Molecular markers in clinical radiation oncology

Targeting cancer stem cells with a pan-BCL-2 inhibitor in preclinical and clinical settings in patients with gastroesophageal carcinoma

OBJECTIVE

Gastro-oesophageal cancers (GEC) are resistant to therapy and lead to poor prognosis. The cancer stem cells (CSCs) and antiapoptotic pathways often confer therapy resistance. We sought to elucidate the antitumour action of a BCL-2 inhibitor, AT101 in GEC in vitro, in vivo and in a clinical trial.

METHODS

Extensive preclinical studies in vitro and in vivo were carried out to establish the mechanism action of AT101 on targeting CSCs and antiapoptotic proteins. A pilot clinical trial in patients with GEC was completed with AT-101 added to standard chemoradiation.

RESULTS

Overexpression of BCL-2 and MCL-1 was noted in gastric cancer tissues (GC). AT-101 induced apoptosis, reduced proliferation and tumour sphere formation in MCL-1/BCL-2 high GC cells. Interestingly, AT101 dramatically downregulated genes (YAP-1/Sox9) that control CSCs in GEC cell lines regardless of BCL-2/MCL-1 expression. Addition of docetaxel to AT-101 amplified its antiproliferation and induced apoptosis effects. In vivo studies confirmed the combination of AT101 and docetaxel demonstrated stronger antitumour activity accompanied with significant decrease of CSCs biomarkers (YAP1/SOX9). In a pilot clinical trial, 13 patients with oesophageal cancer (EC) received AT101 orally concurrently with chemoradiation. We observed dramatic clinical complete responses and encouraging overall survival in these patients. Clinical specimen analyses revealed that AT-101 dramatically reduced the expression of CSCs genes in treated EC specimens indicating antitumour activity of AT101 relies more on its anti-CSCs activity.

CONCLUSIONS

Our preclinical and clinical data suggest that AT-101 overcomes resistance by targeting CSCs pathways suggesting a novel mechanism of action of AT101 in patients with GEC.

Transient elevation of glycolysis confers radio-resistance by facilitating DNA repair in cells

BACKGROUND

Cancer cells exhibit increased glycolysis for ATP production (the Warburg effect) and macromolecular biosynthesis; it is also linked with therapeutic resistance that is generally associated with compromised respiratory metabolism. Molecular mechanisms underlying radio-resistance linked to elevated glycolysis remain incompletely understood.

METHODS

We stimulated glycolysis using mitochondrial respiratory modifiers (MRMs viz. di-nitro phenol, DNP; Photosan-3, PS3; Methylene blue, MB) in established human cell lines (HEK293, BMG-1 and OCT-1). Glucose utilization and lactate production, levels of glucose transporters and glycolytic enzymes were investigated as indices of glycolysis. Clonogenic survival, DNA repair and cytogenetic damage were studied as parameters of radiation response.

RESULTS

MRMs induced the glycolysis by enhancing the levels of two important regulators of glucose metabolism GLUT-1 and HK-II and resulted in 2 fold increase in glucose consumption and lactate production. This increase in glycolysis resulted in resistance against radiation-induced cell death (clonogenic survival) in different cell lines at an absorbed dose of 5 Gy. Inhibition of glucose uptake and glycolysis (using fasentin, 2-deoxy-D-glucose and 3-bromopyruvate) in DNP treated cells failed to increase the clonogenic survival of irradiated cells, suggesting that radio-resistance linked to inhibition of mitochondrial respiration is glycolysis dependent. Elevated glycolysis also facilitated rejoining of radiation-induced DNA strand breaks by activating both non-homologous end joining (NHEJ) and homologous recombination (HR) pathways of DNA double strand break repair leading to a reduction in radiation-induced cytogenetic damage (micronuclei formation) in these cells.

CONCLUSIONS

These findings suggest that enhanced glycolysis generally observed in cancer cells may be responsible for the radio-resistance, partly by enhancing the repair of DNA damage.

Differences in Prognostic Factors and Failure Patterns Between Invasive Micropapillary Carcinoma and Carcinoma With Micropapillary Component Versus Invasive Ductal Carcinoma of the Breast: Retrospective Multicenter Case-Control Study (KROG 13-06)

PURPOSE

We designed the present study to investigate differences in prognostic factors and failure patterns between patients with invasive micropapillary carcinoma or carcinoma with micropapillary component (IMPC) and randomly matched patients with invasive ductal carcinoma (IDC) of the breast at multiple institutions of the Korean Radiation Oncology Group (KROG).

