The mechanism of action of radiosensitization of conventional chemotherapeutic agents

A rationale for chemoradiation (vs radiotherapy) in salivary gland cancers? On behalf of the REFCOR (French rare head and neck cancer network)

BACKGROUND

Salivary gland carcinomas constitute a heterogeneous group of tumors, with over 20 histological subtypes of various prognoses. The mainstay of treatment is surgery, with radiotherapy advocated for unresectable disease or postoperatively in case of poor prognostic factors such as high grade, locally advanced and/or incompletely resected tumors. Concurrent chemotherapy is sometimes advocated in routine practice based on criteria extrapolated from squamous cell carcinomas of the head and neck, on radioresistance of salivary gland tumors and on results obtained in the metastatic setting. The aim of this review was to identify situations where chemotherapy is advocated.

MATERIAL AND METHODS

A search of literature was performed with the following key words: parotid, salivary gland, neoplasm, cancer, malignant tumor, chemoradiation, chemotherapy, radiotherapy and treatment. Case report and studies published before 2000 were not included.

RESULTS

Platinum-based regimens were the most frequent. Other regimens were reported and seemed dependent on histology. The level of evidence for the concurrent delivery of chemotherapy with radiation therapy is supported by a low level of evidence. Prescribing chemotherapy mostly relies on poor prognostic factors similar to those used to indicate high dose radiotherapy. Protocols vary with histology.

CONCLUSION

The rationale for adding chemotherapy to radiotherapy remains to be demonstrated prospectively. Although the type of systemic treatments used may be adapted on histology, the strongest rationale remains in favor of cisplatin.

Motexafin gadolinium: a novel radiosensitizer for brain tumors

Despite advances in the field of oncology, progress for patients with brain metastases and most primary brain tumors has been slow. New efforts to enhance the therapeutic index of radiation therapy are under way, including the use of radiosensitizers. Motexafin gadolinium (Xcytrin) is one such novel agent with several unique properties that enhance the cytotoxic potential of radiation therapy, as well as several chemotherapeutic agents, and possibly has independent cytotoxicity in certain lymphoid malignancies. Motexafin gadolinium is very well tolerated with tumor specific uptake. The rationale for the use of this drug as well as its current and future role as a radiation enhancer in the management of brain tumors is reviewed.

Improving therapeutic ratio in head and neck cancer with adjuvant and cisplatin-based treatments

Advanced head and neck cancers are difficult to manage despite the large treatment arsenal currently available. The multidisciplinary effort to increase disease-free survival and diminish normal tissue toxicity was rewarded with better locoregional control and sometimes fewer side effects. Nevertheless, locoregional recurrence is still one of the main reasons for treatment failure. Today, the standard of care in head and neck cancer management is represented by altered fractionation radiotherapy combined with platinum-based chemotherapy. Targeted therapies as well as chronotherapy were trialled with more or less success. The aim of the current work is to review the available techniques, which could contribute towards a higher therapeutic ratio in the treatment of advanced head and neck cancer patients.

A Phase II Study of Additional Four-Week Chemotherapy With Capecitabine During the Resting Periods After Six-Week Neoadjuvant Chemoradiotherapy in Patients With Locally Advanced Rectal Cancer

Purpose

The aim of this study is to evaluate the efficacy and the safety of additional 4-week chemotherapy with capecitabine during the resting periods after a 6-week neoadjuvant chemoradiotherapy (NCRT) in patients with locally advanced rectal cancer.

Methods

Radiotherapy was delivered to the whole pelvis at a total dose of 50.4 Gy for 6 weeks. Oral capecitabine was administered at a dose of 825 mg/m² twice daily for 10 weeks. Surgery was performed 2-4 weeks following the completion of chemotherapy.

Results

Between January 2010 and September 2011, 44 patients were enrolled. Forty-three patients underwent surgery, and 41 patients completed the scheduled treatment. Pathologic complete remission (pCR) was noted in 9 patients (20.9%). T down-staging and N down-staging were observed in 32 patients (74.4%) and 33 patients (76.7%), respectively. Grade 3 to 5 toxicity was noted in 5 patients (11.4%). The pCR rate was similar with the pCR rates obtained after conventional NCRT at our institute and at other institutes.

Conclusion

This study showed that additional 4-week chemotherapy with capecitabine during the resting periods after 6-week NCRT was safe, but it was no more effective than conventional NCRT.

Stomach cancer risk after treatment for hodgkin lymphoma

PURPOSE

Treatment-related stomach cancer is an important cause of morbidity and mortality among the growing number of Hodgkin lymphoma (HL) survivors, but risks associated with specific HL treatments are unclear.

PATIENTS AND METHODS

We conducted an international case-control study of stomach cancer nested in a cohort of 19,882 HL survivors diagnosed from 1953 to 2003, including 89 cases and 190 matched controls. For each patient, we quantified cumulative doses of specific alkylating agents (AAs) and reconstructed radiation dose to the stomach tumor location.

RESULTS

Stomach cancer risk increased with increasing radiation dose to the stomach (Ptrend < .001) and with increasing number of AA-containing chemotherapy cycles (Ptrend = .02). Patients who received both radiation to the stomach ≥ 25 Gy and high-dose procarbazine (≥ 5,600 mg/m(2)) had strikingly elevated stomach cancer risk (25 cases, two controls; odds ratio [OR], 77.5; 95% CI, 14.7 to 1452) compared with those who received radiation < 25 Gy and procarbazine < 5,600 mg/m(2) (Pinteraction < .001). Risk was also elevated (OR, 2.8; 95% CI, 1.3 to 6.4) among patients who received radiation to the stomach ≥ 25 Gy but procarbazine < 5,600 mg/m(2); however, no procarbazine-related risk was evident with radiation < 25 Gy. Treatment with dacarbazine also increased stomach cancer risk (12 cases, nine controls; OR, 8.8; 95% CI, 2.1 to 46.6), after adjustment for radiation and procarbazine doses.

CONCLUSION

Patients with HL who received subdiaphragmatic radiotherapy had dose-dependent increased risk of stomach cancer, with marked risks for patients who also received chemotherapy containing high-dose procarbazine. For current patients, risks and benefits of exposure to both procarbazine and subdiaphragmatic radiotherapy should be weighed carefully. For patients treated previously, GI symptoms should be evaluated promptly.

The status of targeted agents in the setting of neoadjuvant radiation therapy in locally advanced rectal cancers

Radiotherapy has a longstanding and well-defined role in the treatment of resectable rectal cancer to reduce the historically high risk of local recurrence. In more advanced borderline or unresectable cases, where the circumferential resection margin (CRM) is breached or threatened according to magnetic resonance imaging (MRI), despite optimized local multimodality treatment and the gains achieved by modern high quality total mesorectal excision (TME), at least half the patients fail to achieve sufficient downstaging with current schedules. Many do not achieve an R0 resection. In less locally advanced cases, even if local control is achieved, this confers only a small impact on distant metastases and a significant proportion of patients (30-40%) still subsequently develop metastatic disease. In fact, distant metastases have now become the predominant cause of failure in rectal cancer. Therefore, increasing the intensity and efficacy of chemotherapy and chemoradiotherapy by integrating additional cytotoxics and biologically targetted agents seems an appealing strategy to explore-with the aim of enhancing curative resection rates and improving distant control and survival. However, to date, we lack validated biomarkers for these biological agents apart from wild-type KRAS. For cetuximab, the appearance of an acneiform rash is associated with response, but low levels of magnesium appear more controversial. There are no molecular biomarkers for bevacizumab. Although some less invasive clinical markers have been proposed for bevacizumab, such as circulating endothelial cells (CECS), circulating levels of VEGF and the development of overt hypertension, these biomarkers have not been validated and are observed to emerge only after a trial of the agent. We also lack a simple method of ongoing monitoring of 'on target' effects of these biological agents, which could determine and pre-empt the development of resistance, prior to radiological and clinical assessessments or even molecular imaging. These shortcomings probably explain our current relative lack of success in the arena of combining these agents with chemoradiation.

