Drug repurposing of mito-atovaquone for cancer treatment

Repurposing of approved drugs in a new strategy to combat cancer that leads to savings in time and investment. Atovaquone is a US FDA-approved drug for treatment of Pneumocystis carinii pneumonia and malaria. Patent US2023017373 describe the use of mito-atovaquone for the treatment of several types of cancer. Mito-atovaquone demonstrated antiproliferative activity in cell lines of pancreatic cancer, lung cancer and brain cancer and inhibited tumor growth in syngeneic mouse models and in animals genetically prone to breast cancer. Mito-atovaquone has the potential to be used successfully in the treatment of various types of tumors.

Estrogens as a Possible Therapeutic Strategy for the Management of Neuroinflammation and Neuroprotection in COVID-19

The Coronavirus disease 2019 (COVID-19) affects several tissues, including the central and peripheral nervous system. It has also been related to signs and symptoms that suggest neuroinflammation with possible effects in the short, medium, and long term. Estrogens could have a positive impact on the management of the disease, not only due to its already known immunomodulator effect, but also activating other pathways that may be important in the pathophysiology of COVID-19, such as the regulation of the virus receptor and its metabolites. In addition, they can have a positive effect on neuroinflammation secondary to pathologies other than COVID-19. The aim of this study is to analyze the molecular mechanisms that link estrogens with their possible therapeutic effect for neuroinflammation related to COVID-19. Advanced searches were performed in scientific databases as Pub- Med, ProQuest, EBSCO, the Science Citation index, and clinical trials. Estrogens have been shown to participate in the immune modulation of the response to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). In addition to this mechanism, we propose that estrogens can regulate the expression and activity of the Angiotensin-converting enzyme 2 (ACE2), reestablishing its cytoprotective function, which may be limited by its interaction with SARS-CoV-2. In this proposal, estrogens and estrogenic compounds could increase the synthesis of Angiotensin-(1-7) (Ang-(1-7)) that acts through the Mas receptor (MasR) in cells that are being attacked by the virus. Estrogens can be a promising, accessible, and low-cost treatment for neuroprotection and neuroinflammation in patients with COVID-19, due to its direct immunomodulatory capacity in decreasing cytokine storm and increasing cytoprotective capacity of the axis ACE2/Ang (1-7)/MasR.

Approaches for development of LAG-3 inhibitors and the promise they hold as anticancer agents

INTRODUCTION

LAG-3 is considered to be the third point of immunological control in relation to clinical trials that address cancer treatment, only behind PD-1 and CTLA-4, due to its role as a suppressor of the immune response and enhancer of differentiation of Treg cells.

AREAS COVERED

The authors focus on emphasizing the strategy of development of LAG-3 inhibitors to develop anticancer therapeutics, especially from the perspective of designing new monoclonal and bispecific antibodies against LAG-3. This article also covers details of patents and clinical trials of LAG-3 inhibitors reported in the literature. In addition, we highlight as future research challenges the design and development of peptides and small molecules as inhibitors of LAG-3 function.

EXPERT OPINION

Three approaches have been used for the development of LAG-3 inhibitors, and they include inhibitory LAG-3 binding peptides and antagonist monoclonal and multispecific antibodies. These approaches include more than 100 clinical trials of 21 molecules that bind to LAG-3 and block its binding to MHC II. However, these approaches do not cover the design and development of peptides and small molecules that could inhibit the function of LAG-3, for which it is necessary to develop new alternatives that cover this gap.

Small-molecule inhibitor PD-1/PD-L1 interaction for colorectal cancer treatment

Inhibition of the PD-1/PD-L1 pathway is a target for the development of new therapies. US10710986 patent describes a small molecule that targets PDL-1/PD-1 interactions and triggers antitumor activity against colorectal cancer. However, it does not describe biological assays that allow us to suppose that this small molecule may be active in other types of cancer. So far, there are no reports of clinical trials to evaluate the safety, toxicity and efficacy, but it will be of great interest to analyze in the future if this compound surpasses the action of therapy in cancer.