MATERIALS AND METHODS

This retrospective multicenter study was performed using subjects treated from January 1999 to November 2011. Female patients who had undergone curative resection for breast cancer without neoadjuvant chemotherapy were considered for this study. Exact matches were made for age (± 3 years), pathologic tumor and node stage, treatment method (surgery with or without radiotherapy), and period when surgery was performed (within 1 year) at the same institution.

RESULTS

A total of 534 patients were analyzed. The median follow-up period was 59 months in both groups. In the comparison of clinicopathologic characteristics, rates of lymphovascular invasion (LVI) and nuclear grade III were both significantly higher in IMPC than in IDC (P < .001, P = .01, respectively). During the follow-up period, recurrences developed in 40 patients with IMPC (15.0%) and 21 with IDC (7.9%). Locoregional recurrence (LRR) developed in 22 patients with IMPC (8.2%) and 10 with IDC (3.7%). The rate of distant metastasis did not differ between the 2 groups (P = .52). LRR-free survival (P = .03) and recurrence-free survival (P = .007) were significantly different between the 2 groups, but overall survival was not (P = .67).

CONCLUSION

IMPC is associated with a higher rate of LVI, high nuclear grade, and a propensity for LRR compared to IDC. Modification of the locoregional treatment modality might be needed in this pathologic subtype of breast cancer.

Interferon-induced protein with tetratricopeptide repeats 1 (IFIT1) as a prognostic marker for local control in T1-2 N0 breast cancer treated with breast-conserving surgery and radiation therapy (BCS + RT)

Interferon-induced protein with tetratricopeptide repeats 1 (IFIT1) expression, involved in the regulation of translation, has been implicated to mediate resistance to chemotherapy and radiation in cancer cells in vitro. The purpose of this study was to evaluate the prognostic significance of IFIT1 protein expression in patients with breast cancer treated with Breast-Conserving Surgery and Radiation Therapy (BCS + RT). A tissue microarray was constructed with specimens from 282 women with node-negative, early-stage (I/II) breast cancer who were treated with BCS + RT. Immunohistochemistry was used to stain for the IFIT1 protein. Cytoplasmic IFIT1 protein expression levels were correlated with clinicopathologic factors, local relapse-free survival (LRFS), disease-free survival (DFS), and overall survival (OS). IFIT1 positivity was found in 123 (49%) of cases. The median follow-up time was 7.3 years. Eighty percent of the patients had T1 disease, 88% were human epidermal growth factor receptor 2 (HER2) negative, and 20% had triple-negative breast cancer (TNBC). IFIT1 positivity was associated with estrogen receptor negative status (p = 0.002), progesterone receptor negative status (p = 0.02), TNBC (p = 0.01), and HER2-positive status (p = 0.006). In univariate and multivariate analysis, IFIT1 positivity was associated with improved LRFS (p = 0.055 and p = 0.04, respectively). Using a log-rank test, IFIT1 positivity was found to be associated with improved LRFS (94% versus 85%, p = 0.046) but not DFS or OS at 10 years. On subset analysis of the TNBC patients, IFIT1 positivity was found to correlate with improved LRFS (100% versus 53%, p = 0.004) and DFS in (87% versus 49%, p = 0.048) at 10 years. Elevated IFIT1 protein expression is associated with improved LRFS. In addition, our data suggest that IFIT1 expression may help risk stratify patients with TNBC who may benefit from more aggressive therapy. As there is limited data on IFIT1 in breast cancer, additional work is needed to ascertain its significance.

Identification of inositol polyphosphate 4-phosphatase type II as a novel tumor resistance biomarker in human laryngeal cancer HEp-2 cells

Although tumor resistance remains a significant impediment to successful radiotherapy, associated regulatory markers and detailed molecular mechanisms underlying this phenomenon are not well defined. In this study, we identified inositol polyphosphate 4-phosphatase type II (INPP4B) as a novel marker of radioresistance by systematically analyzing Unigene libraries of laryngeal cancer. INPP4B was highly expressed in radioresistant laryngeal cancer cells and was induced by treatment with either radiation or anticancer drugs in various types of cancer cells. Ectopic INPP4B overexpression increased radioresistance and anticancer drug resistance by suppressing apoptosis in HEp-2 cells. Conversely, INPP4B depletion with small interfering RNA resensitized HEp-2 as well as A549 and H1299 cells to radiation- and anticancer drug-induced apoptosis. Furthermore, radiation-induced INPP4B expression was blocked by inhibition of extracellular signal-regulated kinase (ERK). INPP4B depletion significantly attenuated radiation-induced increases in Akt phosphorylation, indicating an association of INPP4B-mediated radioresistance with Akt survival signaling. Taken together, our data suggest that ERK-dependent induction of INPP4B triggers the development of a tumor-resistance phenotype via Akt signaling and identify INPP4B as a potentially important target molecule for resolving the radioresistance of cancer cells.

