Covalent Attachment of Horseradish Peroxidase to Single-Walled Carbon Nanotubes for Hydrogen Peroxide Detection

Single-walled carbon nanotubes (SWCNTs) are desirable nanoparticles for sensing biological analytes due to their photostability and intrinsic near-infrared fluorescence. Previous strategies for generating SWCNT nanosensors have leveraged nonspecific adsorption of sensing modalities to the hydrophobic SWCNT surface that often require engineering new molecular recognition elements. An attractive alternate strategy is to leverage pre-existing molecular recognition of proteins for analyte specificity, yet attaching proteins to SWCNT for nanosensor generation remains challenging. Towards this end, we introduce a generalizable platform to generate protein-SWCNT-based optical sensors and use this strategy to synthesize a hydrogen peroxide (H 2 O 2 ) nanosensor by covalently attaching horseradish peroxidase (HRP) to the SWCNT surface. We demonstrate a concentration-dependent response to H 2 O 2 , confirm the nanosensor can image H 2 O 2 in real-time, and assess the nanosensor's selectivity for H 2 O 2 against a panel of biologically relevant analytes. Taken together, these results demonstrate successful covalent attachment of enzymes to SWCNTs while preserving both intrinsic SWCNT fluorescence and enzyme function. We anticipate this platform can be adapted to covalently attach other proteins of interest including other enzymes for sensing or antibodies for targeted imaging and cargo delivery.

Reduced mitophagy is an early feature of NAFLD and liver-specific PARKIN knockout hastens the onset of steatosis, inflammation and fibrosis

Nonalcoholic fatty liver disease (NAFLD) encompasses a spectrum of pathologies that includes steatosis, steatohepatitis (NASH) and fibrosis and is strongly associated with insulin resistance and type 2 diabetes. Changes in mitochondrial function are implicated in the pathogenesis of NAFLD, particularly in the transition from steatosis to NASH. Mitophagy is a mitochondrial quality control mechanism that allows for the selective removal of damaged mitochondria from the cell via the autophagy pathway. While past work demonstrated a negative association between liver fat content and rates of mitophagy, when changes in mitophagy occur during the pathogenesis of NAFLD and whether such changes contribute to the primary endpoints associated with the disease are currently poorly defined. We therefore undertook the studies described here to establish when alterations in mitophagy occur during the pathogenesis of NAFLD, as well as to determine the effects of genetic inhibition of mitophagy via conditional deletion of a key mitophagy regulator, PARKIN, on the development of steatosis, insulin resistance, inflammation and fibrosis. We find that loss of mitophagy occurs early in the pathogenesis of NAFLD and that loss of PARKIN accelerates the onset of key NAFLD disease features. These observations suggest that loss of mitochondrial quality control in response to nutritional stress may contribute to mitochondrial dysfunction and the pathogenesis of NAFLD.

Connecting Gut Microbial Diversity with Plasma Metabolome and Fecal Bile Acid Changes Induced by the Antibiotics Tobramycin and Colistin Sulfate

The diversity of microbial species in the gut has a strong influence on health and development of the host. Further, there are indications that the variation in expression of gut bacterial metabolic enzymes is less diverse than the taxonomic profile, underlying the importance of microbiome functionality, particularly from a toxicological perspective. To address these relationships, the gut bacterial composition of Wistar rats was altered by a 28 day oral treatment with the antibiotics tobramycin or colistin sulfate. On the basis of 16S marker gene sequencing data, tobramycin was found to cause a strong reduction in the diversity and relative abundance of the microbiome, whereas colistin sulfate had only a marginal impact. Associated plasma and fecal metabolomes were characterized by targeted mass spectrometry-based profiling. The fecal metabolome of tobramycin-treated animals had a high number of significant alterations in metabolite levels compared to controls, particularly in amino acids, lipids, bile acids (BAs), carbohydrates, and energy metabolites. The accumulation of primary BAs and significant reduction of secondary BAs in the feces indicated that the microbial alterations induced by tobramycin inhibit bacterial deconjugation reactions. The plasma metabolome showed less, but still many alterations in the same metabolite groups, including reductions in indole derivatives and hippuric acid, and furthermore, despite marginal effects of colistin sulfate treatment, there were nonetheless systemic alterations also in BAs. Aside from these treatment-based differences, we also uncovered interindividual differences particularly centering on the loss of Verrucomicrobiaceae in the microbiome, but with no apparent associated metabolite alterations. Finally, by comparing the data set from this study with metabolome alterations in the MetaMapTox database, key metabolite alterations were identified as plasma biomarkers indicative of altered gut microbiomes resulting from a wide activity spectrum of antibiotics.