OX40 agonists for cancer treatment: a patent review

INTRODUCTION

OX40 is an immune checkpoint in cancer and its presence in cancer is a good prognosis, making it a highly relevant target for the development of new immunotherapies.

AREAS COVERED

The patent literature reveals vital information on new trends in cancer therapies. The authors used the patent databases of the six major patent offices in the world: United States Patent and Trademark Office, European Patent Office, World Intellectual Property Organization, Japan Patent Office, State Office of Intellectual Property of China and Korean Intellectual Property Office, to generate a panorama of patents related to OX40 agonists. Specific patents have been grouped into innovative patents and adoption patents.

EXPERT OPINION

An increasing trend in the development of OX40 agonists in cancer, particularly in the years 2018 and 2019. United States was the leader in generating patents, followed by China and England. Major pharmaceutical companies have at least one anti-OX40 agonist, MEDI6469 and MEDI-0562 (AstraZeneca), PF-04518600 (Pfizer), GSK3174998 (GlaxoSmithKline), BMS-986,178 (Bristol-Myers Squibb) and MOXR0916 (Roche), which represent 68% of clinical trials conducted with OX40 agonists.

[Molecular diagnosis of breast cancer: prognostic and therapeutic implications]

Breast cancer is the most frequent type of cancer in women in the world. In Mexico, since 2006, this disease has become the leading cancer-related cause of death in women. It is estimated that incidence and mortality will continue to rise due to population aging, to changes in reproductive patterns, to a higher prevalence of risk factors and to limited access to medical care, resulting in delayed early diagnosis and timely treatment. The latter factors are the ones to improve in developing countries to decrease the high incidence and mortality associated with this disease. Recently, there is a great interest regarding breast cancer heterogeneity, and it is anticipated that the application of new technologies will improve our comprehension of this disease and will be reflected in a benefit for patients in the short term. Here, we review updated information on molecular diagnosis and therapeutics, as well as recent highlights in the biology of breast cancer.

Colon carcinoma treatment using bispecific anti-GITR/CTLA-4 antibodies: a patent evaluation of WO2018091739

Introduction: GITR is a receptor that increases the activation of T lymphocytes against tumor cells. There is a great need to discover and develop new therapies focused on activating GITR to increase the immune response in various types of cancer. The authors of WO2018091739 patent propose a method to eradicate cancer by using bispecific anti-GITR/anti-CTLA-4 antibodies.Areas covered: WO2018091739 patent describes anti-GITR/anti-CTLA-4 antibodies, pharmaceutical composition that contains it, and their application for cancer treatment, particularly colon carcinoma. Anti-GITR/anti-CTLA-4 antibodies are used at a dosage of 0.0003-3 mg antibody/kg patient weight and is suspended in an isotonic solution consisting of sodium phosphate, sucrose, NaCl, and polysorbate 80.Expert opinion: WO2018091739 only demonstrates that bispecific antibodies activate T cells, an antibody-dependent cellular cytotoxicity of CHO cells, and tumor inhibition in murine models of colon carcinoma. There are no clinical trials that show that treatment with bispecific antibodies can induce an antitumor response in cancer patients.

Nanostructured Systems in Advanced Drug Targeting for the Cancer Treatment: Recent Patents

BACKGROUND

Cancer is one of the leading causes of death in the world and it is necessary to develop new strategies for its treatment because most therapies have limited access to many types of tumors, as well as low therapeutic efficacy and high toxicity.

OBJECTIVE

The present research aims to identify recent patents of drug delivery nanostructured systems that may have application in improving cancer treatment.

METHODS

Recent patents regarding the drug delivery nanostructured systems for cancer treatment were obtained from the patent databases of the six main patent offices of the world: United States Patent and Trademark Office, European Patent Office, World Intellectual Property Organization, Japan Patent Office, State Intellectual Property Office of China and Korean Intellectual Property Office.

RESULTS

A total of 1710 patent documents from 1998 to 2017 including "drug delivery nanostructured systems for cancer treatment" were retrieved. The top five countries in patent share were USA, China, South Korea, Canada and Germany. The universities and enterprises of USA had the highest amount of patents followed by institutions from China.