A bioinformatics filtering strategy for identifying radiation response biomarker candidates

The number of biomarker candidates is often much larger than the number of clinical patient data points available, which motivates the use of a rational candidate variable filtering methodology. The goal of this paper is to apply such a bioinformatics filtering process to isolate a modest number (<10) of key interacting genes and their associated single nucleotide polymorphisms involved in radiation response, and to ultimately serve as a basis for using clinical datasets to identify new biomarkers. In step 1, we surveyed the literature on genetic and protein correlates to radiation response, in vivo or in vitro, across cellular, animal, and human studies. In step 2, we analyzed two publicly available microarray datasets and identified genes in which mRNA expression changed in response to radiation. Combining results from Step 1 and Step 2, we identified 20 genes that were common to all three sources. As a final step, a curated database of protein interactions was used to generate the most statistically reliable protein interaction network among any subset of the 20 genes resulting from Steps 1 and 2, resulting in identification of a small, tightly interacting network with 7 out of 20 input genes. We further ranked the genes in terms of likely importance, based on their location within the network using a graph-based scoring function. The resulting core interacting network provides an attractive set of genes likely to be important to radiation response.

Cancer-associated adipocytes promotes breast tumor radioresistance

Mature adipocytes are excellent candidates to influence tumor behavior through heterotypic signaling processes since these cells produce hormones, growth factors, cytokines and other molecules, a heterogeneous group of molecules named adipokines. Using a 2D coculture system, we demonstrate that breast tumor cells previously co-cultivated with mature adipocytes exhibit radioresistance and an earlier and higher increase in the effector kinase Chk1, a phenotype that was associated with decreased cell death as compared to tumor cells grown alone. Interestingly, the adipocytes-induced tumor changes taking place during the coculture time preceding the exposure to IR were sufficient to confer the radioresistant effect. Notorious among the changes brought by adipocytes was the significant increase of IL-6 expression in tumor cells, whose activity may well account for the observed tumor cell protection from IR toxicity. Indeed, our data confirmed the protective role of this cytokine as tumor cells incubated after irradiation with recombinant IL-6 exhibit an increased in Chk1 phosphorylation and a radioresistant phenotype, thus far recapitulating the effects observed in the presence of adipocytes. Our current study sheds light on a new role of tumor-surrounding adipocytes in fostering a radioresistant phenotype in breast tumors, a finding that might have important clinical implications in obese patients that frequently exhibit aggressive diseases.

CUL2 and STK11 as novel response-predictive genes for neoadjuvant radiochemotherapy in esophageal cancer

AIMS

Neoadjuvant treatment strategies have been developed to improve the survival of patients with locally advanced esophageal cancer. Since only patients with major histopathological response benefit from multimodality treatment, we profiled the genome of patients with esophageal cancer for markers indicating response or nonresponse.

PATIENTS AND METHODS

Pretreatment biopsies of responding and nonresponding patients with locally advanced esophageal cancer, as well as the corresponding normal epithelium, were analyzed by human genome microarrays. Differential gene expression was associated with histomorphological tumor regression. Quantitative real-time reverse transcriptase-PCR was applied for verification of the predictive value of a panel of the identified marker genes, including 66 patients.

RESULTS

We detected differentially expressed candidate genes with regard to response and nonresponse to neoadjuvant radiochemotherapy. The response-predictive impact of the novel markers, CUL2 and STK11, was confirmed by the verification study including 66 patients. Whereas CUL2 mRNA expression levels of greater than 1.7 was predictive for major response (p = 0.02) in adeno- and squamous cell carcinoma, STK11 was predominantly response predictive for adenocarcinomas. Downregulation of CUL2 (p = 0.04) and STK11 (p = 0.02) mRNA also correlated with a more favorable prognosis.

CONCLUSION

We identified two novel markers, CUL2 and STK11, for response prediction in esophageal cancer. They will be applied to complement our panel of response-predictive markers to further individualize therapy.

Trade-offs between cancer and other diseases: do they exist and influence longevity?