Gut Microbiota as Well as Metabolomes of Wistar Rats Recover within Two Weeks after Doripenem Antibiotic Treatment

An understanding of the changes in gut microbiome composition and its associated metabolic functions is important to assess the potential implications thereof on host health. Thus, to elucidate the connection between the gut microbiome and the fecal and plasma metabolomes, two poorly bioavailable carbapenem antibiotics (doripenem and meropenem), were administered in a 28-day oral study to male and female Wistar rats. Additionally, the recovery of the gut microbiome and metabolomes in doripenem-exposed rats were studied one and two weeks after antibiotic treatment (i.e., doripenem-recovery groups). The 16S bacterial community analysis revealed an altered microbial population in all antibiotic treatments and a recovery of bacterial diversity in the doripenem-recovery groups. A similar pattern was observed in the fecal metabolomes of treated animals. In the recovery group, particularly after one week, an over-compensation was observed in fecal metabolites, as they were significantly changed in the opposite direction compared to previously changed metabolites upon 28 days of antibiotic exposure. Key plasma metabolites known to be diagnostic of antibiotic-induced microbial shifts, including indole derivatives, hippuric acid, and bile acids were also affected by the two carbapenems. Moreover, a unique increase in the levels of indole-3-acetic acid in plasma following meropenem treatment was observed. As was observed for the fecal metabolome, an overcompensation of plasma metabolites was observed in the recovery group. The data from this study provides insights into the connectivity of the microbiome and fecal and plasma metabolomes and demonstrates restoration post-antibiotic treatment not only for the microbiome but also for the metabolomes. The importance of overcompensation reactions for health needs further studies.

8-HQA adjusts the number and diversity of bacteria in the gut microbiome of Spodoptera littoralis

Quinolinic carboxylic acids are known for their metal ion chelating properties in insects, plants and bacteria. The larval stages of the lepidopteran pest, Spodoptera littoralis, produce 8-hydroxyquinoline-2-carboxylic acid (8-HQA) in high concentrations from tryptophan in the diet. At the same time, the larval midgut is known to harbor a bacterial population. The motivation behind the work was to investigate whether 8-HQA is controlling the bacterial community in the gut by regulating the concentration of metal ions. Knocking out the gene for kynurenine 3-monooxygenase (KMO) in the insect using CRISPR/Cas9 eliminated production of 8-HQA and significantly increased bacterial numbers and diversity in the larval midgut. Adding 8-HQA to the diet of knockout larvae caused a dose-dependent reduction of bacterial numbers with minimal effects on diversity. Enterococcus mundtii dominates the community in all treatments, probably due to its highly efficient iron uptake system and production of the colicin, mundticin. Thus host factors and bacterial properties interact to determine patterns of diversity and abundance in the insect midgut.