CONCLUSION

There is a strong tendency for the development of new nanostructured systems for the release of drugs; particularly, in recent years, the development of nanoparticles has focused on nanodiscs, gold nanoparticles and immunoliposomes.

Cancer immunotherapy using anti-TIM3/PD-1 bispecific antibody: a patent evaluation of EP3356411A1

Introduction: TIM3 and PD-1 are checkpoint inhibitors in cancer that coordinate the downregulation of the proliferation of antigen-specific lymphocytes. There is a great need to discover and develop new therapies focused on inhibiting the action of TIM3 and PD-1 and consequently improving the immune response in the various types of cancer. The authors of patent EP3356411A1 propose several anti-TIM3/anti-PD-1 bispecific antibodies, as well as the method for producing them and their pharmacological application in the treatment of cancer. Areas covered: Patent EP3356411A1 describes a method by producing anti-TIM3/anti-PD-1 bispecific antibodies and their potential in cancer treatment. Expert opinion: Data supporting the patent demonstrate the ability by producing anti-TIM3/anti-PD-1 bispecific antibodies. Although the proposed methodology is very interesting and promising, further studies are necessary to assess the clinical applicability of the inventions on cancer.

Breast Cancer Subtypes Present a Differential Production of Reactive Oxygen Species (ROS) and Susceptibility to Antioxidant Treatment

Due to their crucial role in cell metabolism and homeostasis, alterations in mitochondrial biology and function have been related to the progression of diverse diseases including cancer. One of the consequences associated to mitochondrial dysfunction is the production of reactive oxygen species (ROS). ROS are known to have a controversial role during cancer initiation and progression and although several studies have tried to manipulate intracellular ROS levels using antioxidants or pro-oxidation conditions, it is not yet clear how to target oxidation for cancer therapy. In this study, we found differences in mitochondrial morphology in breast cancer cells when compared to a non-tumorigenic cell line and differences in mitochondrial function among breast cancer subtypes when exploring gene-expression data from the TCGA tumor dataset. Interestingly, we found increased ROS levels in triple negative breast cancer (TNBC) cell lines and a dependency on ROS for survival since antioxidant treatment induced cell death in TNBC cells but not in an estrogen receptor positive (ER+) cell line. Moreover, we identified the mitochondria as the main source of ROS in TNBC cell lines. Our results indicate a potential use for ROS as a target for therapy in the TNBC subtype which currently has the worst prognosis among all breast cancers and remains as the only breast cancer subtype which lacks a targeted therapy.

Emerging Drugs for the Treatment of Breast Cancer Brain Metastasis: A Review of Patent Literature

BACKGROUND

Despite dramatic advances in cancer treatment that lead to long-term survival, there is an increasing number of patients presenting with clinical manifestations of cerebral metastasis in breast cancer, for whom only palliative treatment options exist.

OBJECTIVE

The present review based on researches aims to provide identification of recent patens of breast cancer brain metastasis that may have application in improving cancer treatment.

METHODS

Recent patents regarding the breast cancer brain metastasis were obtained from USPTO patent databases, Esp@cenet, Patentscope and Patent Inspiration®.

RESULTS

A total of 55 patent documents and 35 drug targets were recovered. Of these, a total of 45 patents and 10 patents were biotech drugs and chemical drugs, respectively. Among the target drugs analyzed were neurotrophin-3, protocadherin 7, CXCR4, PTEN, GABA receptor 3, L1CAM, PI3K-Akt / mTOR, VEGFR2, Claudin-5, Occludin, and NKG2A, among others.

CONCLUSION

In this study, we found 35 drug targets for metastasis to the brain in breast cancer, with 60% of them including only one patent, which establishes that this area of research is very recent, and that these targets have recently been linked to metastasis to the brain. On the other hand, 19 drug targets, among them VEGF, VEGFR2, CXCL12, and CXCR4, have been addressed for the first time until 6 years ago, confirming that the development of drugs for brain metastasis in breast cancer is an incipient area, but with interesting potential. Interestingly, the stage of inside the brain, was the stage with the lowest amount of drug targets, which places it as a priority for research and drug development.

