Pax-1 in the development of the cervico-occipital transitional zone

The Pax-1 gene has been found to play an important role in the development of the vertebral column. The cervico-occipital transitional zone is a specialized region of the vertebral column, and malformations of this region have frequently been described in humans. The exact embryonic border between head and trunk is a matter of controversy. In order to determine a possible role of Pax-1 in the development of the cervico-occipital transitional zone we studied the expression of this gene in a series of quail embryos and murine fetuses with in situ hybridization and immunohistochemistry. Pax-1 is expressed in all somites of the embryo, including the first five occipital ones. During embryonic days 3–5 the gene is down-regulated in the caudal direction within the first five somites, whereas more caudally Pax-1 is strongly expressed in the cells of the perinotochordal tube. In 5-day-old quail embryos, the cartilaginous anlage of the basioccipital bone has developed and there is no more expression of Pax-1 in this region. The fusion of the dens axis with the body of the axis also coincides with switching off of the Pax-1 gene. More caudally, the gene is continuously expressed in the intervertebral discs of murine embryos and therefore seems to be important for the process of resegmentation. Quail embryos do not possess permanent intervertebral discs. Hyper- or hyposegmentation defects may be explained by an over- or under-expression of Pax-1 during development. We also reinvestigated the border between the head and trunk in chick embryos by performing homotopical grafting experiments of the 5^th somite between chick and quail embryos. Grafted quail cells formed mainly the caudal end of the basioccipital bone. They were also located in the cranial half of the ventral atlantic arch, and only a few cells were found in the tip of the dens axis.     

Dynamic Contrast-Enhanced MR Imaging for Soft Tissue Sarcomas

Dynamic contrast-enhanced magnetic resonance imaging has recently emerged as an important method for evaluating soft tissue sarcomas for biopsy localization, chemotherapeutic response, and long-term follow-up because of its ability to detect viable tumor. This article presents the basic principles of contrast kinetics in soft tissue sarcomas after bolus injection of contrast agent and discusses the current postprocessing methods (subtraction, first-pass image and time-intensity curves with region of interest, and color-encoded techniques) used to display these dynamic studies. Because of its excellent temporal resolution, dynamic MR imaging can delineate the early uptake of contrast agent in sarcomas within seconds after injection, almost synchronous with arterial enhancement, and thereby differentiate the rapidly enhancing viable tumor from the nonenhancing necrotic tumor and the late enhancing changes after surgery, radiation therapy, and chemotherapy.     

Effects of the enantiomers of disopyramide and its major metabolite on the electrophysiological characteristics of the guinea-pig papillary muscle

Summary Disopyramide, a Class la antiarrhythmic drug, is clinically used as a racemic mixture; R(–)disopyramide and S(+)disopyramide. The major metabolite in man is desisopropyldisopyramide: R(–)desisopropyl-disopyramide and S(+)desisopropyldisopyramide. The effects of the four compounds were compared on the electrophysiological characteristics of the guinea-pig papillary muscle using the standard microelectrode technique. At an external K⁺ concentration of 5.4 mmol/l and a stimulation frequency of 1 Hz, S(+)disopyramide (20 mol/l) increased action potential duration (APD) by more than 18%, while it was diminished by 6% in the presence of R(–)disopyramide. Resting membrane potential amounted to –87.1 ± 0.5 mV (n = 14) and –85.6 ± 1.2 mV (n = 10), respectively. Also a small but significant difference in effect on the maximal rate of depolarization was observed, R(–)disopyramide being more potent, related with a slower recovery of the maximal rate of depolarization.The enantiomers of the metabolite appeared to be three times less potent than those of the parent drug in their effect on the maximal rate of depolarization. The characteristics of the enantiomers of the metabolite correlated with those of the parent drug: also the R(–)-enantiomer was more potent in decreasing the maximal rate of depolarization and caused more shortening of the action potential than the S(+)enantiomer.Time constants for onset and recovery of/from rate dependent block of the maximal rate of depolarization were dependent upon the external K⁺ concentration, both for the enantiomers of the parent drug and those of the metabolite. Onset slowed down while recovery accelerated when external K⁺ was increased. Time constants were lower for the metabolite.When stimulation interval was shortened, the effect on the maximal rate of depolarisation increased. Only for the metabolite statistical significant stereoselective differences were observed at all stimulation intervals. The effects on the action potential duration were dependent upon stimulation interval; for all enantiomers the action potential duration tended to be relatively (% of control) higher at short stimulation intervals than at large stimulation intervals. The effect on the maximal rate of depolarization was also voltage dependent, but no significant differences were observed between the enantiomers, for the parent drug as well as for the metabolite. Send offprint requests to N. Verbeke at the above address     

