Biomedical subjects

T L DeWeese

Publications and source records attributed to T L DeWeese.

24 records · Page 2Linked to original sources

PubMed1998

Radiation-induced impairment of bone healing can be overcome by recombinant human bone morphogenetic protein-2.

Radiotherapy of head and neck tumors very often results in impaired healing of craniomaxillofacial bones in the vicinity. Management of radionecrosis of bones after radiotherapy is an important clinical challenge. Bone morphogenetic proteins (BMPs) induce new bone differentiation. The aim of this study is to investigate the potential of BMPs in ameliorating radiation-induced impaired bone repair. Two 3-mm diameter defects were created in the calvaria of rats. The defects were treated with different doses of recombinant human (rh) BMP-2 using collagen type I as a carrier. Irradiation with a single dose of 1,200 rad was performed 2 or 7 days preoperatively. Unirradiated animals served as controls. New bone formation was assessed by quantitation of radiographs of the calvaria and histology on day 21 after surgery. Untreated, unirradiated defects showed a spontaneous osseous regeneration of 90 +/- 7% of the defect area within 21 days. Irradiation of the site (1,200 rad 2 days preoperatively) resulted in a profound decrease in the bone fill of the untreated defect (5 +/- 2%). Recombinant human BMP-2 in soluble collagen type I carrier delivered to the defect resulted in a significant increase of new bone formation (34 +/- 14%, P < 0.01 for 25 micrograms rhBMP-2; 77 +/- 19% for 35 micrograms rhBMP-2, P < 0.01). Type I collagen carrier alone resulted in only 7 +/- 2% healing. In conclusion, radiation-induced impairment of calvarial repair can be overcome by rhBMP-2. Thus, the concept of BMP-2-induced regeneration has potential applications in reconstructive craniomaxillofacial surgery after irradiation.

Animals↗

PubMed1998

Comparison of radical prostatectomy and iodine 125 interstitial radiotherapy for the treatment of clinically localized prostate cancer: a 7-year biochemical (PSA) progression analysis.

OBJECTIVES: To evaluate the relative efficacy of brachytherapy to radical prostatectomy, we compared biochemical progression rates from a published series of men who underwent iodine 125 (125I) interstitial radiotherapy for localized prostate cancer to a similar group of men who underwent anatomic radical prostatectomy using appropriate end points. METHODS: Seventy-six men who underwent anatomic radical prostatectomy between 1988 and 1990 were carefully matched for Gleason score and clinical stage to a recently reported contemporary series of patients treated at another institution with 125I brachytherapy without adjuvant treatment. The definition of biochemical progression was a serum PSA level greater than 0.2 ng/mL after anatomic radical prostatectomy and greater than 0.5 ng/mL for brachytherapy-treated patients. RESULTS: The 7-year actuarial PSA progression-free survival following anatomic radical prostatectomy was 97.8% (95% confidence interval [CI], 85.6% to 99.7%) for this group of men selected to match the brachytherapy group, compared to 79% (95% CI not published) for men treated with 125I interstitial radiotherapy. CONCLUSIONS: Using comparative end points for biochemical-free progression, failure rates may be higher following 125I interstitial radiotherapy compared to anatomic radical prostatectomy. These data provide a better comparison of biochemical progression than previously published studies and emphasize the need for caution in interpreting the relative efficacy of brachytherapy in controlling localized prostate cancer.

Adult↗

PubMed1997

Human papillomavirus E6 and E7 oncoproteins alter cell cycle progression but not radiosensitivity of carcinoma cells treated with low-dose-rate radiation.

PURPOSE: Low-dose-rate radiation therapy has been widely used in the treatment of urogenital malignancies. When continuously exposed to low-dose-rate ionizing radiation, target cancer cells typically exhibit abnormalities in replicative cell-cycle progression. Cancer cells that arrest in the G2 phase of the cell cycle when irradiated may become exquisitely sensitive to killing by further low-dose-rate radiation treatment. Oncogenic human papillomaviruses (HPVs), which play a major role in the pathogenesis of uterine cervix cancers and other urogenital cancers, encode E6 and E7 transforming proteins known to abrogate a p53-dependent G1 cell-cycle checkpoint activated by conventional acute-dose radiation exposure. This study examined whether expression of HPV E6 and E7 oncoproteins by cancer cells alters the cell-cycle redistribution patterns accompanying low-dose-rate radiation treatment, and whether such alterations in cell-cycle redistribution affect cancer cell killing. METHODS AND MATERIALS: RKO carcinoma cells, which contain wild-type P53 alleles, and RKO cell sublines genetically engineered to express HPV E6 and E7 oncoproteins, were treated with low-dose-rate (0.25-Gy/h) radiation and then assessed for p53 and p21WAF1/CIP1 polypeptide induction by immunoblot analysis, for cell-cycle redistribution by flow cytometry, and for cytotoxicity by clonogenic survival assay. RESULTS: Low-dose-rate radiation of RKO carcinoma cells triggered p53 polypeptide elevations, p21WAF1/CIP1 induction, and arrest in the G1 and G2 phases of the cell cycle. In contrast, RKO cells expressing E6 and E7 transforming proteins from high-risk oncogenic HPVs (HPV 16) arrested in G2, but failed to arrest in G1, when treated with low-dose-rate ionizing radiation. Abrogation of the G1 cell-cycle checkpoint activated by low-dose-rate radiation exposure appeared to be a characteristic feature of transforming proteins from high-risk oncogenic HPVs: RKO cells expressing E6 from a low-risk nononcogenic HPV (HPV 11) exposed to low-dose-rate radiation arrested in both G1 and G2. Surprisingly, despite differences in cell-cycle redistribution accompanying low-dose-rate radiation treatment associated with high-risk HPV transforming protein expression, no consistent differences in clonogenic survival following low-dose-rate radiation treatment were found for RKO cell sublines expressing high-risk HPV oncoproteins and arresting only in G2 during low-dose-rate radiation exposure vs. RKO cell sublines exhibiting both G1 and G2 cell-cycle arrest when irradiated. CONCLUSION: The results of this study demonstrate that neither HPV oncoprotein expression nor loss of the radiation-activated G1 cell-cycle checkpoint alter the sensitivity of RKO carcinoma cell lines to low-dose-rate radiation exposure in vitro. Perhaps for urogenital malignancies associated with oncogenic HPVs in vivo, HPV oncoprotein-mediated abrogation of the G1 cell-cycle checkpoint may not limit the potential efficacy of low-dose-rate radiation therapy.

