XR11576 (MLN576) is a novel monophenazine with a mechanism of action that includes interaction with both topoisomerase (Topo) I and II. The aim of this study was to evaluate its cytotoxicity against fresh tumor cells taken from patients with a variety of solid tumors. Cells were obtained from 89 patients and exposed for 6 days to XR11576 alone, or in combination with doxorubicin, cisplatin, treosulfan, paclitaxel or vinorelbine. Cell survival was measured using the ATP-Tumor Chemosensitivity Assay (ATP-TCA). Immunohistochemical staining of Topo I, Topo IIα and MDR1 was performed on paraffin-embedded blocks in those tumors for which tissue was available (n=49). Overall, the median IC90 and IC50 values of XR11576 in tumor-derived cells were 242 and 110 nM, respectively. In all samples XR11576 was more potent than the other cytotoxics tested. Breast and gynecological malignancies were most sensitive to XR11576, while the potency of this compound was slightly attenuated in gastrointestinal tumors, in which the median IC90 and IC50 values were 308 and 212 nM, respectively. Cases of synergism were identified when combining XR11576 with vinorelbine (nine of 30 samples) and doxorubicin (12 of 38 samples), while the addition of paclitaxel resulted in an antagonistic effect (CI50>1.2) in 38 of 42 tumors. A very modest correlation by linear regression analysis was found between the intensity of MDR1 staining and the IC50 of XR11576 (r=0.311, p=0.0312), but not with the IC90 (r=0.247, NS). These data support the rapid introduction of XR11576 to clinical trials and suggest that it may be effective against a broad spectrum of tumor types.
The tricyclic antidepressants have previously been shown to exert activity against glioma cells in vitro. Initial studies in cell lines suggested that this might extend to melanoma cells. We have therefore conducted a study in primary cell cultures from metastatic cutaneous melanoma deposits using a well established ATP-based tumour chemosensitivity assay to confirm and extend these findings. Two cell lines and eight primary cell cultures from metastatic melanoma deposits were exposed to three tricyclic drugs, amitriptyline, nortriptyline and clomipramine, at concentrations ranging from 200 to 6.25 µmol/l in the ATP-based tumour chemosensitivity assay. All three drugs showed activity, although nortriptyline was more active than clomipramine or amitriptyline in both cell lines and primary cell cultures, with an IC50 of 9, 27 and 33 µmol/l, respectively. Tricyclic agents show activity against melanoma in vitro. This could be related to the lysosomal effects based on their cationic amphiphilic properties, or effects at the mitochondrial membrane.
Advanced colorectal cancer (CRC) has a poor prognosis with a 5-year survival of only 5% despite treatment with chemotherapeutic agents. Response rate and overall survival varies little between the commonly used single agents, although combinations achieve better outcomes. It is well established that considerable heterogeneity exists between cancers of the same tissue type, but it has been difficult to establish this for CRC. We therefore investigated the heterogeneity of chemosensitivity in CRC using a modified version of the ex vivo ATP-tumor chemosensitivity assay (ATP-TCA) capable of handling infected tumor tissue. Fifty-three specimens of primary solid or malignant effusions of CRC were tested, of which 46 (87%) were evaluable. There were considerable differences in sensitivities between individuals. The most active single cytotoxic agents in the assay were identified as 5-fluorouracil, irinotecan and mitomycin C (MMC). Cells were exposed to combinations of drugs added simultaneously at the same concentrations tested as single agents. All drug combinations achieved greater growth inhibition than drugs used alone. MMC+gemcitabine was found to be the most effective combination in 83% of specimens. The ATP-TCA has previously been shown to be a good predictor of response to chemotherapy in other tissue types. The degree of heterogeneity demonstrated from these results suggests that the ATP-TCA could be used to identify patients who might benefit from specific chemotherapeutic agents alone or in combination.
