Practice costs in diagnostic radiology.

PURPOSE: To report on practice costs and their variation. MATERIALS AND METHODS: In 1996 and 1997, practices were surveyed, and data on costs and other operational characteristics were obtained from approximately 170 practices. Several components of practice costs (eg, physician-related costs, administrative and business costs) were calculated separately for different group types (eg, academic, private hospital-only), each on four bases: per full-time equivalent (FTE) radiologist, per relevant procedure, per relevant relative value unit (RVU), and as a percentage of revenue. RESULTS: Median total practice costs per FTE radiologist ranged from approximately $90,000 to $190,000, depending on group type. Per procedure, the median ranged from $9 to $21; and as a percentage of revenue, it ranged from 27% to 41%. Median technical costs were approximately $36 per technical RVU in private hospital-and-office groups. Within any category of group, for every cost category, there was substantial variation among groups. CONCLUSION: The sizable variation implies that means or medians should not be regarded as norms. Nonetheless, the data on 75th and 25th percentile costs can show a radiology group where savings and inadequate resources, respectively, are relatively likely to be found. Physician-related costs are best measured per FTE. Technical costs and administrative and business costs are best measured per RVU or for categories of groups defined by having similar percentages of nonhospital services.

Raf-1 causes growth suppression and alteration of neuroendocrine markers in DMS53 human small-cell lung cancer cells.

Ras mutations are common in lung adenocarcinomas and squamous-cell cancers, which are non-small-cell lung cancers (NSCLCs). However, small-cell lung cancers (SCLCs) rarely have ras mutations, suggesting that ras activation may not confer a growth advantage in these cells. In one SCLC cell line DMS53, activated ras expression induced increased neuroendocrine differentiation and decreased cell proliferation. We show here that DMS53 cells undergo differentiation and G1-specific growth arrest in response to ras/raf/ mitogen-activated protein kinase kinase (MEK)/mitogen-activated protein kinase (MAPK) pathway activation. To assess the consequences of activating the raf/MEK/MAPK pathway downstream of ras, we transfected a DMS53 cell line with DeltaRaf-1:ER, an activatable form of c-raf-1. DeltaRaf-1:ER activation suppressed cell proliferation and cloning on soft agar by 90% without evidence of apoptosis. Cell cycle analysis showed a reduced proportion of cells in S phase, and was associated with induction of the cyclin-dependent kinase (cdk) inhibitor p16(INK4). Expression of the cell cycle-specific proteins pRb, Rb2/p130, p107, cyclin A, cdc-2, and E2F-1 was decreased after DeltaRaf-1:ER activation in DMS53 cells. The activity cdk4 and cdk2 was also reduced, as consistent with cell cycle arrest in cells with activated DeltaRaf-1:ER cells. In addition, DeltaRaf-1:ER reduced the expression of neuroendocrine markers, gastrin releasing peptide, and ret gene in DMS53:DeltaRaf-1:ER cells. These results provide further evidence that activation of the raf/MEK/ MAPK signaling pathway, which is associated with transformation in many circumstances, can reduce the growth of SCLC cells, and suggest that activation of this pathway might be clinically efficacious in some settings.

Retinoic acid-mediated growth inhibition of small cell lung cancer cells is associated with reduced myc and increased p27Kip1 expression.

Human lung cancer cells, including small cell lung carcinoma (SCLC), frequently lose expression of retinoic acid receptor beta (RAR-beta) and are resistant to the growth inhibitory activity of all-trans retinoic acid (RA). To elucidate the role of RAR-beta in the growth regulation of SCLC by retinoids, we restored RAR-beta expression in RAR-beta-negative H209 SCLC cells by retroviral transduction (H209-RAR-beta). We found that H209-RAR-beta, but not parental H209 cells, underwent growth inhibition upon RA treatment. RA-treated H209-RAR-beta cells arrested in G1 and displayed reduced L-myc expression and cyclin-dependent kinase 2 (cdk2) activity compared with untreated cells. RA treatment of H209-RAR-beta cells was also accompanied by increased expression of the cdk inhibitor p27Kip1, whereas no differences in the expression of L-myc or p27Kip1 were detected upon RA treatment of parental H209 cells. The RA-induced growth arrest of H82 SCLC cells, which express endogenous RAR-beta, was also associated with reduced c-myc and increased p27Kip1 expression. We found that ectopic expression of p27Kip1 induced growth inhibition in both H209 and H82 cells, and that sustained myc expression in H209-RAR-beta cells promoted the induction of apoptosis upon RA addition. Our observations indicate that RAR-beta gene transfer can restore RA sensitivity in SCLC cells and suggest that myc and p27Kip1 may represent critical mediators of the RA-induced cell cycle arrest in SCLC cells expressing RAR-beta.

