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Cancer cells generally exhibit increased iron uptake, which contributes to their abnormal growth and metastatic ability. Iron chelators have thus recently attracted attention as potential anticancer agents. Here, we show that deferriferrichrysin (Dfcy), a natural product from Aspergillus oryzae acts as an iron chelator to induce paraptosis (a programmed cell death pathway characterized by ER dilation) in MCF-7 human breast cancer cells and H1299 human lung cancer cells. We first examined the anticancer efficacy of Dfcy in cancer cells and found that Dfcy induced ER dilation and reduced the number of viable cells. Extracellular signal-related kinase (ERK) was activated by Dfcy treatment, and the MEK inhibitor U0126, a small molecule commonly used to inhibit ERK activity, prevented the increase in ER dilation in Dfcy-treated cells. Concomitantly, the decrease in the number of viable cells upon treatment with Dfcy was attenuated by U0126. Taken together, these results demonstrate that the iron chelator Dfcy exhibits anticancer effects via induction of ERK-dependent paraptosis., (© 2023 Molecular Biology Society of Japan and John Wiley & Sons Australia, Ltd.)

Background: Mutant TP53 interacts with other proteins to produce gain-of-function properties that contribute to cancer metastasis. However, the underlying mechanisms are still not fully understood., Methods: Using immunoprecipitation and proximity ligation assays, we evaluated breast cancer anti-estrogen resistance 1 (BCAR1) as a novel binding partner of TP53 R273H , a TP53 mutant frequently found in human cancers. The biological functions of their binding were examined by the transwell invasion assay. Clinical outcome of patients was analysed based on TP53 status and BCAR1 expression using public database., Results: We discovered a novel interaction between TP53 R273H and BCAR1. We found that BCAR1 translocates from the cytoplasm into the nucleus and binds to TP53 R273H in a manner dependent on SRC family kinases (SFKs), which are known to enhance metastasis. The expression of full-length TP53 R273H , but not the BCAR1 binding-deficient mutant TP53 R273H Δ102-207, promoted cancer cell invasion. Furthermore, among the patients with mutant TP53, high BCAR1 expression was associated with a poorer prognosis., Conclusions: The interaction between TP53 R273H and BCAR1 plays an important role in enhancing cancer cell invasion. Thus, our study suggests a disruption of the TP53 R273H -BCAR1 binding as a potential therapeutic approach for TP53 R273H -harbouring cancer patients.

Bats are unusual mammals, with the ability to fly, and long lifespans. In addition, bats have a low incidence of cancer, but the mechanisms underlying this phenomenon remain elusive. Here we discovered that bat cells are more resistant than human and mouse cells to DNA damage induced by genotoxic drugs. We found that bat cells accumulate less chemical than human and mouse cells, and efficient drug efflux mediated by the ABC transporter ABCB1 underlies this improved response to genotoxic reagents. Inhibition of ABCB1 triggers an accumulation of doxorubicin, DNA damage, and cell death. ABCB1 is expressed at higher levels in several cell lines and tissues derived from bats compared to humans. Furthermore, increased drug efflux and high expression of ABCB1 are conserved across multiple bat species. Our findings suggest that enhanced efflux protects bat cells from DNA damage induced by genotoxic compounds, which may contribute to their low cancer incidence.

MEKK1 (also known as MAP3K1), which plays a major role in MAPK signaling, has been implicated in mechanical processes in cells, such as migration. Here, we identify the actin-binding protein calponin-3 as a new MEKK1 substrate in the signaling that regulates actomyosin-based cellular contractility. MEKK1 colocalizes with calponin-3 at the actin cytoskeleton and phosphorylates it, leading to an increase in the cell-generated traction stress. MEKK1-mediated calponin-3 phosphorylation is attenuated by the inhibition of myosin II activity, the disruption of actin cytoskeletal integrity and adhesion to soft extracellular substrates, whereas it is enhanced upon cell stretching. Our results reveal the importance of the MEKK1-calponin-3 signaling pathway to cell contractility., (© 2016. Published by The Company of Biologists Ltd.)

Genetic alterations which impair the function of the TP53 signaling pathway in TP53 wild-type human tumors remain elusive. To identify new components of this pathway, we performed a screen for genes whose loss-of-function debilitated TP53 signaling and enabled oncogenic transformation of human mammary epithelial cells. We identified transglutaminase 2 (TGM2) as a putative tumor suppressor in the TP53 pathway. TGM2 suppressed colony formation in soft agar and tumor formation in a xenograft mouse model. The depletion of growth supplements induced both TGM2 expression and autophagy in a TP53-dependent manner, and TGM2 promoted autophagic flux by enhancing autophagic protein degradation and autolysosome clearance. Reduced expression of both CDKN1A, which regulates the cell cycle downstream of TP53, and TGM2 synergized to promote oncogenic transformation. Our findings suggest that TGM2-mediated autophagy and CDKN1A-mediated cell cycle arrest are two important barriers in the TP53 pathway that prevent oncogenic transformation.