Bursera copallifera Extracts Have Cytotoxic and Migration-Inhibitory Effects in Breast Cancer Cell Lines

Plants from the Bursera genus are widely distributed in the tropical dry forests of Mexico. In traditional medicine, extracts from different species of Bursera have been used for a wide range of biological activities, including the treatment of cancer-related symptoms. Compounds present in the Bursera genus include lignans, flavonoids, steroids, short-chain aliphatic alkanes, acetates, alcohols, ketones, and terpenoids. In some instances, secondary metabolites of these classes of compounds may induce cytotoxicity, and therefore we sought to investigate the effects of B. copallifera leaf extracts in breast cancer cell lines to evaluate their potential therapeutic value for the treatment of breast cancer, one of the most prevalent types of cancer in women worldwide. Two B. copallifera leaf extracts exerted cytotoxic effects on both the MCF7 and MDA-MB-231 breast cancer cell line models. The cytotoxic effect was more evident in the MDA-MB-231 triple negative cell line inhibiting also the migration of these cells. We identified hydroxycinnamic acid and flavonol derivatives as major phenolic components of the extracts. Our results strongly suggest a potential use of the Bursera leaf extracts rich in phenolic compounds, their individual phenolic compounds, or their combinations for the treatment of breast cancer.

Mitochondrial dynamics and cancer

Cancer is among the leading causes of death worldwide, and the number of new cases continues to rise. Despite recent advances in diagnosis and therapeutic strategies, millions of cancer-related deaths occur, indicating the need for better therapies and diagnostic strategies. Mitochondria and metabolic alterations have been recognized as important for cancer progression. However, a more precise understanding of how to manipulate mitochondria-related processes for cancer therapy remains to be established. Mitochondria are highly dynamic organelles which continually fuse and divide in response to diverse stimuli. Participation in the aforementioned processes requires a precise regulation at many levels that allows the cell to couple mitochondrial activity to nutrient availability, biosynthetic demands, proliferation rates, and external stimuli. The many functions of these organelles are intimately linked to their morphology. Recent evidence suggests an important link between mitochondrial morphology and disease, including neurodegenerative, inflammatory diseases and cancer. Here, we review recent advances in the understanding of mitochondrial dynamics with a special focus on its relationship to tumor progression.

Contribution of Latin American Countries to Cancer Research and Patent Generation: Recent Patents

BACKGROUND

Data mining publications and patent data can provide decision support for scientists, inventors and industry in the field of cancer research.

OBJECTIVE

The main objective of this article it to identify trends of research and patent generation productivity originating from Latin American countries in the field of cancer.

METHOD

Publications were collected from the Scopus, Web of Science, PubMed database; and patents were collected from Latipat Espacenet databases. Data from January 1, 2000 until December 31, 2014 were searched for documents with specific words in cancer as a ''topic'' and a list of 20 Latin American countries as affiliation country.

RESULTS

A total of 12,989 items published and 244 patent applications including "cancer" were retrieved. Brazil, Mexico, Argentina, Chile and Peru were highest contributors in cancer research, while Brazil, Mexico, Cuba and Argentina were highest contributors in cancer patent applications.

CONCLUSION

The analysis of the data from this study provides an overview of research and patent activity in Latin America in the cancer field, which can be useful to help health policy makers and people in academia to shape up cancer research in the future.

Neural Transdifferentiation: MAPTau Gene Expression in Breast Cancer Cells

BACKGROUND

In tumor cells, aberrant differentiation programs have been described. Several neuronal proteins have been found associated with morphological neuronal-glial changes in breast cancer (BCa). These neuronal proteins have been related to mechanisms that are involved in carcinogenesis; however, this regulation is not well understood. Microtubule-associated protein-tau (MAP-Tau) has been describing in BCa but not its variants. This finding could partly explain the neuronal-glial morphology of BCa cells. Our aim was to determine mRNA expression of MAP-tau variants 2, 4 and 6 in breast cancer cell lines.