Raf-1-induced cell cycle arrest in LNCaP human prostate cancer cells.

Prostate cancer is the most commonly diagnosed neoplasm in men. LNCaP cells continue to possess many of the molecular characteristics of in situ prostate cancer. These cells lack ras mutations, and mitogen-activated protein kinase (MAPK) is not extensively phosphorylated in these cells. To determine the effects of ras/raf/MAPK pathway activation in these cells, we transfected LNCaP cells with an activatable form of c-raf-1(deltaRaf-1:ER). Activation of deltaRaf-1:ER, with resultant MAPK activation, reduced plating efficiency and soft agarose cloning efficiency 30-fold in LNCaP cells. Cell cycle distribution showed an accumulation of cells in G1 and was associated with the induction of CDK inhibitor p21WAF1/CIP1 at the protein and mRNA levels. p21WAF1/CIP1 mRNA stability was increased after deltaRaf-1:ER activation. In addition, activated deltaRaf-1:ER induced the senescence associated-beta-galactosidase in LNCaP cells. These data demonstrate that raf activation can activate growth inhibitory pathways leading to growth suppression in prostate carcinoma cells and also suggest that raf/MEK/MAPK pathway activation, rather than inhibition, may be a therapeutic target for some human prostate cancer cells.

A phase II study of all-trans-retinoic acid plus cisplatin and etoposide in patients with extensive stage small cell lung carcinoma: an Eastern Cooperative Oncology Group Study.

BACKGROUND: The dysregulation of both myc gene expression and retinoid signaling pathways commonly occurs in small cell lung carcinoma (SCLC). Because preclinical data showed that all-trans-retinoic acid (RA) inhibited SCLC growth, altered myc expression, and blocked transition to a treatment-resistant phenotype, a Phase II trial was designed to determine the effects of the combination of RA, cisplatin, and etoposide in patients with SCLC. METHODS: Patients with untreated, extensive stage SCLC were treated with up to 8 cycles of cisplatin, 60 mg/m2, intravenously (i.v.) on Day 1 and etoposide, 120 mg/m2, i.v. on Days 1-3 in addition to up to 1 year of oral RA, 150 mg/m2/day. RESULTS: Of 22 assessable patients 1 had a complete response and 9 had a partial response, for an overall response rate of 45% (95% confidence interval, 24-68%). The median survival was 10.9 months and the 1-year survival was 41%. The median duration of chemotherapy was 6 cycles and the median duration of RA treatment was 2.8 months. Thirteen patients discontinued RA prematurely due to toxicity and only 4 responders were receiving RA at the time of recurrence. Toxicity-limiting RA treatment mainly was comprised of mucocutaneous changes and headaches. CONCLUSIONS: RA at a dose of 150 mg/m2/day was tolerated poorly in combination with cisplatin plus etoposide, leading to early discontinuation of RA in the majority of patients. The hematologic toxicity, response rate, and survival were similar to those associated with cisplatin and etoposide in prior trials. Further studies with more active and less toxic agents will be required to determine the role of retinoids in the treatment of SCLC.

Induction of gastrin releasing peptide by all-trans retinoic acid in small cell lung cancer cells.

