Compatibility of Topical Products to Manage Skin Irritation Associated with TTFields

PURPOSE/OBJECTIVE(S)

Tumor Treating Fields (TTFields) are electric fields that disrupt cellular processes critical for cancer cell viability and tumor progression. TTFields therapy is approved for the treatment of recurrent glioblastoma (GBM), newly diagnosed GBM, and pleural mesothelioma, and is currently under clinical investigations for the treatment of other types of cancers. TTFields therapy is delivered continuously and non-invasively, using a portable signal generator connected to 4 arrays attached to the skin. Treatment of at least 18 hours per day is recommended for increasing effectiveness. The main treatment-related adverse effect reported in clinical trials and post-marketing surveillance studies has been low-grade skin irritation under the arrays, which may be treated in most cases with the use of topical steroids or intermittent treatment interruptions. However, for maintaining treatment effectiveness, skin care products suitable for use under the TTFields arrays are those that do not affect field currents. The goal of this study was to investigate strategies to alleviate skin irritation without compromising treatment effectiveness.

MATERIALS/METHODS

TTFields (200 kHz) were applied to rats (Sprague Dawley, 10-20 weeks of age, body weight over 250 gr) using ceramic disks and hydrogels identical to those used with human arrays. The rat torso was depilated, and TTFields were applied to the rat torso before and after applying various skin care products to the surface beneath the arrays. After reaching a steady state, average currents were extracted from the device's log files. Percent change in current was calculated from the measurements with and without the product.

RESULTS

Tested products could be divided into groups according to their medical use: antibiotics, antiseptics, cleansers/adhesive removers, skin barriers, moisturizers, topical corticosteroids, and antiperspirants. The products could also be categorized by their type: creams, gels, soaps, sprays, ointments, wipes/pads, foams, and lotions. Skin care products that significantly reduced currents were mainly ointments. Typical ingredients of ointments are mineral oil and petrolatum, which are expected to create a hydrophobic layer, thereby reducing ionic conduction and hence field currents. These ingredients also hinder adherence of the acrylic-based tape to the skin thus compromising mechanical fixation of the arrays, leading to poor connectivity and hence reduced currents.

CONCLUSION

Identification of products for treating skin irritation that are compatible with TTFields therapy is important for improving patient's quality of life and increasing device usage. Skin care products containing petrolatum should not be applied under the arrays to avoid compromising treatment effectiveness.

Abstract 2666: Preclinical investigations of concomitant tumor treating fields (TTFields) with cisplatin or paclitaxel for treatment of cervical cancer

Introduction: Cervical cancer is a serious health problem despite the fact it is highly preventable. Early-stage cervical cancer treatment often involves surgery; however advanced, recurrent, or metastatic cases require systemic therapy. Chemotherapy, mainly cisplatin, is the most commonly used systemic therapy for this cancer type. Combination regimens may be needed in the recurrent or metastatic settings, with first-line treatments including cisplatin with paclitaxel. TTFields are electric fields that disrupt cellular processes critical for cancer cell viability and tumor progression. Concomitant treatment with TTFields and cisplatin or paclitaxel has shown benefit in other tumor types. In the current in vitro study, we tested the effectiveness of TTFields for the treatment of cervical cancer, and the possible benefit of applying TTFields together with first-line treatments for cervical cancer.

Methods: Human cervical cancer cell lines - squamous cell carcinoma Ca Ski and SiHa cells, and adenocarcinoma HeLa cells - were treated with TTFields (72 h, 1 V/cm RMS) at frequencies of 100 to 400 kHz, and tested for cell count. For examining the efficacy of TTFields concomitant with cisplatin or paclitaxel, various doses of the drugs were applied together with TTFields (200 kHz), followed by measurements of cell count, colony formation, and apoptosis. Overall effect was defined as the product of percent reductions in cell count and colony formation.

Results: TTFields treatment reduced cell count in all tested cervical cancer cell lines. 200 kHz were found to be effective and were used throughout the experiments. Dose response effects were seen with cisplatin or paclitaxel, and were augmented when TTFields were co-applied to the cells.

Conclusions: These preclinical data suggest that TTFields may be an effective treatment against cervical cancer, and that applying them concomitantly with first-line treatment for this malignancy may provide enhanced effectiveness.