Relationships between aging, disease risks, and longevity are not yet well understood. For example, joint increases in cancer risk and total survival observed in many human populations and some experimental aging studies may be linked to a trade-off between cancer and aging as well as to the trade-off(s) between cancer and other diseases, and their relative impact is not clear. While the former trade-off (between cancer and aging) received broad attention in aging research, the latter one lacks respective studies, although its understanding is important for developing optimal strategies of increasing both longevity and healthy life span. In this paper, we explore the possibility of trade-offs between risks of cancer and selected major disorders. First, we review current literature suggesting that the trade-offs between cancer and other diseases may exist and be linked to the differential intensity of apoptosis. Then we select relevant disorders for the analysis (acute coronary heart disease [ACHD], stroke, asthma, and Alzheimer disease [AD]) and calculate the risk of cancer among individuals with each of these disorders, and vice versa, using the Framingham Study (5209 individuals) and the National Long Term Care Survey (NLTCS) (38,214 individuals) data. We found a reduction in cancer risk among old (80+) men with stroke and in risk of ACHD among men (50+) with cancer in the Framingham Study. We also found an increase in ACHD and stroke among individuals with cancer, and a reduction in cancer risk among women with AD in the NLTCS. The manifestation of trade-offs between risks of cancer and other diseases thus depended on sex, age, and study population. We discuss factors modulating the potential trade-offs between major disorders in populations, e.g., disease treatments. Further study is needed to clarify possible impact of such trade-offs on longevity.

Biomarkers in radiation oncology

The discovery of biomarkers in patients receiving radiation therapy for cancer is occurring at an exceptional pace. There are a number of ways to conduct biomarker investigations, although the majority of clinically relevant biomarker studies have used immunohistochemistry (IHC) on tissue specimens. Using IHC, expression of several pre-radiation biomarkers, such as VEGF, EGFR, YKL-40, murine double minute 2 and Rad51, has been associated with a poor outcome. Because tumor tissue may be difficult to obtain and IHC studies can be difficult to reproduce and standardize, investigators have attempted to find similar results when studying biomarkers of nontumor biospecimens, such as serum and urine. This has led to the discovery of a number of soluble biomarkers predictive of outcome (e.g., YKL-40, VEGF and matrix metallopeptidase-2). As we transition from the use of biopsy-based markers to surrogate soluble biomarkers in the hope of bringing these biomarkers into clinical use, we must ensure methods of standardization in sample collection, processing, storage and analysis to allow widespread reproducibility and accuracy of results.

Mediator of DNA damage checkpoint protein 1 (MDC1) expression as a prognostic marker for nodal recurrence in early-stage breast cancer patients treated with breast-conserving surgery and radiation therapy

The mediator of DNA damage checkpoint protein 1 (MDC1) regulates cell cycle checkpoints and recruits repair proteins to sites of double-stranded DNA damage using its BRCA1 carboxy-terminal (BRCT) domains. MDC1 under-expression has been associated with radiosensitivity in cells. The purpose of this study was to evaluate the clinico-pathologic and prognostic significance of MDC1 expression in a cohort of early-stage breast cancer patients treated with breast conservation therapy. Paraffin specimens from 489 women with early-stage breast cancer treated with breast conservation therapy were constructed into tissue microarrays. The arrays were stained for estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER2), and MDC1. This was correlated with clinico-pathologic factors and outcomes. MDC1 expression was evaluable in 351 cases (72%). Decreased MDC1 expression was found to be correlated with nodal failure (P = 0.05), but not ipsilateral breast relapse-free survival (IBRFS), distant metastasis-free survival (DMFS), or overall survival (OS). Subset analysis in node-negative patients revealed that decreased MDC1 expression predicted for nodal failure (P < 0.01). Our study is the first to assess the clinico-pathologic and prognostic significance of MDC1 expression in patients with early-stage breast cancer treated with lumpectomy and radiotherapy. MDC1 under-expression predicted for nodal failure, but not for IBRFS, DM, or OS. The role of other proteins involved in the DNA damage repair pathway and their effects on MDC1 expression, as well as the level of MDC1 expression in patients with BRCA1 mutations warrant further investigation.

TaqMan low-density arrays and analysis by artificial neuronal networks predict response to neoadjuvant chemoradiation in esophageal cancer

AIMS

Neoadjuvant radiochemotherapy of locally advanced esophageal cancer is only effective for patients with major histopathological response. A total of 17 genes were selected to predict histopathologic tumor response to chemoradiation (cisplatin, 5-fluorouracil, 36 Gy).

MATERIALS & METHODS

For gene-expression analysis quantitative TaqMan low-density arrays were applied. Expression levels in pretreatment biopsies of 41 patients (cT2-4, Nx, M0) were compared with the degree of histopathologic regression in resected specimens applying univariate, multivariate and artificial neuronal network analyses.

