The septin modifier, forchlorfenuron, activates NLRP3 via a potassium-independent mitochondrial axis.

The Nod-like receptor protein 3 (NLRP3) inflammasome is activated by stimuli that induce perturbations in cell homeostasis, which commonly converge on cellular potassium efflux. NLRP3 has thus emerged as a sensor for ionic flux. Here, we identify forchlorfenuron (FCF) as an inflammasome activator that triggers NLRP3 signaling independently of potassium efflux. FCF triggers the rearrangement of septins, key cytoskeletal proteins that regulate mitochondrial function. We report that FCF triggered the rearrangement of SEPT2 into tubular aggregates and stimulated SEPT2-independent NLRP3 inflammasome signaling. Similar to imiquimod, FCF induced the collapse of the mitochondrial membrane potential and mitochondrial respiration. FCF thereby joins the imidazoquinolines as a structurally distinct class of molecules that triggers NLRP3 inflammasome signaling independent of potassium efflux, likely by inducing mitochondrial damage.

microRNA regulates cytokinin induced parthenocarpy in cucumber (Cucumis sativus L.).

Parthenocarpy is one of the most important agronomic traits for fruit yield in cucumbers. However, the precise gene regulation and the posttranscriptional mechanism are elusive. In the presented study, one parthenocarpic line DDX and non-parthenocarpic line ZK were applied to identify the microRNAs (miRNAs) involved in parthenocarpic fruit formation. The differential expressed miRNAs among parthenocarpic fruit of forchlorfenuron (CPPU) treated ZK (ZK-CPPU), pollinated ZK (ZK-P), non-pollinated DDX (DDX-NP) were compared with the non-parthenocarpic fruits of non-pollinated ZK (ZK-NP). It indicated 98 miRNAs exhibited differential expression were identified. Notably, a significant proportion of these miRNAs were enriched in the signal transduction pathway of plant hormones, as identified by the KEGG pathway analysis. qRT-PCR validation indicated that CsmiR156 family was upregulated in the ZK-NP while downregulated in ZK-CPPU, ZK-P, and DDX-NP at 1 day after anthesis. Meanwhile, the opposite trend was observed for CsmiR164a. In ZK-CPPU, ZK-P, and DDX-NP, CsmiRNA156 genes (CsSPL16 and CsARR9-like) were upregulated while CsmiRNA164a genes (CsNAC6, CsCUC1, and CsNAC100) were downregulated. The GUS and dual luciferase assay validated that CsmiR156a inhibited while CsmiR164a induced their target genes' transcription. This study presents novel insights into the involvement of CsmiR156a and CsmiR164a in the CK-mediated posttranscriptional regulation of cucumber parthenocarpy, which will aid future breeding programs.

Sandwich-like CuNPs@AgNPs@PSB SERS substrates for sensitive detection of R6G and Forchlorfenuron.

The development of a highly sensitive, synthetically simple and economical SERS substrate is technically very important. A fast, economical, sensitive and reproducible CuNPs@AgNPs@ Porous silicon Bragg reflector (PSB) SERS substrate was prepared by electrochemical etching and in situ reduction method. The developed CuNPs@AgNPs@PSB has a large specific surface area and abundant "hot spot" region, which makes the SERS performance excellent. Meanwhile, the successful synthesis of CuNPs@AgNPs can not only modulate the plasmon resonance properties of nanoparticles, but also effectively prolong the time stability of Cu nanoparticles. The basic performance of the substrate was evaluated using rhodamine 6G (R6G). (Detection limit reached 10-15 M, R2 = 0.9882, RSD = 5.3 %) The detection limit of Forchlorfenuron was 10 µg/L. The standard curve with a regression coefficient of 0.979 was established in the low concentration range of 10 µg/L -100 µg/L. This indicates that the prepared substrates can accomplish the detection of pesticide residues in the low concentration range. The prepared high-performance and high-sensitivity SERS substrate have a very promising application in detection technology.

