The BRAF and NRAS mutation prevalence in dermoscopic subtypes of acquired naevi reveals constitutive mitogen-activated protein kinase pathway activation.

BACKGROUND: Acquired naevi can have unique dermoscopic patterns that correspond to distinct microanatomical growth patterns. Previous studies on acquired naevi stratified according to dermoscopic pattern focused on the frequency of somatic BRAF mutations, whereas NRAS mutations remained to be elucidated. OBJECTIVES: To investigate the BRAF and NRAS mutation prevalence and activation of the mitogen-activated protein kinase (MAPK) pathway in distinct dermoscopic subtypes of acquired naevi. METHODS: Common mutations present in BRAF and NRAS were assessed in 40 globular, reticular and peripheral rim of globules (PG) subtypes of acquired naevi from 27 participants (19 male, 8 female; mean age 46·7 years) selected from 1261 eligible volunteers. Mutations were determined using the highly sensitive and quantitative QX200 droplet digital™ polymerase chain reaction (ddPCR) system. RESULTS: The BRAF V600E (c.1799T>A or c.1799_1800delTGinsA) and BRAF V600K mutations were detected in 85% (n = 34/40) of naevi. All BRAF wild-type naevi (15%; n = 6/40) harboured an NRAS codon 12/13 or 61 mutation. BRAF mutations were present in 92% (n = 12/13) of globular and 100% (n = 12/12) of PG naevi, whereas reticular naevi were 67% (n = 10/15) BRAF- and 33% (n = 5/15) NRAS-mutant (P = 0·037). CONCLUSIONS: We discovered that 100% of the assessed acquired naevi had either a BRAF or NRAS mutation. Using sensitive techniques capable of single-cell mutation detection, it is likely that all acquired naevi will be mutated for BRAF or NRAS. Because both of these mutations are prevalent in distinct dermoscopic naevus subsets, our study supports the role of the MAPK pathway in the development of benign melanocytic proliferations, indicating that additional genomic events besides somatic mutations in BRAF or NRAS are required for melanoma development.

Diphenylcyclopropenone for the treatment of cutaneous in-transit melanoma metastases - results of a prospective, non-randomized, single-centre study.

BACKGROUND: Current treatments for in-transit melanoma (ITM) metastases are frequently invasive and do not improve overall survival. Recently, there has been increasing investigation into the use of topical agents. Diphenylcyclopropenone or diphencyprone (DPCP) is a novel, topical therapy that has been reported to have immune-sensitizing properties useful in the treatment of ITM. OBJECTIVE: To assess the clinical outcomes of patients treated within a prospective, non-randomized, non-comparative study using DPCP for cutaneous ITM metastases. METHODS: A review was conducted assessing the outcomes of 58 patients prospectively treated using DPCP. Patients had satellite or in-transit disease (stage IIIB+), with all lesion morphology types included. The patients were treated through a single, specialized clinic with regular outpatient follow-up. DPCP was topically applied as an aqueous cream in 0.005-1% concentrations once to twice per week for up to 24-48 h of duration. To assess variables associated with response, a per-protocol statistical analysis was performed. RESULTS: Fifty-four patients were treated who satisfied eligibility criteria for analysis. The overall response rates were as follows: complete response 22%, partial response 39%, stable disease 24% and progressive disease 15%. The mean time to complete response was 10.5 months, mean duration (disease-free interval) 12.3 months and recurrence rate in complete responders 41%. Lesion morphology was predictive of clinical benefit with a higher response in epidermotropic disease (P < 0.05). CONCLUSIONS: DPCP provided a well-tolerated, convenient and efficacious treatment for cutaneous ITM metastases. Identifying patterns of response may assist treatment selection and improve patient-rated outcomes.

Pregnancy as a driver for melanoma.

