Regulation of FGF2-induced proliferation by inhibitory GPCR in normal pituitary cells

Introduction

Intracellular communication is essential for the maintenance of the anterior pituitary gland plasticity. The aim of this study was to evaluate whether GPCR-Gαi modulates basic fibroblast growth factor (FGF2)-induced proliferative activity in normal pituitary cell populations.

Methods

Anterior pituitary primary cell cultures from Wistar female rats were treated with FGF2 (10ng/mL) or somatostatin analog (SSTa, 100nM) alone or co-incubated with or without the inhibitors of GPCR-Gαi, pertussis toxin (PTX, 500nM), MEK inhibitor (U0126, 100µM) or PI3K inhibitor (LY 294002, 10 μM).

Results

FGF2 increased and SSTa decreased the lactotroph and somatotroph BrdU uptak2e (p<0.05) whereas the FGF2-induced S-phase entry was prevented by SSTa co-incubation in both cell types, with these effects being reverted by PTX, U0126 or LY294002 pre-incubation. The inhibition of lactotroph and somatotroph mitosis was associated with a downregulation of c-Jun expression, a decrease of phosphorylated (p) ERK and pAKT. Furthermore, SSTa was observed to inhibit the S-phase entry induced by FGF2, resulting in a further increase in the number of cells in the G1 phase and a concomitant reduction in the number of cells in the S phases (p< 0.05), effects related to a decrease of cyclin D1 expression and an increase in the expression of the cell cycle inhibitors p27 and p21.

Discussion

In summary, the GPCR-Gαi activated by SSTa blocked the pro-proliferative effect of FGF2 in normal pituitary cells via a MEK-dependent mechanism, which acts as a mediator of both anti and pro-mitogenic signals, that may regulate the principal effectors of the G1 to S-phase transition.

The epigenetic EZH2/H3K27me3 axis modulates lactotroph tumor cell proliferation

Interest in epigenetics has gained substantial momentum as a result of their identified role in the regulation of tumor progression as well as their ability to pharmacologically target genes. Pituitary neuroendocrine tumors (PitNETs) tend to be inactivated via epigenetic modification, and although emerging evidence has suggested a role for epigenetic factors in PitNET tumorigenesis, the degree to which these factors may be targeted by new therapeutic strategies still remains poorly understood. The objective of the present study was to examine the participation of the EZH2/H3K27me3 axis in the proliferation of lactotroph tumor cells. We demonstrated that the levels of EZH2 and H3K27me3 were increased in murine experimental prolactin (PRL) tumors with respect to a control pituitary, in contrast with the low p21 mRNA levels encountered, with an H3K27me3 enrichment being observed in its promoter region in a GH3 tumor cell. Furthermore, specific EZH2/H3K27me3 axis inhibition blocked the proliferation of primary tumor cell culture and GH3 cells, thereby making it an attractive therapeutic target for PRL PitNETs.

Cuprous oxide nanoparticles incorporated into a polymeric matrix embedded in fabrics to prevent spread of SARS-CoV-2

This paper describes the development of a coating for cotton and polypropylene (PP) fabrics based on a polymeric matrix embedded with cuprous oxide nanoparticles (Cu₂O@SDS NPs) in order to inactivate SARS-CoV-2 and manufactured by a simple process using a dip-assisted layer-by-layer technology, at low curing temperature and without the need for expensive equipment, capable of achieving disinfection rates of up to 99%. The polymeric bilayer coating makes the surface of the fabrics hydrophilic, enabling the transportation of the virus-infected droplets to achieve the rapid inactivation of SARS-CoV-2 by contact with the Cu₂O@SDS NPs incorporated in the coated fabrics.

Ultrastructural and molecular evidence of macroautophagy in functioning PitNETs and experimental pituitary tumors

INTRODUCTION

Macroautophagy is a lysosome-mediated degradation process that controls the quality of cytoplasmic components and organelles, with its regulation depending on autophagy-related proteins (Atg) and with Beclin1/Atg6 and microtubule-associated protein light chain 3 (LC3/Atg8) being key players in the mammalian autophagy. As reports on this mechanism in the field of pituitary neuropathology and neuroendocrinology are scarce, our study analyzed the ultrastructural signs of macroautophagy and the expression of Beclin1 and LC3 proteins in human functioning PitNETs and in experimental pituitary tumors.