All-trans retinoic acid (RA) has been shown to inhibit cell proliferation while increasing neuroendocrine differentiation in small cell lung cancer (SCLC) cells. RA and related compounds are rapidly becoming integrated into clinical trials to prevent lung cancers and other aerodigestive neoplasms. We found that expression of gastrin releasing peptide (GRP), which can promote lung tumorigenesis in model systems, was increased by RA in SCLC cells which have functional retinoid signaling. In SCLC cells that possess functional GRP receptors, ectopic expression of RARc increased GRP expression and augmented cloning efficiency, demonstrating that these maneuvers result in biologically active GRP. SCLC cells with defects in RA pathway signaling did not efficiently induce GRP upon RA exposure. In these cells, transfection of RARs rendered the cells competent to induce GRP upon RA exposure. These data show that activation of intact retinoid signaling by RA can induce GRP, a growth factor that can act as a tumor promoter. Our findings suggest the possibility that retinoids may increase, rather than decrease, lung cancer risks in some individuals.

Activated Raf-1 causes growth arrest in human small cell lung cancer cells.

Small cell lung cancer (SCLC) accounts for 25% of all lung cancers, and is almost uniformly fatal. Unlike other lung cancers, ras mutations have not been reported in SCLC, suggesting that activation of ras-associated signal transduction pathways such as the raf-MEK mitogen-activated protein kinases (MAPK) are associated with biological consequences that are unique from other cancers. The biological effects of raf activation in small cell lung cancer cells was determined by transfecting NCI-H209 or NCI-H510 SCLC cells with a gene encoding a fusion protein consisting of an oncogenic form of human Raf-1 and the hormone binding domain of the estrogen receptor (DeltaRaf-1:ER), which can be activated with estradiol. DeltaRaf-1:ER activation resulted in phosphorylation of MAPK. Activation of this pathway caused a dramatic loss of soft agar cloning ability, suppression of growth capacity, associated with cell accumulation in G1 and G2, and S phase depletion. Raf activation in these SCLC cells was accompanied by a marked induction of the cyclin-dependent kinase (cdk) inhibitor p27(kip1), and a decrease in cdk2 protein kinase activities. Each of these events can be inhibited by pretreatment with the MEK inhibitor PD098059. These data demonstrate that MAPK activation by DeltaRaf-1:ER can activate growth inhibitory pathways leading to cell cycle arrest. These data suggest that raf/MEK/ MAPK pathway activation, rather than inhibition, may be a therapeutic target in SCLC and other neuroendocrine tumors.

Second primary cancers related to smoking and treatment of small-cell lung cancer. Lung Cancer Working Cadre.

BACKGROUND: An increased risk of second primary cancers has been reported in patients who survive small-cell carcinoma of the lung. The treatment's contribution to the development of second cancers is difficult to assess, in part because the number of long-term survivors seen at any one institution is small. We designed a multi-institution study to investigate the risk among survivors of developing second primary cancers other than small-cell lung carcinoma. METHODS: Demographic, smoking, and treatment information were obtained from the medical records of 611 patients who had been cancer free for more than 2 years after therapy for histologically proven small-cell lung cancer, and person-years of follow-up were cumulated. Population-based rates of cancer incidence and mortality were used to estimate the expected number of cancers or deaths. The actuarial risk of second cancers was estimated by the Kaplan-Meier method. RESULTS: Relative to the general population, the risk of all second cancers among these patients (mostly non-small-cell cancers of the lung) was increased 3.5-fold. Second lung cancer risk was increased 13-fold among those who received chest irradiation in comparison to a sevenfold increase among nonirradiated patients. It was higher in those who continued smoking, with evidence of an interaction between chest irradiation and continued smoking (relative risk = 21). Patients treated with various forms of combination chemotherapy had comparable increases in risk (9.4- to 13-fold, overall), except for a 19-fold risk increase among those treated with alkylating agents who continued smoking. IMPLICATIONS: Because of their substantially increased risk, survivors should stop smoking and may consider entering trials of secondary chemoprevention.

An achaete-scute homologue essential for neuroendocrine differentiation in the lung.

