Biomedical subjects

Craig Stevens

Publications and source records attributed to Craig Stevens.

14 recordsLinked to original sources

PubMed2005

Histone deacetylase inhibitors radiosensitize human melanoma cells by suppressing DNA repair activity.

PURPOSE: Histone deacetylase (HDAC) inhibitors have emerged recently as promising anticancer agents. They arrest cells in the cell cycle and induce differentiation and cell death. The antitumor activity of HDAC inhibitors has been linked to their ability to induce gene expression through acetylation of histone and nonhistone proteins. However, it has recently been suggested that HDAC inhibitors may also enhance the activity of other cancer therapeutics, including radiotherapy. The purpose of this study was to evaluate the ability of HDAC inhibitors to radiosensitize human melanoma cells in vitro. EXPERIMENTAL DESIGN: A panel of HDAC inhibitors that included sodium butyrate (NaB), phenylbutyrate, tributyrin, and trichostatin A were tested for their ability to radiosensitize two human melanoma cell lines (A375 and MeWo) using clonogenic cell survival assays. Apoptosis and DNA repair were measured by standard assays. RESULTS: NaB induced hyperacetylation of histone H4 in the two melanoma cell lines and the normal human fibroblasts. NaB radiosensitized both the A375 and MeWo melanoma cell lines, substantially reducing the surviving fraction at 2 Gy (SF2), whereas it had no effect on the normal human fibroblasts. The other HDAC inhibitors, phenylbutyrate, tributyrin, and trichostatin A had significant radiosensitizing effects on both melanoma cell lines tested. NaB modestly enhanced radiation-induced apoptosis that did not correlate with survival but did correlate with functional impairment of DNA repair as determined based on the host cell reactivation assay. Moreover, NaB significantly reduced the expression of the repair-related genes Ku70 and Ku86 and DNA-dependent protein kinase catalytic subunit in melanoma cells at the protein and mRNA levels. Normal human fibroblasts showed no change in DNA repair capacity or levels of DNA repair proteins following NaB treatment. We also examined gamma-H2AX phosphorylation as a marker of radiation response to NaB and observed that compared with controls, gamma-H2AX foci persisted long after ionizing exposure in the NaB-treated cells. CONCLUSIONS: HDAC inhibitors radiosensitize human tumor cells by affecting their ability to repair the DNA damage induced by ionizing radiation and that gamma-H2AX phosphorylation can be used as a predictive marker of radioresponse.

Acetylation↗

PubMed2004

Adenoviral-mediated mda-7 expression suppresses DNA repair capacity and radiosensitizes non-small-cell lung cancer cells.

The melanoma differentiation-associated gene-7 (mda-7) was identified by virtue of its enhanced expression in human melanoma cells induced into terminal differentiation. Enforced expression of mda-7 in human cancer cell lines of diverse origins results in the suppression of growth and induction of apoptosis. We have shown that adenoviral-mediated mda-7 (Ad-mda7) radiosensitizes non-small-cell lung cancer (NSCLC) cells by enhancing the apoptotic pathway. To identify the mechanism of this radiosensitization, we examined the level of proteins involved in the nonhomologous end-joining (NHEJ) pathway of DNA double-strand break (DSB) repair. Western blot analysis indicated that the expression of NHEJ pathway components Ku70, XRCC4, and DNA ligase IV was downregulated in NSCLC cells--A549 with Ad-mda7 treatment. No such change was observed in normal human CCD16 fibroblasts previously shown not to be radiosensitized by Ad-mda7. The biological significance of these changes of expression of proteins critical for repair of radiation-induced DSBs was confirmed via the analysis of DSB rejoining kinetics using pulsed field gel electrophoresis and assessment of host cell reactivation capacity following Ad-mda7 treatment. Based on these results, we hypothesize that Ad-mda7 sensitizes NSCLC cells to ionizing radiation by suppressing the activity of NHEJ, a pathway essential for repair of radiation-induced DSBs.

Adenoviridae↗

PubMed2004

Dose and volume reduction for normal lung using intensity-modulated radiotherapy for advanced-stage non-small-cell lung cancer.