Cancer cells possess unique characteristics such as invasiveness, the ability to undergo epithelial-mesenchymal transition, and an inherent stemness. Cell morphology is altered during these processes and this is highly dependent on actin cytoskeleton remodeling. Regulation of the actin cytoskeleton is, therefore, important for determination of cell fate. Mutations within the TP53 (tumor suppressor p53) gene leading to loss or gain of function (GOF) of the protein are often observed in aggressive cancer cells. Here, we highlight the roles of p53 and its GOF mutants in cancer cell invasion from the perspective of the actin cytoskeleton; in particular its reorganization and regulation by cell adhesion molecules such as integrins and cadherins. We emphasize the multiple functions of p53 in the regulation of actin cytoskeleton remodeling in response to the extracellular microenvironment, and oncogene activation. Such an approach provides a new perspective in the consideration of novel targets for anti-cancer therapy.

The tumor suppressor ARF enhances the SUMOylation of target proteins; however, the physiological function of ARF-mediated SUMOylation has been unclear due to the lack of a known, associated E3 SUMO ligase. Here we uncover TRIM28/KAP1 as a novel ARF-binding protein and SUMO E3 ligase for NPM1/B23. ARF and TRIM28 cooperate to SUMOylate NPM1, a nucleolar protein that regulates centrosome duplication and genomic stability. ARF-mediated SUMOylation of NPM1 was attenuated by TRIM28 depletion and enhanced by TRIM28 overexpression. Coexpression of ARF and TRIM28 promoted NPM1 centrosomal localization by enhancing its SUMOylation and suppressed centrosome amplification; these functions required the E3 ligase activity of TRIM28. Conversely, depletion of ARF or TRIM28 increased centrosome amplification. ARF also counteracted oncogenic Ras-induced centrosome amplification. Centrosome amplification is often induced by oncogenic insults, leading to genomic instability. However, the mechanisms employed by tumor suppressors to protect the genome are poorly understood. Our findings suggest a novel role for ARF in maintaining genome integrity by facilitating TRIM28-mediated SUMOylation of NPM1, thus preventing centrosome amplification., (Copyright © 2015, American Society for Microbiology. All Rights Reserved.)

Tumor suppressor p53 prevents tumorigenesis and tumor growth by suppressing the activation of several transcription factors, including nuclear factor-κB (NF-κB) and STAT3. On the other hand, p53 stimulates actin cytoskeleton remodeling and integrin-related signaling cascades. Here, we examined the p53-mediated link between regulation of the actin cytoskeleton and activation of NF-κB and STAT3 in MCF-7 cells and mouse embryonic fibroblasts (MEFs). In the absence of p53, STAT3 was constitutively activated. This activation was attenuated by depleting the expression of p65, a component of NF-κB. Integrin β3 expression and lamellipodia formation were also downregulated by NF-κB depletion. Inhibition of integrin αvβ3, Rac1 or Arp2/3, which diminished lamellipodia formation, suppressed STAT3 activation induced by p53 depletion. These results suggest that loss of p53 leads to STAT3 activation via NF-κB-dependent lamellipodia formation. Our study proposes a novel role for p53 in modulating the actin cytoskeleton through suppression of NF-κB, which restricts STAT3 activation., (2013 Wiley Periodicals, Inc.)

Oncogenic Ras induces cell transformation and promotes an invasive phenotype. The tumor suppressor p53 has a suppressive role in Ras-driven invasion. However, its mechanism remains poorly understood. Here we show that p53 induces activation of the mitochondrial protease high-temperature requirement A2 (HtrA2; also known as Omi) and prevents Ras-driven invasion by modulating the actin cytoskeleton. Oncogenic Ras increases accumulation of p53 in the cytoplasm, which promotes the translocation of p38 mitogen-activated protein kinase (MAPK) into mitochondria and induces phosphorylation of HtrA2/Omi. Concurrently, oncogenic Ras also induces mitochondrial fragmentation, irrespective of p53 expression, causing the release of HtrA2/Omi from mitochondria into the cytosol. Phosphorylated HtrA2/Omi therefore cleaves β-actin and decreases the amount of filamentous actin (F-actin) in the cytosol. This ultimately down-regulates p130 Crk-associated substrate (p130Cas)-mediated lamellipodia formation, countering the invasive phenotype initiated by oncogenic Ras. Our novel findings provide insights into the mechanism by which p53 prevents the malignant progression of transformed cells.