Citation Format: Roni Frechtel-Gerzi, Daria Gerasimova, Einav Zeevi, Inbar Schlachet-Drukerman, Helena Mumblat, Antonia Martinez-Conde, Eyal Dor-On, Itai Tzchori, Adi Haber, Moshe Giladi, Uri Weinberg, Yoram Palti, Greg Palmer, Angeles A. Secord. Preclinical investigations of concomitant tumor treating fields (TTFields) with cisplatin or paclitaxel for treatment of cervical cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2666.

Correction: Davidi et al. Tumor Treating Fields (TTFields) Concomitant with Sorafenib Inhibit Hepatocellular Carcinoma In Vitro and In Vivo. Cancers 2022, 14, 2959

The authors wish to make minor corrections to Figure 1 and Figure 2 of the following paper [...].

Abstract 1866: Transcriptomics analysis for identification of pathways involved in the response to Tumor Treating Fields (TTFields)

Introduction: Tumor Treating Fields (TTFields) are alternating electric fields that disrupt the function of polarized molecules within cancer cells. Initial data showed an anti-mitotic effect on cancerous cells whilst more recent findings confirmed additional effects such as downregulation of DNA double strand break repair, replication stress, upregulation of autophagy, and immunogenic cell death. Identification of TTFields-driven alterations in pan-cancer and tumor specific pathway is needed to aid selection of therapeutic modalities to be applied concomitant with TTFields for improved treatment outcomes. The aim of this study was to identify common pathways involved in the response to TTFields by comparing transcriptomics of various tumor type.

Methods: Control and TTFields-treated non-small cell lung carcinoma cell lines and animal model, glioblastoma (GBM) cell lines and patient-derived cell lines, and a hepatocellular carcinoma animal model were examined. Samples from GBM patients treated with concomitant TTFields and temozolomide (TMZ) were compared to samples from patients treated with TMZ alone. A list of differentially expressed genes (DEGs) was generated from transcriptomics analysis. Enrichment analysis was conducted according to the Gene Set Enrichment Analysis (GSEA) of MSigDB, Reactome, and Kegg pathway databases. Significantly overlapping pathways were identified using ActivePathways package according to the Reactome and Kegg gene sets, and an enrichment map was created according to the number of datasets supporting each pathway.

Results: DEGs in response to TTFields application included genes of the cytoskeleton, immune system, and some secretion proteins. Common pathways downregulated by TTFields (negative GSEA) included DNA repair, DNA and RNA synthesis, and cell cycle regulation, specifically the G2M checkpoint, E2F targets, and Myc targets. Common pathways upregulated by TTFields (positive GSEA) included the immune response, specifically complement cascades, coagulation, and lysosome activity. ActivePathways enrichment map results agreed with the gene set enrichment results, and revealed additional pathways involved in the response to TTFields, such as SUMOylation, metabolism of carbohydrates, unfolded protein response, and signaling by interleukins.

Conclusions: Transcriptomic analysis revealed common pathways involved in the responses to TTFields, regardless of the origin of the sample. Some identified pathways were in line with previously demonstrated effect of TTFields, such as mitotic interference, inhibition of DNA damage repair and upregulation of the innate immune response. New pathways revealed in this work support the examination of novel combination strategies with TTFields to increase the therapeutic effect in patients bearing various solid tumor types.

Citation Format: Kerem Wainer-Katsir, Gitit Lavy-Shahaf, Shiri Davidi, Sara Jacobovitch, Tali Voloshin, Itai Tzchori, Yaara Porat, Lianghao Ding, Michael Story, Niv Pencovich, Ilan Volovitz, Joshua Branter, Stuart J. Smith, Adi Haber, Moshe Giladi, Uri Weinberg, Yoram Palti. Transcriptomics analysis for identification of pathways involved in the response to Tumor Treating Fields (TTFields) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1866.

Tumor treating fields (TTFields) in combination with sorafenib inhibit hepatocellular carcinoma in vitro and in vivo

