Clinical study of a survivin long peptide vaccine (SurVaxM) in patients with recurrent malignant glioma.

Survivin is an anti-apoptotic protein that is highly expressed in many cancers, including malignant gliomas. Preclinical studies established that the conjugated survivin peptide mimic SurVaxM (SVN53-67/M57-KLH) could stimulate an anti-tumor immune response against murine glioma in vivo, as well as human glioma cells ex vivo. The current clinical study was conducted to test safety, immunogenicity and clinical effects of the vaccine. Recurrent malignant glioma patients whose tumors were survivin-positive, and who had either HLA-A*02 or HLA-A*03 MHC class I allele-positivity, were given subcutaneous injections of SurVaxM (500 µg) in Montanide ISA 51 with sargramostim (100 µg) at 2-week intervals. SurVaxM was well tolerated with mostly grade one adverse events (AE) and no serious adverse events (SAE) attributable to the study drug. Six patients experienced local injection site reactions; three patients reported fatigue (grades 1 and 2), and 2 patients experienced myalgia (grade 1). Six of eight immunologically evaluable patients developed both cellular and humoral immune responses to vaccine. The vaccine also stimulated HLA-A*02, HLA-A*03 and HLA-A*24 restricted T cell responses. Three patients maintained a partial clinical response or stable disease for more than 6 months. Median progression-free survival was 17.6 weeks, and median overall survival was 86.6 weeks from study entry with seven of nine patients surviving more than 12 months.

Analysis of factors influencing Dysphagia severity following treatment of head and neck cancer.

The aim was to assess the influence of treatment, tumor stages and sites on the severity of dysphagia following treatment. Sequential modified barium swallow (MBS) examinations were performed in patients who complained of chronic dysphagia following treatment of their head and neck cancer. Patients were selected if they were cancer free at their last MBS and had 2 or more MBS studies. Dysphagia severity was graded on a scale of 1 to 7. Dysphagia grade was compared between the first and last MBS to assess its evolution. Between 1996 and 2005, 63 patients with chronic dysphagia underwent MBS to assess dysphagia severity for nutritional support. Twenty-one patients (33%) had improvement of their dysphagia. Two of these patients (3%) achieved normalization of the swallowing. Twenty-five patients (40%) had no change of the dysphagia severity. Dysphagia grade increased in 17 patients (27%). Analysis of patient characteristics did not show any significant difference between these three groups of patients. MBS is a useful tool to monitor dysphagia severity and to identify aspiration risk. Stages of disease and treatment modality do not seem to impact on the course of dysphagia.

Aspiration risk and postoperative radiation for head and neck cancer.

The aim of the study was to assess the aspiration risk following postoperative radiation for head and neck cancer. Thirty-seven patients had Modified Barium Swallow before and following treatment. Dysphagia severity was graded from 1 to 7. Before treatment there were sixteen grade 1, seventeen grade 2, three grade 3 and one grade 5. Following postoperative radiation, two patients had grade 1, eleven patients had grade 2, thirteen patients had grade 3, four patients had grade 4, four patients had grade 5, one patients had grade 6, and two patients had grade 7. Nineteen percent (7/37) of the patients developed aspiration (grade 5-7). Aspiration is life-threatening and may develop for all tumor sites and stages.

Silencing survivin results in synergy between methylseleninic acid and paclitaxel against skov3 ovarian cancer cells.

This study evaluates methylseleninic acid (MSeA) improvement of paclitaxel efficacy against human ovarian cancer (skov3) with regard to survivin expression. MSeA and paclitaxel alone and in concurrent or sequential combination treatments were tested. Cell growth/death was evaluated using SRB, trypan blue, colony formation and ELISA assays. Cells were transfected with survivin shRNA and survivin's expression was measured using RT-PCR and Western blots. Drugs interaction was further evaluated using isobologram analyses. Different treatments with MSeA did not enhance paclitaxel's efficacy in the wild type skov3. Silencing survivin had no effect on MSeA or paclitaxel efficacy when used alone or in concurrent combination. After sequential combination treatment, synergy and significant induction of apoptosis were observed in cells transfected with survivin shRNA. However, antagonism and minimal induction of apoptosis were observed in empty or scramble survivin shRNA transfected cells. In conclusion, these data suggest that synergy between MSeA and paclitaxel in skov3 is associated with silencing survivin expression.