In Drosophila and in vertebrates, the achaete-scute family of basic helix-loop-helix transcription factors plays a critical developmental role in neuronal commitment and differentiation. Relatively little is known, however, about the transcriptional control of neural features in cells outside a neuronal context. A minority of normal bronchial epithelial cells and many lung cancers, especially small-cell lung cancer, exhibit a neuroendocrine phenotype that may reflect a common precursor cell population. We show here that human achaete-scute homologue-1 (hASH1) is selectively expressed in normal fetal pulmonary neuroendocrine cells, as well as in the diverse range of lung cancers with neuroendocrine features. Strikingly, newborn mice bearing a disruption of the ASH1 gene have no detectable pulmonary neuroendocrine cells. Depletion of this transcription factor from lung cancer cells by antisense oligonucleotides results in a significant decrease in the expression of neuroendrocrine markers. Thus, a homologue of Drosophila neural fate determination genes seems to be necessary for progression of lung epithelial cells through a neuroendocrine differentiation pathway that is a feature of small-cell lung cancer, the most lethal form of human lung cancer.

Mechanism of all-trans-retinoic acid-mediated L-myc gene regulation in small cell lung cancer.

The L-myc oncogene is commonly expressed in small cell lung cancer (SCLC) cells and is associated with SCLC cells with a high level of neuroendocrine differentiation and a relatively low proliferative index. We have previously reported that all-trans-retinoic acid (RA) inhibits the growth of NCI-H82 SCLC cells in association with increased neuroendocrine differentiation, increased L-myc gene expression and decreased c-myc gene expression. In the present report, the mechanism of RA-mediated L-myc up-regulation in NCI-H82 SCLC cells was determined by analysing transcriptional and post-transcriptional control of L-myc gene expression. Increases in steady-state levels of L-myc mRNA occurred in a dose-dependent manner after exposure to RA at a time-point prior to discernible changes in cellular morphology or growth. By nuclear run-on analysis, there was a clear increase in L-myc transcript initiation in NCI-H82 cells treated with 1 microM RA, but no alteration was noted in the baseline degree of transcript attenuation when compared to control cells. L-myc transcript half-life remained unchanged after exposure to 1 microM RA, indicating that post-transcriptional regulation is not a major factor in the control of L-myc gene expression. A marked dose-dependent increase in RARbeta expression was also demonstrated in RA-treated NCI-H82 cells. We conclude that RA-mediated up-regulation of L-myc gene expression occurs through stimulation of transcript initiation and that the biological effects of RA in SCLC cells may be mediated through RARbeta-dependent pathways.

Selective radiosensitization of p53-deficient cells by caffeine-mediated activation of p34cdc2 kinase.

The induction of tumor cell death by anticancer therapy results from a genetic program of autonomous cell death termed apoptosis. Because the p53 tumor suppressor gene is a critical component for induction of apoptosis in response to DNA damage, its inactivation in cancers may be responsible for their resistance to genotoxic anticancer agents. The cellular response to DNA damage involves a cell-cycle arrest at both the G1/S and G2/M transitions; these checkpoints maintain viability by preventing the replication or segregation of damaged DNA. The arrest at the G1 checkpoint is mediated by p53-dependent induction of p21WAF1/CIP1, whereas the G2 arrest involves inactivation of p34cdc2 kinase. Following DNA damage, p53-deficient cells fail to arrest at G1 and accumulate at the G2/M transition. We demonstrate that abrogation of G2 arrest by caffeine-mediated activation of p34cdc2 kinase results in the selective sensitization of p53-deficient primary and tumor cells to irradiation-induced apoptosis. These data suggest that pharmacologic activation of p34cdc2 kinase may be a useful therapeutic strategy for circumventing the resistance of p53-deficient cancers to genotoxic anticancer agents.

RREB-1, a novel zinc finger protein, is involved in the differentiation response to Ras in human medullary thyroid carcinomas.

An activated ras oncogene induces a program of differentiation in the human medullary thyroid cancer cell line TT. This differentiation process is accompanied by a marked increase in the transcription of the human calcitonin (CT) gene. We have localized a unique Ras-responsive transcriptional element (RRE) in the CT gene promoter. DNase I protection indicates two domains of protein-DNA interaction, and each domain separately can confer Ras-mediated transcriptional inducibility. This bipartite RRE was also found to be Raf responsive. By affinity screening, we have cloned a cDNA coding for a zinc finger transcription factor (RREB-1) that binds to the distal RRE. The consensus binding site for this factor is CCCCAAACCACCCC. RREB-1 is expressed ubiquitously in human tissues outside the adult brain. Overexpression of RREB-1 protein in TT cells confers the ability to mediate increased transactivation of the CT gene promoter-reporter construct during Ras- or Raf-induced differentiation. These data suggest that RREB-1 may play a role in Ras and Raf signal transduction in medullary thyroid cancer and other cells.

