhesion, NF-κB and integrin signalling. Tumor subtype 3, associated with longer LRFS, PFS and OS, showed a high degree of differentiation and overexpressed genes located in chromosomal regions 19q13 and 1q21. Tumor subtype 2, which had an intermediate clinical outcome between subtype 1 and subtype 3, overexpressed genes involved in branching morphogenesis. Finally, we validated the association between gene cluster classification and patient survival using Gene Set Enrichment Analysis and two HNSCC data sets obtained from two independent patient cohorts. In conclusion, we generated a gene prognostic signature associated with survival in locally advanced patients using the expression profile of the pre-treatment tumor biopsy. Independent prospective studies would be necessary to assess if the proposed survival signature could help to guide clinical management of HNSCC.

DNA-PKcs expression predicts response to radiotherapy in prostate cancer

PURPOSE

Double-strand breaks, the most lethal DNA lesions induced by ionizing radiation, are mainly repaired by the nonhomologous end-joining system. The expression of the nonhomologous end-joining pathway has never been studied in prostate cancer, and its prognostic value for patients undergoing radiotherapy remains unknown.

METHODS

Pretreatment biopsies from 238 patients treated with exclusive external beam radiotherapy for localized prostate cancer with ≥ 2 years of follow-up were reviewed to reassess the Gleason score. Of these 238 cases, 179 were suitable for in situ analysis and were included in the tissue microarrays. Expression of the nonhomologous end-joining proteins Ku70, Ku80, DNA-dependent protein kinase, catalytic subunits (DNA-PKcs), and X-ray repair cross complementing 4-like factor was studied by immunohistochemistry, together with the proliferation marker Ki67.

RESULTS

The predictive value of the Gleason score for biochemical relapse (using the Phoenix criteria) was markedly improved after review (P<.0001) compared with the initial score (P=.003). The clinical stage, pretreatment prostate-specific antigen level, and perineural invasion status were also associated with progression-free survival (P=.005, P<.0001, and P=.03, respectively). High proliferation (>4%) tends to be associated with biochemical recurrence; however, the difference did not reach statistical significance (P=.06). Although the expression of Ku70, Ku80, and X-ray repair cross complementing 4-like factor was not predictive of relapse, positive DNA-PKcs nuclear staining was closely associated with biochemical recurrence (P=.0002). On multivariate analysis, only the Gleason score, prostate-specific antigen level, and DNA-PKcs status remained predictive of recurrence (P=.003, P=.002, and P=.01, respectively).

CONCLUSIONS

The results of the present study highly suggest that DNA-PKcs could be a predictive marker of recurrence after radiotherapy, independently of the classic prognostic markers, including the Gleason score modified after review.

BCL-2, in combination with MVP and IGF-1R expression, improves prediction of clinical outcome in complete response cervical carcinoma patients treated by radiochemotherapy

OBJECTIVES

To investigate whether BCL-2 expression would improve MVP/IGF-1R prediction of clinical outcome in cervix carcinoma patients treated by radiochemotherapy, and suggest possible mechanisms behind this effect.

METHODS

Fifty consecutive patients, who achieved complete response to treatment, from a whole series of 60 cases suffering from non-metastatic localized cervical carcinoma, were prospectively included in this study from July 1999 to December 2003. Follow-up was closed in January 2011. All patients received pelvic radiation (45-64.80 Gy in 1.8-2 Gy fractions) with concomitant cisplatin at 40 mg/m2/week doses followed by brachytherapy. Oncoprotein expression was studied by immunohistochemistry in paraffin-embedded tumour tissue.

RESULTS

No relation was found between BCL-2 and clinicopathological variables. High MVP/IGF-1R/BCL-2 tumour expression was strongly related to poor local and regional disease-free survival (P<0.0001), distant disease-free survival (P=0.010), disease-free survival (P<0.0001), and cause-specific survival (P<0.0001). NHEJ repair protein Ku70/80 expression was significantly repressed in tumours overexpressing all three oncoproteins (P=0.047). No differences were observed in proliferation (Ki67 expression) or P53 alteration.

CONCLUSIONS

BCL-2, MVP, and IGF-1R overexpression were related to poorer clinical outcome in cervical cancer patients who achieved clinical complete response to radiochemotherapy. The NHEJ repair protein Ku70/80 expression could be involved in the regulation of these oncoproteins.