Aspiration in head and neck cancer patients: a single centre experience of clinical profile, bacterial isolates and antibiotic sensitivity pattern

Most patients with head and neck cancer have dysphagia and are at increased risk of having aspiration and subsequent pneumonia. It can cause prolonged hospitalization, treatment delay and/or interruption and mortality in cancer patients. The treatment of these infections often relies on empirical antibiotics based on local microbiology and antibiotic sensitivity patterns. The aim of present study is to analyse respiratory tract pathogens isolated by sputum culture in head and neck cancer patients undergoing treatment at a tertiary cancer centre in South India who presented with features of aspiration. The study is carried out to establish empirical antibiotic policy for head and neck cancer patients who present with features of aspiration. This was a retrospective study. The study included sputum samples sent for culture and sensitivity from January 2011 to December 2012. Analysis of microbiologic species isolated in sputum specimen and the antibiotic sensitivity pattern of the bacterial isolates was performed. A detailed study of case files of all patients was done to find out which is the most common site prone for producing aspiration. There were 47 (31.54 %) gram positive isolates and 102 (68.45 %) gram negative isolates. The most common bacterial isolates were Klebsiella pneumoniae (25.50 %), Pseudomonas aeruginosa (16.77 %) and Haemophilus influenzae (15.43 %). Levofloxacin was the most effective antibiotic with excellent activity against both gram positive and gram negative isolates. Most patients with aspiration had laryngeal cancer (34.89 %). Aspiration pneumonia was present in 14 (9.39 %) patients. Gram negative bacteria are common etiologic agents in head and neck cancer patients presenting with features of aspiration. Levofloxacin should be started as empirical antibiotic in these patients while awaiting sputum culture sensitivity report. As aspiration in head and neck cancer is an underreported event such institutional antibiotic sensitivity studies should be encouraged for prompt initiation of antibiotic that is most likely to be effective against etiologic pathogens.

Sensitization of tumor to ²¹²Pb radioimmunotherapy by gemcitabine involves initial abrogation of G2 arrest and blocked DNA damage repair by interference with Rad51

PURPOSE

To elucidate the mechanism of the therapeutic efficacy of targeted α-particle radiation therapy using (212)Pb-TCMC-trastuzumab together with gemcitabine for treatment of disseminated peritoneal cancers.

METHODS AND MATERIALS

Mice bearing human colon cancer LS-174T intraperitoneal xenografts were pretreated with gemcitabine, followed by (212)Pb-TCMC-trastuzumab and compared with controls.

RESULTS

Treatment with (212)Pb-TCMC-trastuzumab increased the apoptotic rate in the S-phase-arrested tumors induced by gemcitabine at earlier time points (6 to 24 hours). (212)Pb-TCMC-trastuzumab after gemcitabine pretreatment abrogated G2/M arrest at the same time points, which may be associated with the inhibition of Chk1 phosphorylation and, in turn, cell cycle perturbation, resulting in apoptosis. (212)Pb-TCMC-trastuzumab treatment after gemcitabine pretreatment caused depression of DNA synthesis, DNA double-strand breaks, accumulation of unrepaired DNA, and down-regulation of Rad51 protein, indicating that DNA damage repair was blocked. In addition, modification in the chromatin structure of p21 may be associated with transcriptionally repressed chromatin states, indicating that the open structure was delayed at earlier time points.

CONCLUSION

These findings suggest that the cell-killing efficacy of (212)Pb-TCMC-trastuzumab after gemcitabine pretreatment may be associated with abrogation of the G2/M checkpoint, inhibition of DNA damage repair, and chromatin remodeling.

The crystal structure analysis of the relative binding of cisplatin and carboplatin in a mixture with histidine in a protein studied at 100 and 300 K with repeated X-ray irradiation

The anticancer agents cisplatin and carboplatin bind to histidine in a protein. This crystal structure study at data-collection temperatures of 100 and 300 K examines their relative binding affinities to a histidine side chain and the effect of a high X-ray radiation dose of up to ∼1.8 MGy on the stability of the subsequent protein-Pt adducts. Cisplatin binding is visible at the histidine residue, but carboplatin binding is not. Five refined X-ray crystal structures are presented: one at 100 K as a reference and four at 300 K. The diffraction resolutions are 1.8, 2.0, 2.8, 2.9 and 3.5 Å.

Effects of ionizing radiation in combination with Erufosine on T98G glioblastoma xenograft tumours: a study in NMRI nu/nu mice

Background

Erufosine is a promising anticancer drug that increases the efficacy of radiotherapy in glioblastoma cell lines in vitro. Moreover, treatment of nude mice with repeated intraperitoneal or subcutaneous injections of Erufosine is well tolerated and yields drug concentrations in the brain tissue that are higher than the concentrations required for cytotoxic drug effects on glioblastoma cell lines in vitro.

Methods

In the present study we aimed to evaluate the effects of a combined treatment with radiotherapy and Erufosine on growth and local control of T98G subcutaneous glioblastoma xenograft-tumours in NMRI nu/nu mice.

Results

We show that repeated intraperitoneal injections of Erufosine resulted in a significant drug accumulation in T98G xenograft tumours on NMRI nu/nu mice. Moreover, short-term treatment with 5 intraperitoneal Erufosine injections caused a transient decrease in the growth of T98G tumours without radiotherapy. Furthermore, an increased radiation-induced growth delay of T98G xenograft tumours was observed when fractionated irradiation was combined with short-term Erufosine-treatment. However, no beneficial drug effects on fractionated radiotherapy in terms of local tumour control were observed.

Conclusions

We conclude that short-term treatment with Erufosine is not sufficient to significantly improve local control in combination with radiotherapy in T98G glioblastoma xenograft tumours. Further studies are needed to evaluate efficacy of extended drug treatment schedules.

Current status of intensified neo-adjuvant systemic therapy in locally advanced rectal cancer

The addition of 5-fluorouracil (5-FU) or its prodrug capecitabine to radiotherapy (RT) is a standard approach in the neo-adjuvant treatment of patients with rectal tumors extending beyond the muscularis propria (stage II) and/or with clinical evidence of regional lymph node metastases (stage III). According to European randomized trials, the combined treatment modality resulted in favorable local control rates as compared with radiotherapy (RT) alone, but no improvement was found regarding the occurrence of distant metastases or overall survival. In an effort to further enhance the response rates and to decrease the high incidence of distant metastases in locally advanced rectal cancer patients, the addition of other chemotherapeutical drugs and biologic agents as radiation sensitizers to neo-adjuvant 5-FU based chemoradiotherapy (CRT) has been recently investigated. The role of those agents is however questionable as first results from phase III data do not show improvement on pathologic complete remission and circumferential resection margin negative resection rates as compared to 5-FU based CRT, nevertheless an increased toxicity.

Oxaliplatin as a radiosensitiser for upper and lower gastrointestinal tract malignancies: what have we learned from a decade of translational research?