Whether or not pregnancy favours the occurrence and growth of melanoma is a source of controversy in the literature. Several case reports have shown dramatic courses of diseases in pregnancy. We present a case of a 36-year-old woman with multiple naevi with one melanoma detected in 2009 in the first trimester and a second primary melanoma in 2010 in the third trimester of her pregnancy. Both lesions have been present for at least 5 years and have been interpreted as dysplastic naevi. Because of their growth during pregnancy they were removed. No metastatic disease has been found between 2010 and early 2017. This case shows the difficulty of detecting melanomas in pregnancy, particularly when they mimic dysplastic naevi in women with multiple naevi, who are at higher risk. Therefore, we suggest that pregnant women with numerous naevi should be precautious of any changes of their naevi in size, shape and colour. Every suspicious lesion should be either excised or documented/monitored carefully, for example with sequential digital dermoscopy imaging.

Heritability of naevus patterns in an adult twin cohort from the Brisbane Twin Registry: a cross-sectional study.

BACKGROUND: Heritability of naevi counts is widely acknowledged as a potential surveillance parameter for prevention purposes. The contribution of heritability to the changes seen in naevus number and morphology over time and their corresponding dermoscopic characteristics is unknown, but is important to understand in order to account for adequate prevention measures. OBJECTIVES: To identify naevus characteristics that are strongly influenced by heritability. METHODS: This cross-sectional study included 220 individuals [76 monozygotic (MZ), 144 dizygotic (DZ)], recruited from the Brisbane Twin Naevus Study. Participants received full body imaging and dermoscopy of naevi ≥ 5 mm in diameter. Dermoscopic type, total naevus count (TNC), change in TNC with age, and naevus distribution, size, colour and profile were compared between MZ and DZ twins. Heritability of these traits was assessed via Falconer's estimate. RESULTS: Significant differences were found in comparing MZ and DZ twins for TNC, numbers of naevi 5·0-7·9 mm in diameter, counts of light-brown naevi, naevi on the back and sun-protected sites, and naevi with the 'nonspecific' dermoscopic pattern. CONCLUSIONS: This study strongly supports a heritable component to TNC, as well as changes in TNC, and the number of medium-sized naevi, light-brown naevi, specific sites and certain dermoscopic features in adults. These characteristics should be taken into account by naevus surveillance programmes and further studied to identify candidate gene associations for clinical and dermoscopic patterns in conjunction with melanoma risk stratification.

A systematic review of non-surgical treatments for lentigo maligna.

Lentigo maligna (LM) is the most common melanocytic malignancy of the head and neck. If left untreated, LM can progress to lentigo maligna melanoma (LMM). Complete surgical excision is the gold standard for treatment, however, due to the location, size, and advanced age of patients, surgery is not always acceptable. As a result, there is ongoing interest in alternative, less invasive treatment modalities. The objective was to provide a structured review of key literature reporting the use of radiotherapy, imiquimod and laser therapy for the management of LM in patients where surgical resection is prohibited. An independent review was conducted following a comprehensive search of the National Library of Medicine using MEDLINE and PubMed, Embase, Scopus, ScienceDirect and Cochrane Library databases. Data were presented in tabular format, and crude data pooled to calculate mean recurrence rates for each therapy. 29 studies met the inclusion criteria: radiotherapy 10; topical imiquimod 10; laser therapies 9. Radiotherapy demostrated recurrence rates of up to 31% (mean 11.5%), with follow-up durations of 1-96 months. Topical imiquimod recurrence rates were up to 50% (mean 24.5%), with follow-up durations of 2-49 months. Laser therapy yielded recurrence rates of up to 100% (mean 34.4%), and follow-up durations of 8-78 months. in each of the treatment series the I(2) value measuring statistical heterogeneity exceeded the accepted threshold of 50% and as such a meta-analysis of included data were inappropriate. For non-surgical patients with LM, radiotherapy and topical imiquimod were efficacious treatments. Radiotherapy produced superior complete response rates and fewer recurrences than imiquimod although both are promising non-invasive modalities. There was no consistent body of evidence regarding laser therapy although response rates of up to 100% were reported in low quality studies. A prospective comparative trial is indicated and would provide accurate data on the long-term efficacy and overall utility of these treatments.