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Background: Hepatocellular carcinoma (HCC) is a highly malignant liver cancer and a leading cause of cancer related mortality. Sorafenib was the first approved systemic treatment for HCC, and remains one of few front-line treatments for this malignancy. Tumor treating fields (TTFields) are low intensity (1-3 V/cm), intermediate frequency (100-500 kHz), alternating electric fields that exert antimitotic effects on cancerous cells. Results of the phase 2 HEPANOVA study of TTFields (150 kHz) plus sorafenib for advanced HCC support investigation of TTFields in a randomized controlled phase 3 study. The current research aimed to describe the in vitro and in vivo efficacy of this combination and to elucidate details regarding the underlying mechanism of action. Methods: In vitro examinations were performed in HepG2 and Huh-7D12 human HCC cell lines, to which TTFields at a frequency of 150 kHz were applied using the inovitro system. Autophagy was examined by western blot and fluorescence detection of microtubule-associated protein light chain 3 (LC3) levels, an accepted autophagy marker. The effect of TTFields in combination with sorafenib was evaluated using cytotoxic, clonogenic, and apoptotic assays. In vivo, SD rats were inoculated orthotopically into the left hepatic lobe with N1S1 HCC cells. 7 days later, TTFields or sham (heat) were applied to the abdominal region of the rats, continuously for 6 days. Daily intraperitoneal injections of sorafenib (10 mg/kg/day) or vehicle were performed during this time. To determine tumor volume growth, MRI images were acquired before and after treatment. Levels of autophagy and apoptosis were examined in tumor sections by immunohistochemistry for LC3 and cleaved PARP, respectively. Results: Application of TTFields induced autophagy in HCC cells. TTFields delivery was cytotoxic to the cells, reduced their colony forming ability, and induced apoptosis while combination with sorafenib elevated these effects. In vivo, tumor volume increased 6-fold in control animals vs 1.6-fold in animals treated with TTFields plus sorafenib. This effect was accompanied by significantly elevated levels of cleaved PARP and LC3 within the tumors of treated relative to control rats. Conclusions: The results demonstrate induction of autophagy and apoptosis in HCC following treatment with TTFields. Concomitant application of TTFields with sorafenib enhanced efficacy via a mechanism that may involve overwhelming autophagy, in vitro and in vivo.

Improved Patency of ePTFE Grafts as a Hemodialysis Access Site by Seeding Autologous Endothelial Cells Expressing Fibulin-5 and VEGF

Small caliber synthetic vascular grafts used for dialysis access sites have high failure rates due to neointima formation and thrombosis. Seeding synthetic grafts with endothelial cells (ECs) provides a biocompatible surface that may prevent graft failure. We tested the use of ePTFE grafts seeded with autologous ECs expressing fibulin-5 and vascular endothelial growth factor (VEGF), as a dialysis access site in a porcine model. We connected the carotid arteries and jugular veins of 12 miniature pigs using 7-mm ePTFE grafts; five grafts were seeded with autologous venous ECs modified to express fibulin-5 and VEGF, and seven unseeded grafts were implanted at the same location and served as controls. At 6 months, after completion of angiography, the carotid arteries and jugular veins with the connecting grafts were excised and fixed. Autologous EC isolation and transduction and graft seeding were successful in all animals. At 3 months, 4 of 5 seeded grafts and 3 of 7 control grafts were patent. At 6 months, 4 of 5 (80%) seeded grafts and only 2 of 7 (29%) control grafts were patent. Seeding ePTFE vascular grafts with genetically modified ECs improved long term small caliber graft patency. The biosynthetic grafts offer a novel therapeutic modality for vascular access in hemodialysis.

Fibulin-5 regulates keloid-derived fibroblast-like cells through integrin beta-1

OBJECTIVE

Keloid scar is pathological tissue that appears after skin injury, and that is more aggressive than hypertrophic scars. Keloid scars are characterized by increased proliferation of fibroblast-like cells (FLCs) and the accumulation of extracellular matrix, mainly collagen. Fibulin-5, a glycoprotein secreted by many cell types, is a component of the extracellular matrix. We investigated the effect of fibulin-5 on the adhesion and proliferation of FLCs derived from keloid scars and the role of integrin beta-1 in these activities.

METHODS

Fibroblast-like cells were isolated from six keloid scars and cultured on plates coated with fibulin-5 or with gelatin. Cells were incubated for 72-96 h to examine proliferation rates and incubated for 240 min, with washings at 20, 40, 60, 90, 120, 180 min, to assess adhesion rates. To examine the role of integrin beta-1, the anti-human integrin beta-1 (CD29) antibody was added to the culture medium.

RESULTS

Fibroblast-like cells from keloids cultured on a fibulin-5-coated surface showed a significantly reduced proliferation rate and a delayed adhesion rate, compared to cells cultured on gelatin-coated dishes. Adherence of these cells to fibulin-5 pre-coated wells was significantly reduced in the presence of anti-human integrin beta-1 (CD29) antibodies. Our current findings are similar to previously observed reduced proliferation in vascular smooth muscle cells overexpressing fibulin-5. We did not test the effects of fibulin-5 on normal fibroblasts.

