Accuracy of bound peptide structures determined by exchange transferred nuclear Overhauser data: a simulation study.

The exchange-transferred NOE method to determine the three-dimensional structure of peptides bound to proteins, or other macromolecular systems, is becoming increasingly important in drug design efforts and for large or multicomponent assemblies, such as membrane receptors, where structural analysis of the full system is intractable. The exchange-transferred nuclear Overhauser effect spectroscopy (etNOESY) method allows the determination of the bound-state conformation of the peptide from the intra-molecular NOE interactions between ligand protons. Because only ligand-ligand NOEs are generally observable, the etNOESY method is restricted to fewer NOEs per residue than direct protein structure determination. In addition, the averaging of relaxation rates between free and bound states affects the measured cross-peak intensities, and possibly the accuracy of distance estimates. Accordingly, the study reported here was conducted to examine the conditions required to define a reliable structure. The program CORONA was used to simulate etNOE data using a rate-matrix including magnetic relaxation and exchange rates for two peptide-protein complexes derived from the reference complex of cAMP-dependent protein kinase ligated with a 24-residue inhibitor peptide. The results indicate that reasonably accurate peptide structures can be determined with relatively few NOE interactions when the interactions occur between non-neighboring residues. The reliability of the structural result is suggested from the pattern of NOE interactions. A structure with an accuracy of approximately 1.3 A rms difference for the main-chain atoms can be obtained when etNOE interactions between non-neighboring residues occur over the length of the peptide. The global precision is higher (approximately 0.9 A rms difference) but is not correlated to global accuracy. A local definition of precision along the backbone appears to be a good indicator of the local accuracy.

Enhanced mucosal reactions in AIDS patients receiving oropharyngeal irradiation.

The oropharynx and hypopharynx are common sites of involvement in AIDS patients with mucocutaneous Kaposi's sarcoma. The radiotherapist is often asked to intervene with these patients due to problems with pain, difficulty in swallowing, or impending airway obstruction. We have noted an unexpected decrease in normal tissue tolerance of the oropharyngeal mucosa to irradiation in AIDS patients treated in our department. Data on 12 patients with AIDS and Kaposi's sarcoma receiving oropharyngeal irradiation are presented here. Doses ranged from 1000 cGy to 1800 cGy delivered in 150-300 cGy fractions. Seven of eight patients receiving doses of 1200 cGy or more developed some degree of mucositis, four of these developed mucositis severe enough to require termination of treatment. All patients in this study received some form of systemic therapy during the course of their disease, but no influence on mucosal response to irradiation was noted. Four patients received total body skin electron treatments, but no effect on degree of mucositis was seen. Presence or absence of oral candidiasis was not an obvious factor in the radiation response of the oral mucosa in these patients. T4 counts were done on 9 of the 12 patients. Although the timing of the T4 counts was quite variable, no correlation with immune status and degree of mucositis was found. The degree of mucositis seen in these patients occurred at doses much lower than expected based on normal tissue tolerances seen in other patient populations receiving head and neck irradiations. We believe that the ability of the oral mucosa to repair radiation damage is somehow altered in patients with AIDS.

Human leg heating using a mini-annular phased array.

The energy deposition pattern within an isolated human leg heated with a mini-annular phased array (MAPA) hyperthermia applicator has been determined. The non-tumor-bearing lower portion of a human leg amputated at the hip due to the presence of a large tumor in the thigh was "fixed" in a 50% ethanol in 0.9% saline solution. Subsequent to this fixation process, the leg was rehydrated in 0.9% saline and heated four times using a MAPA operating at 122 MHz. Specific absorption rates and electric field strengths were calculated from the rates of change of temperature with time measured at 143 different anatomical locations within the leg. When the leg was coaxial with the MAPA and the MAPA was axially positioned midway between the knee and the ankle, the points of maximum heating were skewed away from the center of the MAPA, towards the ankle of the leg and along the central axis of the MAPA. Significant temperature rise was measured inside the bone and the fat as well as inside the muscle of the leg. Bone heating was reduced when the leg was shifted away from the MAPA axis.