A stress-induced early innate response causes multidrug tolerance in melanoma.

Correction to: Oncogene (2015) 34, 4448­4459; doi:10.1038/onc.2014.372; published online 24 November 2014. In this article, published online 24 November 2014, the authors have noticed that the latest supplementary information was not used. The corrected supplementary information (Supplementary Materials) appears online together with this corrigendum. The authors would like to apologise for any inconvenience this may cause

A stress-induced early innate response causes multidrug tolerance in melanoma.

Acquired drug resistance constitutes a major challenge for effective cancer therapies with melanoma being no exception. The dynamics leading to permanent resistance are poorly understood but are important to design better treatments. Here we show that drug exposure, hypoxia or nutrient starvation leads to an early innate cell response in melanoma cells resulting in multidrug resistance, termed induced drug-tolerant cells (IDTCs). Transition into the IDTC state seems to be an inherent stress reaction for survival toward unfavorable environmental conditions or drug exposure. The response comprises chromatin remodeling, activation of signaling cascades and markers implicated in cancer stemness with higher angiogenic potential and tumorigenicity. These changes are characterized by a common increase in CD271 expression concomitantly with loss of differentiation markers such as melan-A and tyrosinase, enhanced aldehyde dehydrogenase (ALDH) activity and upregulation of histone demethylases. Accordingly, IDTCs show a loss of H3K4me3, H3K27me3 and gain of H3K9me3 suggesting activation and repression of differential genes. Drug holidays at the IDTC state allow for reversion into parental cells re-sensitizing them to the drug they were primarily exposed to. However, upon continuous drug exposure IDTCs eventually transform into permanent and irreversible drug-resistant cells. Knockdown of CD271 or KDM5B decreases transition into the IDTC state substantially but does not prevent it. Targeting IDTCs would be crucial for sustainable disease management and prevention of acquired drug resistance.

Distinct signatures of B-cell homeostatic and activation-dependent chemokine receptors in the development and progression of extragastric MALT lymphomas.

Chemokine receptors mediate migration and activation of lymphocytes through binding of their ligands. Recent studies have revealed important contributions of chemokine receptors to the development, progression, and dissemination of haematopoietic neoplasms. Because the chemokine receptor expression profile in extragastric MALT lymphoma is unknown, we performed a comprehensive study on tissue samples of parotid glands, parotid glands affected by Sjögren syndrome, extragastric MALT lymphoma, and extranodal diffuse large B-cell lymphoma (eDLBCL) originating from MALT lymphoma (transformed MALT lymphoma). By investigating the expression of 19 chemokine receptors by real-time PCR using a semi-quantitative approach and of four chemokine receptors (CCR1, CCR5, CXCR6, and XCR1) by immunohistochemistry, we show that the chemokine receptor expression profiles of extragastric MALT lymphomas differ substantially from those of extranodal DBLCL, with lower expression of CCR1, CCR8, and CXCR3, and the absence of expression of CX3CR1 and XCR1 in eDLBCL. Expression of CCR6, CCR7, CXCR3, CXCR4, and CXCR5, responsible for B-cell homing to secondary lymphoid tissue, was detected in both B-cell malignancies. Expression of CCR4 was just detected in trisomy 3-positive MALT lymphoma cases. Comparing gastric with extragastric MALT lymphomas, up-regulation of CXCR1 and CXCR2 accompanied by down-regulation of CCR8 and CX3CR1 and loss of XCR1 expression in extragastric MALT lymphomas appear to be key determinants for the site of origin of MALT lymphomagenesis. Our results support a model of stepwise progression of extragastric MALT lymphoma from a non-neoplastic event to Sjögren syndrome, to MALT lymphoma, and finally to overt eDLBCL, guided by differentially expressed B-cell homeostatic and activation-dependent chemokine receptors and their ligands.