METHODS

a group of functioning humans PitNETs and an experimental lactotroph model in rats of the F344 strain stimulated with oestradiol benzoate (BE) were used. Ultrastructural and molecular evidence of the macroautophagic process was evaluated using different techniques.

RESULTS

In functioning PitNETs cohort, 60% exhibited evidence of macroautophagy, with a significant difference found for Beclin1 and LC3 between macro and micro PitNETs (p < 0.05). In the experimental model, the expression of both Beclin1 and LC3 proteins was immunopositive in normal and tumoral glands when analyzed by immunofluorescence, western blot and immunohistochemistry. In the experimental model, protein expression was associated with increased glandular size and weight.

CONCLUSIONS

Our study revealed evidence of macroautophagy at the pituitary level and the important role of Beclin1 and LC3 in the progression of functioning PitNETs, implying that this mechanism participate in regulating pituitary cell growth.

Changes of stem cell niche during experimental pituitary tumor development

To investigate the putative stem cell/tumor stem cell (SC/TSC) niche contribution to hyperplasic/adenomatous pituitary lesions, we analyzed variation in the pituitary stem cell population during the development of experimental pituitary tumors. Pituitary tumors were induced in female F344 rats with estradiol benzoate for 5, 10, 20 and 30 days. Cells positive for GFRa2, Sox2, Sox9, Nestin, CD133 and CD44 were identified in the marginal zone and in the adenoparenchyma in both control and 30D groups, with predominant adenoparenchyma localization of GRFa2 and SOX9 found in tumoral pituitaries. GFRa2, Nestin, CD133 and CD44 were upregulated at the initial stages of tumor growth, whereas Sox9 significantly decreased at 5D, with Sox2 remaining invariable during the hyperplasic/adenomatous development. In addition, isolated pituispheres from normal and tumoral pituitary glands enriched in SC/TSC were characterized. Pituispheres from the 30D glands were positive for the above-mentioned markers and showed a significant increase in the proliferation. In conclusion, our data revealed pituitary SC pool fluctuations during hyperplastic/adenomatous development, with differential localization of the SC/TSC niche in this process. These findings may help to provide a better understanding of these cell populations, which is crucial for achieving advancements in the field of pituitary tumor biology.

Association of PTP4A3 expression and tumour size in functioning pituitary adenoma: a descriptive study

BACKGROUND

PTP4A3 is a subclass of a protein tyrosine phosphatase super family and is expressed in a range of epithelial neoplasms. We evaluated PTP4A3 expression and its association with clinicopathological parameters in different types of functioning pituitary adenomas.

METHODS

A total of 34 functioning pituitary adenomas samples were evaluated in this observational study. PTP4A3 expression was examined by immunohistochemical staining, and, possible correlations between PTP4A3 and some clinicopathological variables were investigated.

RESULTS

PTP4A3 was expressed in 19 out of 34 tumours (55%), at the cytoplasmic level of tumorous cells. Moreover, there was significant association (p=0.042) between PTP4A3 expression and tumorous size.

CONCLUSIONS

PTP4A3 was expressed in more than half of the tumours analysed, with there being a significant association with the tumorous size of functioning adenomas. This allows to speculate that PTP4A3 may regulate tumour growth, although further investigations are necessary to determine if this phosphatase can serve as a biomarker or used as a therapeutic target in pituitary macroadenomas.

TGFβ1 regulates prolactin secretion during postnatal development: gender differences

Serum prolactin levels gradually increase from birth to puberty in both male and female rats, with higher levels observed in female since the first days of life. The increase in lactotroph secretion was attributed to the maturation of prolactin-inhibiting and prolactin-releasing factors; however, those mechanisms could not fully explain the gender differences observed. Prolactin secretion from isolated lactotrophs, in the absence of hypothalamic control, also increases during the first weeks of life, suggesting the involvement of intra-pituitary factors. We postulate that pituitary transforming growth factor beta 1 (TGFβ1) is involved in the regulation of prolactin secretion as well as in the gender differences observed at early postnatal age. Several components of the local TGFβ1 system were evaluated during postnatal development (11, 23, and 45 days) in female and male Sprague-Dawley rats. In vivo assays were performed to study local TGFβ1 activation and its impact on prolactin secretion. At day 11, female pituitaries present high levels of active TGFβ1, concomitant with the highest expression of TGFβ1 target genes and the phospho-Smad3 immunostaining in lactotrophs. The steady increase in prolactin secretion inversely correlates with active TGFβ1 levels only in females. Dopamine and estradiol induce TGFβ1 activation at day 11, in both genders, but its activation induces the inhibition of prolactin secretion only in females. Our findings demonstrate that: (1) TGFβ1 activation is regulated by dopamine and estradiol; (2) the inhibitory regulation of local TGFβ1 on prolactin secretion is gender specific; and (3) this mechanism is responsible, at least partially, for the gender differences observed being relevant during postnatal development.

