Increased Osteoblastic and Osteocytic in Vitro Cell Viability by Yerba Mate (Ilex paraguariensis).

BACKGROUND: Yerba mate (YM, Ilex paraguariensis) consumption beneficially affects the bones. However, whether YM components exert their effect on bone cells directly remains elusive. METHODS: We evaluated how main YM components affect osteoblastic (MC3T3-E1) and osteocytic (MLO-Y4) cells in vitro when administered separately or in an aqueous extract. MC3T3-E1 and MLO-Y4 cells were exposed to three different experimental conditions: (1) Caffeine, chlorogenic acid, and their combinations; (2) Caffeine, rutin, and their combinations; (3) Aqueous YM extract. RESULTS: All polyphenol and caffeine concentrations as well as that of their tested combinations significantly increased MC3T3-E1 cell viability from 16.6% to 34.8% compared to the control. In MLO-Y4 cells, the lowest rutin and the two highest caffeine concentrations significantly increased cell viability by 11.9, 14.9, and 13.7%, respectively. While rutin and caffeine combinations tended to increase MLO-Y4 cell viability, different chlorogenic acid and caffeine combinations did not affect it. Finally, the aqueous YM extract significantly increased MLO-Y4, MC3T3-E1, and differentiated MC3T3-E1 cell viability compared to the control without treatment. CONCLUSIONS: YM components (rutin, chlorogenic acid, and caffeine) positively affected bone cells, mainly pre-osteoblast cells. Moreover, the aqueous YM extract significantly increased MLO-Y4, MC3T3-E1, and differentiated MC3T3-E1 cell viabilities indicating an additional relevant nutritional property of YM infusion. Further studies would be required to elucidate the underlying effector mechanism of YM on the bones and its relationship with previously described in vivo positive effects.

Use of sodium dichloroacetate for cancer treatment: a scoping review.

In recent years, drug repurposing (DR) has gained significant attention as a promising strategy for identifying new therapeutic uses of existing drugs. One potential candidate for DR in cancer treatment is sodium dichloroacetate (DCA), which has been shown to alter tumor metabolism and decrease apoptosis resistance in cancer cells. In this paper, we present a scoping review of the use of DCA for cancer treatment in adult patients, aiming to identify key research gaps in this area. This scoping review aims to explore the existing scientific literature to provide an overview of the use of DCA (any dose, frequency, or route of administration) in adults with cancer. A comprehensive literature search of the medical databases MEDLINE/PubMed, LILACS, EPISTEMONIKOS, the Cochrane Library, and ClinicalTrials was performed. We included publications reporting on adult patients diagnosed with any type of cancer treated with sodium dichloroacetate in combination or not with other drugs. All types of study design were included. A total of 12 articles were included, most of them were case reports. We found a high degree of heterogeneity between them. The most frequent adverse events in the evaluated studies were asthenia, reversible toxicity, and an increase in liver enzymes. Effectiveness was difficult to evaluate. We conclude that there is insufficient evidence to affirm that treatment with DCA in cancer patients is effective or is safe.

El reposicionamiento de fármacos (RF) es un enfoque terapéutico reciente que se presenta como una estrategia prometedora para identificar nuevos usos terapéuticos de fármacos existentes. Un candidato potencial para RF en el tratamiento del cáncer es el dicloroacetato de sodio (DCA), el cual ha mostrado la capacidad de alterar el metabolismo tumoral y disminuir la resistencia a la apoptosis de células tumorales. La presente es una revisión (scoping review) del uso del DCA para el tratamiento del cáncer en pacientes adultos, que tiene como objetivo identificar brechas de investigación claves en esta área. Esta revisión pretende explorar la literatura científica existente, para proporcionar una visión general del uso del DCA (cualquier dosis, frecuencia o vía de administración) en individuos adultos con cáncer. Se llevó a cabo una búsqueda exhaustiva de la literatura en las bases médicas de datos MEDLINE/PubMed, LILACS, EPISTEMONIKOS, the Cochrane Library y ClinicalTrials. Se incluyeron publicaciones que informaban sobre pacientes adultos diagnosticados con cualquier tipo de cáncer, tratados con DCA, en combinación o no con otros fármacos. Dichos estudios presentaban distintos tipos de diseño. Se incluyó un total de 12 artículos, la mayoría de los cuales fueron reportes de casos. Se encontró un alto grado de heterogeneidad entre los mismos. Los eventos adversos más frecuentes fueron astenia, toxicidad reversible y aumento de las enzimas hepáticas, siendo la efectividad terapéutica difícil de evaluar. Concluimos que existe evidencia insuficiente para afirmar que el tratamiento con DCA en pacientes con cáncer es efectivo y/o seguro.