Forchlorfenuron-Induced Mitochondrial Respiration Inhibition and Metabolic Shifts in Endometrial Cancer.

Forchlorfenuron (FCF) is a widely used plant cytokinin that enhances fruit quality and size in agriculture. It also serves as a crucial pharmacological tool for the inhibition of septins. However, the precise target of FCF has not yet been fully determined. This study reveals a novel target of FCF and elucidates its downstream signaling events. FCF significantly impairs mitochondrial respiration and mediates metabolic shift toward glycolysis, thus making cells more vulnerable to glycolysis inhibition. Interestingly, FCF's impact on mitochondrial function persists, even in cells lacking septins. Furthermore, the impaired mitochondrial function leads to the degradation of HIF-1α, facilitated by increased cellular oxygen. FCF also induces AMPK activation, suppresses Erk1/2 phosphorylation, and reduces the expression of HER2, ß-catenin, and PD-L1. Endometrial cancer is characterized by metabolic disorders such as diabetes and aberrant HER2/Ras-Erk1/2/ß-catenin signaling. Thus, FCF may hold promise as a potential therapeutic in endometrial cancer.

Fungal-Mediated Biotransformation of the Plant Growth Regulator Forchlorfenuron by Cunninghamella elegans.

The synthetic cytokinin forchlorfenuron (FCF), while seemingly presenting relatively low toxicity for mammalian organisms, has been the subject of renewed scrutiny in the past few years due to its increasing use in fruit crops and potential for bioaccumulation. Despite many toxicological properties of FCF being known, little research has been conducted on the toxicological effects of its secondary metabolites. Given this critical gap in the existing literature, understanding the formation of relevant FCF secondary metabolites and their association with mammalian metabolism is essential. To investigate the formation of FCF metabolites in sufficient quantities for toxicological studies, a panel of four fungi were screened for their ability to catalyze the biotransformation of FCF. Of the organisms screened, Cunninghamella elegans (ATCC 9245), a filamentous fungus, was found to convert FCF to 4-hydroxyphenyl-forchlorfenuron, the major FCF secondary metabolite identified in mammals, after 26 days. Following the optimization of biotransformation conditions using a solid support system, media screening, and inoculation with a solid pre-formed fungal mass of C. elegans, this conversion time was significantly reduced to 7 days-representing a 73% reduction in total reaction time as deduced from the biotransformation products and confirmed by LC-MS, NMR spectroscopic data, as well as a comparison with synthetically prepared metabolites. Our study provides the first report of the metabolism of FCF by C. elegans. These findings suggest that C. elegans can produce FCF secondary metabolites consistent with those produced via mammalian metabolism and could be used as a more efficient, cost-effective, and ethical alternative for producing those metabolites in useful quantities for toxicological studies.

The Septin Gene StSep4 Contributes to the Pathogenicity of Setosphaeria turcica by Regulating the Morphology, Cell Wall Integrity, and Pathogenic Factor Biosynthesis.

Septins are a conserved group of GTP-binding proteins found in all eukaryotes and are the fourth-most abundant cytoskeletal proteins. Septins of some pathogenic fungi are involved in morphological changes related to infection. Our previous studies have identified four core septins (StSep1-4) in Setosphaeria turcica, the causal agent of northern corn leaf blight, while only StSep4 is significantly upregulated during the invasive process. We therefore used forchlorfenuron (FCF), the specific inhibitor of septin, and ΔStSep4 knockout mutants to further clarify the role of septins in S. turcica pathogenicity. FCF treatment caused a dose-dependent reduction in S. turcica colony growth, delayed the formation of infection structures, and reduced the penetration ability. ΔStSep4 knockout mutants displayed abnormal mycelium morphology, slow mycelial growth, conidiation deficiency, delayed appressorium development, and weakened pathogenicity. StSep4 deletion also broke cell wall integrity, altered chitin distribution, decreased the melanin content, and disrupted normal nuclear localization. A transcriptomic comparison revealed that genes differentially expressed between ΔStSep4 and WT were enriched in terms of ribosomes, protein translation, membrane components, and transmembrane transport activities. Our results demonstrate that StSep4 is required for morphology and pathogenicity in S. turcica, making it a promising target for the development of novel fungicides.