Non-small-cell lung cancer. Major cause of late mortality in patients with small cell lung cancer.

Among 360 patients with small cell lung cancer treated in National Cancer Institute therapeutic trials from 1973 to 1982, 40 were two-year cancer-free survivors. Of these 40 patients, six had later development of non-small-cell lung cancer at 3.5 to 8.0 years (median 5.1) after the diagnosis of small cell lung cancer. Three had the second malignant tumor in the contralateral lung, one in a different lobe, and two in the same lobe as the initial small cell lung cancer. Ten patients had relapses of small cell lung cancer at 2.1 to 6.2 years (median 3.2) from diagnosis. Three recurrences were in the same site or lobe as the initial lesion, four in the same lobe and in sites outside the thorax, and three solely in sites outside the thorax. It is concluded that these non-small-cell lung cancers usually represent second primary lung tumors and that most late small cell lung cancers represent relapses occurring up to 6.2 years from diagnosis. In this study, the risk of development of non-small-cell lung cancer after two years of disease-free survival following small cell lung cancer is 4.4 percent per person-year, approximately 10 times higher than the rate of 0.5 percent previously determined in screening studies of men at high risk for lung cancer. Non-small-cell lung cancer represents more than a third of lung cancer deaths in patients with small cell lung cancer surviving beyond two years from diagnosis and more than half of lung cancer deaths beyond three years. It is recommended that all patients treated for small cell lung cancer discontinue smoking.

The tolerance of skin grafts to postoperative radiation therapy in patients with soft-tissue sarcoma.

During the last ten years at the National Cancer Institute, 11 patients have received 12 courses of postoperative adjuvant radiation therapy to skin grafts used for wound closure after the resection of soft-tissue sarcomas. The intervals between grafting and the initiation of radiation ranged between 3 and 20 weeks, and 4 patients received chemotherapy at the same time as their radiation. Ten of the 12 irradiated grafts remained intact after the completion of therapy. One graft had several small persistently ulcerated areas that required no further surgical treatment, and one graft required a musculocutaneous flap for reconstruction of a persistent large ulcer. Acute radiation effects on the grafted skin sometimes developed at slightly lower doses than usually seen with normal skin, but these acute effects necessitated a break in therapy on only five occasions. Concurrent chemotherapy and a relatively short interval between grafting and the initiation of radiation seemed to contribute to more severe radiation reactions. This experience indicates that postoperative adjuvant radiation therapy can be delivered to skin grafted areas without undue fear of complications, especially if the graft is allowed to heal adequately prior to initiating therapy and if chemotherapy is not given in conjunction with radiation.

Pulmonary toxicity with combined modality therapy for limited stage small-cell lung cancer.

To assess the pulmonary toxicity of radiation therapy combined with chemotherapy v chemotherapy alone, we reviewed the clinical course of 80 patients with limited stage small-cell lung cancer treated in a randomized prospective trial. Life-threatening pulmonary toxicity, defined as bilateral pulmonary infiltrates extending beyond radiation ports with symptoms requiring hospital admission, developed in 11 patients (28%) receiving combined modality therapy and in two (5%) receiving chemotherapy alone. Eight of these 13 patients died from pulmonary complications with no clinical evidence of tumor in five. Pulmonary toxicity initially presented at a median of 63 days (range, 21 to 150 days) after the start of combined modality therapy and at a median of 217 days after chemotherapy alone. Biopsies obtained in 11 patients with severe toxicity revealed only interstitial fibrosis with no evidence of an infectious agent. Review of pretreatment parameters such as age, performance status, and radiation portal area failed to reveal any significant differences between patients with or without pulmonary complications. However, initial pulmonary function tests (PFTs) revealed a significantly lower vital capacity (P = .03) and forced expiratory volume (FEV/1.0 second) (P = .04) in patients with subsequent pulmonary complications. Pulmonary toxicity was significantly more common with combined modality therapy than with chemotherapy alone (P = .017) and worse than expected with radiotherapy alone. Six- or 12-month PFTs in completely responding patients revealed improvement within the chemotherapy alone group and no clear trend within the combined modality group. For the group treated with radiation therapy and chemotherapy, there was significantly less improvement after 6 or 12 months in the forced vital capacity (P less than .005) and FEV/1.0 second (P less than .005) than observed for the group treated with chemotherapy alone. Despite the increased incidence of pulmonary toxicity, overall survival favored the combined modality arm (P = .07). Enhanced local control and disease-free survival appeared to compensate for the initial increased pulmonary morbidity and mortality in the group with combined modality therapy.