Transforming growth factor-beta1 increases survival of human melanoma through stroma remodeling.

Transforming growth factor (TGF)-beta is growth inhibitory for normal epithelial cells and melanocytes but can stimulate mesenchymal cells. Resistance to its inhibitory effects is characteristic of human melanoma, the growth of which may instead be promoted by TGF-beta, because its production is increased with melanoma progression. Whether TGF-beta has an autocrine function for melanoma cells or is important for paracrine stimulation of the tumor stroma is not known. In this study, TGF-beta1 was expressed in melanoma cells via adenoviral gene transfer, and tumor growth was analyzed in vitro, in human skin grafts, and in mixtures with fibroblasts that were injected s.c. into immunodeficient mice. The TGF-beta1 produced by the melanoma cells activated the fibroblasts to produce matrix within and around the tumor mass, whereas control tumors showed less stroma and more cell death. High expression of collagen, fibronectin, tenascin, and alpha2 integrin was detected in the TGF-beta1-expressing tumors by immunohistochemistry. Number and size of lung metastases were significantly increased. cDNA expression array analysis of TGF-beta1-transduced fibroblasts embedded in type I collagen and of TGF-beta1-transduced melanoma cells demonstrated induction of types XV, XVIII, and VI collagens, tenascin, plasminogen activator inhibitor-I, vascular endothelial growth factor, cysteine-rich fibroblast growth factor receptor-1, and platelet-derived growth factor receptor-beta, which could be linked to promotion of growth and survival in melanoma. These data suggest that remodeling of the neighboring stroma, which provides a supporting scaffolding and a positive feedback stimulation of tumor growth, is an important function of TGF-beta1 in melanoma.

Alpha5 and alpha2 integrin gene transfers mimic the PDGF-B-induced transformed phenotype of fibroblasts in human skin.

Platelet-derived growth factor (PDGF)-B is a proto-oncogene capable of transforming fibroblasts. Using adenoviral vectors, we tested whether endogenous PDGF-B expression in human skin xenotransplants leads to changes in the expression of alpha5 and alpha2 integrin subunits and whether integrin overexpression leads to PDGF-related changes in the skin. In vitro, transduction of fibroblasts with PDGF-B or the integrin alpha5 subunit stimulated multilayered growth and spindle-type morphology, both markers of mesenchymal cell transformation. In vivo, PDGF-B transduction of the human dermis was associated with up-regulation of collagen and fibronectin synthesis, increases in alpha5 and alpha2 integrin subunit expression, vessel formation, and proliferation of fibroblasts, keratinocytes, and pericytes. A similar stromal response was induced when alpha5 and alpha2 integrin subunits were overexpressed in the human dermis, suggesting that integrins play a major role in the induction of a transformed phenotype of fibroblasts by PDGF-B.

Low-level monocyte chemoattractant protein-1 stimulation of monocytes leads to tumor formation in nontumorigenic melanoma cells.

Tumors commonly produce chemokines for recruitment of host cells, but the biological significance of tumor-infiltrating inflammatory cells, such as monocytes/macrophages, for disease outcome is not clear. Here, we show that all of 30 melanoma cell lines secreted monocyte chemoattractant protein-1 (MCP-1), whereas normal melanocytes did not. When low MCP-1-producing melanoma cells from a biologically early, nontumorigenic stage were transduced to overexpress the MCP-1 gene, tumor formation depended on the level of chemokine secretion and monocyte infiltration; low-level MCP-1 secretion with modest monocyte infiltration resulted in tumor formation, whereas high secretion was associated with massive monocyte/macrophage infiltration into the tumor mass, leading to its destruction within a few days after injection into mice. Tumor growth stimulated by monocytes/macrophages was due to increased angiogenesis. Vessel formation in vitro was inhibited with mAbs against TNF-alpha, which, when secreted by cocultures of melanoma cells with human monocytes, induced endothelial cells under collagen gels to form branching, tubular structures. These studies demonstrate that the biological effects of tumor-derived MCP-1 are biphasic, depending on the level of secretion. This correlates with the degree of monocytic cell infiltration, which results in increased tumor vascularization and TNF-alpha production.