Long-term aspiration following treatment for head and neck cancer.

BACKGROUND: Dysphagia and aspiration are long-term complications with life-threatening consequences following treatment of head and neck cancer. We would like to assess the prevalence of aspiration in patients with long-term persistence of dysphagia (1 year or more) following treatment for head and neck cancer and to identify potential risk factors of aspiration. METHODS: Modified barium swallow (MBS) examinations were performed in cancer-free patients who complained of dysphagia following treatment for head and neck cancer. The severity of the dysphagia was graded on a scale of 1-7. RESULTS: Between 1992 and 2004, 74 patients with dysphagia underwent MBS 12-152 months following treatment (median 29 months). There were 2 grade 1, 22 grade 3, 21 grade 4, 11 grade 5, 7 grade 6, and 11 grade 7 cases. Twenty-nine patients (39%) had long-term aspiration at a median follow-up of 25 months (range 12-82). Eighteen patients (24%) required permanent gastrostomy because of severe aspiration. Type of treatment and disease stage did not seem to influence long-term aspiration risk. CONCLUSION: Patients with long-term dysphagia after treatment for head and neck cancer are at risk of aspiration. MBS should be performed to identify these patients.

Dysphagia severity and aspiration following postoperative radiation for locally advanced oropharyngeal cancer.

UNLABELLED: The aim of the present study was to assess dysphagia severity following postoperative radiation for locally advanced oropharyngeal cancer. PATIENTS AND METHODS: Eighteen patients with oropharyngeal carcinoma had undergone postoperative radiation. There were eight base of tongue, eight tonsils, and two soft palate carcinomas. All the patients had undergone modified barium swallow (MBS) to assess the persistence of dysphagia (more than one month) post-treatment. All the patients were cancer-free at the time of the swallowing study. Dysphagia severity was graded as 1-7. RESULTS: At a median follow-up of 12 months, there were three grade 2, four grade 3, two grade 4, five grade 5, two grade 6, and two grade 7. Only three patients (17%) had normal swallow post-treatment. Six patients (33%) had mild to moderate dysphagia (grade 3-4). Nine patients (50%) developed aspiration (grade 5-7). Among the patients who developed aspiration, four (22%) required tube feeding for severe aspiration. CONCLUSION: Long-term (more than one year) dysphagia following postoperative radiation for oropharyngeal cancer may be symptomatic of permanent damage to the swallowing mechanism. Evaluation of patients who complain of persistence of dysphagia a year or more following treatment should include MBS, because of the increased risk of aspiration.

Prevalence of pharyngeal and esophageal stenosis following radiation for head and neck cancer.

OBJECTIVE: To evaluate the risk and outcome of pharyngoesophageal stenosis in patients who complained of dysphagia following radiation for head and neck cancer. DESIGN: Retrospective study. SETTING: Veterans Administration hospital. PATIENTS: Patients who complained of persistent dysphagia following radiation alone or combined with surgery or chemotherapy for head and neck cancer. Patients were selected if they were cancer free at the time of the swallowing study. All patients had modified barium swallow (MBS) and an endoscopic examination for initial evaluation of their dysphagia. Traditional barium swallow was requested when there was a suspicion of pharyngoesophageal stenosis on MBS. RESULTS: Two hundred twenty-two patients underwent MBS for evaluation of dysphagia posttreatment. Traditional barium swallow confirmed the diagnosis of pharyngeal (n = 2) or esophageal (n = 14) stenosis in 16 patients. Eight patients had esophageal stenosis on endoscopic examination. All patients underwent dilatation for relief of their dysphagia. The number of dilatations performed was, respectively, one in 12 patients, two in 4 patients, three in 3 patients, four in 3 patients, five in one patient, and six in one patient. CONCLUSION: Pharyngeal and/or cervical esophageal stenosis may be the cause of dysphagia following radiation for head and neck cancer. Esophageal dilatations often offer temporary relief of the dysphagia.

Risk of aspiration following radiation for non-nasopharyngeal head and neck cancer.