CONCLUSION

This study demonstrates the pivotal role of the extracellular protein, fibulin-5, on the adhesion and proliferation of human keloid-derived cells, through binding to integrin beta-1.

Tensile forces applied on a cell-embedded three-dimensional scaffold can direct early differentiation of embryonic stem cells toward the mesoderm germ layer

Mechanical forces play an important role in the initial stages of embryo development; yet, the influence of forces, particularly of tensile forces, on embryonic stem cell differentiation is still unknown. The effects of tensile forces on mouse embryonic stem cell (mESC) differentiation within a three-dimensional (3D) environment were examined using an advanced bioreactor system. Uniaxial static or dynamic stretch was applied on cell-embedded collagen constructs. Six-day-long cyclic stretching of the seeded constructs led to a fourfold increase in Brachyury (BRACH-T) expression, associated with the primitive streak phase in gastrulation, confirmed also by immunofluorescence staining. Further examination of gene expression characteristic of mESC differentiation and pluripotency, under the same conditions, revealed changes mostly related to mesodermal processes. Additionally, downregulation of genes related to pluripotency and stemness was observed. Cyclic stretching of the 3D constructs resulted in actin fiber alignment parallel to the stretching direction. BRACH-T expression decreased under cyclic stretching with addition of myosin II inhibitor. No significant changes in gene expression were observed when mESCs were first differentiated in the form of embryoid bodies and then exposed to cyclic stretching, suggesting that forces primarily influence nondifferentiated cells. Understanding the effects of forces on stem cell differentiation provides a means of controlling their differentiation for later use in regenerative medicine applications and sheds light on their involvement in embryogenesis.

The formation of an anti-restenotic/anti-thrombotic surface by immobilization of nitric oxide synthase on a metallic carrier

Coronary stenosis due to atherosclerosis, the primary cause of coronary artery disease, is generally treated by balloon dilatation and stent implantation, which can result in damage to the endothelial lining of blood vessels. This leads to the restenosis of the lumen as a consequence of migration and proliferation of smooth muscle cells (SMCs). Nitric oxide (NO), which is produced and secreted by vascular endothelial cells (ECs), is a central anti-inflammatory and anti-atherogenic player in the vasculature. The goal of the present study was to develop an enzymatically active surface capable of converting the prodrug l-arginine, to the active drug, NO, thus providing a targeted drug delivery interface. NO synthase (NOS) was chemically immobilized on the surface of a stainless steel carrier with preservation of its activity. The ability of this functionalized NO-producing surface to prevent or delay processes involved in restenosis and thrombus formation was tested. This surface was found to significantly promote EC adhesion and proliferation while inhibiting that of SMCs. Furthermore, platelet adherence to this surface was markedly inhibited. Beyond the application considered here, this approach can be implemented for the local conversion of any systemically administered prodrug to the active drug, using catalysts attached to the surface of the implant.

Isl1 and Ldb co-regulators of transcription are essential early determinants of mouse limb development

BACKGROUND

The developing limb has served as an excellent model for studying pattern formation and signal transduction in mammalians. Many of the crucial genes that regulate growth and patterning of the limb following limb bud formation are now well known. However, details regarding the control of limb initiation and early stages of outgrowth remain to be defined. This report is focused on genetic events that pave the way for the establishment of a hindlimb bud.

RESULTS

Fgf10 and Tbx are crucial for early phases of limb bud initiation. Here we show that in the absence of Isl1 or of Ldb1/2, there is no hindlimb bud development. Fgf10 expression in the bud mesenchyme is dependent on Isl1 and its Ldb co-regulators.

CONCLUSIONS

Thus, Isl1 and the Ldb co-regulators of transcription are essential early determinants of mouse limb development. Isl1/Ldb complexes regulate Fgf10 to orchestrate the earliest stages of hindlimb formation.