Downregulation of E-cadherin and Desmoglein 1 by autocrine hepatocyte growth factor during melanoma development.

During melanoma development, transformed cells evade keratinocyte-mediated control by downregulating cell adhesion molecules. This study investigated the regulation of cell adhesion by hepatocyte growth factor (HGF) in melanoma. Melanocytes and two melanoma lines, WM164 and WM35, expressed normal level E-cadherin and Desmoglein 1, whereas most melanomas (18 out of 20) expressed no E-cadherin and significantly reduced Desmoglein 1. Overexpression of dominant negative E-cadherin and Desmoglein in melanocytes demonstrated that both molecules contribute to adhesion between melanocytes and keratinocytes. In contrast to melanocytes, most melanomas expressed HGF. All melanocytic cells expressed the HGF receptor c-Met, and autocrine HGF caused constitutive activation of c-Met, MAPK and PI3K. When autocrine activation was induced with HGF-expressing adenovirus, E-cadherin and Desmoglein 1 were decreased in melanocytes, WM164 and WM35. MAPK inhibitor PD98059 and PI3K inhibitor wortmannin partially blocked the downregulation, suggesting that both pathways are involved in this process. c-Met was coimmunoprecipitated with E-cadherin, Desmoglein 1 and Plakoglobin, suggesting that they form a complex (es) that acts to regulate intercellular adhesion. Together, the results indicate that autocrine HGF decouples melanomas from keratinocytes by downregulating E-cadherin and Desmoglein 1, therefore frees melanoma cells from the control by keratinocytes and allows dissemination of the tumor mass.

Interleukin-8 overexpression is present in pyoderma gangrenosum ulcers and leads to ulcer formation in human skin xenografts.

Interleukin-8 (IL-8) is a potent chemotactic polypeptide for neutrophils. However, the role of this cytokine during inflammation remains unclear. Skin specimens from patients with pyoderma gangrenosum demonstrated IL-8 overexpression in skin ulcers, which suggests a role for IL-8 in the development of the disease. We therefore constructed a recombinant adenovirus expressing the complementary deoxyribonucleic acid encoding human IL-8 (IL-8/Ad5) that induces a 2000-fold increase in IL-8 expression of infected human fibroblasts in vitro. Human skin engrafted to severe combined immunodeficiency mice and then injected with the recombinant virus demonstrated erythema, an intense perivascular infiltration of neutrophils, and extravasation of erythrocytes after 8 hours. By 12 hours after injection, neutrophils had accumulated beneath the epidermis, which then necrotized, and one or more ulcers that remained for approximately 2 weeks were observed. Clinically and histologically, the ulcers resembled pyoderma gangrenosum. These clinical and experimental findings suggest an etiologic role of IL-8 in the pathogenesis of pyoderma gangrenosum.

Hexadecylphosphocholine inhibits invasion of mouse T-cell lymphoma cells in two different invasion assays.