OBJECTIVE: We assessed the rate of aspiration following radiation for non-nasopharyngeal head and neck cancer. DESIGN: Retrospective study. SETTING: Veterans Administration Hospital. PATIENTS: Thirty-three patients who underwent radiation for head and neck cancer. Modified barium swallow was performed prior to and following treatment to assess the persistence of dysphagia and aspiration risk. All patients were cancer free at the time of the swallowing study. Dysphagia severity was graded from 1 to 7. RESULTS: Preradiation baseline dysphagia was observed as follows: 10 grade 1, 14 grade 2, 9 grade 3, and 1 grade 4. Following radiation, at a median follow-up of 3 months, nine patients had grade 1, eight patients had grade 2, six patients had grade 3, two patients had grade 4, three patients had grade 5, two patients had grade 6, and three patients had grade 7. Overall, 24% (8 of 33) of the patients developed aspiration (grades 5-7). Fifteen percent (5 of 33) of the patients had severe aspiration (grades 6-7) requiring tube feedings. All patients who developed severe aspiration continued to require tube feedings more than 1 year following treatment completion. CONCLUSION: Aspiration is a significant source of morbidity following radiation for non-nasopharyngeal head and neck cancer. Aspiration may develop for all tumour stages or sites. Diagnostic studies such as modified barium swallow should be included in future prospective head and neck cancer studies to assess the prevalence of aspiration because of its often silent nature.

Effectiveness of the cough reflex in patients with aspiration following radiation for head and neck cancer.

The effectiveness of the cough reflex in patients who aspirated following radiation for head and neck cancer was evaluated in 89 patients (49 chemoradiation, 33 postoperative radiation, and 7 radiation alone). All patients had modified barium swallow because of dysphagia. The cough reflex was graded as present and effective, ineffective, intermittently effective, or absent. All patients were cancer-free at the time of the swallowing study. The cough reflex was present and effective in 46 patients (52%), ineffective in 17 patients (19%), and absent in 26 patients (29%) on initial investigation. Among the 43 patients who had ineffective or absent cough reflex, their treatment was chemoradiation (26), postoperative radiation (13), and radiation alone (4). In 30 patients who had sequential modified barium swallow, the cough reflex was constantly effective, ineffective, or intermittently effective in 12 (40%), 13 (43%), and 5 (17%) patients, respectively. The cough reflex was frequently ineffective or absent in patients who aspirated following radiation for head and neck cancer. Cough may also be intermittently ineffective to protect the airways following radiation.

Aspiration rate following nonsurgical therapy for laryngeal cancer.

The aim of this study was to evaluate the aspiration rate following nonsurgical therapy, i.e. chemoradiation or radiation alone for laryngeal cancer. Modified barium swallow was performed in 43 patients who complained of dysphagia following chemoradiation (n = 22) or radiation alone (n = 21) for laryngeal cancer. Patients were selected if they were cancer free at the time of the swallowing study. Dysphagia severity was graded on a scale of 1-7. Patients were grouped according to the dysphagia severity: no aspiration (grade 1-4), and severe (grade 5-7). Mean and median dysphagia grades were 4.4/5 and 3.5/3 for chemoradiation and radiation, respectively. Aspiration occurred in 12 patients (54%) of the chemoradiation group and 7 (33%) of the radiation alone group (p = 0.13). There was a higher proportion of patients with large tumor (T3-T4) in the chemoradiation group (64%) compared to the radiation group (5%) (p = 0.0001). Aspiration is a significant source of morbidity in patients treated for laryngeal cancer with chemoradiation or radiation alone. Aspiration occurred in both groups. Although the observed difference in aspiration rates did not achieve statistical significance, the higher aspiration rate in the chemoradiation group may be due to a higher proportion of large tumors, to the additional toxic effect of chemotherapy, or to the small number of patients in both groups. Diagnostic studies such as modified barium swallow should be part of future laryngeal cancer prospective studies to assess the prevalence of aspiration as it may be silent.

Impact of swallowing therapy on aspiration rate following treatment for locally advanced head and neck cancer.