H3K9 histone acetylation predicts pluripotency and reprogramming capacity of ES cells

The pluripotent genome is characterized by unique epigenetic features and a decondensed chromatin conformation. However, the relationship between epigenetic regulation and pluripotency is not altogether clear. Here, using an enhanced MEF/ESC fusion protocol, we compared the reprogramming potency and histone modifications of different embryonic stem cell (ESC) lines (R1, J1, E14, C57BL/6) and found that E14 ESCs are significantly less potent, with significantly reduced H3K9ac levels. Treatment of E14 ESCs with histone deacetylase (HDAC) inhibitors (HDACi) increased H3K9ac levels and restored their reprogramming capacity. Microarray and H3K9ac ChIP-seq analyses, suggested increased extracellular matrix (ECM) activity following HDACi treatment in E14 ESCs. These data suggest that H3K9ac may predict pluripotency and that increasing pluripotency by HDAC inhibition acts through H3K9ac to enhance the activity of target genes involved in ECM production to support pluripotency.

Nuclear adaptor Ldb1 regulates a transcriptional program essential for the maintenance of hematopoietic stem cells

The nuclear adaptor Ldb1 functions as a core component of multiprotein transcription complexes that regulate differentiation in diverse cell types. In the hematopoietic lineage, Ldb1 forms a complex with the non-DNA-binding adaptor Lmo2 and the transcription factors E2A, Scl and GATA-1 (or GATA-2). Here we demonstrate a critical and continuous requirement for Ldb1 in the maintenance of both fetal and adult mouse hematopoietic stem cells (HSCs). Deletion of Ldb1 in hematopoietic progenitors resulted in the downregulation of many transcripts required for HSC maintenance. Genome-wide profiling by chromatin immunoprecipitation followed by sequencing (ChIP-Seq) identified Ldb1 complex-binding sites at highly conserved regions in the promoters of genes involved in HSC maintenance. Our results identify a central role for Ldb1 in regulating the transcriptional program responsible for the maintenance of HSCs.

LIM homeobox transcription factors integrate signaling events that control three-dimensional limb patterning and growth

Vertebrate limb development is controlled by three signaling centers that regulate limb patterning and growth along the proximodistal (PD), anteroposterior (AP) and dorsoventral (DV) limb axes. Coordination of limb development along these three axes is achieved by interactions and feedback loops involving the secreted signaling molecules that mediate the activities of these signaling centers. However, it is unknown how these signaling interactions are processed in the responding cells. We have found that distinct LIM homeodomain transcription factors, encoded by the LIM homeobox (LIM-HD) genes Lhx2, Lhx9 and Lmx1b integrate the signaling events that link limb patterning and outgrowth along all three axes. Simultaneous loss of Lhx2 and Lhx9 function resulted in patterning and growth defects along the AP and the PD limb axes. Similar, but more severe, phenotypes were observed when the activities of all three factors, Lmx1b, Lhx2 and Lhx9, were significantly reduced by removing their obligatory co-factor Ldb1. This reveals that the dorsal limb-specific factor Lmx1b can partially compensate for the function of Lhx2 and Lhx9 in regulating AP and PD limb patterning and outgrowth. We further showed that Lhx2 and Lhx9 can fully substitute for each other, and that Lmx1b is partially redundant, in controlling the production of output signals in mesenchymal cells in response to Fgf8 and Shh signaling. Our results indicate that several distinct LIM-HD transcription factors in conjunction with their Ldb1 co-factor serve as common central integrators of distinct signaling interactions and feedback loops to coordinate limb patterning and outgrowth along the PD, AP and DV axes after limb bud formation.

Enhancing spawning in the grey mullet (Mugil cephalus) by removal of dopaminergic inhibition

A dot-blot immunoassay for the detection of vitellogenin (Vtg) in plasma of adult grey mullet (Mugil cephalus) was developed. The assay identified the sex of the tested fish prior to detectable gonadal development, enabling the establishment of broodstock at the desired ratio of 7:4 females to males. This broodstock was maintained under natural photoperiod, and used to study the relative effect of gonadotropin-releasing hormone (GnRH) and dopamine antagonists on oocyte maturation and ovulation, as well as the effect of 17alpha-methyltestosterone (MT) on spermiation. Three groups of females were treated with: (i) a single injection of dopamine antagonist, domperidone (Dom), (ii) GnRH analog (GnRHa) administered via ethylene-vinyl acetate copolymer (EVAc) slow-release implants or (iii) a combination of both Dom and GnRHa. Males were treated with MT, administered via EVAc slow-release implants. An additional group of untreated fish was used as a control. The Dom treatment proved to be more potent than the GnRHa treatment, and did not differ significantly from the combined treatment. The Dom and Dom+GnRHa treatments accelerated oocyte development and increased plasma estradiol levels equally, whereas the GnRHa treatment did not vary significantly from the control. MT was found to be a potent spermiating agent, which enhanced steady milt production in all treated males. In contrast, no spontaneous spermiation occurred in untreated males. Plasma 11-ketotestosterone (11-KT) levels were significantly higher in MT-treated males than in the controls. Interestingly, MT-treated males held with the GnRHa+Dom-treated females showed higher levels of plasma 11-KT than those held with GnRHa-treated females, indicating an additive effect which is probably attributable to female pheromones. Fully mature females were induced to spawn by injecting GnRHa alone or coupled with metaclopramide (a dopamine D2 receptors antagonist). The combined treatment, which included a dopamine antagonist, was found to be more potent in inducing ovulation and spawning as compared to GnRHa alone. In conclusion, our data suggest that dopaminergic inhibition is a major barrier along the reproductive axis that arrests spontaneous spawning in captive mullets.