Editor—There are many reports of partial trisomy 8p in the offspring of balanced translocation carriers.1-3 However, in these cases the effect of the partial trisomy is usually masked by the phenotypic consequences of partial monosomy of the partner chromosome.
Partial trisomy for 8p also results from the well known inverted duplication of 8p usually described as inv dup(8)(p11.2p23); this rearrangement, however, also results in partial monosomy for the segment 8p23.1→8pter.4-6 The inv dup(8) is associated with a well defined clinical syndrome,5-9 the childhood phenotype of which includes neonatal feeding problems, hypotonia, structural brain abnormalities, facial dysmorphology, malformed, low set ears, and severe developmental delay. In older patients the facial traits are less characteristic, mental retardation is profound, and spastic paraplegia and orthopaedic problems are frequent. It is known that patients with deletion of 8p23→pter as their sole chromosome abnormality have a near normal phenotype with only mild mental retardation and minimal dysmorphology.10-12 The phenotypic findings of inv dup(8)(p11.2p23) are therefore considered to arise primarily as a result of the duplicated segment 8p21.
More recent reports have described smaller, more distal duplications of 8p in which there is no evidence of any monosomic segment.13-17 Dhooge et al 13 described the transmission of a duplication dup(8)(p22→p23.1) or (p21.3→p22) from a mother to her two children. The associated clinical features were mild mental retardation, short stature, and hypertelorism. Engelen et al 14 described a similar case of transmission of partial trisomy 8p resulting from dup(8)(p22→p23.1) from a mother to her two sons. In this family, mental retardation was mild and there was no growth retardation, only the mother showed slight facial dysmorphology. Barber et al 15recently described seven families with small duplications of 8p23.1 and reviewed five families previously reported in abstract form.16 17 …
Pentamidine is a small molecule inhibitor of the Ca2+-binding protein S100B and disrupts the S100B–p53 protein–protein interaction; this is thought to restore wild-type p53 tumour suppressor function in melanoma. Additional anticancer effects may be the result of inhibition of regenerating liver family phosphatases. In this study, we have used a standardized ATP-tumour chemosensitivity assay to investigate the effect of pentamidine on cells derived from 18 skin melanoma samples and one uveal melanoma sample. The cells were tested at six concentrations from which the IC50 and IC90 were calculated. To allow comparison between samples, an indexsum was calculated based on the percentage of tumour growth inhibition at each concentration. Of the skin melanoma samples tested, 78% exhibited an indexsum less than 300 indicating strong inhibition. The median indexsum of 237 also indicates considerable activity against these samples. The median IC90 (30.2 μmol/l) may be clinically achievable in a proportion of patients. The uveal melanoma sample exhibited an indexsum of 333 indicating moderate inhibition, and 86% inhibition at test drug concentration (37.96 μmol/l). These results show that pentamidine has activity against melanoma, and support the prospect of its development for therapeutic use.
Algorithms for detecting molecular co-evolution have until now been applied only to individual protein families, but not to the human proteome. Linked to this is the problem that performing the computations for identifying co-evolving sites in the human proteome would take a prohibitively long time using the serial algorithms already in use. In addition, co-evolving sites have not been pursued as a possible way of classifying mutations according to their likelihood to cause disease. The main contributions of this thesis are as follows: identification of three suitable methods for detecting molecular co-evolution by comparing the performance of published state-of-the-art methods on simulated data; implementation of these methods in the parallel architecture CUDA, and evaluation of these methods’ performance in comparison to serial implementations of the same methods; and identification of co-evolving sites across the entire human proteome, and analysis of these sites according to what is already known about disease-causing mutations. Beyond demonstrating the effectiveness of CUDA for implementing molecular co-evolution detection algorithms, we derive insights into techniques for efficient implementation of algorithms in CUDA (particularly algorithms which require tree-based structures, such as parametric methods), and our results provide preliminary insights into the relationship between co-evolving sites and mutation pathogenicity.
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