Some of the greatest advances in the treatment of solid malignancies have resulted from the combination of chemotherapy and radiotherapy treatments. This article comprehensively reviews the current clinical evidence for oxaliplatin-based chemo-radiotherapy that may improve local control and survival. In order to understand how clinical studies should be designed, the pre-clinical evidence for the use of oxaliplatin chemotherapy as a radiosensitising agent is appraised. Particular focus is placed on oxaliplatin's biological mechanisms of action, including cell cycle effects, the formation of DNA adducts and interstrand cross-links and the role of DNA repair proteins. At a clinical level, there is currently no evidence to suggest that oxaliplatin provides an additional benefit to concurrent chemo-radiation regimes that utilise fluoropyrimidines; we evaluate the reasons for this observation, the limitations of clinical trial design and the opportunities that currently exist to design clinical trials which are underpinned by an understanding of the basic biology.

Failure to adhere to protocol specified radiation therapy guidelines was associated with decreased survival in RTOG 9704--a phase III trial of adjuvant chemotherapy and chemoradiotherapy for patients with resected adenocarcinoma of the pancreas

PURPOSE

In Radiation Therapy Oncology Group 9704, as previously published, patients with resected pancreatic adenocarcinoma received continuous infusion 5-FU and concurrent radiotherapy (5FU-RT). 5FU-RT treatment was preceded and followed by randomly assigned chemotherapy, either 5-FU or gemcitabine. This analysis explored whether failure to adhere to specified RT guidelines influenced survival and/or toxicity.

METHODS AND MATERIALS

RT requirements were protocol specified. Adherence was scored as per protocol (PP) or less than per protocol (

RESULTS

RT was scored for 416 patients: 216 PP and 200

CONCLUSIONS

This is the first Phase III, multicenter, adjuvant protocol for pancreatic adenocarcinoma to evaluate the impact of adherence to specified RT protocol guidelines on protocol outcomes. Failure to adhere to specified RT guidelines was associated with reduced survival and, for patients receiving gemcitabine, trend toward increased nonhematologic toxicity.

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Key Words

• radiotherapy
• quality assurance
• pancreatic adenocarcinoma
• adjuvant therapy
• chemoradiotherapy

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MESH Headings

• Adenocarcinoma/mortality
• Adenocarcinoma/pathology
• Adenocarcinoma/therapy
• Adult
• Aged
• Aged, 80 and over
• Antimetabolites, Antineoplastic/therapeutic use
• Chemoradiotherapy/adverse effects
• Chemoradiotherapy/methods
• Chemotherapy, Adjuvant/adverse effects
• Deoxycytidine/adverse effects
• Deoxycytidine/analogs & derivatives
• Deoxycytidine/therapeutic use
• Female
• Fluorouracil/adverse effects
• Fluorouracil/therapeutic use
• Guideline Adherence
• Humans
• Male
• Middle Aged
• Multivariate Analysis
• Pancreatic Neoplasms/mortality
• Pancreatic Neoplasms/pathology
• Pancreatic Neoplasms/therapy
• Survival Analysis
• Gemcitabine

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Grants

• UL1 RR025741 NCRR NIH HHS
• CA21661 NCI NIH HHS
• U10 CA021661 NCI NIH HHS
• U10 CA037422 NCI NIH HHS
• CA37422 NCI NIH HHS

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Affiliation(s)

Ross A. Abrams Rush University Medical Center, Chicago, IL
Kathryn A. Winter Radiation Therapy Oncology Group Statistical Center, Philadelphia, PA
William F. Regine University of Maryland, Baltimore, MD
Howard Safran Brown University, Providence, RI
John P. Hoffman Fox Chase Cancer Center, Philadelphia, PA
Robert Lustig Radiation Therapy Oncology Group Statistical Center, Philadelphia, PA
Andre A. Konski Wayne State Medical Center, Detroit, MI
Al B. Benson Northwestern University, Chicago, IL
John S. Macdonald St. Vincent's Cancer Care Center, New York, NY
Tyvin A. Rich University of Virginia, Charlottesville, VA
Christopher G. Willett Duke University, Durham, NC

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Collaborators Collapse

Can drugs enhance hypofractionated radiotherapy? A novel method of modeling radiosensitization using in vitro data

PURPOSE

Hypofractionated radiotherapy (hRT) is being explored for a number of malignancies. The potential benefit of giving concurrent chemotherapy with hRT is not known. We sought to predict the effects of combined modality treatments by using mathematical models derived from laboratory data.

METHODS AND MATERIALS

Data from 26 published clonogenic survival assays for cancer cell lines with and without the use of radiosensitizing chemotherapy were collected. The first three data points of the RT arm of each assay were used to derive parameters for the linear quadratic (LQ) model, the multitarget (MT) model, and the generalized linear quadratic (gLQ) model. For each assay and model, the difference between the predicted and observed surviving fractions at the highest tested RT dose was calculated. The gLQ model was fitted to all the data from each RT cell survival assay, and the biologically equivalent doses in 2-Gy fractions (EQD2s) of clinically relevant hRT regimens were calculated. The increase in cell kill conferred by the addition of chemotherapy was used to estimate the EQD2 of hRT along with a radiosensitizing agent. For comparison, this was repeated using conventionally fractionated RT regimens.

RESULTS

At a mean RT dose of 8.0 Gy, the average errors for the LQ, MT, and gLQ models were 1.63, 0.83, and 0.56 log units, respectively, favoring the gLQ model (p < 0.05). Radiosensitizing chemotherapy increased the EQD2 of hRT schedules by an average of 28% to 82%, depending on disease site. This increase was similar to the gains predicted for the addition of chemotherapy to conventionally fractionated RT.

CONCLUSIONS

Based on published in vitro assays, the gLQ equation is superior to the LQ and MT models in predicting cell kill at high doses of RT. Modeling exercises demonstrate that significant increases in biologically equivalent dose may be achieved with the addition of radiosensitizing agents to hRT. Clinical study of this approach is warranted.

Chemoradiation therapy in the management of gastrointestinal malignancies

Concurrent administration of chemotherapy and radiotherapy has been increasingly used in cancer treatment, leading to improvements in survival as well as quality of life. Currently, it is a feasible preference, often regarded as the standard therapeutic option, for many locally confined solid tumors, including anal, bladder, cervical, esophageal, gastric, head and neck, lung, pancreatic and rectal cancers. In patients with these tumors, combined modality therapy improves local tumor control and survival while, in some instances, obviating the need for surgical removal of the organ of origin. The scientific rationale for the use of chemoradiation derives from the preclinical and clinical observations of synergistic interactions between radiotherapy and chemotherapy. When chemotherapy and radiotherapy are administered together, the chemotherapeutic agents can sensitize the cancer cells to the effects of ionizing radiation, leading to increased tumor-killing effects within the radiotherapy field. This, in turn, can improve local control of the primary tumor and, in some cancers, render surgical resection unnecessary. In other cases, patients with tumors that were initially considered unresectable are able to undergo curative interventions after completing chemoradiation. The chemotherapy component can address any potential micrometastatic disease that, without therapy, leads to an increased risk of distant recurrence. A large body of evidence exists that supports the use of chemoradiotherapy in gastrointestinal cancers. In fact, one of the first tumor types in which the superior efficacy of chemoradiation was described was anal cancer. Since then, chemoradiotherapy has been explored in other gastrointestinal malignancies with superior outcomes when compared with either radiation or chemotherapy alone. This article aims to recapitulate the clinical evidence supporting the use of chemoradiotherapy in a variety of gastrointestinal tumor types.