Rifampicin loaded in alginate/chitosan nanoparticles as a promising pulmonary carrier against Staphylococcus aureus

This study aims to explore the antimicrobial activity of rifampicin (RIF) and ascorbic acid (ASC) co-loaded into alginate (ALG)/chitosan (CS) nanoparticles (RIF/ASC NPs) and tested for their antibacterial activity against several strains of methicillin-sensitive Staphylococcus aureus (MSSA) and methicillin-resistant Staphylococcus aureus (MRSA). Also, the present research focused on exploring the possible antibacterial mechanism of action of these RIF/ASC NPs, which demonstrated a significant biocide activity against the S. aureus strains with minimum inhibitory concentrations (MIC) between 2- and 8-fold lower than those one exhibited with the free antibiotic RIF. The proposed antimicrobial mechanism of action of the RIF/ASC NPs seems to be the result of collaborative effects between NPs and the RIF/ASC antibiotic combination. Moreover, results indicated that the functionalized RIF/ASC NP surface played a crucial role on the processes of NP adhesion into the bacterial surface, the alterations on the cell membrane integrity, and the cell uptake of the RIF/ASC antibiotic into bacteria. Further, the in vivo lung deposition pattern of empty NPs labeled (NPs-FITC) with isothiocyanate fluorescein in rats was investigated post intratracheal instillation of NPs. In summary, findings from this work show that our novel designed engineered RIF/ASC co-loaded NPs could be a suitable system for antibiotic lung administration with promising perspectives for effective treatments of pulmonary intracellular infections for those known antibiotics that are losing effectiveness due to antimicrobial resistance problems. Graphical Abstract.

Trastuzumab inhibits pituitary tumor cell growth modulating the TGFB/SMAD2/3 pathway

In pituitary adenomas, early recurrences and resistance to conventional pharmacotherapies are common, but the mechanisms involved are still not understood. The high expression of epidermal growth factor receptor 2 (HER2)/extracellular signal-regulated kinase (ERK1/2) signal observed in human pituitary adenomas, together with the low levels of the antimitogenic transforming growth factor beta receptor 2 (TBR2), encouraged us to evaluate the effect of the specific HER2 inhibition with trastuzumab on experimental pituitary tumor cell growth and its effect on the antiproliferative response to TGFB1. Trastuzumab decreased the pituitary tumor growth as well as the expression of ERK1/2 and the cell cycle regulators CCND1 and CDK4. The HER2/ERK1/2 pathway is an attractive therapeutic target, but its intricate relations with other signaling modulators still need to be unraveled. Thus, we investigated possible cross-talk with TGFB signaling, which has not yet been studied in pituitary tumors. In tumoral GH3 cells, co-incubation with trastuzumab and TGFB1 significantly decreased cell proliferation, an effect accompanied by a reduction in ERK1/2 phosphorylation, an increase of SMAD2/3 activation. In addition, through immunoprecipitation assays, a diminution of SMAD2/3-ERK1/2 and an increase SMAD2/3-TGFBR1 interactions were observed when cells were co-incubated with trastuzumab and TGFB1. These findings indicate that blocking HER2 by trastuzumab inhibited pituitary tumor growth and modulated HER2/ERK1/2 signaling and consequently the anti-mitogenic TGFB1/TBRs/SMADs cascade. The imbalance between HER2 and TGFBRs expression observed in human adenomas and the response to trastuzumab on experimental tumor growth may make the HER2/ERK1/2 pathway an attractive target for future pituitary adenoma therapy.