Hexadecylphosphocholine (HePC), an ether lipid analogue, is a new antineoplastic drug which has been shown to exert a remarkable antiproliferative effect in vitro and in vivo. The signal transduction pathway and the phospholipid synthesis are thought to be the main putative molecular targets of HePC, yet the exact mechanism of action is still unclear. To investigate the antiinvasive activity of HePC on a mouse T-cell lymphoma cell line (BW-O-Li1), we used a type I collagen gel and devitalized dermis as substrate to evaluate the migration of BW-O-Li1 after exposure to HePC. BW-O-Li1 cells were exposed for 24 h to a non-cytotoxic (10 microM) as well as to cytotoxic concentrations of HePC. Afterwards, BW-O-Li1 cells were seeded on top of a reconstituted collagen gel layer or pippeted into a steel ring placed on the dermal site of a devitalized dermis. Lymphoma cells, which invaded the collagen layer were counted by light microscopy, invasion into devitalized dermis was measured by an image analysis system. Compared to unexposed cells, invasion into the collagen gel differed significantly even at 10 microM HePC, whereas the absolute number of invading cells, independently of the HePC concentration, showed no difference in the amount of counted cells. Migration into devitalized dermis was significantly reduced for 10 microM and 40 microM HePC. These data show that complementary information can be obtained by application of the two invasion assays and that the antiinvasive effect of HePC emerges at non-cytotoxic concentrations of the substance.

CD44 and variants in melanocytic skin neoplasms.

Expression of cell surface molecules that mediate cell-matrix and cell-cell interactions largely contributes to the ability of melanoma cells to migrate and spread beyond the primary site of the tumor. CD44, the principal cell-surface receptor for hyaluronate, and its numerous splice variants have been reported to play a crucial role in invasion and the metastatic process of different human neoplasms, including primary malignant melanoma (PMM). The aim of this study was to clarify which isoforms of CD44 (standard CD44 and CD44 variants) are distributed in PMM with a vertical tumor thickness of >1.4 mm. Staining of CD44 standard (CD44s) and splice variants was further examined for diagnostic and prognostic relevance in a panel of melanocytic skin lesions. Ten cases of PMM with Breslow >1.4 mm were analysed by immunohistochemistry using monoclonal antibodies specific for CD44s and the splice variants v3, v5, v6, v7, v7-8, and v10. In addition, using anti-CD44s, v5, and v6 antibodies, 55 melanocytic lesions, including dermal nevi (n=12), Clark nevi (dysplastic nevi) (CN; n=11), melanoma in situ (Mis; n=8), PMM (n=18), and cutaneous metastasis of malignant melanoma (cMMM; n=6) were assessed. Staining intensities were scored visually and evaluated by means of a staining index. In ten cases of PMM with a Breslow index >1.4 mm positive staining was ascertained for CD44s, v5 and for v6 in three cases. No staining was found for v3, v7, v7-8, and v10. Examination of CD44s, v5, and v6 in 55 melanocytic skin lesions revealed a high index for CD44s in all specimens and a weak staining of v5 in Mis; dermal nevi and CN did not stain for v5. However, in PMM and cMMM we found v5 to be strongly positive. The isoform v6 showed a variable index only in PMM, but without connection to established prognostic criteria. We conclude that CD44s and splice variants can not be regarded as indicators for tumor progression in malignant melanomas. However, v5 may potentially serve as a diagnostic marker for melanocytic skin lesions.

Deletion analysis of the p16 tumor suppressor gene in gastrointestinal mucosa-associated lymphoid tissue lymphomas.

BACKGROUND & AIMS: The molecular mechanisms responsible for initiation and progression of gastrointestinal mucosa-associated lymphoid tissue (MALT) lymphomas are largely unknown. The aim of this study was to analyze the p16 tumor suppressor gene in MALT lymphomas of the stomach and colon. METHODS: Tumor samples were obtained from 28 patients with low-grade (n = 12) and high-grade (n = 14) gastric MALT lymphomas and from 2 patients with colonic MALT lymphomas. DNA was extracted from microdissected areas with at least 80% tumor cells. To detect homozygous p16 deletions, a semiquantitative polymerase chain reaction assay was used, whereby either p16 exon 1 or exon 2 was coamplified with an unrelated sequence as internal control. RESULTS: Homozygous p16 deletions were found in 2 of 14 (14%) cases with high-grade gastric MALT lymphomas. Both patients had Helicobacter pylori-associated gastritis; however, DNA extracted from areas of gastritis showed a normal p16 complement. No deletion was found in any of the low-grade gastric or the colonic MALT lymphoma specimens. CONCLUSIONS: In a subset of gastric MALT lymphomas, homozygous p16 deletions are acquired and may contribute to the transformation from a low-grade to a high-grade malignancy.