In vitro models to detect in vivo bile acid changes induced by antibiotics

Bile acid homeostasis plays an important role in many biological activities through the bile-liver-gut axis. In this study, two in vitro models were applied to further elucidate the mode of action underlying reported in vivo bile acid changes induced by antibiotics (colistin sulfate, tobramycin, meropenem trihydrate, and doripenem hydrate). 16S rRNA analysis of rat fecal samples anaerobically incubated with these antibiotics showed that especially tobramycin induced changes in the gut microbiota. Furthermore, tobramycin was shown to inhibit the microbial deconjugation of taurocholic acid (TCA) and the transport of TCA over an in vitro Caco-2 cell layer used as a model to mimic intestinal bile acid reuptake. The effects induced by the antibiotics in the in vitro model systems provide novel and complementary insight explaining the effects of the antibiotics on microbiota and fecal bile acid levels upon 28-day in vivo treatment of rats. In particular, our results provide insight in the mode(s) of action underlying the increased levels of TCA in the feces upon tobramycin exposure. Altogether, the results of the present study provide a proof-of-principle on how in vitro models can be used to elucidate in vivo effects on bile acid homeostasis, and to obtain insight in the mode(s) of action underlying the effect of an antibiotic, in this case tobramycin, on bile acid homeostasis via effects on intestinal bile acid metabolism and reuptake.

Practical consensus recommendations regarding the use of hormonal therapy in metastatic breast cancer

Metastatic breast cancer (MBC) is cancer that has spread from the breast to another part of the body or has come back in another distant location. Treatment options for MBC depend on several factors. One of these factors is the levels of hormone receptors (HRs) in the tumor. Cancers with high levels of HRs, called HR-positive, use the hormones estrogen and progesterone to grow and spread. Hormonal therapy is a type of treatment specifically for HR-positive breast cancer. This expert group used data from published literature, practical experience and opinion of a large group of academic oncologists to arrive at these practical consensus recommendations in regards with the use of hormonal therapy and the management of HR-positive MBC for the benefit of community oncologists.

Autosomal dominant retinitis pigmentosa with toxic gain of function: Mechanisms and therapeutics

Autosomal dominant retinitis pigmentosa is a form of retinitis pigmentosa, an inherited retinal degenerative disorder characterized by progressive loss of photoreceptors eventually leading to irreversible loss of vision. Mutations in genes involved in the basic functions of the visual system give rise to this condition. These mutations can either lead to loss of function or toxic gain of function phenotypes. While autosomal dominant retinitis pigmentosa caused by loss of function can be ideally treated by gene supplementation with a single vector to address a different spectrum of mutations in a gene, the same strategy cannot be applied to toxic gain of function phenotypes. In toxic gain of function phenotypes, the mutation in the gene results in the acquisition of a new function that can interrupt the functioning of the wildtype protein by various mechanisms leading to cell toxicity, thus making a single approach impractical. This review focuses on the genes and mechanisms that cause toxic gain of function phenotypes associated with autosomal dominant retinitis pigmentosa and provide a bird's eye view on current therapeutic strategies and ongoing clinical trials.

Bruch's membrane pathology: A mechanistic perspective

Bruch's membrane, an extracellular matrix located between the retinal pigment epithelium and the choroid, plays a vital role as structural and functional support to the retinal pigment epithelium. Dysfunction of Bruch's membrane in both age-related macular degeneration and other ocular diseases is caused mostly by extracellular matrix degeneration, deposit formation, and angiogenesis. Although these factors are dealt in greater detail with respect to the cells that are degenerated such as the retinal pigment epithelium and the endothelial cells, the pathology involving the Bruch's membrane is often underrated. Since in most of the macular degenerations early degenerative changes are also observed in the Bruch's membrane, addressing only the cellular component without the underlying membrane will not yield an ideal clinical benefit. This review aims to discuss the factors and the mechanisms affecting the integrity of the Bruch's membrane, which would aid in developing an effective therapy for these pathologies.