Nociception, warning of injury that should be avoided, serves an important protective function in animals. In this study, we show that adult Drosophila avoids noxious heat by a jump response. To quantitatively analyze this nociceptive behavior, we developed two assays. In the CO2 laser beam assay, flies exhibit this behavior when a laser beam heats their abdomens. The consistency of the jump latency in this assay meets an important criterion for a good nociceptive assay. In the hot plate assay, flies jump quickly to escape from a hot copper plate (>45 degrees C). Our results demonstrate that, as in mammals, the latency of the jump response is inversely related to stimulus intensity, and innoxious thermosensation does not elicit this nociceptive behavior. To explore the genetic mechanisms of nociception, we examined several mutants in both assays. Abnormal nociceptive behavior of a mutant, painless, indicates that painless, a gene essential for nociception in Drosophila larvae, is also required for thermal nociception in adult flies. painless is expressed in certain neurons of the peripheral nervous system and thoracic ganglia, as well as in the definite brain structures, the mushroom bodies. However, chemical or genetic insults to the mushroom bodies do not influence the nociceptive behavior, suggesting that different painless-expressing neurons play diverse roles in thermal nociception. Additionally, no-bridge(KS49), a mutant that has a structural defect in the protocerebral bridge, shows defective response to noxious heat. Thus, our results validate adult Drosophila as a useful model to study the genetic mechanisms of thermal nociception.

Memory consolidation in Drosophila was investigated using cold anesthesia- and hypoxia-induced amnesia. Individual flies were operantly trained to avoid the specific flight orientations with respect to the landmarks surrounding them when paired with heat reinforcement at a flight simulator. Cold anesthesia, introduced immediately after training, exerted a significantly diminishing effect on memory between 15 and 150 min after training. Hypoxia delivered immediately after training had a significantly diminishing effect on memory between 30 and 150 min after training. In addition, cold anesthesia disrupted memory only when introduced within the first 20 min, while hypoxia worked only when delivered within the first 2 min after training. When interpreted in the context of a four-phase model of memory consolidation, the results suggest that 1) cold anesthesia disrupts both short-term memory (STM) and anesthesia-resistant memory (ARM), 2) hypoxia disrupts ARM specifically, 3) both of them leave long-term memory (LTM) intact, and 4) LTM may be independent of availability of STM and ARM in flies.

Previous work on classical olfactory learning and memory in flies has suggested at least four distinct phases of memory consolidation. Similarly, our behavioral and pharmacological analyses also provided clear evidence for at least four pharmacologically distinct memory phases in flies after operant conditioning. Anesthesia-resistant memory (ARM) is present between about 20 and 120 min after training, and susceptible to disruption by the ATPase deactivating chemicals such as ouabain and ethacrynic acid (EA). Long-term memory (LTM) is activated at least 150 min after training, and can be disrupted by protein synthesis inhibitors such as cycloheximide (CXM). In addition, a very short-term memory (pre-STM) is demonstrated by feeding flies with potassium chloride (KCl), which has been shown to disrupt the short-term memory. These observations confirm our previous argument that memory formation in flies involves an intricate, multiple-phase pathway of consolidation.

The nutritional effects on operant visual learning behavior were investigated in a flight simulator. Operant visual learning and memory formation were normal in Drosophila (S-flies) reared on standard medium, but absent in flies (P-flies) raised on Peking medium. S- and P-flies were transferred to the alternative medium soon after hatching and their progeny was also raised on corresponding medium for several generations. respectively. S-flies transferred showed significantly reduced learning acquisition and 20 min memory retention, and operant visual learning along with memory formation was abolished in their progeny within three generations. Transferred P-flies recovered slowly their learning acquisition and memory formation to normal levels within five generations. Further studies suggested that low protein and minerals or high carbohydrate contents in Peking medium might be related to abnormal performance of P-flies. These results confirm the feasibility of affecting learning behavior by dietary regimens and developing an insect model of maternal malnutrition for pre- or post-natal malnutrition in Drosophila.

This paper concerns certain difficult problems in image processing and perception: neurocomputation of visual motion information. The first part of this paper deals with the spatial physiological integration by the figure-ground discrimination neural network in the visual system of the fly. We have outlined the fundamental organization and algorithms of this neural network, and mainly concentrated on the results of computer simulations of spatial physiological integration. It has been shown that the gain control mechanism, the nonlinearity of synaptic transmission characteristic, the interaction between the two eyes, and the directional selectivity of the pool cells play decisive roles in the spatial physiological integration. In the second part, we have presented a self-organizing neural network for the perception of visual motion by using a retinotopic array of Reichardt's motion detectors and Kohonen's self-organizing maps. It has been demonstrated by computer simulations that the network is able to learn to solve the ambiguities given by local motion detection mechanism. The resultant self-organized configuration in the output layer is resembling direction selective columns which first appear in area MT of the primate visual system. It has been explored that the spatio-temporal coherences, mapping, cooperation, competition, and Hebb rule are the basic neural principles for visual motion perception.

Figure-ground discrimination and pattern discrimination represent one of the most important problems in computer vision. Based on computational neuronal network model proposed by Reichardt et al. for figure-ground discrimination in the visual system of the fly, entire systematic computer simulations were carried out under nonstationary conditions. Results show that the model network and simulations have predictive power for behavioural experimental results. This paper proposes that motion perception and elementary pattern discrimination in human visual system may be mediated by some kind of figure-ground system with movement detectors as input layer.