Antitumor activity of new chemical compounds in triple negative mammary adenocarcinoma models.

AIM: According to the need for the development of new anticancer agents, we have synthetized novel bioactive compounds and aimed to determine their antitumor action. MATERIALS & METHODS: We describe in vitro studies evaluating the effect of 35 novel chemical compounds on two triple negative murine mammary adenocarcinoma tumors. RESULTS & CONCLUSION: Three compounds were selected because of their high antitumor activity and their low toxicity to normal cells. Their effect on tumor cells apoptosis, clonogenicity and migratory capacity, were determined. We found that the selected compounds showed inhibition of viability and clonogenic capacity, and promotion of apoptosis. They also decreased the migratory capacity of tumor cells. The results obtained suggest the likelihood of their future use as antitumor and/or antimetastatic agents.

Synthesis of propargylamines via the A3 multicomponent reaction and their biological evaluation as potential anticancer agents.

Propargylamines have gained importance in the area of anticancer research. We synthesized 1-substituted propargylic tertiary amines using the A3-coupling as the key step. Both, solution and solid-phase protocols, were used to provide a library of 1-substituted propargylic tertiary amines with interesting structural diversity. The triple negative breast cancer subtype is the most aggressive and it lacks effective therapeutic options, while pancreatic cancer is one of the neoplasms with worse prognosis and limited therapeutic possibilities. The development of tumor-selective drugs has always been a major challenge in cancer treatment. From our library, two propargylamines displayed a high degree of cytotoxic selectivity. These levels of selectivity give a very interesting perspective for further development of 1-substituted propargylic tertiary amines as new potential chemotherapeutic antitumor agents.

Achievements and challenges in the use of metronomics for the treatment of breast cancer.

Two interesting therapeutic proposals for cancer treatment emerged at the beginning of the 21st century. The first one was metronomic chemotherapy, which refers to the chronic administration of chemotherapeutic agents, in low doses, without extended drug-free periods. Then, the idea of drug repositioning in oncology, the use of well-known drugs that were created for other uses to be utilized in oncology, gained strength. Shortly after, the two strategies were merged in one, named metronomics. Both approaches share several features which make metronomics an appealing choice for cancer treatment: use of known and approved drugs, thus diminishing the time necessary to enter to the clinic, therapeutic effect, low toxicity, oral administration, better life quality, low costs because of the use of, generally, out of patent drugs, possibility of use, even in countries with very low economic resources. Many chemotherapy and repurposed drugs were tested with metronomics approaches for the treatment of mammary cancer, the most common malignancy in women worldwide, leading to high rates of mortality. The wide range of therapeutic models studied, paralleled the wide range of responses obtained, like tumor growth and metastasis inhibition, overall survival increase, lack of toxicity, better life quality, among others. The accomplishments reached, and the challenges faced by researchers, are discussed.

Paclitaxel delivery system based on poly(lactide-co-glycolide) microparticles and chitosan thermo-sensitive gel for mammary adenocarcinoma treatment.

OBJECTIVES: To evaluate the combination of more than one release system in the same formulation as a useful strategy to achieve paclitaxel delivery in a more sustained and controlled manner. METHODS: The present study deals with the preparation of poly(lactide-co-glycolide) microparticles loaded with paclitaxel and included in a chitosan thermo-sensitive gelling solution. The microparticles were characterized by their size, shape and drug loading. The formulation was characterized by scanning electron microscopy, in vitro release experiments and was evaluated in mice bearing mammary adenocarcinoma. KEY FINDINGS: The formation of paclitaxel crystals in a pharmaceutical formulation reduces its efficacy. In this work, the use of microparticles avoided this phenomenon. Combining more than one delivery system allowed delivering paclitaxel in a more sustained and controlled manner leading to a long-term effect in the site of action. The formulation showed an inhibition in tumour volume of 63.0% in comparison with the control group. CONCLUSIONS: One intratumour injection of gelling solution containing the microparticles was at least as efficacious as four intraperitoneal injections of a commercial formulation. In addition, the delivery system was nontoxic, and the treated mice presented the highest percentage of tumour regression and median survival time.

Putative Biomarkers of Response to Treatment in Breast Cancer Patients: A Pilot Assay.