This study examines the efficacy of swallowing therapy in cancer-free patients who developed aspiration following treatment for locally advanced head and neck cancer. The records of 41 patients who underwent swallowing therapy for aspiration were reviewed. All patients were cancer free at a median follow-up of 25 months (6-150 months). Their treatment were respectively chemoradiation (24), and postoperative radiation (17). All patients had two or more modified barium swallow (MBS). Dysphagia severity was graded from 1 to 7. Dysphagia grade was compared before and following swallowing therapy. Before swallowing therapy, there were 16 grade 5 (trace aspiration), and 25 grade 6-7 (severe aspiration). In the chemoradiation group, there were nine grade 5, five grade 6, and 10 grade 7. Corresponding numbers for the postoperative group were: seven grade 5, seven grade 6, and three grade 7. Following swallowing therapy, there were six grade 3, seven grade 4, 10 grade 5, six grade 6, and 12 grade 7. In the chemoradiation group, there were four grade 3, three grade 4, four grade 5, five grade 6, and eight grade 7. In the postoperative group, there were two grade 3, four grade 4, six grade 5, one grade 6, and four grade 7. Overall, 13 patients (32%) had improvement of their dysphagia severity. Seven of them were in the chemoradiation group (29%), and six (35%) were in the postoperative group. Among 25 patients who presented with grade 6-7 aspiration, only nine (36%) improved to grade 5 or less. Four of them (27%) were in the chemoradiation group, and five (29%) were in the postoperative group. Swallowing therapy is effective to improve dysphagia severity and reduce the need for tube feedings. However, a significant number of patients still suffered from chronic severe aspiration. New strategies must be devised to improve their outcome.

The mechanism of methylselenocysteine and docetaxel synergistic activity in prostate cancer cells.

The study was designed to evaluate the combination treatment of methylselenocysteine (MSeC) and docetaxel and to delineate the underlying mechanism associated with observed in vitro synergy between MSeC and docetaxel in prostate cancer cells. Cells were treated with different concentrations and schedules (concurrent or sequential) of MSeC and docetaxel alone or in combination. Cell growth/death was assessed with sulforhodamine B assay, trypan blue assay, and time-lapse video. Loewe synergism/antagonism model was used to determine whether the combination effect was additive, synergistic, or antagonistic. Apoptosis and caspase-3 activity were evaluated with cell death ELISA assay and caspase activity assay, respectively. Synergy between MSeC and docetaxel was further assessed in the presence and absence of z-VAD-fmk, a pan-caspase inhibitor. Effect of MSeC and docetaxel alone or in combination on the cellular expression of the antiapoptotic protein survivin was measured with Western blot analyses. Pretreatment with MSeC was crucial to enhance docetaxel antitumor activity. The enhanced antitumor activity of the sequential combination treatment of MSeC and docetaxel (MSeC/docetaxel) was highly synergistic. Apoptosis increased after MSeC/docetaxel, compared with each drug alone or concurrent treatment. Pretreatment with z-VAD-fmk converted the synergy into antagonism, suggesting that the synergy is caspase-dependent apoptosis. The survivin level was down-regulated following MSeC/docetaxel treatment when compared with each drug alone. In conclusion, pretreatment with MSeC was essential to markedly sensitize cells to docetaxel. The synergy between MSeC and docetaxel in C2G prostate cancer cells is associated with increased level of caspase-dependent apoptosis and decreased level of survivin.

Aspiration rate following chemoradiation for head and neck cancer: an underreported occurrence.

BACKGROUND AND PURPOSE: We would like to assess the prevalence of aspiration before and following chemoradiation for head and neck cancer. PATIENTS AND METHODS: We reviewed retrospectively the Modified Barium Swallow (MBS) in 63 patients who underwent concurrent chemotherapy and radiation for head and neck cancer. MBS was performed prior to treatment to determine the need for immediate gastrostomy tube placement. MBS was repeated following treatment to assess the safety of oral feeding prior to removal of tube feeding. All patients were cancer free at the time of the swallowing study. No patient had surgery. Dysphagia severity was graded on a scale of 1-7. Tube feedings were continued if patients were diagnosed to have severe aspiration (grade 6-7) or continued weight loss. Patients with abnormal swallow (grade 3-7) received swallowing therapy following MBS. RESULTS: Before treatment, there were 18 grade 1, 18 grade 2, 9 grade 3, 8 grade 4, 3 grade 5, 3 grade 6, and 4 grade 7. Following chemoradiation, at a median follow-up of 2 months (1-10 months), one patient had grade 1, eight patients had grade 2, nine patients had grade 3, eight patients had grade 4, 13 patients had grade 5, seven patients had grade 6, and 11 patients had grade 7. Six patients died from aspiration pneumonia (one before, three during, and two post-treatment), and did not have the second MBS. Overall, 37/63 (59%) patients developed aspiration, six of them (9%) fatal. If we excluded the 10 patients who had severe aspiration at diagnosis and the six patients who died from pneumonia, the prevalence of severe aspiration was 33% (21/63). CONCLUSIONS: Aspiration remained a significant morbidity following chemoradiation for head and neck cancer. Its prevalence is underreported in the literature because of its often silent nature. Diagnostic studies such as MBS should be part of future head and neck cancer prospective studies to assess the prevalence of aspiration, and for rehabilitation.