The genotype of the human cancer cell: implications for risk analysis.

An extremely large database describes genotypes associated with the human cancer phenotype and genotypes of human populations with genetic predisposition to cancer. Aspects of this database are examined from the perspective of risk analysis, and the following conclusions and hypotheses are proposed: (1) The genotypes of human cancer cells are characterized by multiple mutated genes. Each type of cancer is characterized by a set of mutated genes, a subset from a total of more than 80 genes, that varies between tissue types and between different tumors from the same tissue. No single cancer-associated gene nor carcinogenic pathway appears suitable as an overall indicator whose induction serves as a quantitative marker for risk analysis. (2) Genetic defects that predispose human populations to cancer are numerous and diverse, and provide a model for associating cancer rates with induced genetic changes. As these syndromes contribute significantly to the overall cancer rate, risk analysis should include an estimation of the effect of putative carcinogens on individuals with genetic predisposition. (3) Gene activation and inactivation events are observed in the cancer genotype at different frequencies, and the potency of carcinogens to induce these events varies significantly. There is a paradox between the observed frequency for induction of single mutational events in test systems and the frequency of multiple events in a single cancer cell, suggesting events are not independent. Quantitative prediction of cancer risk will depend on identifying rate-limiting events in carcinogenesis. Hyperproliferation and hypermutation may be such events. (4) Four sets of data suggest that hypermutation may be an important carcinogenic process. Current mechanisms of risk analysis do not properly evaluate the potency of putative carcinogens to induce the hypermutable state or to increase mutation in hypermutable cells. (5) High-dose exposure to carcinogens in model systems changes patterns of gene expression and may induce protective effects through delay in cell progression and other processes that affect mutagenesis and toxicity. Paradigms in risk analysis that require extrapolation over wide ranges of exposure levels may be flawed mechanistically and may underestimate carcinogenic effects of test agents at environmental levels. Characteristics of the human cancer genotype suggest that approaches to risk analysis must be broadened to consider the multiplicity of carcinogenic pathways and the relative roles of hyperproliferation and hypermutation. Further, estimation of risk to general human populations must consider effects on hypersusceptible individuals. The extrapolation of effects over wide exposure levels is an imprecise process.

Expression of prokaryotic HhaI DNA methyltransferase is transforming and lethal to NIH 3T3 cells.

In neoplastic cells, levels of DNA methyltransferase activity are often increased, and evidence is accruing to suggest an important role for this event in tumorigenesis. To evaluate this possibility further, and to investigate the contribution of increasing de novo, as opposed to maintenance, DNA methylation in mammalian cells, we expressed the bacterial HhaI methyltransferase in cultured murine fibroblasts. This enzyme is a pure de novo DNA methyltransferase that methylates the internal C in the sequence GCGC. We find that both constitutive and induced expression of the wild-type HhaI results, primarily, in lethality to the cells. However, surviving cell clones that express low levels of M. HhaI demonstrate increased tumorigenicity as assessed by soft agar cloning efficiency (8.6% for sense HhaI-transduced PA 317 cells versus 0.4% for antisense controls; 1.7% for sense HhaI-transfected NIH 3T3 cells versus 0% for a mutant HhaI control) and tumorigenicity in nude mouse heterotransplants (75% for sense HhaI-transduced PA 317 cells versus 18.5% for antisense controls). DNA isolated from the clonogenic sense HhaI clones, versus clones expressing the mutant HhaI gene, has no increase in overall CpG methylation but an average of 27% (range, 16.7-38.9) increase in methylcytosine content at GCGC sites. These findings suggest that eukaryotic cells tolerate a narrow window of increase de novo DNA methylating capacity, above which cell death occurs and within cell transformation results. Our results further emphasize the potential role of increased DNA methyltransferase activity in the evolution of cancer.

Effect of v-rasH on sensitivity of NCI-H82 human small cell lung cancer cells to cisplatin, etoposide, and camptothecin.