Combination radioimmunotherapy and chemoimmunotherapy involving different or the same targets improves therapy of human pancreatic carcinoma xenograft models

Chemoimmunotherapy with antibody-drug conjugates (ADC) is emerging as a promising therapy for solid tumors, whereas radioimmunotherapy (RAIT) of solid tumors has been relatively ineffective because of their resistance to radiation. We developed antibody-SN-38 conjugates that have significant antitumor activity in xenograft models at nontoxic doses. The goal of this study was to determine if an ADC could be combined with RAIT to enhance efficacy without a commensurate increase in host toxicity. Nude mice bearing human pancreatic cancer xenografts (Capan-1 and BxPC-3) were treated with a single dose of 90Y-labeled antimucin antibody (hPAM4; clivatuzumab tetraxetan) alone or in combination with an anti-Trop-2-SN-38 conjugate, typically administered twice weekly over 4 weeks. The combination, even at RAIT's maximum tolerated dose, controlled tumor progression and cured established xenografts significantly better than the individual treatments without appreciable toxicity. The ADC could be started 1 week after or up to 2 weeks before RAIT with similar enhanced responses, but delaying RAIT for 2 weeks after the ADC was less effective. A nonspecific ADC provided additional benefit over using free drug (irinotecan), but the response was enhanced with the specific ADC. When targeting Capan-1 with ample mucin, hPAM4 could be used as the RAIT and the ADC agent without losing effectiveness, but in BxPC-3 with less mucin, targeting of different antigens was preferred. These studies show the feasibility of combining ADC and RAIT for improved efficacy without increased toxicity.

Radiosensitization of human breast cancer cells to ultraviolet light by 5-fluorouracil

Ultraviolet light B (UVB) phototherapy is widely used to treat dermatological diseases and therefore may be a potential optional strategy in the treatment of a skin lesion infiltrated by a malignant tumor. Currently, little is known regarding the effect of UVB phototherapy on human breast cancer cells. The present study aimed to investigate the effect of UVB phototherapy, as well as the potential effect of 5-fluorouracil (5-FU), the first-line anticancer drug for breast cancer, on radiosensitizing MCF-7 human breast cancer cells, in an attempt to develop new therapeutic strategies for the treatment of locoregional recurrence of breast cancer. MCF-7 cells were incubated in the presence of 5-FU for 48 h, and UVB irradiation at 750 mJ/cm(2) was administered in the midterm of 5-FU treatment. The viability of MCF-7 cells was analyzed by the trypan blue staining method. Apoptosis was quantified by flow cytometry and Hoechst 33258 staining. The cell cycle was evaluated by flow cytometry after the staining of cells with propidium iodide. The combination treatment of 5-FU and UVB resulted in a strong potentiation of the inhibitory effect of MCF-7 cell growth, dependent on the intra-S phase cell cycle arrest and induction of apoptosis, when compared to treatment with 5-FU or UVB alone. In conclusion, 5-FU sensitized human breast cancer cells to UVB phototherapy, and this combination therapy is an effective and promising strategy for the treatment of breast cancer, particularly for locoregional recurrence.

Cyclopentenylcytosine does not enhance cisplatin-induced radiosensitization in human lung tumour cells

The search for agents that enhance the effect of ionizing radiation has been an object of study for decades. In this study, the sensitizing properties of cyclopentenylcytosine (CPEC) on radiation and cisplatin-induced radiosensitization in human squamous lung carcinoma cells were investigated. Human lung tumour SW-1573 cells (SWp, parental; SWg, gemcitabine-resistant) were incubated with CPEC and cisplatin and subsequently irradiated with different doses of γ-rays. Clonogenic survival was determined to measure the effectiveness of the treatments. CPEC (1 or 2 μM) treatment for 4 h decreased the plating efficiency to 75 and 50% in SWp and SWg cells, respectively. In the SWg cells, 0.1 and 1 μM CPEC for 4 h enhanced the cell killing effect of cisplatin. However, an increase was not noted in the SWp cells. Due to the moderate toxicity of 1 μM for 4 h, this CPEC dose was used in the radiosensitization experiments. However, CPEC neither radiosensitized the lung tumour cells nor enhanced the radiosensitizing effect of cisplatin. A 2-h incubation with 4 μM cisplatin also decreased the plating efficiency to 75-80% in the two cell lines. Using this cisplatin dose, radiosensitization was obtained in the two cell lines. Although cisplatin treatment clearly radiosensitized the lung tumour cells, CPEC treatment did not. Cisplatin-induced radiosensitization was also not enhanced by CPEC.

Cetuximab and chemoradiation for rectal cancer--is the water getting muddy?

The epidermal growth factor receptor (EGFR) inhibitor cetuximab has been successfully combined with radical radiotherapy in head and neck cancer. In colorectal cancer, increased response rates are achieved by cetuximab and panitumumab within standard chemotherapy schedules, but not in chemoradiation regimens. This review examines the clinical evidence and potential mechanisms for an interaction when EGFR inhibitors are added to fluoropyrimidine-based chemoradiation in rectal adenocarcinoma.

METHODS

This review was compiled by searching PubMed and Medline for English language articles published until 2009 with established search strategies, supplemented by hand searching of abstracts from the proceedings of relevant international meetings. The primary outcome measure was pathological complete response (pCR).

RESULTS

Only 13 publications and three presentations in abstract of 13 phase I/II trials of preoperative chemoradiation with cetuximab in rectal cancer were identified. A total of 316 patients were identified who received cetuximab in combination with radiotherapy and 5-fluorouracil or capecitabine preoperatively. One hundred and thirty eight of these patients received either additional irinotecan or oxaliplatin. One study with panitumumab with safety but no efficacy results was identified, and two studies with gefinitib. The pCR rate ranged from 0-20%. The overall pooled pCR for cetuximab based chemoradiation was 9.1% (29/316). The rate of G3/G4 gastrointestinal toxicity, in terms of diarrhoea, varied from 5-30%, with an overall pooled rate of 47/313 (15%).

DISCUSSION

Potential reasons for the disappointing results of EGFR inhibition with fluoropyrimidine-based preoperative chemoradiation include a less critical role of repopulation in rectal adenocarcinoma using a non-curative radiation dose; or antagonistic effects on 5FU-based chemoradiation and oxaliplatin, if some cells arrest in G1 or G2-M and fail to pass through S phase.

CONCLUSION

Cetuximab combined with fluoropyrimidine-based chemoradiation is not currently recommended. A better understanding of the mechanisms involved in combinations of chemotherapy and radiotherapy might allow more effective future scheduling of biological and chemical agents in combination with radiation.

Methotrexate, paclitaxel, and doxorubicin radiosensitize HER2-amplified human breast cancer cells to the Auger electron-emitting radiotherapeutic agent (111)In-NLS-trastuzumab

Our goal in this study was to elucidate the mechanisms by which methotrexate radiosensitizes HER2-positive human breast cancer cells to the Auger electron emitter (111)In-trastuzumab modified with nuclear-localization sequence peptides ((111)In-NLS-trastuzumab) and to compare these mechanisms with the potential sensitizing effects of paclitaxel and doxorubicin when combined with this radiopharmaceutical.

METHODS

Experiments were performed in MDA-MB-231 human breast cancer cells, their HER2-transfected subclones (231-H2N), and 2 trastuzumab-resistant variants (trastuzumab-resistant-1 and -2 [TrR1 and TrR2]). Effects of coexposure of these cells to (111)In-NLS-trastuzumab and low-dose, radiosensitizing methotrexate, paclitaxel, or doxorubicin were assessed by clonogenic cell-survival assay. Quantification of residual DNA damage was measured by the gammaH2AX-immunofluorescence assay, and cell cycle distribution was measured by fluorescence-activated cell sorting analysis. The radiation-enhancement ratio was calculated as the ratio of the surviving fraction (SF) of cells treated with (111)In-NLS-trastuzumab alone to that of cells treated concurrently with (111)In-NLS-trastuzumab and methotrexate, paclitaxel, or doxorubicin.