Fabrication of Ag-CaCO3 Nanocomposites for SERS Detection of Forchlorfenuron.

In this study, Ag-CaCO3 nanocomposites were synthesized using silver nitrate as the precursor solution based on calcium carbonate nanoparticles (CaCO3 NPs). The synthesis involved the reaction of calcium lignosulphonate and sodium bicarbonate. The properties of Ag-CaCO3 nanocomposites were studied by various technologies, including an ultraviolet-visible spectrophotometer, a transmission electron microscope, and a Raman spectrometer. The results showed that Ag-CaCO3 nanocomposites exhibited a maximum UV absorption peak at 430 nm, the surface-enhanced Raman spectroscopy (SERS) activity of Ag-CaCO3 nanocomposites was evaluated using mercaptobenzoic acid (MBA) as the marker molecule, resulting in an enhancement factor of 6.5 × 104. Additionally, Ag-CaCO3 nanocomposites were utilized for the detection of forchlorfenuron. The results demonstrated a linear relationship in the concentration range of 0.01 mg/mL to 2 mg/mL, described by the equation y = 290.02x + 1598.8. The correlation coefficient was calculated to be 0.9772, and the limit of detection (LOD) was determined to be 0.001 mg/mL. These findings highlight the relatively high SERS activity of Ag-CaCO3 nanocomposites, making them suitable for analyzing pesticide residues and detecting toxic and harmful molecules, thereby contributing to environmental protection.

Spatial Distribution and Migration Characteristic of Forchlorfenuron in Oriental Melon Fruit by Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry Imaging.

Forchlorfenuron is a widely used plant growth regulator to support the pollination and fruit set of oriental melons. It is critical to investigate the spatial distribution and migration characteristics of forchlorfenuron among fruit tissues to understand its metabolism and toxic effects on plants. However, the application of imaging mass spectrometry in pesticides remains challenging due to the usually extremely low residual concentration and the strong interference from plant tissues. In this study, a matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) method was developed for the first time to obtain the dynamic images of forchlorfenuron in oriental melon. A quantitative assessment has also been performed for MALDI-MSI to characterize the time-dependent permeation and degradation sites of forchlorfenuron in oriental melon. The majority of forchlorfenuron was detected in the exocarp and mesocarp regions of oriental melon and decreased within two days after application. The degradation rate obtained by MALDI-MSI in this study was comparable to that obtained by HPLC-MS/MS, indicating that the methodology and quantification approach based on the MALDI-MSI was reliable and practicable for pesticide degradation study. These results provide an important scientific basis for the assessment of the potential risks and effects of forchlorfenuron on oriental melons.

Migration of Myogenic Cells Is Highly Influenced by Cytoskeletal Septin7.

Septin7 as a unique member of the GTP binding protein family, is widely expressed in the eukaryotic cells and considered to be essential in the formation of hetero-oligomeric septin complexes. As a cytoskeletal component, Septin7 is involved in many important cellular processes. However, its contribution in striated muscle physiology is poorly described. In skeletal muscle, a highly orchestrated process of migration is crucial in the development of functional fibers and in regeneration. Here, we describe the pronounced appearance of Septin7 filaments and a continuous change of Septin7 protein architecture during the migration of myogenic cells. In Septin7 knockdown C2C12 cultures, the basic parameters of migration are significantly different, and the intracellular calcium concentration change in migrating cells are lower compared to that of scrambled cultures. Using a plant cytokinin, forchlorfenuron, to dampen septin dynamics, the altered behavior of the migrating cells is described, where Septin7-depleted cells are more resistant to the treatment. These results indicate the functional relevance of Septin7 in the migration of myoblasts, implying its contribution to muscle myogenesis and regeneration.