Oxidative stress and mitochondrial adaptive shift during pituitary tumoral growth

The cellular transformation of normal functional cells to neoplastic ones implies alterations in the cellular metabolism and mitochondrial function in order to provide the bioenergetics and growth requirements for tumour growth progression. Currently, the mitochondrial physiology and dynamic shift during pituitary tumour development are not well understood. Pituitary tumours present endocrine neoplastic benign growth which, in previous reports, we had shown that in addition to increased proliferation, these tumours were also characterized by cellular senescence signs with no indication of apoptosis. Here, we show clear evidence of oxidative stress in pituitary cells, accompanied by bigger and round mitochondria during tumour development, associated with augmented biogenesis and an increased fusion process. An activation of the Nrf2 stress response pathway together with the attenuation of the oxidative damage signs occurring during tumour development were also observed which will probably provide survival advantages to the pituitary cells. These neoplasms also presented a progressive increase in lactate production, suggesting a metabolic shift towards glycolysis metabolism. These findings might imply an oxidative stress state that could impact on the pathogenesis of pituitary tumours. These data may also reflect that pituitary cells can modulate their metabolism to adapt to different energy requirements and signalling events in a pathophysiological situation to obtain protection from damage and enhance their survival chances. Thus, we suggest that mitochondria function, oxidative stress or damage might play a critical role in pituitary tumour progression.

The expansion of adult stem/progenitor cells and their marker expression fluctuations are linked with pituitary plastic adaptation during gestation and lactancy

Extensive evidence has revealed variations in the number of hormone-producing cells in the pituitary gland, which occur under physiological conditions such as gestation and lactancy. It has been proposed that new hormone-producing cells differentiate from stem cells. However, exactly how and when this takes place is not clear. In this work, we used immunoelectron microscopy to identify adult pituitary stem/progenitor cells (SC/P) localized in the marginal zone (MZ), and additionally, we detected GFRa2-, Sox2-, and Sox9-positive cells in the adenoparenchyma (AP) by fluorescence microscopy. Then, we evaluated fluctuations of SC/P mRNA and protein level markers in MZ and AP during gestation and lactancy. An upregulation in stemness markers was shown at term of gestation (AT) in MZ, whereas there were more progenitor cell markers in the middle of gestation and active lactancy. Concerning committed cell markers, we detected a rise in AP at beginning of lactancy (d1L). We performed a BrdU uptake analysis in MZ and AP cells. The highest level of BrdU uptake was observed in MZ AT cells, whereas in AP this was detected in d1L, followed by a decrease in both the MZ and AP. Finally, we detected double immunostaining for BrdU-GFRa2 in MZ AT cells and BrdU-Sox9 in the AP d1L cells. Taken together, we hypothesize that the expansion of the SC/P niche took place mainly in MZ from pituitary rats in AT and d1L. These results suggest that the SC niche actively participates in pituitary plasticity during these reproductive states, contributing to the origin of hormone cell populations.

Evidence of cellular senescence during the development of estrogen-induced pituitary tumors

Although pituitary adenomas represent 25% of intracranial tumors, they are usually benign, with the mechanisms by which these tumors usually avoid an invasive profile and metastatic growth development still remaining unclear. In this context, cellular senescence might constitute a plausible explanation for the benign nature of pituitary adenomas. In this study, we investigated the emergence of cellular senescence as a growth control mechanism during the progression of estrogen-induced pituitary tumors. The quantification of Ki67-immunopositive cells in the pituitaries of estrogenized male rats after 10, 20, 40, and 60 days revealed that the mitogenic potential rate was not sustained for the whole period analyzed and successively decreased after 10 days of estrogen exposure. In addition, the expression of cellular senescence features, such as the progressive rise in the enzymatic senescence-associated b-galactosidase (SA-b-gal) activity, IL6, IL1b, and TGFb expression, was observed throughout pituitary tumor development. Furthermore, tumoral pituitary cells also displayed nuclear pATM expression, indicating activated DNA damage signaling, with a significant increase in p21 expression also being detected. The associations among DNA damage signaling activation, SA-b-gal expression, and p21 may provide a reliable combination of senescence-associated markers for in vivo pituitary senescence detection. These results suggest a role for this cellular process in the regulation of pituitary cell growth. Thus, cellular senescence should be conceived as a contributing component to the benign nature of pituitary adenomas, thereby influencing the capability of the pituitary gland to avoid unregulated cell proliferation.