PURPOSE: To investigate dosimetric improvements with respect to tumor-dose conformity and normal tissue sparing using intensity-modulated radiotherapy (IMRT) compared with three-dimensional conformal radiotherapy (3D-CRT) for advanced-stage non-small-cell lung cancer (NSCLC). METHODS AND MATERIALS: Forty-one patients with Stage III-IV and recurrent NSCLC who previously underwent 3D-CRT were included. IMRT plans were designed to deliver 63 Gy to 95% of the planning target volume using nine equidistant coplanar 6-MV beams. Inverse planning was performed to minimize the volumes of normal lung, heart, esophagus, and spinal cord irradiated above their tolerance doses. Dose distributions and dosimetric indexes for the tumors and critical structures in both plans were computed and compared. RESULTS: Using IMRT, the median absolute reduction in the percentage of lung volume irradiated to >10 and >20 Gy was 7% and 10%, respectively. This corresponded to a decrease of >2 Gy in the total lung mean dose and of 10% in the risk of radiation pneumonitis. The volumes of the heart and esophagus irradiated to >40-50 Gy and normal thoracic tissue volume irradiated to >10-40 Gy were reduced using the IMRT plans. A marginal increase occurred in the spinal cord maximal dose and lung volume >5 Gy in the IMRT plans, which could be have resulted from the significant increase in monitor units and thus leakage dose in IMRT. CONCLUSION: IMRT planning significantly improved target coverage and reduced the volume of normal lung irradiated above low doses. The spread of low doses to normal tissues can be controlled in IMRT with appropriately selected planning parameters. The dosimetric benefits of IMRT for advanced-stage non-small-cell lung cancer must be evaluated further in clinical trials.

Adult↗

PubMed2004

Equivalent outcome of patients with clinical Stage IIIA non-small-cell lung cancer treated with concurrent chemoradiation compared with induction chemotherapy followed by surgical resection.

PURPOSE: To compare the outcome of induction chemotherapy followed by surgery (C/S) and concurrent chemoradiotherapy (CRT) for clinical Stage IIIA non-small-cell lung cancer (NSCLC). METHODS AND MATERIALS: Between 1990 and 2000, 107 patients underwent either induction C/S (n = 55) or concurrent CRT (n = 52) for clinical Stage IIIA NSCLC at The University of Texas M. D. Anderson Cancer Center. Patient and tumor characteristics were balanced in the two treatment groups with respect to T and N stage, race, median age, performance status, weight loss, and histologic findings. In the C/S group, induction chemotherapy included two to four cycles of cisplatin-based chemotherapy followed by lobectomy and mediastinal lymph node dissection. Postoperative RT was delivered in 35 patients, with referral for RT made at the discretion of the treating physician. CRT consisted of three cycles of cisplatin-based chemotherapy given every 3 weeks concurrent with RT to 60-63 Gy in 30-35 fractions in 27 patients and 69.6 Gy in 58 fractions (b.i.d.) in 25 patients. Local control, overall disease-free survival, and distant metastasis-free survival rates were calculated using the Kaplan-Meier method. The median follow-up duration was 20 months in all patients and 32 months in surviving patients. RESULTS: No statistically significant differences were found in the end points measured in the two treatment groups. Specifically, the median survival time was 31 and 27 months and the 5-year overall survival rate was 33% and 30% in the C/S and CRT groups, respectively. Likewise, the 5-year local control (58% vs. 61%), disease-free (24% vs. 23%), and distant metastasis-free (44% vs. 36%) survival rates in the two groups were not significantly different. In the C/S group, postoperative RT significantly improved the 5-year local control rate from 33.8% to 81.5% (p = 0.007) but did not significantly improve overall survival. Additionally, patients in the C/S group whose disease responded to induction chemotherapy had a significantly improved 5-year overall survival rate (50%) compared with those who had stable or progressive disease (16%, p = 0001). CONCLUSION: Treatment of Stage IIIA NSCLC using either induction C/S or CRT resulted in similar outcomes in terms of local control and median overall, 5-year overall, distant metastasis-free, and disease-free survival. However, patients undergoing induction C/S often needed postoperative RT to achieve local control equivalent to that achieved with concurrent CRT. Advances in radiation-based treatment as reflected in this study have resulted in similar outcomes compared with modern induction C/S. To improve survival, however, newer systemic agents that reduce and control distant metastasis are required.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed2004

Heterogeneous planning for homogeneous protocols.