MATERIALS AND METHODS

Cultured cell lines MCF-10A, MDA-MB-231, SKBR3 and T47D were observed under phase-contrast microscopy for neural morphology and analyzed for gene expression of MAP-Tau transcript variants 2, 4 and 6 by real-time PCR.

RESULTS

Regarding morphology like neural/glial cells, T47D line shown more cells with these features than MDA-MB-231 and SKBR. In another hand, we found much greater mRNA expression of MAP-Tau transcript variants 2, and to a lesser extent 4 and 6, in T47D cells than the other lines. In conclusion, regulation of MAP- Tau could bring about changes in cytoskeleton, cell morphology and motility; these findings cast further light on neuronal transdifferentiation in BCa.

Effect of botulinum neurotoxin type A (BoNTA) on the morphology and viability of 3T3 murine fibroblasts

AIM

BoNTA is used in the treatment of ophthalmological disorders, muscular hyperactivity and pain. In recent years it has been described that BoNTA reduces cellular viability and induces apoptosis in prostate cells lines. Studies about the effect of BoNTA are no well known. There have been studies about the effect of BoNTA on the expression levels of collagenase in fibroblasts, but not on its morphological impact on these cells. The aim of this study was to determine the effect of BoNTA on the morphology and viability of the 3T3 fibroblast cell line.

MATERIAL AND METHODS

The 3T3 fibroblast cell line was cultured and the experimental group received 10 U BoNTA added to a 0.9% sterile saline solution in a reconstituted vial. The control group received saline solution only. Cultured cells were observed and photographed at 5, 10, 15 and 20 h. Cell viability was evaluated by means of the trypan blue test, and cell proliferation with the Proliferation Assay kit (PROMEGA).

RESULTS

The application of BoNTA to 3T3 fibroblast cells induced morphological changes, such as a loss of normal fibroblast morphology. Additionally, we observed the cytoplasmic retraction and spread phenomena. The nuclei showed other important changes with Giemsa staining.

CONCLUSION

The results indicate that BoNTA induced a loss of spindle form, increase in cytoplasmic vesicles, and the presence of nuclear vesicles (compacted chromatin surrounded by a nuclear envelope). This suggests an apoptotic process and decreased cell viability. Further studies are needed to explore the mechanisms of these alterations.

Cervical cancer trends in Mexico: incidence, mortality and research output

PURPOSE

To evaluate the recent incidence and mortality of and scientific research trends in cervical cancer in Mexican females.

MATERIALS AND METHODS

Data between 2000 and 2010 from the Department of Epidemiology of the Ministry of Health, and International Agency for Research on Cancer (IARC) of World Health Organization were analyzed, and age-standardized rates (ASRs) were calculated. In addition, scientific research data were retrieved from the Web of Science database from 2003 to 2012, using different terms related to cervical cancer.

RESULTS

The incidence rate decreased during last five years, while mortality rates showed an annual decrease of 4.93%. A total of 780 articles were retrieved, and the institutions with the majority of publications were National Autonomous University of Mexico (34.87%), Social Security Mexican Institute (16.02%), and National Institute of Cancerology (15%). The main types of research were treatment, diagnosis, and prevention.

CONCLUSIONS

The above results show that incidence of cervical cancer decreased over time in Mexico during last five years; similarly, the downturn observed in mortality mainly reflects improved survival as a result of earlier diagnosis and cancer treatment. Also, this article demonstrates the usefulness of bibliometrics to address key evaluation questions and to establish priorities, define future areas of research, and develop cervical cancer control strategies in Mexico.

Botulinum neurotoxin type A inhibits synaptic vesicle 2 expression in breast cancer cell lines

AIM

It is known that botulinum neurotoxin type A (BoNTA) improves some kinds of cancer (e.g. prostate) and that synaptic vesicle glycoprotein 2 (SV2) is the molecular target of this neurotoxin. Besides having potential therapeutic value, this glycoprotein has recently been proposed as a molecular marker for several types of cancer. Although the mechanisms of cancer development and the improvement found with botulinum treatment are not well understood, the formation of the botulinum-SV2 complex may influence the presence and distribution of SV2 and the function of vesicles. To date, there are no reports on the possible effect of botulinum on breast cancer of unknown causes, which have a great impact on women's health. Thus we determined the presence of SV2 in three breast cancer cell lines and the alterations found with botulinum application.