Chemiluminescence method based on the KIO4 -K2 CO3 -Mn2+ reaction for rapid and sensitive determination of forchlorfenuron in dried fruit.

Forchlorfenuron is a low-toxic phenylurea plant growth regulator. Excessive intake of forchlorfenuron can lead to metabolic disorders of the matrix and be harmful to human health. The chemiluminescence intensity of the KIO4 -K2 CO3 -Mn2+ reaction decreased in the presence of forchlorfenuron. Based on this result, a rapid and sensitive chemiluminescence method was established to determine forchlorfenuron by combining it with a batch injection static device. The injection speed, injection volume and reagent concentration of the forchlorfenuron-KIO4 -K2 CO3 -Mn2+ chemiluminescence reaction were optimized. Under these optimized conditions, the linear range of the method was 1.0-200.0 µg/L, and the limit of detection was 0.29 µg/L (S/N = 3). The chemiluminescence method for the determination of forchlorfenuron could be completed in 10 s. The method was applied to detect the residual forchlorfenuron in dried fruit samples, and the results are consistent with high-performance liquid chromatography-mass spectrometry. This method has the advantages of high sensitivity, rapid response, less reagent consumption, and convenient operation. It will provide a new perspective for chemiluminescence for the rapid and sensitive determination of forchlorfenuron in various complex samples.

A Magnetic-Bead-Based Immunoassay with a Newly Developed Monoclonal Antibody for Rapid and Highly Sensitive Detection of Forchlorfenuron.

Forchlorfenuron (CPPU) is a widely used plant growth regulator in agriculture, and CPPU residue in food can cause harm to human health. Thus, it is necessary to develop a rapid and sensitive detection method for CPPU monitoring. In this study, a new monoclonal antibody (mAb) against CPPU with high affinity was prepared by a hybridoma technique, and a magnetic bead (MB)-based analytical method was established for the determination of CPPU by a one-step procedure. Under optimized conditions, the detection limit of the MB-based immunoassay was as low as 0.0004 ng/mL, which was five times more sensitive than the traditional indirect competitive ELISA (icELISA). In addition, the detection procedure took less than 35 min, a significant improvement over the 135 min required for icELISA. The selectivity test of the MB-based assay also showed negligible cross-reactivity with five analogues. Furthermore, the accuracy of the developed assay was assessed by the analysis of spiked samples, and the results agreed well with those obtained by HPLC. The excellent analytical performance of the proposed assay suggests its great potential for routine screening of CPPU, and it provides a basis for promoting the application of more immunosensors in the quantitative detection of low concentrations of small organic molecules in food.

Discovery and Identification of the Key Contributor to the Bitter Taste in Oriental Melon after Forchlorfenuron Application.

Forchlorfenuron is a cytokinin-like plant growth regulator, which on application to oriental melon fruit often produces a bitter taste due to the accumulation of cucurbitacin. In the present study, the relationship between forchlorfenuron treatment and bitterness in oriental melon fruit was revealed by human sensory analysis coupled with highly sensitive quantitative analyses. Nine cucurbitacins as the major bitter compounds were identified in the oriental melon, with their concentration ranging from 0.001 to 32.263 mg/kg. And these cucurbitacins mainly accumulated in the peel and pedicle pulp of oriental melon fruits at maturation. Application of forchlorfenuron increased the concentration of cucurbitacin B and decreased arvenin I in total cucurbitacins for the oriental melons. Calculation of the impact of the bitter taste of these compounds based on a dose/activity relationship indicated that cucurbitacin B and arvenin I were the key contributor to the bitter taste in oriental melon fruit after high-dose forchlorfenuron application. These results are helpful in understanding the source of bitterness of oriental melon and provide a practical guide on the rational use of forchlorfenuron.

Identification and expression analysis of invertase family genes during grape (Vitis vinifera L.) berry development under CPPU and GA treatment.