RESULTS

A reduction in the SF in HER2-positive 231-H2N (55.7% +/- 1.3%) and TrR1 (62.6% +/- 6.5%) cells was demonstrated after exposure to (111)In-NLS-trastuzumab (approximately 0.2 MBq/microg, 100 nmol/L) but not in MDA-MB-231 or TrR2 cells expressing low levels of HER2 (SF > 90%, P > 0.05). Coadministration of methotrexate, paclitaxel, or doxorubicin enhanced the cytotoxicity of (111)In-NLS-trastuzumab toward 231-H2N and TrR1 cells but not toward MDA-MB-231 or TrR2 cells. The radiation-enhancement ratios for methotrexate, paclitaxel, and doxorubicin for 231-H2N or TrR1 cells were 2.0-2.2, 1.6-1.8, and 2.7-2.8, respectively. Methotrexate or doxorubicin combined with (111)In-NLS-trastuzumab, compared to treatment with (111)In-NLS-trastuzumab alone, significantly increased residual gammaH2AX foci in 231-H2N and TrR1 cells but not in MDA-MB-231 or TrR2 cells or in any cell line treated concurrently with paclitaxel and (111)In-NLS-trastuzumab. Cells exposed to low-dose methotrexate accumulated in the G(1)/S phase of the cell cycle, whereas low-dose paclitaxel or doxorubicin caused cells to arrest in the G(2)/M phase.

CONCLUSION

Low-dose methotrexate, paclitaxel, or doxorubicin potently sensitized HER2-overexpressing human breast cancer cells, with and without acquired trastuzumab-resistance, to the Auger electron emissions from (111)In-NLS-trastuzumab through cell cycle distribution changes and in part through the inhibitory effects of these agents on DNA damage repair.

Novel 4,4'-diether-2,2'-bipyridine cisplatin analogues are more effective than cisplatin at inducing apoptosis in cancer cell lines

The synthesis and characterization of dichloro(4,4'-bis[methoxy]-2,2'-bipyridine)platinum (1) and dichloro(4,4'-bis[3-methoxy-n-propyl]-2,2'-bipyridine)platinum (2) are described. As analogues to CDDP, these 4,4'-disubstituted 2,2'-bipyridine complexes exhibit decreased EC(50) values of 10-100 times in cancer cell lines of the lung, prostate, and melanoma with several combinations of complex and cell line less than 10 microM. Flow cytometry data indicate 'blocks' of MDA-MD-435 cycle by 1 (G2/M) and 2 (S). Observed cell survival trends in the presence of 1, 2 under ionizing radiation mimic those of CDDP. Preliminary structure activity relationships are discussed for the 4,4'-substitutions made on the bipyridine ring.

Stochastic modelling of the role of cisplatin in altered fractionation schedules for head and neck cancer

Advanced head and neck cancers are one of the most challenging cancers facing the oncologists due to their aggressiveness attributable to the high hypoxic content and the tumour's ability to repopulate during radiotherapy. Alterations of radiotherapy fractionation schedules are possible ways to improve tumour control. Clinical trials have shown that both hyperfractionated radiotherapy (multiple fractions a day, over the same treatment time), and accelerated radiotherapy (higher doses per fraction, six days a week, over 5 weeks or less) are more effective than conventional radiotherapy in the management of head and neck cancer. However, the treatment choice between hyperfractionated and accelerated radiotherapy is still debated, due to very similar results obtained regarding tumour control. Furthermore, while radiotherapy alone has an impact on the short-term prognosis of advanced head and neck cancer, the long-term benefits have been moderate. Cisplatin is a chemotherapeutic agent which combined with conventional radiotherapy has shown to improve patient survival. The present paper employs a Monte Carlo modelling approach in assessing the effect of combined cisplatin-altered fractionation schedule on tumour response. The growth of a head and neck carcinoma has been modelled using probabilistic functions sampled by computer generated random number sequences, maintaining the biological constitution of a tumour. The tumour growth model has been built to simulate the in vivo processes taking place before and after radiotherapy/chemotherapy. The model has shown that adding cisplatin to radiotherapy improves tumour control in both hyperfractionated and accelerated radiotherapy.

Pharmacokinetics and biodistribution of Erufosine in nude mice--implications for combination with radiotherapy

BACKGROUND

Alkylphosphocholines represent promising antineoplastic drugs that induce cell death in tumor cells by primary interaction with the cell membrane. Recently we could show that a combination of radiotherapy with Erufosine, a paradigmatic intravenously applicable alkylphosphocholine, in vitro leads to a clear increase of irradiation-induced cell death. In view of a possible combination of Erufosine and radiotherapy in vivo we determined the pharmacokinetics and bioavailability as well as the tolerability of Erufosine in nude mice.

METHODS

NMRI (nu/nu) nude mice were treated by intraperitoneal or subcutaneous injections of 5 to 40 mg/kg body weight Erufosine every 48 h for one to three weeks. Erufosine-concentrations were measured in brain, lungs, liver, small intestine, colon, spleen, kidney, stomach, adipoid tissue, and muscle by tandem-mass spectroscopy. Weight course, blood cell count and clinical chemistry were analyzed to evaluate general toxicity.

RESULTS

Intraperitoneal injections were generally well tolerated in all dose groups but led to a transient loss of the bodyweight (<10%) in a dose dependent manner. Subcutaneous injections of high-dose Erufosine caused local reactions at the injection site. Therefore, this regimen at 40 mg/kg body weight Erufosine was stopped after 14 days. No gross changes were observed in organ weight, clinical chemistry and white blood cell count in treated compared to untreated controls except for a moderate increase in lactate dehydrogenase and aspartate-aminotransferase after intensive treatment. Repeated Erufosine injections resulted in drug-accumulation in different organs with maximum concentrations of about 1000 nmol/g in spleen, kidney and lungs.

CONCLUSION

Erufosine was well tolerated and organ-concentrations surpassed the cytotoxic drug concentrations in vitro. Our investigations establish the basis for a future efficacy testing of Erufosine in xenograft tumor models in nude mice alone and in combination with chemo- or radiotherapy.

Radiosensitizing effects of temozolomide observed in vivo only in a subset of O6-methylguanine-DNA methyltransferase methylated glioblastoma multiforme xenografts

PURPOSE

Concurrent temozolomide (TMZ) and radiation therapy (RT) followed by adjuvant TMZ is standard treatment for patients with glioblastoma multiforme (GBM), although the relative contribution of concurrent versus adjuvant TMZ is unknown. In this study, the efficacy of TMZ/RT was tested with a panel of 20 primary GBM xenografts.

METHODS AND MATERIALS

Mice with intracranial xenografts were treated with TMZ, RT, TMZ/RT, or placebo. Survival ratio for a given treatment/line was defined as the ratio of median survival for treatment vs. placebo.

RESULTS

The median survival ratio was significantly higher for O6-methylguanine-DNA methyltransferase (MGMT) methylated tumors versus unmethylated tumors following treatment with TMZ (median survival ratio, 3.6 vs. 1.5, respectively; p = 0.008) or TMZ/RT (5.7 vs. 2.3, respectively; p = 0.001) but not RT alone (1.7 vs. 1.6; p = 0.47). In an analysis of variance, MGMT methylation status and p53 mutation status were significantly associated with treatment response. When we analyzed the additional survival benefit conferred specifically by combined therapy, only a subset (5 of 11) of MGMT methylated tumors derived substantial additional benefit from combined therapy, while none of the MGMT unmethylated tumors did. Consistent with a true radiosensitizing effect of TMZ, sequential treatment in which RT (week 1) was followed by TMZ (week 2) proved significantly less effective than TMZ followed by RT or concurrent TMZ/RT (survival ratios of 4.0, 9.6 and 12.9, respectively; p < 0.0001).