Anti-quorum sensing and antibiofilm potential of Alternaria alternata, a foliar endophyte of Carica papaya, evidenced by QS assays and in-silico analysis

In the present study, secondary metabolites from an endophytic fungus, Alternaria alternata, colonizing Carica papaya, demonstrated antiquorum sensing properties against Pseudomonas aeruginosa. This study reports the antagonistic effects of fungal crude extract of A. alternata against the various quorum sensing (QS) associated virulent factors such as percentage decrease in production of pyocyanin, alginate, chitinase and rhamnolipid; significant decrease in proteases activity such as LasA protease activity, staphylolytic activity, Las B elastase; and a marked decrease in biofilm formation and associated factors such as exopolysaccharide (EPS) production and cell surface hydrophobicity (CSH). Further, motility pattern i.e., swimming and swarming was also found to be inhibited. This down regulation of QS and associated factors are further supported by in-silico analysis of interaction between QS receptor LasR and bioactive molecules viz., sulfurous acid, 2-propyl tridecyl ester and 1,2-benzenedicarboxylic acid, bis(2-methylpropyl) ester present in fungal crude extract, found based on GCMS analysis, sketches the modulating ability of QS expression. This is the first report on an endophytic fungus of C. papaya having a role in QS inhibition against P. aeruginosa and lays a platform to explore further the endophytes for potent therapeutic agents in QS.

Electron paramagnetic resonance and photoluminescence investigation on ultraviolet-emitting gadolinium-ion-doped CaAl₁₂O₁₉ phosphors

The gadolinium doped CaAl12O19 phosphor has been prepared by a low temperature solution combustion method in a short time and characterized using powder X-ray diffraction, energy dispersive analysis of X-ray mapping, electron paramagnetic resonance (EPR) and photoluminescence spectroscopic techniques. EPR and optical analysis of the sample confirm the presence of Gd(3+) in the CaAl12O19 matrix.

Reversible symptoms and clearance of mutant prion protein in an inducible model of a genetic prion disease in Drosophila melanogaster

Prion diseases are progressive disorders that affect the central nervous system leading to memory loss, personality changes, ataxia and neurodegeneration. In humans, these disorders include Creutzfeldt-Jakob disease, kuru and Gerstmann-Straüssler-Scheinker (GSS) syndrome, the latter being a dominantly inherited prion disease associated with missense mutations in the gene that codes for the prion protein. The exact mechanism by which mutant prion proteins affect the central nervous system and cause neurological disease is not well understood. We have generated an inducible model of GSS disease in Drosophila melanogaster by temporally expressing a misfolded form of the murine prion protein in cholinergic neurons. Flies accumulating this mutant protein develop motor abnormalities which are associated with electrophysiological defects in cholinergic neurons. We find that, upon blocking the expression of the mutant protein, both behavioral and electrophysiological defects can be reversed. This represents the first case of reversibility reported in a model of genetic prion disease. Additionally, we observe that endogenous mechanisms exist within Drosophila that are capable of clearing the accumulated prion protein.

Kikuchi's disease: an uncommon cause of cervical lymphadenopathy

Kikuchi Fujimoto's disease is a benign self limiting disorder presenting with localised cervical lymphadenopathy, fever, weight loss and night sweats. It is a rare disease with worldwide distribution but commonly reported from Asia. It is diagnosed by excision biopsy of the lymph nodes. Clinical features suggest a viral aetiology though not proven. It is often misdiagnosed as either systemic lupus erythematosus or malignant lymphoma. Better understanding as well as high clinical suspicion would aid in the diagnosis of the disease. Treatment is mainly symptomatic, with non-steroidal analgesics and antipyretics. Corticosteroids are rarely indicated. Although patients show a spontaneous recovery in 1-4 months, a follow-up of several years would be required to study the development of SLE in these patients.