Identifying tumor biomarkers associated with clinical behavior in breast cancer patients may allow higher accuracy in the selection of treatment. Different types of cells were determined in the primary tumors of stage I, II, and III of breast cancer patients, who were assigned to one of the two groups: (1) disease-free or (2) relapsed/progressed, at 5 years after primary treatment. We studied 32 tumor samples. CD4+ lymphocytes and CD44+CD24-/low cells (cancer stem cells) showed a significant association with clinical outcome at 5 years of primary treatment, while CD8+, Foxp3+, CD34+, and myeloid-derived suppressor cells did not show any association. Coincident with the results of individual analysis, we identified CD4+ cells and CD44+CD24-/low cells as good predictors of long-term clinical outcome in a logistic regression.

Highlights from the 1st Latin American meeting on metronomic chemotherapy and drug repositioning in oncology, 27-28 May, 2016, Rosario, Argentina.

Following previous metronomic meetings in Marseille (2011), Milano (2014), and Mumbai (2016), the first Latin American metronomic meeting was held in the School of Medical Sciences, National University of Rosario, Rosario, Argentina on 27 and 28 of May, 2016. For the first time, clinicians and researchers with experience in the field of metronomics, coming from different countries in Latin America, had the opportunity of presenting and discussing their work. The talks were organised in three main sessions related to experience in the pre-clinical, and clinical (paediatric and adult) areas. The different presentations demonstrated that the fields of metronomic chemotherapy and repurposing drugs in oncology, known as metronomics, constitute a branch of cancer therapy in permanent evolution, which have strong groups working in Latin America, both in the preclinical and the clinical settings including large, adequately designed randomised studies. It was shown that metronomics offers treatments, which, whether they are combined or not with the standard therapeutic approaches, are not only effective but also minimally toxic, with the consequent improvement of the patient's quality of life, and inexpensive, a feature very important in low resource clinical settings. The potential use of metronomic chemotherapy was proposed as a cost/effective treatment in low-/middle-income countries, for adjuvant therapy in selected tumours. The fundamental role of the governmental agencies and non-governmental alliances, as the Metronomic Global Health Initiative, in supporting this research with public interest was underlined.

Quality of life in patients with metastatic breast cancer treated with metronomic chemotherapy.

AIM: The objective of the study was to detect changes in quality of life (QoL) in metastatic breast cancer patients treated with metronomic chemotherapy with daily low doses of cyclophosphamide and celecoxib. MATERIAL & METHODS: Patients included in a Phase II trial, treated with metronomic cyclophosphamide and celecoxib were included in the QoL study. Assessment of QoL was carried out every 2 months by the Functional Assessment of Cancer Therapy Breast (FACT-B) questionnaire, Brief Pain Inventory and Eastern Cooperative Oncologic Group scale. Data were analyzed at three time points: baseline (BL); middle of treatment (MT); and end of treatment (ET). RESULTS: A total of 20 patients were included. All patients were heavily pretreated. Treatment showed a good and safe therapeutic profile. With FACT-B questionnaire, no significant differences were observed during the response period (BL-MT). However, a significant increase was observed in the Emotional well-being and Additional concerns axes, when the last time point was included in the analysis (BL-MT-ET). A significant decrease in the proportion of patients with pain was found when comparing BL with ET (p = 0.046). The assessment with Eastern Cooperative Oncologic Group scale showed that 26.7% (4/15) of the patients improved their functional status and 40% (6/15) showed no changes, while 33.3% (5/10) worsened it. CONCLUSION: Patients treated metronomically for several months did not worsen their QoL. A high proportion of patients showed improvement or no changes and there were less patients with pain at the end of the treatment.

Safety and therapeutic effect of metronomic chemotherapy with cyclophosphamide and celecoxib in advanced breast cancer patients.

Metronomic chemotherapy (MCT), the chronic administration, at regular intervals, of low doses of chemotherapeutic drugs without extended rest periods, allows chronic treatment with therapeutic efficacy and low toxicity. Our preclinical results suggested that combined MCT with cyclophosphamide and celecoxib could inhibit breast cancer growth. The aim of this study was to determine the toxicity, safety and efficacy of oral MCT with cyclophosphamide 50 mg per orem daily and celecoxib 400 mg (200 mg per orem two-times a day) in advanced breast cancer patients. During the first stage of the study, the therapeutic response consisted of prolonged stable disease for ≥24 weeks in six out of 15 (40%) patients with a median duration of 37.5 weeks and a partial response in one out of 15 (response rate: 6.7%) patients lasting 6 weeks. The overall clinical benefit rate was 46.7%. The median time to progression was 14 weeks. Progression-free survival at 24 weeks was 40% and the 1-year overall survival rate was 46.7%. The adverse events were mild (gastric, grade 1; and hematologic, grade 1 or 2). No grade 3 or 4 toxicities were associated with the treatment. Evaluation of patients' quality of life showed no changes during the response period. MCT with cyclophosphamide plus celecoxib is safe and shows a therapeutic effect in advanced breast cancer patients.