CONCLUSIONS

Concurrent treatment with TMZ and RT provides significant survival benefit only in a subset of MGMT methylated tumors and provides superior antitumor activity relative to sequential administration of RT and TMZ.

A review of risk factors and genetic alterations in head and neck carcinogenesis and implications for current and future approaches to treatment

Head and neck cancer is the fifth most common cancer worldwide but the most common malignant disease site in central Asia. The treatment of head and neck cancer is one of the most challenging in clinical oncology because of the high content of hypoxic cells of the cancer which increases resistance to therapy and also because of the high capacity of the cancer to regrow during treatment. For unresectable tumours, radiotherapy and chemotherapy alone or more often in combination is the treatment of choice. The aim of this paper is to review current understanding of carcinogenesis of head and neck cancer in relation to predisposing risk factors in general and for specific sub-sites and how these risk factors interact with the main reported genetic alterations in the progression of the cancer. The implications of these changes in determining choice of therapy are also discussed from a brief historical perspective of the various treatment approaches of head and neck cancer.

The radiosensitizer 2-benzoyl-3-phenyl-6,7-dichloroquinoxaline 1,4-dioxide induces DNA damage in EMT-6 mammary carcinoma cells

Background

DCQ (2-benzoyl-3-phenyl-6,7-dichloroquinoxaline 1,4-dioxide), a synthetic quinoxaline 1,4-dioxide, enhances the cytotoxic effect of ionizing radiation (IR) in vivo and in vitro. We sought to clarify whether increased radiation-induced DNA damage, decreased rate of damage repair, and the generation of reactive oxygen species (ROS) contribute to DCQ enhancement of IR.

Methods

Murine mammary adenocarcinoma EMT-6 cells were treated with DCQ for 4 h before exposure to 10 Gy IR. Treated cells were monitored for modulations in cell cycle, induction of DNA damage, and generation of ROS.

Results

Combined DCQ and IR treatments (DCQ+IR) induced rapid cell-cycle arrests in EMT-6 cells, particularly in S and G₂/M phases. Alkaline comet assays revealed high levels of DNA damage in cells after exposure to DCQ+IR, consistent with damage-induced arrest. Unlike IR-only and DCQ-only treated cells, the damage induced by combined DCQ+IR was repaired at a slower rate. Combined treatment, compared to separate DCQ and IR treatments, activated DNA-protein kinase and induced more p-ATM, supporting a role for double strand breaks (DSBs), which are more toxic and difficult to repair than single strand breaks (SSBs). Contributing factors to DCQ radiosensitization appear to be the induction of ROS and DSBs.

Conclusion

Collectively, our findings indicate that radiosensitization by DCQ is mediated by DNA damage and decreased repair and that ROS are at least partially responsible.

Role of cell cycle in epidermal growth factor receptor inhibitor-mediated radiosensitization

Epidermal growth factor receptor (EGFR) inhibitors are increasingly used in combination with radiotherapy in the treatment of various EGFR-overexpressing cancers. However, little is known about the effects of cell cycle status on EGFR inhibitor-mediated radiosensitization. Using EGFR-overexpressing A431 and UMSCC-1 cells in culture, we found that radiation activated the EGFR and extracellular signal-regulated kinase pathways in quiescent cells, leading to progression of cells from G(1) to S, but this activation and progression did not occur in proliferating cells. Inhibition of this activation blocked S-phase progression and protected quiescent cells from radiation-induced death. To determine if these effects were caused by EGFR expression, we transfected Chinese hamster ovary (CHO) cells, which lack EGFR expression, with EGFR expression vector. EGFR expressed in CHO cells also became activated in quiescent cells but not in proliferating cells after irradiation. Moreover, quiescent cells expressing EGFR underwent increased radiation-induced clonogenic death compared with both proliferating CHO cells expressing EGFR and quiescent wild-type CHO cells. Our data show that radiation-induced enhancement of cell death in quiescent cells involves activation of the EGFR and extracellular signal-regulated kinase pathways. Furthermore, they suggest that EGFR inhibitors may protect quiescent tumor cells, whereas radiosensitization of proliferating cells may be caused by downstream effects such as cell cycle redistribution. These findings emphasize the need for careful scheduling of treatment with the combination of EGFR inhibitors and radiation and suggest that EGFR inhibitors might best be given after radiation in order to optimize clinical outcome.

Myelopathy After Radiation Therapy and Chemotherapy with Capecitabine and Gemcitabine

This article describes a woman with metastatic upper gastrointestinal cancer who developed thoracic myelopathy unexpectedly after standard dosage and fractionation radiotherapy. She also was receiving capecitabine and gemcitabine concomitantly. There are few reported cases of chemotherapy potentiation of spinal cord radiation toxicity. These agents are known radiosensitizers, making it likely that they contributed to this adverse outcome. As these agents are increasingly incorporated into clinical trials of combined therapy, caution will be necessary in both trial design and clinical management.

9-bromonoscapine-induced mitotic arrest of cigarette smoke condensate-transformed breast epithelial cells

In the present investigation, we determined the chemotherapeutic efficacy of 9-bromonoscapine (Br-Nos), a more potent noscapine analog, on MCF10A, spontaneously immortalized human normal breast epithelial cells and MCF10A-CSC3, cigarette smoke condensate (CSC)-transformed cells. The results from cytogenetic analysis showed that Br-Nos induced polyploidy and telomeric association in MCF10A-CSC3 cells, while MCF10A cells remained unaffected. Our immunofluorescence data further demonstrated that MCF10A-CSC3 cells were susceptible to mitotic catastrophe on exposure to Br-Nos and failed to recover after drug withdrawal. MCF10A-CSC3 cells exhibited Br-Nos-induced aberrant multipolar spindle formation, which irreversibly impaired the alignment of replicated chromosome to the equatorial plane and finally culminated in cell death. Although MCF10A cells upon Br-Nos treatment showed bipolar spindles with some uncongressed chromosomes, these cells recovered fairly well after drug withdrawal. Our flow-cytometry analysis data reconfirmed that MCF10A-CSC3 cells were more susceptible to cell death compared to MCF10A cells. Furthermore, our results suggest that decreased levels of cdc2/cyclin B1 and cdc2 kinase activity are responsible for Br-Nos-induced mitotic cell arrest leading to cell death in MCF10A-CSC3 cells. This study thus explores the underlying mechanism of Br-Nos-induced mitotic catastrophe in CSC-transformed MCF10A-CSC3 cells and its potential usefulness as a chemotherapeutic agent for prevention of cigarette smoke-induced breast cancer growth.

Chemotherapy synergizes with radioimmunotherapy targeting La autoantigen in tumors

BACKGROUND

To date, inefficient delivery of therapeutic doses of radionuclides to solid tumors limits the clinical utility of radioimmunotherapy. We aim to test the therapeutic utility of Yttrium-90 ((90)Y)-radio-conjugates of a monoclonal antibody, which we showed previously to bind specifically to the abundant intracellular La ribonucleoprotein revealed in dead tumor cells after DNA-damaging treatment.