Sugar is crucial for grape berry, whether used for fresh food or wine. However, berry enlargement treatment with forchlorfenuron (N-(2-chloro4-pyridyl)-N'-phenylurea) (CPPU, a synthetic cytokinin) and gibberellin (GA) always had adverse effects on sugar accumulation in some grape varieties, especially CPPU. Therefore exploring the molecular mechanisms behind these adverse effects could provide a foundation for improving or developing technology to mitigate the effects of CPPU/GA treatments for grape growers. In the present study, invertase (INV) family, the key gene controlling sugar accumulation, was identified and characterized on the latest annotated grape genome. Their express pattern, as well as invertase activity and sugar content, were analyzed during grape berry development under CPPU and GA3 treatment to explore the potential role of INV members under berry enlargement treatment in grapes. Eighteen INV genes were identified and divided into two sub-families: 10 neutral INV genes (Vv-A/N-INV1-10) and 8 acid INV genes containing 5 CWINV (VvCWINV1-5) and 3 VIN (VvVIN1-3). At the early development stage, both CPPU and GA3 treatment decreased the hexose level in berries of 'Pinot Noir' grape, whereas the activity of three types inverstase (soluble acid INV, insoluble acid INV, and neutral INV) increased. Correspondingly, most of INV members were up-regulated by GA3 /CPPU application at least one sampling time point during early berry development, including VvCWINV1, 2, 3, 4, 5, VvVIN1, 2, 3 and Vv-A/N-INV1, 2, 5, 6, 7, 8, 10. At maturity, the sugar content in CPPU-treated berries is still lower than that in the control. Soluble acid INV and neutral INV, rather than insoluble acid INV, presented lower activity in CPPU-treated berries. Meanwhile, several corresponding genes, such as VvVIN2 and Vv-A/N-INV2, 8, 10 in ripening berries were obviously down-regulated by CPPU treatment. These results suggested that most of INV members could be triggered by berry enlargement treatment during early berry development, whereas VvVINs and Vv-A/N-INVs, but not VvCWINVs, could be the limiting factor resulting in decreased sugar accumulation in CPPU-treated berries at maturity. In conclusion, this study identified the INV family on the latest annotated grape genome and selected several potential members involving in the limit of CPPU on final sugar accumulation in grape berry. These results provide candidate genes for further study of the molecular regulation of CPPU and GA on sugar accumulation in grape.

Discrimination and Characterization of Volatile Flavor Compounds in Fresh Oriental Melon after Forchlorfenuron Application Using Electronic Nose (E-Nose) and Headspace-Gas Chromatography-Ion Mobility Spectrometry (HS-GC-IMS).

Aroma is a crucial factor determining the market value and consumer satisfaction of fresh oriental melon. However, few studies focus on the volatile flavor of fresh oriental melon, and the effect of forchlorfenuron application on the aroma profile is unclear. This study characterized the volatile profile of fresh oriental melon fruit after forchlorfenuron application by E-nose and HS-GC-IMS. The holistic variation of volatile compounds exhibited evident distinction based on linear discriminant analysis (LDA) with E-nose. Forty-eight volatile compounds were identified from fresh oriental melon via GC-IMS, mainly esters, alcohols, aldehydes, and ketones, along with smaller quantities of sulfides and terpenes. Compared to pollination melon fruits, 13 critical different volatile flavor compounds were screened out in forchlorfenuron application groups by the PLS-DA model, imparting sweet fruity flavor. The results of the current study provide a valuable basis for evaluating the flavor quality of oriental melon after forchlorfenuron treatment.

Production of a Monoclonal Antibody for the Detection of Forchlorfenuron: Application in an Indirect Enzyme-Linked Immunosorbent Assay and Immunochromatographic Strip.