Treatment of patients with advanced non-small cell lung cancer

In advanced non-small cell lung cancer (NSCLC), an objective response to chemotherapy is of limited value and the impact of chemotherapy on survival is modest. Therefore, endpoints evaluating the patients’ subjective benefit such as symptom control (SC), quality of life (QOL) or clinical benefit (CB) have recently been implemented into clinical trials, mostly as secondary endpoints. Chemotherapy offers SC, not only in patients with an objective response, but also in a proportion of patients with disease stabilization. For this purpose, three to four cycles of platinum-based chemotherapy are recommended. Interpretation of QOL objectives is limited by several methodologic problems. Studies comparing best supportive care alone with either older platinum-based combinations or single-agent chemotherapy with a new cytotoxic drug usually indicate improved survival and improvement of some component(s) of QOL in the active treatment arm. However, results from studies comparing different chemotherapies are less definitive. Trials comparing single-agent therapy with a new drug with new combinations mostly report no difference in QOL. In addition, most trials comparing new platinum-based combinations with older ones, and trials comparing new platinum-based regimens fail to show any differences in QOL. As a whole, it is far from clear whether combination therapy is superior to modern single-agent therapy, when the patient’s benefit is the primary endpoint. Non-platinum-based doublets, compared with platinum-based doublets, may lead to slightly inferior survival, are not always less toxic, and have not been proven to provide better QOL outcomes. The CB response, originally reported in pancreatic cancer, measures more than SC, but not full QOL. Encouraging experience with this tool was reported in advanced NSCLC. Randomized studies designed to look at some form of patient benefit as a primary endpoint should be a priority in advanced NSCLC.     

Fibrosarcoma in Children: A Rare Tumour with Long-Term Survival even with Advanced Disease A Report of 3 Cases

Fibrosarcoma is a rare tumour in children. The potential of malignancy has been questioned. We present three cases of fibrosarcoma in children. The follow-up periods range from 10 to 37 years. The first patient had pulmonary metastases at the time of diagnosis in 1958. The primary tumour in fossa ischio-rectalis was resected in 1960. Lung metastases were resected in 1960 and 1989. Radiotherapy was given in 1992. He is still alive with metastases 37 years after the first manifestation of disease. The second patient had a primary tumour and several local recurrences in the mandible. He is alive without evidence of disease 4 years after resection of pulmonary metastases and 21 years after resection of the primary tumour. The third patient has no signs of recurrence or metastasic spread 10 years after a wide excision of subcutanous tumours of the left upper arm. The cases demonstrate a special tumour-entity of low-grade malignancy, which show a good prognosis and a wide spectrum of biological behaviour.     

Biallelic deletions in INK4 in cutaneous melanoma are common and associated with decreased survival.

PURPOSE: Both the retinoblastoma and p53 pathways are often genetically altered in human cancers and their complex regulation is in part mediated by the three gene products p16, p14(ARF), and p15 of the INK4 locus on chromosome 9p21. Partial or complete biallelic deletions of the INK4 locus have been recognized in a variety of malignant tumors, including malignant melanoma. We have in the present study measured the frequency of INK4 deletions in a large number of melanoma metastases and determined their association with clinicopathologic variables and survival data. EXPERIMENTAL DESIGN: Quantitative real-time PCR, as well as fluorescence-based fragment analysis, has been used to perform measurements of the relative allelic concentrations of the INK4 genes in 112 human melanoma tumor samples from 86 patients. RESULTS: Thirty-eight of 86 melanoma patients (44%) had metastases with biallelic losses in INK4. Ten of 20 patients with multiple metastases showed similar deletion patterns in all analyzed tumors. There was no significant association between any of the clinicopathologic variables and loss of INK4. However, loss of INK4 had an adverse effect on median survival from time of diagnosis. Patients with tumors with diploid INK4 had a median survival of 142 months, whereas those with monoallelic or biallelic loss in INK4 had a median survival of only 47 months (P = 0.006). CONCLUSIONS: Our results point to homozygous deletions in the INK4 region as being one of the most common genetic alterations in malignant cutaneous melanoma. INK4 deletions are associated with an adverse prognosis.     