Hypokalaemic paralysis and normocalcaemic tetany--a rare presentation of Sjogren's syndrome

38 year old woman was admitted with acute onset of quadriplegia. Biochemical investigation revealed severe hypokalaemia with hyperchloraemic metabolic acidosis, alkaline urine, and positive urinary anion gap which are the hallmark of distal tubular acidosis. In addition she also had hypophosphataemia, normoglycaemic glycosuria, aminoaciduria, and hyperphosphaturia suggestive of proximal tubular dysfunction. Further evaluation confirmed the diagnosis of Sjogren's syndrome. Interestingly our patient also had carpopedal spasm despite normal calcium and magnesium level. Quadriplegia and carpopedal spasm improved with correction of hypokalaemia and acidosis. Proximal tubular abnormalities (except albuminuria) were normalised at the time of discharge. Distal tubular acidosis is a well known renal manifestation of Sjogren's syndrome. But this type of transient proximal tubular dysfunction with distal tubular acidosis in Sjogren's syndrome is very rare and hypokalaemic tetany also deserves mention.

"Herbal remedy is natural and safe"--truth or myth?

Neem oil is often used externally as a traditional medicine in India. Its ingestion, even in small doses produces toxic effects like severe metabolic acidosis, seizures, renal failure and encephalopathy. Management is supportive and prognosis is generally good but fatalities may occur. Herein we report an unusual case of neem oil toxicity in a previously normal adult.

Protein losing enteropathy in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a chronic immunologic disorder that may affect multiple organ systems and present with myriad of clinical features. Gastro-intestinal (GI) manifestations are oral ulcers, dysphagia and abdominal pain caused by autoimmune peritonitis/intestinal vasculitis. Hypoalbuminaemia due to GI loss is uncommon. Protein losing enteropathy (PLE) is a group of clinical entities where there is loss of protein through GI tract. PLE due to SLE is rare but it can be the initial manifestation. Patients usually present with pedal oedema mimicking nephrotic syndrome clinically. It is diagnosed by excluding other causes of hypoalbuminaemia. Radio nucleotide labelled albumin scan is useful in confirming albumin loss through GI tract. Often there is a good response to corticosteroids and immunosuppressive drugs. Here we present two SLE patients whose presenting manifestation was protein losing enteropathy and both improved with corticosteroids.

Atrial flutter and pericarditis--a rare complication of right lobe amoebic liver abscess

A 38 year old gentleman presented with fever and right hypochondrial pain. On further evaluation he was detected to have an amoebic liver abscess (ALA) in the right lobe of the liver. The abscess yielded anchovy sauce pus on percutaneous drainage. Following the percutaneous drainage the patient developed tachycardia. Electrocardiogram revealed atrial flutter with rapid ventricular rate and ST elevation in all leads suggestive of pericarditis. The atrial flutter was reverted to sinus rhythm by cardioversion. The patient then had an uncomplicated convalescence. Amoebic pericarditis, though rare, is a serious complication of amoebic liver abscess. Pericardial complications are usually seen with left lobe liver abscess due to its proximity. Both pericarditis and cardiac arrhythmias due to amoebic liver abscess especially from right lobe are very rare.

Disseminated infection with Strongyloides stercoralis in a diabetic patient

A 58-year-old male diabetic who was operated for carcinoma larynx 4 years back was admitted with exertional dyspnoea and bilateral leg swelling for the past 2 years. Over the last 2 months, there was a progressive worsening of symptoms. Echocardiography done 2 years back showed pericardial effusion. Echo done during the current admission also showed pericardial effusion with preserved left ventricular function; cytological examination of the pericardial fluid showed larvae of Strongyloides stercoralis. He was treated with antinematodal drugs. A follow-up echo done at discharge showed no pericardial effusion and the patient was completely asymptomatic. To our knowledge, this is the first reported case of Strongyloides pericardial effusion in a diabetic patient.

Blister beetle dermatitis

Blister beetle dermatitis or paederus dermatitis is an irritant contact dermatitis due to accidental crush of insects belonging to paederus family on the skin. The characteristic features of blister beetle dermatitis are linear erythematous itchy vesicles over the exposed parts of body and kissing lesions. This condition is commonly seen during or after rainy season. The treatment is removal of irritant by gentle washing and topical steroids. It is often misdiagnosed and causes significant morbidity among the rural population.