Circulating adhesion molecules as prognostic factors for cutaneous melanoma.

BACKGROUND: Overexpression of adhesion molecules in tissues of human neoplasms, including malignant melanoma, has been reported to be clinically relevant, but the predictive value of circulating adhesion molecules for clinical outcome and life expectancy in patients with primary malignant melanoma (PMM) and metastases of primary malignant melanoma (MMM) remains undetermined. OBJECTIVE: Our purpose was to examine the prognostic relevance of circulating adhesion molecules, namely circulating CD44 standard (cCD44std), and the isoforms CD44v5 (cv5), CD44v6 (cv6), and CD44v10(cv10), circulating intercellular adhesion molecule-1 (cICAM-1), and circulating platelet/endothelial cell adhesion molecule-1 (cPECAM-1, CD31). METHODS: Levels of cCD44std, cv5, cv6, cv10, cICAM-1, and PECAM-1 were measured by enzyme-linked immunosorbent assays in 119 patients with PMM and MMM, in 12 persons with dysplastic nevi (Clark's nevi), and in 28 patients with inflammatory cutaneous diseases. RESULTS: Patients with PMM, MMM, and inflammatory cutaneous diseases showed an elevation in levels of cCD44std and cICAM-1 compared with normal blood donors, but these levels were not significantly increased. Levels of cv5, cv6, and cv10 were not increased, and cPECAM-1 was only marginally elevated. Even in patients with clinically provable systemic or cutaneous metastases and in five patients who died of MMM, levels did not differ significantly compared with normal blood donors; this was also independent of the mode of therapy. CONCLUSION: Circulating CD44std and the isoforms cv5, cv6, and cv10, cICAM-1, and cPECAM-1 were detectable in persons with dysplastic nevi and in patients with PMM and MMM. None of the measured adhesion molecules was significantly elevated and of prognostic relevance in any of the subgroups studied. However, some of the patients with PMM and MMM showed high levels of cCD44std and cICAM-1; that finding should prompt us to examine these patients in more detail.

Application of alpha-aminoisobutyric acid, L-methionine, thymidine and 2-fluoro-2-deoxy-D-glucose to monitor effects of chemotherapy in a human colon carcinoma cell line.

Up to 4 h after treatment of human SW 707 colon carcinoma cells with the antineoplastic drug 4-amino-N-(2'-aminophenyl)-benzamide (GOE 1734, dinaline), the effects of tumour cell metabolism and proliferation were examined in vitro. Four tracers which can be labelled with isotopes suitable for positron emission tomography (PET) were used for this purpose: alpha-aminoisobutyric acid (AIB) and methionine to study changes in amino acid transport and protein synthesis, thymidine to observe changes in tumour proliferation and 2-fluoro-2-deoxy-D-glucose (FDG) to estimate glucose metabolism. Dinaline showed an inhibition of the sodium-dependent and -independent uptake of AIB. The methionine uptake was found to increase shortly after therapy. Thymidine incorporation into DNA was impaired and the FDG uptake showed a maximally 2.2-fold enhancement. Inhibition of AIB uptake suggests changes in amino acid transport, whereas increased uptake of methionine and FDG points to an enhancement of protein synthesis and glycolysis caused by repair mechanisms. The cytostatic and antiproliferative effect of dinaline, observed in cell growth curves, could be demonstrated by the impaired thymidine incorporation into DNA. This study demonstrates that in vitro screening with radiotracers suitable for PET can help to clarify effects of new antineoplastic substances on tumour cell metabolism. These data may be applied to choose the appropriate time schedule for monitoring therapeutic effects on tumour tissue.