RESULTS

Dihydropyrimidine dehydrogenase was identified as an independent predictor associated with major response (p < 0.002). Multivariate analysis of the marker combination provided response prediction with 75.0% sensitivity, 81.0% specificity and 78.1% accuracy. Artificial neuronal network analysis was the best predictive model for major histopathologic response (80% sensitivity, 90.5% specificity and 85.4% accuracy), representing a clinically practical system.

CONCLUSION

Low-density-array RT-PCR analyzed by artificial neuronal network predicts histopathologic response to neoadjuvant chemoradiation in our patient collective, and could be used to further individualize treatment strategies in esophageal cancer.

Increase in thiol oxidative stress via glutathione reductase inhibition as a novel approach to enhance cancer sensitivity to X-ray irradiation

Depletion of the reduced form of glutathione (GSH) has been extensively studied for its effect on sensitizing cancer to radiation. However, little is known about the effects of thiol oxidative stress created through an increase in glutathione disulfide (GSSG) on cancer sensitivity to radiation. In this study, an increase in GSSG was effectively created using 2-acetylamino-3-[4-(2-acetylamino-2-carboxyethylsulfanylthiocarbonylamino)phenylthiocarbamoylsulfanyl]propionic acid (2-AAPA), an irreversible glutathione reductase (GR) inhibitor. Our results demonstrate that the GSSG increase significantly enhanced cancer sensitivity to X-ray irradiation in four human cancer cell lines (A431, MCF7, NCI-H226, and OVCAR-3). When cells were pretreated with 2-AAPA followed by X-ray irradiation, the IC(50) values for X-ray irradiation of A431, MCF7, NCI-H226, and OVCAR-3 cells were reduced, from 24.2 +/- 2.8, 42.5 +/- 3.0, 43.0 +/- 3.6, and 27.8+/-3.5 Gy to 6.75 +/- 0.9, 8.1 +/- 1.1, 6.75 +/- 1.0, and 12.1 +/- 1.7 Gy, respectively. The synergistic effects observed from the combination of X-rays plus 2-AAPA were comparable to those from the combination of X-rays plus buthionine sulfoximine, a reference compound known to increase cancer sensitivity to radiation. The synergistic effect was correlated with an increase in cell thiol oxidative stress, which was reflected by a five-to sixfold increase in GSSG and 25% increase in total disulfides. No change in GSH or total thiols was observed as a result of GR inhibition.

Molecular markers predict outcome in squamous cell carcinoma of the head and neck after concomitant cisplatin-based chemoradiation

Not all patients with squamous cell carcinomas of the head and neck (HNSCC) benefit from concurrent cisplatin-based chemoradiation, but reliable predictive markers for outcome after chemoradiation are scarce. We have investigated potential prognostic biomarkers for outcome in a large group of patients. Ninety-one tumor biopsies taken from consecutive HNSCC patients were evaluated for protein expression on a tissue microarray. Using immunohistochemistry, 18 biomarkers, involved in various cellular pathways were investigated. Univariable and multivariable proportional hazard analyses were performed to investigate associations between each individual marker and outcome. In addition, the global test was used to test all variables simultaneously and selected combinations of markers for an overall association with local control. Univariable analysis showed statistically significant increased relative risks of RB, P16 and MRP2 for local control and MDR1 and HIF-1alpha for overall survival. MRP2, MDR1 and P16 levels were positively associated with outcome whereas RB and HIF-1alpha had a negative relationship. Using Goeman's global testing no combination of markers was identified that was associated with local control. Grouping the markers according to their function revealed an association between a combination of 3 markers (P16, P21 and P27) and outcome (p = 0.05) was found. In the multivariable analysis, MRP2 and RB remained significant independent predictive markers for local control. This study describes the prognostic value of biomarkers for the outcome in patients uniformly treated with concurrent chemoradiation. MRP2 and RB were found to be associated with outcome in patients treated with concurrent chemoradiation.

Trade-off between cancer and aging: what role do other diseases play? Evidence from experimental and human population studies

The potential gain in life expectancy which could result from the complete elimination of mortality from cancer in the U.S. would not exceed 3 years if one were to consider cancer independently of other causes of death. In this paper, we review evidence of trade-offs between cancer and aging as well as between cancer and other diseases, which, if taken into account, may substantially increase estimates of gain in life expectancy resulting from cancer eradication. We also used the Multiple Causes of Death (MCD) data to evaluate correlations among mortalities from cancer and other major disorders including heart disease, stroke, diabetes, Alzheimer's, Parkinson's diseases, and asthma. Our analyses revealed significant negative correlations between cancer and other diseases suggesting stronger population effects of cancer eradication. Possible mechanisms of the observed dependencies and emerging perspectives of using dependent competing risks models for evaluating the effects of reduction of mortality from cancer on life expectancy are discussed.