Alpha-fetoprotein as a tumor marker in hepatocellular carcinoma: investigations in south Indian subjects with hepatotropic virus and aflatoxin etiologies

OBJECTIVES

The prevalence of hepatitis B virus (HBV) is reportedly the main cause of hepatocellular carcinoma (HCC) in India, where hepatitis C virus (HCV)-associated HCC is believed to be relatively less prevalent. We verified the usefulness of alpha-fetoprotein (AFP) as a tumor marker and analyzed the influence of viral etiology on AFP levels in HCC.

METHODS

Of a total of 1012 cases with liver disease, 202 were investigated for the presence of AFP (142 HCC cases, 30 cirrhosis cases, and 30 chronic liver disease (CLD) cases). In addition, serum samples from 30 healthy patients, 30 hepatitis B surface antigen (HBsAg) carriers, and 30 acute viral hepatitis cases were included as controls. AFP was quantitatively determined using a commercial ELISA (Quorum Diagnostics, Canada). Out of the 142 HCC cases screened for AFP, aflatoxin B1 (AFB1) detection was carried out in 38 HCC cases using an in-house immunoperoxidase test.

RESULTS

In HBV and HCV co-infected HCC cases, the AFP positivity was 85.7%. In HBV alone-associated HCC, the positivity was 62.9%, and 54.5% of AFB1 positive HCC cases showed AFP positivity. In HBV and HCV negative HCC cases, the positivity was 20.5%, and in HCV-associated HCC it was 17.6%. The HBV/HCV co-infected group and HBV alone positive HCC cases had significantly elevated levels of AFP. When AFP positivity was analyzed based on the marker profile of HBV, 89.7% of AFP positive cases were HBV-DNA positive.

CONCLUSIONS

The overall positivity pattern of AFP in HCC does indicate that higher levels of AFP are observed with hepatitis virus positivity, especially with HBV. Further studies must be carried out to correlate the serum levels of AFP with the size, number, and degree of differentiation of HCC nodules.

Prevalence of aflatoxin B1 in liver biopsies of proven hepatocellular carcinoma in India determined by an in-house immunoperoxidase test

Hepatocellular carcinoma (HCC) is the fourth leading cause of cancer-related death in the world. The incidence of HCC in India is reportedly low and varies from 0.2 to 1.9 %. Aflatoxins, secondary metabolites produced by Aspergillus flavus and Aspergillus parasiticus, are potent human carcinogens implicated in HCC. The prevalence of aflatoxin B1 (AFB1) as co-carcinogen was analysed using an in-house immunoperoxidase test in 31 liver biopsies and 7 liver-resection specimens from histopathologically proven HCC, and in 15 liver biopsies from cirrhosis patients (control group). Serum was tested for hepatitis B and C serological markers using commercial assays, and for AFB1 using an in-house ELISA with a sensitivity of approximately 1 ng ml(-1) for AFB1. In spite of positive AFB1 immunostaining in HCC cases, all serum specimens, from both HCC and the control groups, were AFB1-negative. There were 18 (58.1 %) HCC cases that revealed AFB1 in liver biopsies; 68.8 % (n=11) of non-B non-C hepatitis cases with HCC and 46.1 % (n=6) of the hepatitis B surface-antigen-positive subjects were positive for AFB1. Out of the two hepatitis B/hepatitis C virus co-infected cases, one was positive for AFB1. Of seven tumour-resection samples, six were positive for AFB1. Only one case revealed AFB1 in the non-tumour area of the resected material. Thus AFB1 staining was significantly associated with tumour tissue (P=0.03). Aflatoxins proved to have a significant association with HCC in this peninsular part of the subcontinent. The impact seems to be a cumulative process, as revealed by the AFB1 deposits in HCC liver tissue, even though the serum levels were undetectable.