Clinical trials often require homogeneous treatment plans. Many institutions, however, have begun using heterogeneous plans. Is it possible to satisfy the requirements of such a protocol while achieving the superior accuracy of heterogeneous treatment planning? At the University of Texas M. D. Anderson Cancer Center, we currently use conformal treatment planning with heterogeneities for thoracic cancers. This paper describes a procedure that has been developed to satisfy the requirements of a homogeneous protocol, such as RTOG 98-01 (A Phase III Study of Amifostine mucosal protection), while maintaining accuracy in treatment planning.

Amifostine↗

PubMed2003

The relationship between local dose and loss of function for irradiated lung.

PURPOSE: To determine the relationship between the local radiation dose and the decrease in lung function associated with thoracic irradiation. PATIENTS AND METHODS: Twenty-six patients treated with thoracic irradiation for lung cancer, for whom three-dimensional CT-based dosimetry was used in treatment planning, were evaluated with before and after treatment pulmonary function tests. Six patients were treated with radiotherapy alone (2.15 Gy daily fractions), and 20 patients with concurrent chemotherapy (cisplatin, etoposide) with hyperfractionated (HF) radiation therapy (1.2 Gy in twice-daily fractions). Eleven patients treated with concurrent HF chemoradiation also received the radioprotector amifostine. The normalized decrease in the diffusing capacity for carbon monoxide (DL(CO)) was used as an objective measure of the change in lung function. The dose-volume histogram (DVH) data were used to estimate the local dose-response relationship for loss of DL(CO). In each subvolume of lung, the loss in normalized DL(CO) was assumed to be a sigmoid function of dose, ranging from no loss at low doses to total loss at high doses. The whole-lung decrease in DL(CO) was modeled as the sum of the local declines in DL(CO) over all subvolumes. Nonlinear regression analysis was used to estimate the parameters of the local dose-response function. RESULTS: The data are most consistent with a pronounced decrease in DL(CO) when the local dose (for radiotherapy alone or HF concurrent chemoradiation) exceeds 13 Gy (95% CI, 11-15 Gy). In patients who received amifostine in addition to HF radiotherapy with concurrent chemotherapy, this stepwise loss of DL(CO) occurred above 36 Gy (95% CI, 25-48 Gy). Grade 2 or higher pulmonary symptoms were associated with a DL(CO) loss of >30% (p = 0.003). CONCLUSIONS: The decrease in pulmonary diffusion capacity correlates with the local dose to irradiated lung. Amifostine significantly reduces the loss in DL(CO). A local dose-loss relationship for normalized DL(CO) can be extracted from DVH data. This relationship allows an estimate of the loss of function associated with a radiation treatment plan. Different plans can thus be compared without resort to an empiric DVH reduction algorithm. The very low (13 Gy) threshold for deterioration of DL(CO) suggests that it is better to treat a little normal lung to a high dose than to treat a lot to a low dose.

Adult↗

PubMed2003

E2F and cell cycle control: a double-edged sword.

The E2F family of transcription factors plays a central role in regulating cellular proliferation by controlling the expression of both the genes required for cell cycle progression, particularly DNA synthesis, and the genes involved with apoptosis. E2F is regulated in a cell cycle-dependent manner, principally through its temporal association with pocket protein family members, the prototype member being the retinoblastoma tumor suppressor protein. Pocket proteins are, in turn, regulated through phosphorylation by cyclin-dependent kinase (cdk). The kinase activity of cyclin/cdk complexes is negatively regulated by cdk inhibitors, and thus both positive and negative growth regulatory signals impinge on E2F activity. Different E2F family members exhibit distinct cell cycle and apoptotic activities. Thus, E2F appears to play a pivotal role in coordinating events connected with proliferation, cell cycle arrest, and apoptosis.

Animals↗

PubMed2003

Chk2 activates E2F-1 in response to DNA damage.