MATERIALS AND METHODS

With and without adding 10 units of botulinum, SV2 protein expression was determined by optical densitometry in T47D, MDA-MB-231 and MDA-MB-453 cell lines and the distribution of SV2 was observed with immunochemistry (hematoxylin staining).

RESULTS

The SV2 protein was abundant in the cancer cells herein tested, and maximally so in T47D. In all three cancer cell lines botulinum diminished SV2 expression, which was found mostly in the cell periphery.

CONCLUSION

SV2 could be a molecular marker in breast cancer. Its expression and distribution is regulated by botulinum, suggesting an interesting control mechanism for SV2 expression and a possible alternative therapy. Further studies are needed in this sense.

Mexican breast cancer research output, 2003-2012

The objetive of this study was to explore a bibliometric approach to quantitatively assess current research trends with regard to breast cancer in Mexico. Articles were analyzed by scientific output and research performances of individuals, institutes, and collaborative countries with Mexico. Data were retrieved from the Web of Science database from 2003 to 2012; this was searched using different terms related to breast cancer, including "breast cancer", "mammary ductal carcinoma" and "breast tumour". Data were then extracted from each file, transferred to Excel charts and visualised as diagrams. A total of 256 articles were retrieved. The institutions with the majority of publications were the National Autonomous University of Mexico (22.3%), the National Institute of Cancerology (21.9%), and Social Security Mexican Institute (20.3%); clinical observation studies were the dominant investigation type (64%), and the main types of research were metabolics (24.2%) and pathology (21.5%). This article demonstrates the usefulness of bibliometrics to address key evaluation questions and to establish priorities, define future areas of research, and develop breast cancer control strategies in Mexico.

miR-485 acts as a tumor suppressor by inhibiting cell growth and migration in breast carcinoma T47D cells

MicroRNAs (miRNAs) are small, non-coding RNAs (18-25 nucleotides) that post-transcriptionally modulate gene expression by negatively regulating the stability or translational efficiency of their target mRNAs. In this context, the present study aimed to evaluate the in vitro effects of miR-485 mimics in breast carcinoma T47D cells. Forty-eight hours after T47D cells were transfected with miR-485 mimics, an MTT (3-(4,5-dimethylthiazol-2-yl)- 2,5-diphenyltetrazolium bromide) assay was utilized to determine the effects on cell viability. Colony formation and cell migration assays were adopted to determine whether miR-485 affects the proliferation rates and cell migration of breast carcinoma T47D cells. Our results showed that ectopic expression of miR-485 resulted in a significant decrease in cell growth, cell colony formation, and cell migration. These findings suggest that miR- 485 might play an important role in breast cancer by suppressing cell proliferation and migration.

miR-153 silencing induces apoptosis in the MDA-MB-231 breast cancer cell line

MicroRNAs (miRNAs) are small, non-coding RNAs (18-25 nucleotides) that post-transcriptionally modulate gene expression by negatively regulating the stability or translational efficiency of their target mRNAs. In this context, the present study aimed to evaluate the in vitro effects of miR-153 inhibition in the breast carcinoma cell line MDA-MB-231. Forty-eight hours after MDA-MB-231 cells were transfected with the miR-153 inhibitor, an MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay was utilized to determine the effects of miR-153 on cell viability. Flow cytometry analysis and assessment of caspase 3/7 activity were adopted to determine whether miR-153 affects the proliferation rates and apoptosis levels of MDA-MB-231 cells. Our results showed that silencing of miR-153 significantly inhibited growth when compared to controls at 48 hours, reducing proliferation by 37.6%, and inducing apoptosis. Further studies are necessary to corroborate our findings and examine the potential use of this microRNA in future diagnostic and therapeutic interventions.