Dysphagia severity following chemoradiation and postoperative radiation for head and neck cancer.

OBJECTIVE: The purpose of the study is to evaluate dysphagia severity following chemoradiation and postoperative radiation for head and neck cancer, and particularly the aspiration risk because of its potential life-threatening consequence. MATERIALS AND METHODS: We reviewed retrospectively the modified barium swallow (MBS) results in 110 patients who complained of dysphagia following chemoradiation (57) and postoperative radiation (53) of their head and neck cancer. Patients were selected if they were cancer free at the time of the swallowing study. Dysphagia severity was graded on a scale of 1-7. Patients were grouped according to the dysphagia severity: mild (grades 2-3), moderate (grades 4-5), and severe (grades 6-7). RESULTS: Mean and median dysphagia grades were 4.84/5 and 4.12/4 for chemoradiation and postoperative radiation respectively. The mean difference between the two groups is statistically significant (p=0.02). Mild dysphagia occurred in 13 patients (22%) of the chemoradiation group and 17 (32%) of the postoperative group. Corresponding number for the moderate group was 25 (43%) and 25 (48%), respectively. Severe dysphagia was significant in the chemoradiation group (34%) compared to the postoperative group (19%). However, the difference was not statistically significant (p=0.29). There was a higher proportion of patients with large tumor (T3-T4) in the chemoradiation group who developed severe dysphagia. CONCLUSION: Dysphagia remained a significant morbidity of chemoradiation and postoperative radiation for head and neck cancer. Dysphagia may be more severe in the chemoradiation group because of the higher proportion of patients with large tumor, the high radiation dose, and a high number of oropharyngeal tumors. Aspiration occurred in both groups. Diagnostic studies such as MBS should be part of future head and neck cancer prospective studies to assess the prevalence of aspiration, as it may be silent.

Evolution of chronic dysphagia following treatment for head and neck cancer.

We would like to assess the evolution of chronic dysphagia (1 year or more) following treatment for head and neck cancer. Modified barium swallow (MBS) examinations were performed in cancer-free patients who complained of dysphagia following treatment for head and neck cancer. The severity of the dysphagia was graded on a scale of 1-7. Each patient had at least 2 MBS. Severity of dysphagia was compared between the first and last MBS study to determine whether the swallowing dysfunction had returned to normal. Patients with complaint of dysphagia and normal MBS also underwent a regular barium swallow to assess the structural integrity of the pharynx and esophagus. Between 1996 and 2001, 25 patients with dysphagia underwent repeat MBS following treatment. Swallowing dysfunction did not return to normal in the majority of the patients. At a median time of 26 months following treatment (range 15-82 months), only two patient (8%) had normalization of the swallowing. The severity of dysphagia decreased in eight patients (32%), remained unchanged in 12 patients (48%), and worsened in five patients (20%). Eight patients (32%) still had aspiration problems at 12-83 months following treatment. Six patients (24%) required dilation because of pharyngeal stenosis. Three patients who required dilation had improvement of the dysphagia severity. Chronic dysphagia is a relentless process possibly due to excessive scarring. Patients with chronic dysphagia are at risk of malnutrition, and aspiration. Management of chronic dysphagia requires a team approach with nutritional support, psychological counseling, dilation, and tube feedings when indicated.

Severity and duration of chronic dysphagia following treatment for head and neck cancer.