In this study, a monoclonal antibody (mAb) specific to forchlorfenuron (CPPU) with high sensitivity and specificity was produced and designated (9G9). To detect CPPU in cucumber samples, an indirect enzyme-linked immunosorbent assay (ic-ELISA) and a colloidal gold nanobead immunochromatographic test strip (CGN-ICTS) were established using 9G9. The half-maximal inhibitory concentration (IC50) and the LOD for the developed ic-ELISA were determined to be 0.19 ng/mL and 0.04 ng/mL in the sample dilution buffer, respectively. The results indicate that the sensitivity of the antibodies prepared in this study (9G9 mAb) was higher than those reported in the previous literature. On the other hand, in order to achieve rapid and accurate detection of CPPU, CGN-ICTS is indispensable. The IC50 and the LOD for the CGN-ICTS were determined to be 27 ng/mL and 6.1 ng/mL. The average recoveries of the CGN-ICTS ranged from 68 to 82%. The CGN-ICTS and ic-ELISA quantitative results were all confirmed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) with 84-92% recoveries, which indicated the methods developed herein are appropriate for detecting CPPU in cucumber. The CGN-ICTS method is capable of both qualitative and semiquantitative analysis of CPPU, which makes it a suitable alternative complex instrument method for on-site detection of CPPU in cucumber samples since it does not require specialized equipment.

Key metabolites and mechanistic insights in forchlorfenuron controlling kiwifruit development.

Forchlorfenuron (CPPU) is a plant growth regulator widely applied on kiwifruit to improve yield, however, there are rarely reports on its effects on the nutrients of kiwifruits. Based on UHPLC-Q-TOF-MS, the effects of CPPU on metabolism profile and nutrient substances of two kiwifruit varieties during development were investigated by non-targeted metabolomics. A total of 115 metabolites were identified, and 29 differential metabolites were confirmed and quantified using certified reference standards. Metabolic profile indicated that CPPU promoted kiwifruit development during the main expansion stages at the molecular level, and the effects varied slightly for different varieties. In the early and middle stages of kiwifruit development, the anthocyanin, flavone and flavonol biosynthesis were down-regulated in both varieties, and flavanols biosynthesis was down-regulated only in Hayward variety. Arginine biosynthesis was down-regulated at all stages till the harvest. Although the synthesis of these nutrient substances in kiwifruits was mostly down-regulated by CPPU, the negative effects became mild at harvest time, and positively, the significant increase of sucrose and decrease of organic acids at harvest time could help to improve the taste of kiwifruits.

Miniaturized extraction and determination of swelling agents in fruits and vegetables based on deep eutectic solvent-molecularly imprinted hydrophilic resin.

The overuse of swelling agents in fruits and vegetables has rapidly increased, resulting in food safety problems. Hence, a new method for the selective extraction and detection of thidiazuron (TDZ) and forchlorfenuron (KT30) was developed using deep eutectic solvent-molecularly imprinted hydrophilic resin (DES-MIHR) as a pipette tip solid-phase extraction (PT-SPE) adsorbent with excellent molecular recognition in aqueous matrixes. DES-MIHR interacted with TDZ and KT30 via π-π interactions and hydrogen bonding. The miniaturized PT-SPE can be performed with just 5.0 mg adsorbent, 0.3 mL water, and 0.2 mL eluent, thus having the advantage of the low consumption of adsorbent and organic reagents. The performance of the DES-MIHR-PT-SPE-high-performance liquid chromatography (HPLC) method was demonstrated with the recoveries from various fruits and vegetables being 81.1-102.9 % (RSD ≤ 7.1 %). Thereby indicating the general applicability of the developed method for the accurate determination of trace swelling agents in fruits and vegetables.

Validation of simple and efficient analytical methodology for estimation of forchlorfenuron residues.