METHODOLOGY/PRINCIPAL FINDINGS

Immunoconjugates of the DAB4 clone of the La-specific monoclonal antibody, APOMAB, were prepared using the metal chelator, 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA), and then radiolabeled with (90)Y. Mice bearing established subcutaneous tumors were treated with (90)Y-DOTA-DAB4 alone or after chemotherapy. Non-radiosensitizing cyclophosphamide/etoposide chemotherapy was used for the syngeneic EL4 lymphoma model. Radiosensitizing cisplatin/gemcitabine chemotherapy was used for the syngeneic Lewis Lung carcinoma (LL2) model, and for the xenograft models of LNCaP prostatic carcinoma and Panc-1 pancreatic carcinoma. We demonstrate the safety, specificity, and efficacy of (90)Y-DOTA-DAB4-radioimmunotherapy alone or combined with chemotherapy. EL4 lymphoma-bearing mice either were cured at higher doses of radioimmunotherapy alone or lower doses of radioimmunotherapy in synergy with chemotherapy. Radioimmunotherapy alone was less effective in chemo- and radio-resistant carcinoma models. However, radioimmunotherapy synergized with radiosensitizing chemotherapy to retard significantly tumor regrowth and so prolong the survival of mice bearing LL2, LNCaP, or Panc-1 subcutaneous tumor implants.

CONCLUSIONS/SIGNIFICANCE

We report proof-of-concept data supporting a unique form of radioimmunotherapy, which delivers bystander killing to viable cancer cells after targeting the universal cancer antigen, La, created by DNA-damaging treatment in neighboring dead cancer cells. Subsequently we propose that DAB4-targeted ionizing radiation induces additional cycles of tumor cell death, which further augments DAB4 binding to produce a tumor-lethal 'genotoxic chain reaction'. Clinically, this approach may be useful as consolidation treatment after a drug-induced cell death among (small-volume) metastatic deposits, the commonest cause of cancer death. This article is part II of a two-part series providing proof-of-concept for the diagnostic and therapeutic use of the DAB4 clone of the La-specific monoclonal antibody, APOMAB.

Improving gemcitabine-mediated radiosensitization using molecularly targeted therapy: a review

In the last three decades, gemcitabine has progressed from the status of a laboratory cytotoxic drug to a standard clinical chemotherapeutic agent and a potent radiation sensitizer. In an effort to improve the efficacy of gemcitabine, additional chemotherapeutic agents have been combined with gemcitabine (both with and without radiation) but with toxicity proving to be a major limitation. Therefore, the integration of molecularly targeted agents, which potentially produce less toxicity than standard chemotherapy, with gemcitabine radiation is a promising strategy for improving chemoradiation. Two of the most promising targets, described in this review, for improving the efficacy of gemcitabine radiation are epidermal growth factor receptor and checkpoint kinase 1.

Molecular chemotherapy of pancreatic cancer using novel mutant bacterial cytosine deaminase gene

The combination of molecular chemotherapy with radiation therapy has the potential to become a powerful approach for treatment of pancreatic cancer. We have developed an adenoviral vector (AdbCD-D314A) encoding a mutant bacterial cytosine deaminase (bCD) gene, which converts the prodrug 5-fluorocytosine (5-FC) into the active drug 5-fluorouracil. The aim of this study was to investigate AdbCD-D314A/5-FC-mediated cytotoxicity in vitro and therapeutic efficacy in vivo alone and in combination with radiation against human pancreatic cancer cells and xenografts. AdbCD-D314A/5-FC-mediated cytotoxicity alone and in combination with radiation was analyzed using crystal violet inclusion and clonogenic survival assays. CD enzyme activity was determined by measuring conversion of [3H]5-FC to [3H]5-fluorouracil after adenoviral infection of pancreatic cancer cells in vitro and pancreatic tumor xenografts by TLC. S.c. pancreatic tumor xenografts were used to evaluate the therapeutic efficacy of AdbCD-D314A/5-FC molecular chemotherapy in combination with radiation therapy. AdbCD-D314A infection resulted in increased 5-FC-mediated pancreatic cancer cell killing that correlated with significantly enhanced CD enzyme activity compared with AdbCDwt encoding wild-type of bCD. Animal studies showed significant inhibition of growth of human pancreatic tumors treated with AdbCD-D314A/5-FC in comparison with AdbCDwt/5-FC. Also, a significantly greater inhibition of growth of Panc2.03 and MIA PaCA-2 tumor xenografts was produced by the combination of AdbCD-D314A/5-FC with radiation compared with either agent alone. The results indicate that the combination of AdbCD-D314A/5-FC molecular chemotherapy with radiation therapy significantly enhanced cytotoxicity of pancreatic cancer cells in vitro and increased therapeutic efficacy against human pancreatic tumor xenografts.

In vivo efficacy of marimastat and chemoradiation in head and neck cancer xenografts

OBJECTIVE

To assess the effect of combining a synthetic matrix metalloprotease inhibitor and chemoradiation therapy on tumor growth in a murine model of head and neck squamous-cell carcinoma (SCC).

METHODS

Athymic, nude mice bearing SCC-1 xenografts were used to comprise 4 treatment groups: (1) control receiving vehicle alone, (2) marimastat alone, (3) cisplatin + radiation in combination and (4) marimastat + cisplatin + radiation in combination. The marimastat was administered at a dose of 8.7 mg/kg/day over a 14-day period via a subcutaneous osmotic pump. The control group received vehicle only via a subcutaneous osmotic pump. Radiotherapy was given in 4 fractions of 8 Gy divided over days 8, 12, 16 and 20 with 4 intraperitoneal doses of cisplatin (3 mg/kg) 1 h before each fraction of radiation.

RESULTS

Animals receiving triple treatment had delayed growth, measured as lengthened tumor doubling time, compared to the cisplatin + radiation combination (p = 0.03). Also, compared to control, the triple-treatment group (p = 0.005) had delayed growth in terms of doubling time. Factor VIII immunohistochemistry to assess microvessel density did not demonstrate a reduction in neovascularization between the triple-treatment and cisplatin + radiation combination groups. Statistical analysis failed to demonstrate any significant difference among groups.

CONCLUSIONS

Chemoradiation + marimastat therapy had delayed tumor growth, compared to the chemoradiation alone. Based on these results, marimastat may work in combination with chemotherapy and radiation to inhibit tumor growth.

Trastuzumab-resistant breast cancer cells remain sensitive to the auger electron-emitting radiotherapeutic agent 111In-NLS-trastuzumab and are radiosensitized by methotrexate

Our goals in this study were to determine whether (111)In-trastuzumab coupled to peptides harboring nuclear localizing sequences (NLSs) could kill trastuzumab-resistant breast cancer cell lines through the emission of Auger electrons and whether the combination of radiosensitization with methotrexate (MTX) would augment the cytotoxicity of this radiopharmaceutical.

METHODS

Trastuzumab was derivatized with sulfosuccinimidyl-4-(N-maleimidomethyl)cyclohexane-1-carboxylate for reaction with NLS peptides and then conjugated with diethylenetriaminepentaacetic acid for labeling with (111)In. HER2 expression was determined by Western blot and by radioligand binding assay using (111)In-trastuzumab in a panel of breast cancer cell lines, including SK-BR-3, MDA-MB-231 and its HER2-transfected subclone (231-H2N), and 2 trastuzumab-resistant variants (TrR1 and TrR2). Nuclear importation of (111)In-NLS-trastuzumab and (111)In-trastuzumab in breast cancer cells was measured by subcellular fractionation, and the clonogenic survival of these cells was determined after incubation with (111)In-NLS-trastuzumab, (111)In-trastuzumab, or trastuzumab (combined with or without MTX). Survival curves were analyzed according to the dose-response model, and the radiation-enhancement ratio was calculated from the survival curve parameters.