Colonic Neoplasms↗

PubMed1996

Prostate cancer treatment strategies based on tumor-specific biological principles: future directions.

Prostate cancer represents a heterogeneous disease entity with varying degrees of behavior, aggressiveness, patterns of metastasis, and response to therapy. Progressive metastatic prostate cancer is associated with a formidable array of morbidity that ultimately contributes to death of the patient. Thus far, there has been no convincing evidence to support routine use of non-hormonal chemotherapeutic agents or combinations over symptomatic treatment only. Furthermore, no single compound or combination has shown a dramatic improvement in conventional quality of life parameters over symptomatic treatment only. Androgen ablation remains the primary systemic therapeutic modality for this disease, yet the intense delineation of mechanisms involved in tumor cell metastasis has lead to new therapeutic strategies, ranging from cytotoxic to cytostatic, including immunomodulators. Among those strategies currently being studied are granulocyte-macrophage colony-stimulating factor-transduced prostate cancer vaccines, differentiation therapy, gene therapy, inducers of apoptosis, antimetastatic agents, angiogenesis inhibitors, radiation therapy (local and systemic), and systemic approaches targeted at prostate cancer morbidity. The difficult issue is which agents should be developed and how should we best assess the response using standard and newly identified endpoints. Certainly, the future of advanced prostate cancer therapy will undergo dramatic changes as a result of the continued interaction between the laboratory and the clinic.

Antineoplastic Agents↗

PubMed1991

AIDS-related non-Hodgkin's lymphoma: the outcome and efficacy of radiation therapy.

The records of all 16 patients with AIDS-related lymphoma treated with radiation therapy at our institutions were reviewed. All patients were male with a median age of 32 years, and all but one had biopsy proven high-grade NHL. Eleven had lymphoma involving the central nervous system and five had lymphoma involving other sites. Seven of the 11 patients with CNS involvement had primary CNS lymphoma. All patients were treated with megavoltage X rays to doses ranging from 1050 cGy in 1 1/2 weeks to 5037 cGy in 6 weeks. Of those patients with CNS lymphoma, only one responded completely and four responded partially to irradiation. All patients died within a range of 0.2 to 5.3 months (median survival = 2.2 months) from starting radiation therapy. In contrast, 3 of 5 patients (60%) with NHL outside the CNS responded completely and 1 responded partially to involved-field irradiation. These patients survived a median of 12.6 months with one achieving long-term lymphoma-free survival at 40 months. This long-term survivor presented with Stage IE lymphoma as his only manifestation of AIDS. We conclude that AIDS-related lymphomas respond less favorably to radiation therapy than lymphomas in non-immunosuppressed patients. Furthermore, CNS lymphomatous involvement is an ominous occurrence in the AIDS patient. In our experience, cranial irradiation failed to provide significant palliation or survival prolongation in this group of patients. Instead, long-term survival is possible in AIDS patients with limited NHL outside the CNS, and it is in these patients that combination chemotherapy plus involved-field radiation therapy may play a curative role.

Acquired Immunodeficiency Syndrome↗

PubMedDate not supplied

Temporal CT changes after hepatic and renal interstitial radiotherapy in a canine model.

PURPOSE: The purpose of this work was to define the temporal CT characteristics of hepatic and renal ablation following point-source radioablation utilizing a low energy, photon X-ray source emitted from a miniature probe. METHOD: Twelve mongrel dogs underwent each of three hepatic and two renal point-source radiation ablations. Animals underwent serial, dual phase, spiral CT scans and were killed at 1, 3, and 6 months after treatment. RESULTS: Ablative lesions were clearly visible at 1 month following therapy and consistently diminished in size over the 6 months of follow-up. Lesion size tended to be proportional to dose delivered. Both hepatic and renal lesions were low in attenuation with frequent rim enhancement that diminished over time. Hepatic lesions frequently showed transient hepatic attenuation differences (THADs). Lesion size appeared independent of proximity to vessels. CONCLUSION: Following hepatic or renal interstitial radiotherapy, lesions are generated that are similar in CT appearance to those produced by other ablative techniques. The presence of rim or THAD enhancement can be seen early on as part of the normal tissue-healing response.

Animals↗