Biologic activity of a dinuclear Pd(II)-spermine complex toward human breast cancer

A dinuclear palladium-based complex (Pd(2) -Spm) was synthesized and compared with cisplatin (cDDP) on two different human breast cancer cell lines (MCF-7 and MDA-MB-231) as well as toward an untransformed cell line (BJ fibroblasts). The results obtained show that Pd(2) -Spm is more effective against the estrogen receptors [ER(-)] cell line MDA-MB-231, while cDDP displayed better results for the ER(+) MCF-7 cell line. It was shown that, like cDDP, Pd(2) -Spm triggers phosphorylation of H2AX, indicating that this compound damages DNA. Apart from DNA, Pd(2) -Spm also targets the cytoskeleton having a greater impact on cell morphology than cDDP. Pd(2) -Spm and cDDP have opposite antiproliferative activities in the presence of the PI3K inhibitor wortmannin. Furthermore, Pd(2) -Spm at an optimized concentration displays a rapid antiproliferative effect as opposed to cDDP, which seems to have a slower kinetics. The results point to a distinct mechanism of action for each of these complexes, which may explain their synergistic action when coadministrated.

DNA repair biomarker profiling of head and neck cancer: Ku80 expression predicts locoregional failure and death following radiotherapy

PURPOSE

Radiotherapy plays an integral role in the treatment of head and neck squamous cell carcinoma (HNSCC). Although proteins involved in DNA repair may predict HNSCC response to radiotherapy, none has been validated in this context. We examined whether differential expression of double-strand DNA break (DSB) repair proteins in HNSCC, the chief mediators of DNA repair following irradiation, predict for treatment outcomes.

EXPERIMENTAL DESIGN

Archival HNSCC tumor specimens (n = 89) were assembled onto a tissue microarray and stained with antibodies raised against 38 biomarkers. The biomarker set was enriched for proteins involved in DSB repair, in addition to established mechanistic markers of radioresistance. Staining was correlated with treatment response and survival alongside established clinical and pathologic covariates. Results were validated in an independent intramural cohort (n = 34).

RESULTS

Ku80, a key mediator of DSB repair, correlated most closely with clinical outcomes. Ku80 was overexpressed in half of all tumors, and its expression was independent of all other covariates examined. Ku80 overexpression was an independent predictor for both locoregional failure and mortality following radiotherapy (P < 0.01). The predictive power of Ku80 overexpression was confined largely to HPV-negative HNSCC, where it conferred a nine-fold greater risk of death at two years.

CONCLUSIONS

Ku80 overexpression is a common feature of HNSCC, and is a candidate DNA repair-related biomarker for radiation treatment failure and death, particularly in patients with high-risk HPV-negative disease. It is a promising, mechanistically rational biomarker to select individual HPV-negative HNSCC patients for strategies to intensify treatment.

Site-dependent E-cadherin cleavage and nuclear translocation in a metastatic colorectal cancer model

Metastases are frequently found during colorectal cancer diagnoses and are the main determinants of clinical outcome. The lack of reliable models of metastases has precluded their mechanistic understanding and our capacity to improve outcome. We studied the effect of E-cadherin and Snail1 expression on metastagenesis in a colorectal cancer model. We microinjected SW480-ADH human colorectal cancer cells, transfected with an empty vector (Mock) or overexpressing Snail1 (Snail1(OE)) or E-cadherin (E-cadherin(OE)), in the ceca of nude mice (eight per group) and analyzed tumor growth, dissemination, and Snail1, E-cadherin, β-catenin, and Presenilin1 (PS1) expression in local tumors and/or metastatic foci. Snail1(OE) cells disseminated only to lymph nodes, whereas Mock or E-cadherin(OE) cells spread to lymph nodes and peritoneums. Peritoneal tumor foci developed by E-cadherin(OE) cells presented an increase in E-cadherin proteolysis and nuclear translocation, and enhanced expression of proteolytically active PS1, which was linked to increased tumor growth and shortened mouse survival. Interestingly, local and lymph node tumors in mice bearing E-cadherin(OE) cells overexpressed E-cadherin, but they did not show E-cadherin proteolysis or nuclear translocation. Remarkably, E-cadherin nuclear translocation and enhanced expression of active PS1 were found in a patient with colorectal signet-ring cell carcinoma. In conclusion, we have established a colorectal cancer metastasis model in which E-cadherin proteolyis and nuclear translocation associates with aggressive foci growth only in the peritoneal microenvironment.