The E2F-1 transcription factor is regulated during cell cycle progression and induced by cellular stress, such as DNA damage. We report that checkpoint kinase 2 (Chk2) regulates E2F-1 activity in response to the DNA-damaging agent etoposide. A Chk2 consensus phosphorylation site in E2F-1 is phosphorylated in response to DNA damage, resulting in protein stabilization, increased half-life, transcriptional activation and localization of phosphorylated E2F-1 to discrete nuclear structures. Expression of a dominant-negative Chk2 mutant blocks induction of E2F-1 and prevents E2F-1-dependent apoptosis. Moreover, E2F-1 is resistant to induction by etoposide in tumour cells expressing mutant chk2. Therefore, Chk2 phosphorylates and activates E2F-1 in response to DNA damage, resulting in apoptosis. These results suggest a role for E2F-1 in checkpoint control and provide a plausible explanation for the tumour suppressor activity of E2F-1.

Apoptosis↗

PubMed2003

Combination of a COX-2 inhibitor with radiotherapy or radiochemotherapy in the treatment of thoracic cancer.

Cyclooxygenase-2 (COX-2) is an enzyme involved in prostaglandin production in pathologic states such as inflammatory processes and cancer. The enzyme is often overexpressed in premalignant lesions and cancer, including cancers of the lung and esophagus. Inhibition of this enzyme with selective COX-2 inhibitors was found to enhance tumor response to radiation in preclinical studies, suggesting that these agents can improve the response of various cancers to radiotherapy. On the basis of these preclinical findings, clinical trials of the combination of celecoxib, a selective COX-2 inhibitor, with radiotherapy were initiated in patients with lung carcinoma and with chemoradiotherapy in patients with esophageal carcinoma. The rationale for using selective COX-2 inhibitors is discussed, and the current clinical protocols and the initial findings are described.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed2003

Induction of p53-regulated genes and tumor regression in lung cancer patients after intratumoral delivery of adenoviral p53 (INGN 201) and radiation therapy.

PURPOSE: We designed a prospective single arm Phase II study to evaluate the feasibility and mechanisms of apoptosis induction after Ad-p53 (INGN 201) gene transfer and radiation therapy in patients with non-small cell lung cancer. EXPERIMENTAL DESIGN: Nineteen patients with nonmetastatic non-small cell lung cancer who were not eligible for chemoradiation or surgery were treated as outpatients with radiation therapy to 60 Gy over 6 weeks in conjunction with three intratumoral injections of Ad-p53 (INGN 201) on days 1, 18, and 32. RESULTS: Seventeen of 19 patients completed all planned radiation and Ad-p53 (INGN 201) gene therapy as outpatients. The most common adverse events were grade 1 or 2 fevers (79%) and chills (53%). Three months after completion of therapy, pathologic biopsies of the primary tumor revealed no viable tumor (12 of 19 patients, 63%), viable tumor (3 of 19 patients, 16%), and not assessed (4 of 19 patients, 21%). Computed tomography and bronchoscopic findings at the primary injected tumor revealed complete response (1 of 19 patients, 5%), partial response (11 of 19 patients, 58%), stable disease (3 of 19 patients, 16%), progressive disease (2 of 19 patients, 11%), and not evaluable (2 of 19 patients, 11%). Quantitative reverse transcription-PCR analysis of the four p53 related genes [p21 (CDKN1A), FAS, BAK, and MDM2] revealed that Bak expression was increased significantly 24 h after Ad-p53 (INGN 201) injection and levels of CDKN1A and MDM2 expression were increased over the course of treatment. CONCLUSIONS: Intratumoral injection of Ad-p53 (INGN 201) in combination with radiation therapy is well tolerated and demonstrates evidence of tumor regression at the primary injected tumor. Serial biopsies of the tumor suggest that BAK gene expression is most closely related to Ad-p53 (INGN 201) gene transfer.

Adenoviridae↗

PubMed2003

Irinotecan/cisplatin followed by 5-FU/paclitaxel/radiotherapy and surgery in esophageal cancer.