Comparison of different methods of CAIX quantification in relation to hypoxia in three human head and neck tumor lines.

PURPOSE: In head and neck cancer, it has been shown that hypoxic tumors respond poorly to therapy. Methods to identify hypoxic tumors are, therefore, of importance to select patients for oxygenation modifying or other intensified treatments. The aim of this study was to compare tumor cell hypoxia assessed by the hypoxic cell marker pimonidazole (PIMO) with expression of the endogenous hypoxia-related marker carbonic anhydrase IX (CAIX) in three human head and neck tumor lines. MATERIAL AND METHODS: Forty-five tumors of three human head and neck tumor lines, SCCNij3, SCCNij59 and MEC82, xenografted in athymic mice, were used. CAIX was quantified by biodistribution (% injected dose/g tumor) after injecting 3-5 microl 111In-labeled G250 mouse antibody 3 days prior to euthanizing. In a tissue section from the same tumor, fractions of tumor area positive for PIMO, CAIX and Hoechst 33342 (perfusion marker) were assessed after immunohistochemical staining, using a digital image analysis system. RESULTS: SCCNij3 and MEC82 were relatively hypoxic tumor lines with fractions of tumor area positive for pimonidazole of 0.16 and 0.15, respectively. SCCNij59 was a better-oxygenated tumor line with a PIMO-fraction of 0.03. The three tumor lines showed different levels and patterns of CAIX immunohistochemical staining, but only in MEC82 there was a good correlation between PIMO-fraction and CAIX-fraction (r2=0.92, P<0.0001). Correlations between 111In-G250 uptake and CAIX-fraction or PIMO-fraction within tumor lines were weak or absent. CONCLUSIONS: Assessment of CAIX expression depends largely on the techniques and tumor lines used. Furthermore, the immunohistochemical staining pattern of CAIX relative to PIMO differs between human tumor lines of similar anatomical origin. Therefore, the use of CAIX as endogenous marker of tumor hypoxia remains questionable.     

In vivo therapeutic responses contingent on Fanconi anemia/BRCA2 status of the tumor.

PURPOSE: BRCA2, FANCC, and FANCG gene mutations are present in a subset of pancreatic cancer. Defects in these genes could lead to hypersensitivity to interstrand cross-linkers in vivo and a more optimal treatment of pancreatic cancer patients based on the genetic profile of the tumor. EXPERIMENTAL DESIGN: Two retrovirally complemented pancreatic cancer cell lines having defects in the Fanconi anemia pathway, PL11 (FANCC-mutated) and Hs766T (FANCG-mutated), as well as several parental pancreatic cancer cell lines with or without mutations in the Fanconi anemia/BRCA2 pathway, were assayed for in vitro and in vivo sensitivities to various chemotherapeutic agents. RESULTS: A distinct dichotomy of drug responses was observed. Fanconi anemia-defective cancer cells were hypersensitive to the cross-linking agents mitomycin C (MMC), cisplatin, chlorambucil, and melphalan but not to 5-fluorouracil, gemcitabine, doxorubicin, etoposide, vinblastine, or paclitaxel. Hypersensitivity to cross-linking agents was confirmed in vivo; FANCC-deficient xenografts of PL11 and BRCA2-deficient xenografts of CAPAN1 regressed on treatment with two different regimens of MMC whereas Fanconi anemia-proficient xenografts did not. The MMC response comprised cell cycle arrest, apoptosis, and necrosis. Xenografts of PL11 also regressed after a single dose of cyclophosphamide whereas xenografts of genetically complemented PL11(FANCC) did not. CONCLUSIONS: MMC or other cross-linking agents as a clinical therapy for pancreatic cancer patients with tumors harboring defects in the Fanconi anemia/BRCA2 pathway should be specifically investigated.