Radiosensitivity profiles from a panel of ovarian cancer cell lines exhibiting genetic alterations in p53 and disparate DNA-dependent protein kinase activities

The variability of radiation responses in ovarian tumors and tumor-derived cell lines is poorly understood. Since both DNA repair capacity and p53 status can significantly alter radiation sensitivity, we evaluated these factors along with radiation sensitivity in a panel of sporadic human ovarian carcinoma cell lines. We observed a gradation of radiation sensitivity among these sixteen lines, with a five-fold difference in the LD50 between the most radiosensitive and the most radioresistant cells. The DNA-dependent protein kinase (DNA-PK) is essential for the repair of radiation induced DNA double-strand breaks in human somatic cells. Therefore, we measured gene copy number, expression levels, protein abundance, genomic copy and kinase activity for DNA-PK in all of our cell lines. While there were detectable differences in DNA-PK between the cell lines, there was no clear correlation with any of these differences and radiation sensitivity. In contrast, p53 function as determined by two independent methods, correlated well with radiation sensitivity, indicating p53 mutant ovarian cancer cells are typically radioresistant relative to p53 wild-type lines. These data suggest that the activity of regulatory molecules such as p53 may be better indicators of radiation sensitivity than DNA repair enzymes such as DNA-PK in ovarian cancer.

Spermidinyl-CoA-based HAT inhibitors block DNA repair and provide cancer-specific chemo- and radiosensitization

Acetyl group turnover on specific lysine epsilon-amino groups of the core chromosomal histones regulates DNA accessibility function, and the acetylating and deacetylating enzymes that govern the turnover provide important targets for the development of anti-cancer drugs. Histone deacetylase (HDAC) inhibitors have been developed and evaluated extensively in clinical trials, while the development of inhibitors of histone acetyltransferase (HAT) has proceeded more slowly. Here we have examined the cellular effects of an S-substituted coenzyme A (CoA) inhibitor of histone acetylation, consisting of spermidine (Spd) linked to the S-terminus of CoA through a thioglycolic acid linkage (adduct abbreviated as Spd-CoA), as well as the effects of a truncated Spd-CoA derivative lacking the negatively charged portion of the CoA moiety. While exposure of cancer cells to Spd-CoA has little effect on cell viability, it causes a rapid inhibition of histone acetylation that correlates with a transient arrest of DNA synthesis, a transient delay in S-phase progression, and an inhibition of nucleotide excision repair and DNA double strand break repair. These effects correlate with increased cellular sensitivity to the DNA-targeted chemotherapeutic drugs, cisplatin (Platinol()) and 5-fluorouracil, to the DNA damaging drug, camptothecin, and to UV-C irradiation. The sensitization effects of Spd-CoA are not observed in normal cells due to a barrier to uptake. The truncated Spd-CoA derivative displays similar but enhanced chemosensitization effects, suggesting that further modifications of the Spd-CoA structure could further improve potency. The results demonstrate that Spd-CoA and its truncated version are efficiently and selectively internalized into cancer cells, and suggest that the resulting inhibition of acetylation-dependent DNA repair enhances cellular sensitivity to DNA damage. These and related inhibitors of histone acetylation could therefore constitute a novel class of potent therapy sensitizers applicable to a broad range of conventional cancer treatments.

In vitro non-homologous DNA end joining assays--the 20th anniversary

DNA double-strand breaks (DSBs) are the most serious forms of DNA damage in cells. Unrepaired or misrepaired DSBs account for some of the genetic instabilities that lead to mutations or cell death, and consequently, to cancer predisposition. In human cells non-homologous DNA end joining (NHEJ) is the main repair mechanism of these breaks. Systems for DNA end joining study have been developing during the last 20 years. New assays have some advantages over earlier in vitro DSBs repair assays because they are less time-consuming, allow the use of clinical material and examination of the joining DNA ends produced physiologically in mammalian cells. Proteins involved in NHEJ repair pathway can serve as biomarkers or molecular targets for anticancer drugs. Results of studies on NHEJ in cancer could help to select potent repair inhibitors that may selectively sensitize tumor cells to ionizing radiation (IR) and chemotherapy. Here, we review the principles and practice of in vitro NHEJ assays and provide some insights into the future prospects of this assay in cancer diagnosis and treatment.