Oxygen dependence of hematoporphyrin derivative-induced photoinactivation of Chinese hamster cells.

The oxygen dependence of hematoporphyrin derivative (HPD)-induced photoinactivation of Chinese hamster V79 cells was examined. Cells were treated with HPD (25 micrograms/ml) for 2 h and subsequently exposed to red light (greater than 590 nm) under either aerated or hypoxic (less than 10 ppm O2) conditions. Hypoxic cells were found to be extremely resistant to the lethal effects of HPD and light. The electron-affinic X-ray hypoxic cell sensitizer, SR-2508, did not sensitize hypoxic HPD-treated cells to light. The clinical implications of these findings are discussed, with consideration of the possibility that hypoxic areas in tumors may limit HPD phototherapy.

Computed tomography with metrizamide myelography to define the extent of spinal canal block due to tumor.

In five patients with complete spinal block due to tumor, CT was used to show the upper level of the block. In each case metrizamide myelography demonstrated the lower level of the block, but not enough metrizamide leaked past the block to allow myelographic identification of the upper level. However, the subarachnoid space both below and above the level of the block was clearly outlined by metrizamide on CT in each case.

A comparison of computed tomography and radionuclide scanning for detection of brain metastases in small cell lung cancer.

Neurologic history and examination, radionuclide brain scans (RN), and computed tomographic brain scans (CT) were performed at diagnosis and sequentially in 153 consecutive patients with small cell lung cancer (SCLC) to assess the sensitivity and accuracy of these screening methods and to determine whether the early detection of brain metastases influences survival. CT scans (sensitivity, 98%; positive predictive accuracy, 98%) were superior to RN scans (sensitivity, 71%; positive predictive accuracy, 86%) in patients with or without neurologic signs or symptoms. However, CT scans were positive in only 6% of asymptomatic patients at diagnosis and 13% of asymptomatic patients after systemic therapy. Brain metastases detected by CT scan were the sole site of extensive-stage disease in 6% of patients at diagnosis. Despite the enhanced ability of CT scans to detect asymptomatic lesions, survival after therapeutic cranial irradiation was similar for asymptomatic and symptomatic patients. The results suggest that CT brain scans should be used routinely in SCLC patients with neurologic signs or symptoms, at diagnosis (when treatment decisions are based on stage), and at six-month intervals in patients with prior brain metastases and in whom erratic follow-up is likely.

Small-cell carcinoma of lung: reinduction therapy after late relapse.

Some patients with small-cell carcinoma of lung can be expected to achieve long-term disease-free survival. However, relapses may occur even after 2 years. Information on the treatment of these patients is sparse, although response rates to "salvage" therapy in patients with progressive disease while receiving treatment are poor. We report six patients who had relapses after more than 2 years in complete remission. Five patients were retreated with chemotherapy including some or all of the drugs in the initial treatment, and four had responses with a median duration of 10 months (range, 2 to 18 months). Thus retreatment with chemotherapy similar to the initial treatment can occasionally achieve second responses persisting up to 1 year or longer. The high incidence of patients who have relapses after 2 years confirms previous data on relatively slow growth rates in small-cell carcinoma.