An ecto-protein tyrosine phosphatase of Entamoeba histolytica induces cellular detachment by disruption of actin filaments in HeLa cells

Actin cytoskeleton disruption in host cells has been demonstrated for PTPases from pathogenic microorganisms. In this work, we analysed whether the secreted acid phosphatase from Entamoeba histolytica has phosphotyrosine phosphatase activity and the possibility that this activity may participate in damaging host cells. The secreted acid phosphatase of E. histolytica, which catalyses p-nitrophenyl phosphate hydrolysis at acid pH values, was found to have phosphotyrosine phosphatase activity. The enzymatic properties of phosphotyrosine phosphatase and acid phosphatase were virtually identical and included: Km values of 10 x 10(-4) M, no requirement for divalent cations, and sensitivity to molybdate, vanadate, and tungstate. The phosphotyrosyl phosphatase activity caused significant levels of cell rounding and detachment correlating with disruption of the actin stress fibres in HeLa cells. Thus, our data suggest that secreted phosphotyrosine phosphatase could play a cytotoxic role during amoebic infection.

Membrane-bound acid phosphatase (MAP) from Entamoeba histolytica has phosphotyrosine phosphatase activity and disrupts the actin cytoskeleton of host cells

Protein tyrosine phosphatases (PTPases) have been described as virulence factors in different pathogenic microorganisms. The pathogenic process by Enatamoeba histolytica is a multifactorial phenomenon that occurs in 3 steps: adhesion, cytolytic and cytotoxic effect, and phagocytosis. Lytic enzymes may participate during the second part of this process. In this work, we determined that purified membrane-bound acid phosphatase (MAP) from E. histolytica trophozoites has PTPase activity. The enzyme specifically dephosphorylated O-phospho-L-tyrosine at optimum pH of 5.0, with little activity towards O-phospho-L-serine, O-phospho-L-threonine, and ATP. It was inhibited by ammonium molybdate and sodium tungstate, and trifluoperazine did not show any effect. A monoclonal antibody against the catalytic domain of the human placental PTPase 1B, cross-reacted with a 55 kDa molecule present in the solubilized fraction. The interaction of the amoebic PTPase with HeLa cells resulted in the alteration of the cell actin cytoskeleton by disruption of the actin stress fibres.

Entamoeba histolytica: tyrosine kinase activity induced by fibronectin through the beta1-integrin-like molecule

Previously, we characterized a 140-kDa protein from Entamoeba histolytica as a beta1-integrin-like molecule that binds fibronectin. In this work we present data showing that the amoebic receptor is associated with another surface molecule, the 220-kDa lectin, and with protein tyrosine kinase activity. By immunoprecipitation with the alphabeta1Eh antibody, we demonstrated by immune complex assays for tyrosine protein kinases that the amoebic fibronectin receptor was associated with two phosphorylated proteins of 50 and 70 kDa when internal membranes were used as the source of antigen. When cells were stimulated with fibronectin, two proteins of 55 and 90 kDa were tyrosine phosphorylated, as shown by Western blot with alphaPY20, its phosphorylation being time dependent after fibronectin stimulation. However, when the actin cytoskeleton of fibronectin-stimulated trophozoites was stabilized with phalloidin, the level and the pattern of phosphorylated proteins were different. In this case, a high-molecular-weight component, heavily phosphorylated, was present, which may include the 220-kDa lectin. We also present data confirming that the signaling pathway that is activated by fibronectin is specific. This was demonstrated by comparing the pattern of phosphoproteins obtained in immune complexes prepared with alphabeta1Eh, alphaL220, and alphaPY20 from total extracts obtained in the presence of phalloidin, from cells that had been exposed to fibronectin, soluble concanavalin A, or concanavalin-A-coated substrate. The presence of tyrosine kinases associated with the beta1-integrin-like amoebic molecule was confirmed by immunoprecipitation assays along with the combined use of a tyrosine kinase-specific substrate, the peptide RR-SRC, and a tyrosine kinase inhibitor, genistein.