Inmunomodulación y antiangiogénesis en la terapéutica oncológica: De la investigación básica a la clínica / Immunomodulation and antiangiogenesis in cancer therapy: From basic to clinical research

La investigación básica y pre-clínica en oncología celular y molecular son pilares fundamentales en los que se apoyan la mayoría de los adelantos en la terapéutica del cáncer. Los hallazgos obtenidos y su aplicación en la práctica clínica constituyen la causa del avance sostenido en el tratamiento de la enfermedad neoplásica. El objetivo de este trabajo es resumir y discutir los resultados pre-clínicos en inmunomodulación y anti-angiogénesis para el tratamiento de diversos tipos de tumores, obtenidos en nuestro Instituto durante los últimos 15 años, y la posterior traslación y aplicación del conocimiento experimental en un Ensayo Clínico Fase I/II. Se describen los resultados que contribuyeron a descifrar los mecanismos de acción de la inmunomodulación antimetastásica con ciclofosfamida, la quimioterapia metronómica con diferentes drogas únicas o combinaciones, y finalmente el diseño y resultados preliminares de un ensayo clínico de quimioterapia metronómica para pacientes con cáncer de mama avanzado.

Basic and pre-clinic research in cellular and molecular oncology are the main supports accounting for the advancement in cancer therapeutics. The findings achieved, and their implementation in clinical practice are responsible for the permanent improvement in the treatment of the neoplastic disease. Our present objective is to summarize and discuss the pre-clinical findings in immunomodulation and anti-angiogenesis for the treatment of several types of tumors obtained in our Institute during the last 15 years, and the subsequent translation and application of the acquired experimental knowledge in a Phase I/II Clinical Trial. We present the results and mechanisms of action of antimetastatic immunomodulation with cyclophosphamide, the metronomic chemotherapy with different single drugs and their combinations, and finally the design and preliminary results of a clinical trial with metronomic chemotherapy for patients with advanced breast cancer.

Inmunomodulación y antiangiogénesis en la terapéutica oncológica: De la investigación básica a la clínica / Immunomodulation and antiangiogenesis in cancer therapy: From basic to clinical research

La investigación básica y pre-clínica en oncología celular y molecular son pilares fundamentales en los que se apoyan la mayoría de los adelantos en la terapéutica del cáncer. Los hallazgos obtenidos y su aplicación en la práctica clínica constituyen la causa del avance sostenido en el tratamiento de la enfermedad neoplásica. El objetivo de este trabajo es resumir y discutir los resultados pre-clínicos en inmunomodulación y anti-angiogénesis para el tratamiento de diversos tipos de tumores, obtenidos en nuestro Instituto durante los últimos 15 años, y la posterior traslación y aplicación del conocimiento experimental en un Ensayo Clínico Fase I/II. Se describen los resultados que contribuyeron a descifrar los mecanismos de acción de la inmunomodulación antimetastásica con ciclofosfamida, la quimioterapia metronómica con diferentes drogas únicas o combinaciones, y finalmente el diseño y resultados preliminares de un ensayo clínico de quimioterapia metronómica para pacientes con cáncer de mama avanzado.(AU)

Basic and pre-clinic research in cellular and molecular oncology are the main supports accounting for the advancement in cancer therapeutics. The findings achieved, and their implementation in clinical practice are responsible for the permanent improvement in the treatment of the neoplastic disease. Our present objective is to summarize and discuss the pre-clinical findings in immunomodulation and anti-angiogenesis for the treatment of several types of tumors obtained in our Institute during the last 15 years, and the subsequent translation and application of the acquired experimental knowledge in a Phase I/II Clinical Trial. We present the results and mechanisms of action of antimetastatic immunomodulation with cyclophosphamide, the metronomic chemotherapy with different single drugs and their combinations, and finally the design and preliminary results of a clinical trial with metronomic chemotherapy for patients with advanced breast cancer.(AU)

Inmunomodulación y antiangiogénesis en la terapéutica oncológica: De la investigación básica a la clínica / Immunomodulation and antiangiogenesis in cancer therapy: From basic to clinical research