A simple and efficient analytical methodology was standardised for the estimation of forchlorfenuron residues in rice leaves, grains, husk, straw and soil using LC-MS/MS. The methodology was validated in terms selectivity, sensitivity, linearity, limit of detection, limit of quantification, matrix effect, repeatability and reproducibility. The limit of detection and limit of quantification of forchlorfenuron in rice leaves, grains, straw, husk and soil were worked out to be 0.003 and 0.01 mg kg-1, respectively. Recoveries ranged between 81.54 and 99.05% with RSDr below 4.57 and RSDR below 4.19%. This validated method was applied for the determination of forchlorfenuron residues in paddy leaves after foliar application. The residues persisted for 0, 3 and 7 days after application of forchlorfenuron 0.12% EC @ 1.25, 2.50 and 5.00 ppm a.i. The half-life values were estimated to be 1.91 and 2.11 days for 2.50 and 5.00 ppm a.i. concentration. The residues were found to be below the limit of quantification of 0.01 mg kg-1 in straw, grain, husk and soil samples collected at harvest time.

Forchlorfenuron and Novel Analogs Cause Cytotoxic Effects in Untreated and Cisplatin-Resistant Malignant Mesothelioma-Derived Cells.

Malignant mesothelioma (MM) is a currently incurable, aggressive cancer derived from mesothelial cells, most often resulting from asbestos exposure. The current first-line treatment in unresectable MM is cisplatin/pemetrexed, which shows very little long-term effectiveness, necessitating research for novel therapeutic interventions. The existing chemotherapies often act on the cytoskeleton, including actin filaments and microtubules, but recent advances indicate the 'fourth' form consisting of the family of septins, representing a novel target. The septin inhibitor forchlorfenuron (FCF) and FCF analogs inhibit MM cell growth in vitro, but at concentrations which are too high for clinical applications. Based on the reported requirement of the chloride group in the 2-position of the pyridine ring of FCF for MM cell growth inhibition and cytotoxicity, we systematically investigated the importance (cell growth-inhibiting capacity) of the halogen atoms fluorine, chlorine, bromine and iodine in the 2- or 3-position of the pyridine ring. The MM cell lines ZL55, MSTO-211H, and SPC212, and-as a control-immortalized Met-5A mesothelial cells were used. The potency of the various halogen substitutions in FCF was mostly correlated with the atom size (covalent radius); the small fluoride analogs showed the least effect, while the largest one (iodide) most strongly decreased the MTT signals, in particular in MM cells derived from epithelioid MM. In the latter, the strongest effects in vitro were exerted by the 2-iodo and, unexpectedly, the 2-trifluoromethyl (2-CF3) FCF analogs, which were further tested in vivo in mice. However, FCF-2-I and, more strongly, FCF-2-CF3 caused rapidly occurring strong symptoms of systemic toxicity at doses lower than those previously obtained with FCF. Thus, we investigated the effectiveness of FCF (and selected analogs) in vitro in MM cells which were first exposed to cisplatin. The slowly appearing population of cisplatin-resistant cells was still susceptible to the growth-inhibiting/cytotoxic effect of FCF and its analogs, indicating that cisplatin and FCF target non-converging pathways in MM cells. Thus, a combination therapy of cisplatin and FCF (analogs) might represent a new avenue for the treatment of repopulating chemo-resistant MM cells in this currently untreatable cancer.

Confounders for kidney carcinogenesis in rodent cancer bioassays.

In the long-term safety testing of chemicals for carcinogenicity the toxicologist needs to be aware of a number of scenarios where renal tubule tumors, or their precursors, arise that are not due to a carcinogenic action of the test article. Situations producing false positive results in the kidney include exacerbation of chronic progressive nephropathy (CPN) in rats, confusion of atypical tubule hyperplasia (the obligate precursor of renal tubule tumor) with foci of benign CPN-related renal tubule cell proliferation, inclusion of spontaneous tumor entities, such as the amphophilic-vacuolar tumor, in the test article tumor count, the possibility of a link between spontaneous forms of tubule dilatation and renal tubule tumor formation in mice, and the supposed predictivity of chemically-induced karyomegaly for renal carcinogenicity in both rats and mice. Examples of these misleading situations are described and discussed.