Involvement of MEK/ERK1/2 and PI3K/Akt pathways in the refractory behavior of GH3B6 pituitary tumor cells to the inhibitory effect of TGFβ1

Pituitary tumor cells have a poor response to the growth inhibitory effect of TGFβ1, possibly resulting from the cross talk of TGFβ/Smads signal with other signaling pathways, an undescribed mechanism in these tumoral cells. To address this hypothesis, we investigated whether the mitogen-activated extracellular signal-regulated kinase (MEK)/ERK1/2 and phosphoinositide-3 kinase/protein kinase B (PI3K/Akt) pathways were able to regulate the antimitogenic effect of TGFβ1 on GH3B6 cells. TGFβ1 treatment decreased the cell proliferation and induced an activation of mothers against decapentaplegic homolog 2/3 (Smad2/3), effects that were potentiated by MEK and PI3K inhibitors, thus indicating the existence of a cross talk between TGFβ1/Smad with the MEK/ERK1/2 or PI3K/Akt pathways. In addition, through immunoprecipitation assays, a direct interaction was observed between Smad2/3-ERK1/2 and Smad2/3-Akt, which decreased when the GH3B6 cells were incubated with TGFβ1 in the presence of MEK or PI3K inhibitors, thereby suggesting that the ERK1/2- and Akt-activated states were involved. These Smad2/3-ERK1/2 and Smad2/3-Akt associations were also confirmed by confocal and transmission electron microscopy. These findings indicate that the TGFβ1-antimitogenic effect in GH3B6 cells was attenuated by the MEK/ERK1/2 and PI3K/Akt pathways via modulating Smad2/3 phosphorylation. This molecular mechanism could explain in part the refractory behavior of pituitary tumor cells to the inhibitory effect of TGFβ1.

17β-oestradiol acts as a negative modulator of insulin-induced lactotroph cell proliferation through oestrogen receptor α, via nitric oxide/guanylyl cyclase/cGMP

OBJECTIVES

17β-oestradiol interacts with growth factors to modulate lactotroph cell population. However, contribution of isoforms of the oestrogen receptor in these activities is not fully understood. In the present study, we have established participation of α and β oestrogen receptors in effects of 17β-oestradiol on lactotroph proliferation induced by insulin and shown involvement of the NO/sGC/cGMP pathway.

MATERIALS AND METHODS

Cell cultures were prepared from anterior pituitaries of female rats to evaluate lactotroph cell proliferation using bromodeoxyuridine (BrdUrd) detection, protein expression by western blotting and cGMP by enzyme immunoassay.

RESULTS

In serum-free conditions, 17β-oestradiol and α and β oestrogen receptor agonists (PPT and DPN) failed to increase numbers of lactotroph cells undergoing mitosis. Co-incubation of 17β-oestradiol/insulin and PPT/insulin significantly decreased lactotroph mitogenic activity promoted by insulin alone. Both ICI 182780 and NOS inhibitors (L-NMMA and L-NAME) induced reversal of the anti-proliferative effect promoted by 17β-oestradiol/insulin and PPT/insulin. Moreover, 17β-oestradiol, PPT and insulin increased sGC α1 protein expression and inhibited β1, whereas co-incubation of 17β-oestradiol/insulin or PPT/insulin induced increases of the two isoforms α1 and β1. 17β-oestradiol and insulin reduced cGMP production, while 17β-oestradiol/insulin co-incubation increased this cyclic nucleotide.

CONCLUSIONS

Our results suggest that 17β-oestradiol is capable of arresting lactotroph proliferation induced by insulin through ER α with participation of the signalling NO/sGC/cGMP pathway.

GH3B6 pituitary tumor cell proliferation is mediated by PKCalpha and PKCepsilon via ERK 1/2-dependent pathway

BACKGROUND

In this report, we explored the role of PKCalpha and PKCe as mediators of phorbol 12-myristate13-acetate (PMA)-induced proliferation in pituitary tumor GH3B6 cells, and determined if the ERK1/2 and Akt pathways were activated.

METHODS

The GH3B6 cell proliferation was estimated by BrdU incorporation and the cell cycle progression by flow cytometric cell cycle analysis. We determined the expression of PKCalpha and PKCe in membrane and cytosolic fractions by western blotting. The subcellular redistribution of both PKC isozymes was analyzed by confocal microscopy.

RESULTS

Incubation with PMA for 15 min stimulated PKCalpha and PKCe activation, which was correlated with the phosphorylation of ERK1/2 but not Akt. The activation of both these PKC isozymes was closely associated with the stimulation of proliferation and the cell cycle progression induced by PMA in GH3B6 cells, an effect that was blocked by the inhibitors of PKCalpha (Gö6976) and PKCe (eV1-2). In addition, the pretreatment with the inhibitor of ERK1/2 (PD98059) prevented the mitogenic activity induced by treatment with PMA for 15 min.