Antidiabetic and antihyperlipemic effects of Clemeo felina

Petroleum ether and benzene extracts of Clemeo felina, given orally at doses of 300 mg kg(-1) day(-1) for 30 days, were found to be antidiabetic and antihyperlipemic on alloxan diabetic rats. Moreover, a significant decrease in the activities of serum enzymes like alkaline phosphatase, acid phosphatase and HMGCoA reductase activity in the liver was observed. However, treatment of rats with the extracts as well as standard antidiabetic drugs increased liver hexakinase activity and serum LDH activity.

Diagnosis of hepatitis C virus infection by ELISA, RIBA and RT-PCR: a comparative evaluation

OBJECTIVES

To evaluate the efficacy of second-generation ELISA (ELISA-2), third-generation ELISA (ELISA-3) and third-generation recombinant immunoblot assay (RIBA 3.0) for detection of antibodies to hepatitis C virus (anti-HCV) in comparison with reverse transcriptase-polymerase chain reaction (RT-PCR) to detect HCV RNA for the diagnosis of hepatitis C.

METHODS

Sera of 108 patients with chronic liver disease (CLD) were analyzed by ELISA-2, ELISA-3, RIBA 3.0 and RT-PCR in the first part of the study; in the second part, sera of 105 patients with non-chronic liver disease were evaluated with ELISA-3, RIBA 3.0 and RT-PCR.

RESULTS

In the CLD group, anti-HCV was positive in 4.6%, 14.8% and 16.6% by ELISA-2, ELISA-3 and RIBA 3.0, respectively. Among these anti-HCV positive cases, HCV RNA was positive in 100%, 58.9% and 64%, respectively. ELISA-2 did not give false-positive results, but missed substantial number of anti-HCV positive cases (p < 0.001). In the second group, anti-HCV was positive in 76.3% by ELISA-3 and 68.6% by RIBA 3.0 (p:ns). HCV-RNA was positive in 88.7% of ELISA- and RIBA-positive cases; in 60% of ELISA-positive, RIBA-indeterminate cases; and in 46.4% of ELISA-negative, RIBA-negative cases.

CONCLUSIONS

ELISA-2 is not a suitable assay for routine screening. ELISA-3 was at par with RIBA 3.0 and it can be recommended for routine screening for anti-HCV. RT-PCR for HCV is of value in detecting early viremic, anti-HCV negative cases; this may be of importance in the treatment of hepatitis C.

Inhibition of invasion in vitro and stimulation of aggregation by 13-cis retinoic acid correlates with the clustering of N-CAM in c-Ha-ras transformed glial cells

Invasion distinguishes malignant from benign primary brain tumors. The molecular mechanisms which permit malignant brain tumor cells to escape from the primary tumor mass and by which they can migrate through normal brain tissue are largely unknown. 13-cis retinoic acid (cRA) can induce morphological, biochemical and functional differentiation characteristics in various malignant tumors. Upon treatment of diffusely invasive hamster glial cells (CxT24neo3) with 30 mu M cRA, we found a significant reduction in cell proliferation in monolayer and spheroid cultures. cRA also inhibits invasion of CxT24neo3 through a reconstituted basement membrane (Matrigel(R)) in a dose dependent manner. Homotypic cell-cell adhesion, on the contrary, is stimulated in the absence of extracellular Ca++ by either treatment or pretreatment of CxT24neo3 with cRA. These phenotypic changes correlate with the induction of the clustering of the neural cell adhesion molecule: N-CAM at sites of cell-cell contact. This phenomenon is observed following immunohistochemical staining for N-CAM of CxT24neo3 cells that were treated with cRA in monolayer cultures. The relationship between reduction of proliferation and invasion in vitro and the increased homotypic cell-cell adhesion with clustering of N-CAM implicates N-CAM as a molecular effector molecule for reduction of malignancy by cRA.