UNLABELLED: The purpose of this investigation was to evaluate chronic dysphagia (lasting 3 or more months) following treatment for head and neck cancer. Since dysphagia is a common sequela post therapy in cancer survivors, it may be helpful for the clinician to be aware of the persistence of dysphagia as well as its usual severity. Modified Barium Swallow (MBS) examinations were performed in cancer-free patients who complained of dysphagia following treatment for head and neck cancer. The severity of the dysphagia was graded on a scale of 1 to 7. Each patient had sequential MBS and underwent swallowing therapy in between. The severity of dysphagia was compared between the first and last MBS study to determine whether the swallowing function had returned to normal. RESULTS: Between 1996 and 2004, 12 patients with dysphagia underwent repeated MBS following treatment. Swallowing function did not return to normal in all patients. At a median time of 29 months following treatment (range 8 to 94 months), the severity of dysphagia decreased in 8 patients (67%), remained unchanged in 3 patients (25%) and worsened in 1 patient (8%). Chronic dysphagia following treatment is unlikely to resolve with time despite rehabilitation therapy. Excessive scarring following treatment may be responsible for the persistence and severity of dysphagia. Physicians should be aware of the long-term effects of dysphagia on patient nutrition and psychological well-being.

Impact of dysphagia on quality of life after treatment of head-and-neck cancer.

PURPOSE: To evaluate the quality of life (QOL) associated with dysphagia after head-and-neck cancer treatment. METHODS AND MATERIALS: Of a total population of 104, a retrospective analysis of 73 patients who complained of dysphagia after primary radiotherapy (RT), chemoradiotherapy, and postoperative RT for head-and-neck malignancies were evaluated. All patients underwent a modified barium swallow examination to assess the severity of dysphagia, graded on a scale of 1-7. QOL was evaluated by the University of Washington (UW) and Hospital Anxiety and Depression questionnaires. The QOL scores obtained were compared with those from the 31 patients who were free of dysphagia after treatment. The QOL scores were also graded according to the dysphagia severity. RESULTS: The UW and Hospital Anxiety and Depression scores were reduced and elevated, respectively, in the dysphagia group compared with the no dysphagia group (p = 0.0005). The UW scores were also substantially lower among patients with moderate-to-severe (Grade 4-7) compared with no or mild (Grade 2-3) dysphagia (p = 0.0005). The corresponding Hospital Anxiety (p = 0.005) and Depression (p = 0.0001) scores were also greater for the moderate-to-severe group. The UW QOL subscale scores showed a statistically significant decrease for swallowing (p = 0.00005), speech (p = 0.0005), recreation/entertainment (p = 0.0005), disfigurement (p = 0.0006), activity (p = 0.005), eating (p = 0.002), shoulder disability (p = 0.006), and pain (p = 0.004). CONCLUSION: Dysphagia is a significant morbidity of head-and-neck cancer treatment, and the severity of dysphagia correlated with a compromised QOL, anxiety, and depression. Patients with moderate-to-severe dysphagia require a team approach involving nutritional support, physical therapy, speech rehabilitation, pain management, and psychological counseling.

Enhanced 7-ethyl-10-hydroxycamptothecin (SN-38) lethality by methylselenocysteine is associated with Chk2 phosphorylation at threonine-68 and down-regulation of Cdc6 expression.

Methylselenocysteine (MSC) is an organic selenium compound in preventative clinical trials involving prostate, lung, and colon carcinoma. We found that methioninase-activated MSC potentiates 7-ethyl-10-hydroxycamptothecin (SN-38)-induced cell lethality in vitro in the p53-defective human head and neck carcinoma A253 cells. Activated MSC increases chk2 phosphorylation at threonine-68 induced by SN-38, with no significant effect on chk1 phosphorylation. Cell cycle arrest induced by SN-38, however, was not abrogated or potentiated by MSC. These results suggest that the enhanced cellular lethality of SN-38 by MSC was not associated with cell cycle regulation pathways. Because chk2, in addition to its role in cell cycle arrest, can induce apoptosis by phosphorylation/activation, we examined whether increased chk2 phosphorylation could induce preapoptotic DNA fragmentation. DNA damage analysis showed that megabase DNA fragmentation is decreased, accompanied by the increased 30 to 300 kilobase pairs of DNA fragmentation after exposure to SN-38 with MSC, compared with SN-38 alone. No significant changes in the amount of DNA fragments were observed in cells treated with SN-38 or MSC alone. Moreover, proteolytic destruction of DNA replication-associated proteins cdc6, MCM2, and cdc25A may induce a DNA damage checkpoint response. The observed down-regulation of DNA replication proteins cdc6, MCM2, and cdc25A after exposure to SN-38 with MSC further indicates a relationship between drug response and DNA damage. Exposure to SN-38 with MSC resulted in a significant increase of poly(ADP-ribose) polymerasecleavage and caspase 3 activation. All together, the data support the hypothesis that enhanced lethality of this combination is associated with increased chk2 phosphorylation at Thr68 and down-regulation of specific DNA replication-associated proteins, which result in poly(ADP-ribose) polymerase cleavage, caspase 3 activation, and the induction of 30 to 300 kilobase pairs of DNA fragmentation.