Node-Negative Colorectal Cancer at High Risk of Distant Metastasis Identified by Combined Analysis of Lymph Node Status, Vascular Invasion, and Raf-1 Kinase Inhibitor Protein Expression

Purpose: To identify independent clinicopathologic factors and protein markers leading to the identification of colorectal cancer (CRC) patients with mismatch repair proficiency at risk of developing metastasis and, consequently, more likely to benefit from combined modality therapy.

Experimental Design: Immunohistochemistry for 22 tumor markers was done using a tissue microarray. A subset of 387 CRC patients with complete clinicopathologic data and TNM stage was analyzed. Univariate and multivariate analyses were done to identify independent predictive markers of metastasis. The results were validated on 810 CRC patients.

Results: In univariate analysis, T stage (P &lt; 0.001), N stage (P &lt; 0.001), tumor grade (P = 0.005), vascular invasion (P &lt; 0.001), tumor budding (P &lt; 0.001), positive expression of β-catenin (P = 0.015), overexpression of RHAMM (P = 0.008), negative expression of Raf-1 kinase inhibitor protein (RKIP; P = 0.001), and absence of intraepithelial lymphocytes (P = 0.017) were significantly associated with the presence of distant metastasis. In multivariate analysis, higher N stage (P &lt; 0.001), presence of vascular invasion (P = 0.009), and RKIP loss (P = 0.003) independently predicted distant metastatic disease. A subgroup of node-negative patients was identified as high risk for distant metastasis and showed a similar probability of metastatic risk and nearly identical survival times as node-positive patients with absence of vascular invasion and positive RKIP expression (metastatic risk, 24% and 22%; median survival time, 45.0 and 47.0 months, respectively).

Conclusion: The combined analysis of N stage, vascular invasion, and RKIP expression is highly predictive of distant metastasis in patients with mismatch repair–proficient CRC. Additionally, a subgroup of more aggressive N0 tumors can be identified by evaluating vascular invasion and RKIP expression.

Preclinical evaluation of molecular-targeted anticancer agents for radiotherapy

The combination of molecular-targeted agents with irradiation is a highly promising avenue for cancer research and patient care. Molecular-targeted agents are in themselves not curative in solid tumours, whereas radiotherapy is highly efficient in eradicating tumour stem cells. Recurrences after high-dose radiotherapy are caused by only one or few surviving tumour stem cells. Thus, even if a novel agent has the potential to kill only few tumour stem cells, or if it interferes in mechanisms of radioresistance of tumours, combination with radiotherapy may lead to an important improvement in local tumour control and survival. To evaluate the effects of novel agents combined with radiotherapy, it is therefore necessary to use experimental endpoints which reflect the killing of tumour stem cells, in particular tumour control assays. Such endpoints often do not correlate with volume-based parameters of tumour response such as tumour regression and growth delay. This calls for radiotherapy specific research strategies in the preclinical testing of novel anti-cancer drugs, which in many aspects are different from research approaches for medical oncology.

The vitamin-like dietary supplement para-aminobenzoic acid enhances the antitumor activity of ionizing radiation

PURPOSE

To determine whether para-aminobenzoic acid (PABA) alters the sensitivity of tumor cells to ionizing radiation in vitro and in vivo.

METHODS AND MATERIALS

Cellular proliferation was assessed by WST-1 assays. The effects of PABA and radiation on tumor growth were examined with chick embryo and murine models. Real-time reverse transcriptase-polymerase chain reaction and Western blotting were used to quantify p21CIP1 and CDC25A levels.

RESULTS

Para-aminobenzoic acid enhanced (by 50%) the growth inhibitory activity of radiation on B16F10 cells, whereas it had no effect on melanocytes. Para-aminobenzoic acid enhanced (50-80%) the antitumor activity of radiation on B16F10 and 4T1 tumors in vivo. The combination of PABA and radiation therapy increased tumor apoptosis. Treatment of tumor cells with PABA increased expression of CDC25A and decreased levels of p21CIP1.

CONCLUSIONS

Our findings suggest that PABA might represent a compound capable of enhancing the antitumor activity of ionizing radiation by a mechanism involving altered expression of proteins known to regulate cell cycle arrest.

VEGF as a predictive marker of rectal tumor response to preoperative radiotherapy

BACKGROUND

Neoadjuvant radiotherapy for rectal cancer may result in tumor downstaging or complete tumor regression leading to greater sphincter preservation. The identification of molecular predictive markers of tumor response to preoperative radiotherapy would provide an additional tool for selecting patients most likely to benefit from treatment. The aim of this study was to determine whether VEGF expression in preirradiation tumor biopsies is a useful predictive marker of tumor response in patients with rectal cancer undergoing preoperative radiotherapy.