Cloning and developmental expression of the cytochrome P450 aromatase gene (CYP19) in the European eel (Anguilla anguilla)

To characterize the involvement of the aromatase gene during the process of sex determination in the European eel (Anguilla anguilla), the expression of its gonadal form was determined during various developmental stages. The cloned cDNA from the European eel gonad (EeCYP19) contains an open reading frame of 1539 bp, encoding a deduced protein of 513 residues. The predicted amino acid sequence shows 97% identity with that of the Japanese eel, and 59-69% of identity with those of the CYP19 gonadal and brain forms of other teleost fish. Two potential initiation sites (ATG) were found downstream of the first ATG codon. A fluorescent-based method of real-time PCR was developed to quantify EeCYP19 expression. The expression levels of EeCYP19 in the gonads of adult males were approximately 12- and 30-fold lower than the levels in adult females and juvenile eels previously treated with E2, respectively. Expression of aromatase was found only in a single specimen in the control group. In contrast, no difference was found among sexes in the aromatase expression in the brain. Treatment with aromatase inhibitor (AI) of juvenile eel resulted in the total loss of aromatase expression in the gonads and brains. The results of this work revealed that AI treatment not only reduces the synthesis of estradiol, but reduces the expression levels of EeCYP19 as well. No evidence for the presence of a distinct extra-gonadal (brain) form of aromatase in the European eel could be provided.

Growth differences and growth hormone expression in male and female European eels [Anguilla anguilla (L.)]

In this study, we examined the growth differences of males and females following a sex reversion, and the growth hormone (GH) expression variation between sexes of European eels [Anguilla anguilla (L.)]. A high percentage of females (88%) was found in the group fed with estradiol 17beta compared to the control group (comprised of only 6% female eels), which was defined as the male population. Significant differences between growth rate and size were found following 480 days of growth, whereby the males reached 60+/-4.3 g (means+/-SE) in size and the females 73.4+/-5.9 (g+/-SE); after 600 days, the males reached 114.1+/-4.3 and the females 171+/-11.7 (g+/-SE). A cDNA coding for the complete growth hormone of the European eel A. anguilla (eeGH) was cloned by RACE PCR using several sets of degenerate oligonucleotides. The eeGH cDNA coding region is 627 bp long. A sequence comparison of eeGH with Anguilla japonica GH (jeGH) cDNA showed a 98% identical base. Comparison of the deduced amino acid sequence revealed 99% identical residues, meaning that a difference exists in only two of the 209 residues. In both cases, the differing residues in the eeGH amino acid sequence are lysine. We measured the mRNA levels of growth hormone in the pituitaries of male and female eels growing at different rates. A significantly higher expression of eeGH was found in the female eels in comparison to the males. These results show that different levels of GH transcription eeGH can explain the growth rate differences between male and female European eels.

Cloning of European eel (Anguilla anguilla) FSH-β subunit, and expression of FSH-β and LH-β in males and females after sex determination

The European eel (Anguilla anguilla) is a catadromic teleost species with a complex life cycle, both in sea and freshwater environments. The sex determination phase of gonadal development occurs in a freshwater environment. Polymorphism occurs in increasing rates with respect to gender. While males stop growing at approximately 150 g, females continue to grow to being much larger. In this study, we cloned the cDNA FSH-beta subunit of the European eel (A. anguilla), and measured the mRNA levels of FSH-beta and LH-beta in males and females after sex determination. The FSH-beta subunit cDNA consisted of 1068 bp, encoding a 127 amino acid peptide. A comparison between European and Japanese eels of the FSH-beta amino acid sequence showed 98% similarity.