Expression of v-ras(H) in NCI-H82 human small cell lung cancer (SCLC) cells results in a line (NCI-H82ras(H)) with a non-small cell phenotype (Mabry et al., Proc Natl Acad Sci USA 85: 6523-6527, 1988). This v-ras(H) -associated phenotypic change is prevented by treatment with trans-retinoic acid (tRA) (Kalemkarian et al., Cell Growth Differ 5: 55-60, 1994). The present studies were performed to examine changes in drug sensitivity that accompanied these phenotypic changes. v-ras(H) expression was associated with increased metallothionein-IIa (MT-IIa) mRNA and decreased levels of nonprotein sulfhydryls in NCI-H82ras(H) cells compared with -H82 cells. These changes were accompanied by the development of CdCl2 resistance without any change in cisplatin sensitivity. In contrast, growth of parental NCI-H82 cells in 1 microM tRa resulted in increased MT-IIa mRNA without any change in nonprotein sulfhydryls. In these cells, a 3.3-fold increase in cisplatin IC50 was observed. Examination of the action of topoisomerase (topo) poisons revealed that NCI-H82 and -H82ras(H) cells had indistinguishable levels of topo II polypeptides and indistinguishable sensitivities to etoposide, an agent that is often combined with cisplatin clinically. On the other hand, v-ras(H) expression was accompanied by a 2-fold increase in topo I activity and a 1.7-fold decrease in IC50 for the topo I-directed agent camptothecin. These changes resulted in 30-fold lower survival of NCI-H82ras(H) cells compared with -H82 cells at camptothecin concentrations as low as 10 nM. In summary, these studies demonstrate that chronic tRA treatment is accompanied by decreased cisplatin sensitivity in NCI-H82 human SCLC cells. In contrast, v-ras(H) expression is not associated with any change in cisplatin or etoposide sensitivity, but is accompanied by increased camptothecin sensitivity.

Growth inhibition and induction of apoptosis by fenretinide in small-cell lung cancer cell lines.

BACKGROUND: Lung cancer is the major cause of cancer-related death in the United States, with small-cell lung cancer (SCLC) constituting approximately 20% of all cases of lung cancer. Numerous epidemiologic and molecular studies have suggested that alterations in retinoid-signaling pathways play a role in the pathogenesis of lung cancer. Fenretinide [N-(4-hydroxyphenyl)retinamide; HPR] is a synthetic retinoid with minimal toxicity and favorable pharmacokinetics during long-term administration to patients in clinical trials. PURPOSE: The aim of this investigation was to study the effect of HPR on the growth of SCLC cells in vitro. METHODS: Seven SCLC cell lines (NCI-H69, NCI-H82, NCI-H146, NCI-H209, NCI-H345, NCI-H446, and NCI-H510A) were exposed continuously to a broad range of concentrations of HPR or all-trans-retinoic acid (RA), and cell viability was determined on day 3 and day 7 by the trypan blue dye exclusion assay. The growth of these cells was compared with that of control vehicle-treated cells to determine survival fraction and the dose resulting in a 50% inhibition of growth when compared with growth of control cells (IC50). The induction of apoptosis was evaluated by fluorescent microscopy, DNA content analysis, and a terminal deoxyribonucleotidyl transferase-based assay that labels 3'-hydroxyl ends of DNA fragments (TUNEL assay) combined with flow cytometric analysis. RESULTS: HPR inhibited growth of a panel of SCLC cell lines at IC50 values that ranged from 0.1 to 3.0 microM (concentrations that are clinically achievable). In all cell lines tested, HPR was a more potent growth inhibitor than RA. By use of fluorescent microscopy, HPR was found to induce morphologic changes consistent with apoptosis in NCI-H82 SCLC cells, including cellular shrinkage, chromatin condensation, and nuclear fragmentation. Flow cytometric analysis revealed decreased DNA content, and TUNEL assay showed increased digoxigenin-uridine triphosphate incorporation in HPR-treated NCI-H82 SCLC cells; these findings are consistent with the induction of apoptosis. CONCLUSIONS: HPR inhibited the in vitro growth of SCLC cells. In NCI-H82 cells, HPR inhibited growth via the induction of apoptosis.