Phosphorylation of chk1 at serine-345 affected by topoisomerase I poison SN-38.

Human head and neck squamous carcinoma cell lines, A253 and FaDu, were utilized to identify mediators associated with response to topoisomerase I poison, SN-38, a metabolite of irinotecan. The drug sensitivity of FaDu cells to SN-38 was significantly higher than that of the A253 cells. In A253 cells, G2/M arrest following drug treatment (0.35 microM SN-38, 2-h exposure) was accompanied by DNA fragmentation in the 50-300 kb range, but FaDu cells accumulated in S-phase concurrently with induction of smaller DNA fragmentation in the 4-80 kb range. Because the critical regulatory step in activating cdc2 during progression into mitosis appears to be dephosphorylation of Tyrosine 15 (Tyr15), we examined the Tyr15 phosphorylation status of cdc2 in both cell lines. Slightly increased levels of cdc2 phosphorylation was observed in the A253 cells, while reduced levels of cdc2 phosphorylation was noted in the FaDu cells, corresponding to the abrogation of the G2-phase arrest. Increased chk1 phosphorylation at Ser345 induced by SN-38 was accompanied by the observed G2 phase arrest in the A253 cell line, while significant downregulation of chk1 and cdc25C phosphorylation, which resulted in the abrogation of G2/M checkpoint arrest, was noted in FaDu cells at this timepoint. These results suggest that alterations of chk1 signaling are associated with the response to topoisomerase I poison SN-38. Furthermore, A253 cells possess higher levels of endogenous hMLH1, compared to FaDu cells. A deficiency in G2 arrest was observed in FaDu cells, suggesting endogenous hMLH1 protein expression is associated with the abrogation of G2/M arrest, subsequently with the response to topoisomerase I poison SN-38.

Chk1 signaling pathways that mediated G(2)M checkpoint in relation to the cellular resistance to the novel topoisomerase I poison BNP1350.

A novel karenitecin, BNP1350, is a topoisomerase I-targeting anticancer agent with significant antitumor activity in vitro and in vivo. A BNP1350-resistant human head and neck carcinoma A253 cell line, denoted A253/BNPR, was developed. The A253/BNPR cell line was approximately 9-fold resistant to BNP1350 and 4-fold cross-resistant to another topoisomerase I inhibitor SN-38, the active metabolite of irinotecan. After drug treatment with equimolar concentrations of BNP1350 (0.7 microM) for 2h, activation of the DNA double-strand break repair protein complexes was similar in the two cell lines, suggesting that DNA dsb repair is not attributable to resistance to BNP1350 in the A253/BNPR cells. Cell cycle analysis indicates that the A253 cell line accumulated primarily in S phase, but G(2) phase accumulation was observed in the A253/BNPR cell line at 48 h after drug removal. Elevated chk1 phosphorylation at Ser(345) following DNA damage induced by BNP1350 was accompanied by G(2) accumulation in the A253/BNPR cell line, while exposure to equimolar concentrations of BNP1350 (0.7 microM) induced S-phase arrest and no increased phosphorylation of chk1 at Ser(345) in the A253 cell line. Under the same conditions, increased chk1 activity was observed in the A253/BNPR cell line, but not in the A253 cell line. Moreover, stimulated binding of 14-3-3 proteins to chk1 was observed in BNP1350-treated A253/BNPR cells. To confirm relationship between chk1 expression/phosphorylation and drug resistance to topo I poisons, we examined the effects of chk1 or chk2 antisense oligonucleotides on the cellular growth inhibition. Chk1 antisense oligonucleotide can sensitize the A253/BNPR cells to killing by topo I inhibitor BNP1350, but no significant sensitization of BNP1350-induced growth inhibition was observed in the drug-sensitive cell line. Chk2 antisense oligonucleotide has only a small sensitization effect on BNP1350-induced growth inhibition in both cell lines. The data indicate that the chk1 signaling pathways that mediate cell cycle checkpoint are associated with cellular resistance to BNP1350 in the A253/BNPR cell line.