CONCLUSION

We demonstrated that the activation of PKCalpha and PKCe by phorbol ester in tumor pituitary GH3B6 cells led to cell proliferation and cell cycle progression, effects that involved ERK1/2 activation.

Activation of PKC epsilon induces lactotroph proliferation through ERK1/2 in response to phorbol ester

The aim of this investigation was to contribute to current knowledge about intracellular mechanisms that are involved in lactotroph cell proliferation, by evaluating the role of PKCalpha, PKCepsilon and extracellular-signal regulated kinase (ERK) 1/2 in response to phorbol 12-myristate13-acetate (PMA). In primary pituitary cultures, the activation of protein kinase C (PKC) by PMA for 15 min stimulated lactotroph proliferation; whereas a prolonged activation for 3-8h diminished this proliferative effect. The use of PMA for 15 min-activated PKCepsilon and ERK1/2, whereas incubation with PMA for 3 h induced PKCalpha activation and attenuated the PMA-triggered phosphorylation of ERK1/2. The following inhibitors: PKCs (bisindolylmaleimide I), PKCepsilon (epsilonV1 peptide) and ERK1/2 (PD98059) prevented the mitogenic activity induced by PMA for 15 min. Lactotroph cells stimulated with PMA for 15 min showed a translocation of PKCepsilon to membrane compartment and nucleus. These results thus establish that PKCepsilon plays an essential role in the lactotroph proliferation induced by PMA by triggering signals that involve ERK1/2 activation.

Antagonic effects of oestradiol in interaction with IGF-1 on proliferation of lactotroph cells in vitro

The effects of IGF-1, 17 beta oestradiol and its functional interaction on lactotrophs cell proliferation were evaluated. In addition we investigated the involvement of PKC alpha, epsilon and phosphorilated ERK, in the mitogenic process. Primary cell cultures of adenohypophysis from female Wistar rats were studied in serum free conditions. The proliferation of lactotrophs was determined by double immunostaining for BrdU and PRL. The incubation with IGF-1 5, 30 or 100 ng/ml during 48 or 72 h increased lactotrophs proliferation two-threefold depending on IGF-1 concentration. Co-incubation of IGF-1 (30 ng/ml) with genistein (25 microM) or BIM (0.5 or 2 microM), lowered of tyrosine kinase receptor or of PKC respectively, inhibited the induced IGF-1 lactotrophs proliferation. 17 beta oestradiol (1, 10 or 100 nM) had not mitogenic effect, whereas in the presence of serum PRL cells proliferation was stimulated. Co-incubation with 1 nM oestradiol and IGF-1 significantly decreased the lactotroph BrdU-labelling achieved with IGF-1. PKC alpha, epsilon and ERK1/2 levels measured by western blot augmented in the presence of IGF-1 and were inhibited with the addition of genistein, supporting a participation of these enzymes in the proliferate process. Co-incubation of IGF-1 with 1 nM oestradiol decreased both PKC isoforms and activated ERK1/2 levels, suggesting that oestradiol would exert its antiproliferative effect by acting on the signalling pathway of IGF-1. The results revealed antagonic effects of oestradiol on lactotroph proliferation depending on its concentration and the presence of IGF-1.

COX and LOX eicosanoids modulate platelet activation and procoagulation induced by two murine cancer cells

Involvement of arachidonic acid cyclooxygenase (COX) and lipoxygenase (LOX) metabolites in platelet aggregation and coagulation induced by two varieties of cancer cells of murine transplantable tumors was studied. A lung alveolar carcinoma (LAC) and a fibrosarcoma (FS), induced platelet aggregation and plasma coagulation (P<0.05). Pretreatment of both tumor lines with a COX inhibitor did not block the tumor cell induced platelet aggregation (TCIPA). COX [12(S)-HTT] and LOX [12(S)-HETE], metabolites of washed platelets (WP), alone or co-incubated with LAC or FS cells, were analyzed. We observed higher 12(S)-HETE release with respect to 12(S)HHT when WP were co-incubated with LAC cells. With both neoplastic cell (NC) lines prothrombin time (PT) was shortened. Pretreatment of NC with iodoacetic acid, soybean trypsin inhibitor or Factor X-deficient plasma increased the PT. These results indicate that AA metabolites play a role on the procoagulation and platelet aggregation induced by mesenchymal and epithelial murine cancers.