METHODS

Immunohistochemistry for VEGF was performed on 59 preirradiation biopsies from patients with completely responsive (ypT0) or nonresponsive tumors after preoperative radiotherapy. VEGF positivity was evaluated using several scoring methods and the association between VEGF and tumor response was compared. The distribution of VEGF scores was obtained as well as the mean VEGF expression in the two response groups.

RESULTS

The mean VEGF expression in nonresponsive tumors (NR) was significantly greater than in completely responsive tumors (CR) (P = 0.0035). Nearly half (47%) of all CR tumors had a VEGF expression of 10% or less. Eleven tumors were negative (0% immunoreactivity) for the protein and all of these (100%) were complete responders. Fifty-two percent of the NR tumors had VEGF scores of 80% or greater. The four scoring methods used to determine the association between VEGF and tumor response each produced significant results (P < 0.05).

CONCLUSIONS

The results of this study indicate that VEGF assessed immunohistochemically from preirradiation tumor biopsies may be a useful marker of rectal tumor response to preoperative radiotherapy.

Increased expression of ICAM-3 is associated with radiation resistance in cervical cancer

To search for a marker that predicts the efficacy of radiation therapy in human cervical cancer, gene expression profiles between parental SiHa cervical cancer cells and radiation-resistant SiHa/R cells have been compared by the microarray technique. Microarray and Northern blot analyses demonstrated that the ICAM-3 expression was upregulated in SiHa/R cells. This increased expression of ICAM-3 in SiHa cells enhanced cell survival by about 34.3% after a 2 Gy dosage of radiation. In addition, SiHa/ICAM-3 cells showed a 2.45-fold higher level of FAK phosphorylation than that of the control cells. In tumor specimens, ICAM-3 staining was restricted to tumor stromal endothelial cells and lymphocytes. The overexpression of ICAM-3 was significantly more frequent in radiation-resistant cervical cancer specimens when compared with radiation-sensitive specimens (83.3% vs. 35.3%; p = 0.015). With these observations, we can suggest that an increased expression of ICAM-3 is associated with radiation resistance in cervical cancer cells and the expression of ICAM-3 can be used as a valuable biomarker to predict the radiation resistance in cervical cancer that occurs during radiotherapy.

A fast, simple method for screening radiation susceptibility genes by RNA interference

Radiotherapy can cause unacceptable levels of damage to normal tissues in some cancer patients. To understand the molecular mechanisms underlying radiation-induced physiological responses, and to be able to predict the radiation susceptibility of normal tissues in individual patients, it is important to identify a comprehensive set of genes responsible for radiation susceptibility. We have developed a simple and rapid 96-well screening protocol using cell proliferation assays and RNA interference to identify genes associated with radiation susceptibility. We evaluated the performance of alamarBlue-, BrdU-, and sulforhodamine B-based cell proliferation assays using the 96-well format. Each proliferation assay detected the known radiation susceptibility gene, PRKDC. In a trial screen using 28 shRNA vectors, another known gene, CDKN1A, and one new radiation susceptibility gene, ATP5G3, were identified. Our results indicate that this method may be useful for large-scale screens designed to identify novel radiation susceptibility genes.

The Current and Future Application of Adjuvant Systemic Chemotherapy in Patients with Bladder Cancer Following Cystectomy

Urothelial transitional cell cancer has a high rate of response to combination cytotoxic therapy. Approximately 50% of patients with high-grade bladder cancer and deep muscle invasion ultimately die of disseminated disease. Translating the high response seen in locally advanced disease into long-term survival in the metastatic setting and to improved survival in the advanced setting has proved difficult. This article reviews the use of adjuvant chemotherapy in localized or locally advanced transitional cell cancer. The chemotherapy of urological malignancies, including bladder cancer, has recently been reviewed in detail; this article does not contain an extensive review of the drugs used.

Molecular profiles as predictive marker for the effect of overall treatment time of radiotherapy in supraglottic larynx squamous cell carcinomas

BACKGROUND AND PURPOSE

Reduction of the overall treatment time of radiotherapy increases the probability of local tumour control, but it does not benefit all patients. Identification of molecular marker profiles may aid in the selection of patients likely to benefit from accelerated radiotherapy.