Local-regional carcinoma of the esophagus is often diagnosed in advanced stages because the diagnosis is established when symptoms are severe. The prognosis of patients with local-regional carcinoma of the esophagus continues to be grim. While preoperative chemoradiotherapy increases the fraction of patients who achieve pathologic complete response, that percentage is approximately 25%. In an attempt to increase the number of patients with either no cancer in the surgical specimen or only microscopic cancer, we adopted a three-step strategy. The current study utilized up to two 6-week cycles of induction chemotherapy with irinotecan (CPT-11, Camptosar) and cisplatin as step 1. This was followed by concurrent radiotherapy and chemotherapy with continuous infusion fluorouracil (5-FU) and paclitaxel as step 2. Once the patients recovered from chemoradiotherapy, a preoperative evaluation was performed and surgery was attempted. All patients signed an informed consent prior to their participation on the study. A total of 43 patients were enrolled. The baseline endoscopic ultrasonography revealed that 36 patients had a T3 tumor, five patients had a T2 tumor, and two had a T1 tumor. Twenty-seven patients had node-positive cancer (N1). Thirty-nine (91%) of the 43 patients underwent surgery; all had an R0 (curative) resection. A pathologic complete response was noted in 12 of the 39 patients. In addition, 17 patients had only microscopic (< 10%) viable cancer in the specimen. Therefore, a significant pathologic response was seen in 29 (74%) of 39 taken to surgery or 29 (67%) of all 43 patients enrolled on the study. With a median follow up beyond 25 months, 20 patients remain alive and 12 patients remain free of cancer. Our preliminary data suggest that the proportion of patients with significant pathologic response can be increased by using the three-step strategy.

Adult↗

PubMed2002

Twice daily irradiation increases locoregional control in patients with medically inoperable or surgically unresectable stage II-IIIB non-small-cell lung cancer.

PURPOSE: To evaluate the effect of q.d. or b.i.d. radiotherapy (RT) on the outcome of patients with locally advanced non-small-cell lung cancer. METHODS AND MATERIALS: We retrospectively reviewed the outcome of 261 patients with medically inoperable or surgically unresectable Stage II-IIIB non-small-cell lung cancer, who were treated with combined modality cisplatin-based chemotherapy and RT. Chemotherapy was administered either sequentially or concurrently with thoracic RT. The median follow-up was 18 months (range 2-92). Treatment groups included sequential chemotherapy and q.d. RT (n = 109), concurrent chemotherapy and q.d. RT (n = 48), and concurrent chemotherapy and b.i.d. RT (n = 104). Of the 261 patients, 97% had a Karnofsky performance score > or =80, and 86.2% had < or =5% weight loss in the 3 months before diagnosis; 66.7% had nonsquamous cell histologic features. All but 8 patients had Stage IIIA-B disease. RESULTS: The 2- and 5-year locoregional control rate was 42.4% and 25.7% for the q.d. group and 70.6% and 45.8% for the b.i.d. group, respectively (p = 0.0001). The 2- and 5-year disease-free survival rate was 26.7% and 6.5% for the q.d. group and 39.6% and 27.3% for the b.i.d. group, respectively (p = 0.0114). The corresponding overall survival rates were 35.9% and 9.4% for the q.d. group and 38.7% and 26.1% for the b.i.d. group. No difference was found in the rate of distant metastasis between the 2 groups. Multivariate analysis indicated that b.i.d. RT was a favorable prognostic factor for locoregional control and disease-free survival. CONCLUSION: RT b.i.d. significantly improved locoregional control and disease-free survival compared with RT q.d. in patients with Stage IIIA-B non-small-cell lung cancer.

Adult↗

PubMedDate not supplied

The emerging role of E2F-1 in the DNA damage response and checkpoint control.

Genotoxic stress triggers a myriad of cellular responses including cell cycle arrest, stimulation of DNA repair and apoptosis. A central role for the E2F-1 transcription factor in the DNA damage response pathway is gaining support. E2F-1 is phosphorylated by DNA damage responsive protein kinases, which leads to E2F-1 accumulation and the induction of apoptosis. In addition, emerging information suggests that E2F-1 may play a role in the detection and subsequent repair of damaged DNA.

Animals↗

PubMedDate not supplied

A new role for E2F-1 in checkpoint control.

In response to DNA damage, E2F-1 is induced and phosphorylated. Phosphorylated E2F-1 can reside in discrete nuclear structures and induce apoptosis, suggesting a unique role for E2F-1 in DNA repair and checkpoint functions.

Animals↗