RESULTS

The expression of HER2 was highest in SK-BR-3 cells (12.6 x 10(5) receptors/cell), compared with 231-H2N and TrR1 cells (6.1 x 10(5) and 5.1 x 10(5) receptors/cell, respectively), and lowest in MDA-MB-231 and TrR2 cells (0.4 x 10(5) and 0.6 x 10(5) receptors/cell, respectively). NLS peptides increased the nuclear uptake of (111)In-trastuzumab in MDA-MB-231, 231-H2N, TrR1, and TrR2 cells from 0.1%+/-0.01%, 2.5%+/-0.2%, 2.8%+/-0.7%, and 0.5%+/-0.1% to 0.5%+/-0.1%, 4.6%+/-0.1%, 5.2%+/-0.6%, and 1.5%+/-0.2%, respectively. The cytotoxicity of (111)In-NLS-trastuzumab on breast cancer cells was directly correlated with the HER2 expression densities of the cells. On a molar concentration basis, the effective concentration required to kill 50% of 231-H2N and TrR1 cells for (111)In-NLS-trastuzumab was 9- to 12-fold lower than for (111)In-trastuzumab and 16- to 77-fold lower than for trastuzumab. MDA-MB-231 and TrR2 cells were less sensitive to (111)In-NLS-trastuzumab or (111)In-trastuzumab, and both cell lines were completely insensitive to trastuzumab. The radiation-enhancement ratio induced by MTX for 231-H2N and TrR1 cells after exposure to (111)In-NLS-trastuzumab was 1.42 and 1.68, respectively.

CONCLUSION

Targeted Auger electron radioimmunotherapy with (111)In-NLS-trastuzumab can overcome resistance to trastuzumab, and MTX can potently enhance the sensitivity of HER2-overexpressing breast cancer cells to the lethal Auger electrons emitted by this radiopharmaceutical.

A phase I study of gemcitabine plus palliative radiation therapy for advanced lung cancer

PURPOSE

To determine the maximum-tolerated dose (MTD) and antitumor activity of twice-weekly gemcitabine when combined with palliative-dose thoracic radiation therapy (RT) in patients with recurrent or progressive lung cancer.

METHODS

Patients were enrolled in a dose-escalating study of gemcitabine with a starting dose level of 40 mg/m(2) given as 30-minute infusions twice weekly concurrent with RT. The RT dose was 30 Gy in 10 fractions, 5 fractions per week.

RESULTS

A total of 18 patients were enrolled on three dose levels: 40, 50, and 65 mg/m(2). Four patients came off study early due to rapid progression of disease and therefore were not evaluated. The MTD of gemcitabine was found to be 50 mg/m(2). Dose-limiting toxicities were grade-4 esophagitis in one patient and grade-4 neutropenia in another patient. Overall response included 1 partial response (PR). Local response included six PR, four minor response (MR), three stable disease (SD), and one progressive disease (PD).

CONCLUSION

The MTD of gemcitabine with concominant palliative thoracic radiation therapy is 50 mg/m(2) twice weekly. The DLTs observed were grade-4 esophagitis and grade-4 myelotoxicity at 65 mg/m(2).

p53 signaling in response to increased DNA damage sensitizes AML1-ETO cells to stress-induced death

Chromosomal translocation (8;21) is present in 10% to 15% of patients with acute myeloid leukemia. Expression of the AML1-ETO (AE) fusion protein alone is not sufficient to induce leukemia, but the nature of the additional genetic alterations is unknown. It is unclear whether AE facilitates acquisition of these cooperating events. We show that AE down-regulates genes involved in multiple DNA repair pathways, potentially through a mechanism involving direct binding at promoter elements, and increases the mutation frequency in vivo. AE cells display increased DNA damage in vitro and have an activated p53 pathway. This results in increased basal apoptosis and enhanced sensitivity to DNA damaging agents. Intriguingly, microarray data indicate that t(8;21) patient samples exhibit decreased expression of DNA repair genes and increased expression of p53 response genes compared with other acute myeloid leukemia (AML) patient samples. Inhibition of the p53 pathway by RNAi increases the resistance of AE cells to DNA damage. We thus speculate that AML1-ETO may facilitate accumulation of genetic alterations by suppressing endogenous DNA repair. It is possible that the superior outcome of t(8;21) patients is partly due to an activated p53 pathway, and that loss of the p53 response pathway is associated with disease progression.

Antimetabolite radiosensitizers

Radiosensitization with antimetabolites has improved clinical outcome for patients with solid malignancies, especially cancers of the GI tract, cervix, and head and neck. Fluorouracil (FU) and hydroxyurea have been widely used clinically during the last four decades, and promising results have been observed more recently with gemcitabine. Although the antimetabolites all target DNA replication, they differ with respect to the mechanisms by which they produce radiosensitization. The antimetabolite radiosensitizers may inhibit thymidylate synthase (TS) or ribonucleotide reductase, and the nucleoside/nucleobase analogs can be incorporated into DNA. Radiosensitization can result from chemotherapy-induced increase in DNA double-strand breaks or inhibition of their repair. Studies of repair pathways involved in radiosensitization with antimetabolites implicate base excision repair with the TS inhibitors, homologous recombination with gemcitabine, and mismatch repair with FU and gemcitabine. Gemcitabine can also stimulate epidermal growth factor receptor (EGFR) phosphorylation; inhibiting this effect with EGFR inhibitors can potentiate cytotoxicity and radiosensitization. Additional work is necessary to determine more precisely the processes by which antimetabolites act as radiation sensitizers and to define the optimal sequencing of these agents with EGFR inhibitors to provide better guidance for clinical protocols combining these drugs with radiotherapy.

Identification and biological evaluation of a novel and potent small molecule radiation sensitizer via an unbiased screen of a chemical library

For patients with solid tumors, the tolerance of surrounding tissues often limits the dose of radiation that can be delivered. Thus, agents that preferentially increase the cytotoxic effects of radiation toward tumor cells would significantly alter the therapeutic ratio and improve patient survival. Using a high-throughput, unbiased screening approach, we have identified 4'-bromo-3'-nitropropiophenone (NS-123) as a radiosensitizer of human glioma cells in vitro and in vivo. NS-123 radiosensitized U251 glioma cells in a dose-dependent and time-dependent manner, with dose enhancement ratios ranging from 1.3 to 2.0. HT-29 colorectal carcinoma and A549 lung adenocarcinoma cells were also radiosensitized by NS-123 in vitro, whereas NS-123 did not increase the radiation sensitivity of normal human astrocytes or developmental abnormalities or lethality of irradiated Zebrafish embryos. In a novel xenograft model of U251 cells implanted into Zebrafish embryos, NS-123 enhanced the tumor growth-inhibitory effects of ionizing radiation (IR) with no apparent effect on embryo development. Similar results were obtained using a mouse tumor xenograft model in which NS-123 sensitized U251 tumors to IR while exhibiting no overt toxicity. In vitro pretreatment with NS-123 resulted in accumulation of unrepaired IR-induced DNA strand breaks and prolonged phosphorylation of the surrogate markers of DNA damage H2AX, ataxia telangiectasia mutated protein, DNA-dependent protein kinase, and CHK2 after IR, suggesting that NS-123 inhibits a critical step in the DNA repair pathway. These results show the potential of this cell-based, high-throughput screening method to identify novel radiosensitizers and suggest that NS-123 and similar nitrophenol compounds may be effective in antiglioma modalities.