PATIENTS AND METHODS

Two hundred and nine patients with SCC of the supraglottic larynx received primary radiotherapy in the randomised DAHANCA trials to 66-68 Gy, 2 Gy/fx but with different overall treatment times of 9.5 week, 6.5 week and 5.5 week. Formalin-fixed paraffin embedded tumour slides were assessed by immunohistochemistry for expression of EGFr, E-cadherin, KI-67 and Bcl-2 and the TP53 mutation profile was determined using PCR-amplification, DHPLC and sequencing. The profiles were established using a hierarchical clustering algorithm with a Bayesian information criterion for cluster number optimisation.

RESULTS

Full data-set were available for 158 patients and four almost equally sized clusters were identified. One of these clusters differed significantly with respect to local control compared to the other clusters: the cluster (n=36) characterised by wild type TP53, low expression of E-cadherin and Bcl-2, moderate KI-67 and EGFr, was not influenced by a reduction in the overall treatment time (P=0.6) whereas the other clusters showed an increase in local control when the overall treatment time of radiotherapy was reduced. This was also partially seen with disease specific survival as the endpoint.

CONCLUSIONS

Molecular marker profiling may aid in the selection of patients that will benefit of a reduction in overall treatment time of radiotherapy in SCC of the supraglottic larynx.

Relationship between Antiapoptotic Molecules and Metastatic Potency and the Involvement of DNA-Dependent Protein Kinase in the Chemosensitization of Metastatic Human Cancer Cells by Epidermal Growth Factor Receptor Blockade

The failure to treat metastatic cancer with multidrug resistance is a major problem for successful cancer therapy, and the molecular basis for the association of metastatic phenotype with resistance to therapy is still unclear. In this study, we revealed that various metastatic cancer cells showed consistently higher levels of antiapoptotic proteins, including Bcl-2, nuclear factor-kappaB, MDM2, DNA-dependent protein kinase (DNA-PK), and epidermal growth factor receptor (EGFR), and lower levels of proapoptotic proteins, including Bax and p53 than low metastatic parental cells. This was followed by chemo- and radioresistance in metastatic cancer cells compared with their parental cells. EGFR and DNA-PK activity, which are known to be associated with chemo- and radioresistance, were demonstrated to be mutually regulated by each other. Treatment with PKI166, an EGFR inhibitor, suppressed etoposide-induced activation of DNA-PK in A375SM metastatic melanoma cells. In addition, PKI166 enhanced markedly the chemosensitivities of metastatic cancer cell sublines to various anticancer drugs in comparison with those of low metastatic cancer cells. These results suggest that the activities of DNA-PK and EGFR, which is positively correlated with each other, may contribute to metastatic phenotype as well as therapy resistance, and the EGFR inhibitor enhances the effect of anticancer drugs against therapy-resistant metastatic cancer cells via suppression of stress responses, including activation of DNA-PK.

Molecular Marker Profiles Predict Locoregional Control of Head and Neck Squamous Cell Carcinoma in a Randomized Trial of Continuous Hyperfractionated Accelerated Radiotherapy

PURPOSE

Identification of factors that assist prediction of tumor response to radiotherapy may aid in refining treatment strategies and improving outcome. Possible association of molecular marker expression profiles with locoregional control of head and neck squamous cell carcinoma was investigated in a randomized trial of conventional versus continuous hyperfractionated accelerated radiotherapy (CHART).

EXPERIMENTAL DESIGN

Tumor material was obtained from 402 patients. Immunohistochemistry was used to assess Ki-67, CD31, p53, Bcl-2, and cyclin D1 expression. A hierarchical clustering algorithm with a Bayesian information criterion was used to group tumors with similar marker expression; resulting expression profiles were then compared in terms of their difference in outcome after CHART and conventionally fractionated radiotherapy.

RESULTS

Molecular marker profile was an independent prognostic factor for locoregional control. This was confirmed in multivariate analysis, including clinical variables such as tumor and nodal status, primary site, histological grade, age, and gender (P < 0.001 and P = 0.006 for local and nodal relapse, respectively). In particular, Bcl-2-positive tumors responded significantly better than average in both arms of the trial. Tumors negative for p53- and Bcl-2, with high and randomly patterned Ki-67 expression, responded worse than average with no benefit from CHART. Tumors with similarly negative p53 and Bcl-2, but low Ki-67 staining, with an organized pattern, benefit significantly from CHART schedule.

CONCLUSIONS

This study demonstrates the potential of molecular profiles to predict radiotherapy response of head and neck squamous cell carcinoma and for treatment stratification. Distinct expression profiles correlate with three distinct clinical phenotypes, including good locoregional control, poor locoregional control, and an outcome strongly dependent upon fractionation schedule.