La investigación básica y pre-clínica en oncología celular y molecular son pilares fundamentales en los que se apoyan la mayoría de los adelantos en la terapéutica del cáncer. Los hallazgos obtenidos y su aplicación en la práctica clínica constituyen la causa del avance sostenido en el tratamiento de la enfermedad neoplásica. El objetivo de este trabajo es resumir y discutir los resultados pre-clínicos en inmunomodulación y anti-angiogénesis para el tratamiento de diversos tipos de tumores, obtenidos en nuestro Instituto durante los últimos 15 años, y la posterior traslación y aplicación del conocimiento experimental en un Ensayo Clínico Fase I/II. Se describen los resultados que contribuyeron a descifrar los mecanismos de acción de la inmunomodulación antimetastásica con ciclofosfamida, la quimioterapia metronómica con diferentes drogas únicas o combinaciones, y finalmente el diseño y resultados preliminares de un ensayo clínico de quimioterapia metronómica para pacientes con cáncer de mama avanzado.(AU)

Basic and pre-clinic research in cellular and molecular oncology are the main supports accounting for the advancement in cancer therapeutics. The findings achieved, and their implementation in clinical practice are responsible for the permanent improvement in the treatment of the neoplastic disease. Our present objective is to summarize and discuss the pre-clinical findings in immunomodulation and anti-angiogenesis for the treatment of several types of tumors obtained in our Institute during the last 15 years, and the subsequent translation and application of the acquired experimental knowledge in a Phase I/II Clinical Trial. We present the results and mechanisms of action of antimetastatic immunomodulation with cyclophosphamide, the metronomic chemotherapy with different single drugs and their combinations, and finally the design and preliminary results of a clinical trial with metronomic chemotherapy for patients with advanced breast cancer.(AU)

[Immunomodulation and antiangiogenesis in cancer therapy. From basic to clinical research]. / Inmunomodulación y antiangiogénesis en la terapéutica oncológica. De la investigación básica a la clínica.

Basic and pre-clinic research in cellular and molecular oncology are the main supports accounting for the advancement in cancer therapeutics. The findings achieved, and their implementation in clinical practice are responsible for the permanent improvement in the treatment of the neoplastic disease. Our present objective is to summarize and discuss the pre-clinical findings in immunomodulation and anti-angiogenesis for the treatment of several types of tumors obtained in our Institute during the last 15 years, and the subsequent translation and application of the acquired experimental knowledge in a Phase I/II Clinical Trial. We present the results and mechanisms of action of antimetastatic immunomodulation with cyclophosphamide, the metronomic chemotherapy with different single drugs and their combinations, and finally the design and preliminary results of a clinical trial with metronomic chemotherapy for patients with advanced breast cancer.

Antitumoral and antimetastatic effects of metronomic chemotherapy with cyclophosphamide combined with celecoxib on murine mammary adenocarcinomas.

PURPOSE: Metronomic chemotherapy (MCT) refers to the chronic and equally spaced administration of low doses of different chemotherapy drugs, without extended interruptions. Previously, we demonstrated the antitumor effect of MCT with cyclophosphamide (Cy) in a mouse mammary adenocarcinoma model. Herein, we investigated the therapeutic efficacy of metronomic Cy combined with celecoxib (Cel) in two murine mammary adenocarcinoma models. METHODS: Mice were s.c. challenged with M-234 p or M-406 mammary tumors and from day 5 or 8 on, respectively, treated with: (I) no treatment (controls); (II) Cy in the drinking water (25-30 mg/kg body weight/day); (III) Cel (30 mg/kg p.o.), five times/week; (IV) treated as II + III. Mice challenged i.v. with M-234 p or M-406 tumor cells received, on day 3, the same treatments. RESULTS: We found that MCT with Cy plus Cel inhibited tumor growth decreased lung metastases, and increased the median survival time, in both tumor models, having very low toxicity. MCT with Cy combined with Cel was more effective than each monotherapy. CONCLUSIONS: The therapeutic benefits of combined MCT with cyclophosphamide plus celecoxib on mammary adenocarcinomas together with its very low toxicity profile warrant further study in an attempt to make the translation into the clinic.

The immune response and the therapeutic effect of metronomic chemotherapy with cyclophosphamide.

Metronomic chemotherapy (MCT) is a novel therapeutic strategy for cancer treatment endowed with an antiangiogenic effect. It refers to regular administration of low doses of cytotoxic drugs, with minimal or no drug-free breaks. Previously, we demonstrated the immunomodulating activity of a single low-dose of cyclophosphamide (Cy) and the antitumor effect of MCT with Cy on established rat lymphomas and sarcomas. Here, we examined whether the immune response is responsible for the antitumor effect of MCT with Cy on L-TACB lymphoma. Inbred e rats and nude mice were subcutaneously challenged with L-TACB. After 7 days, they were distributed into two experimental groups: 1) treated animals, which were injected IP with Cy (10 mg/kg body weight) three times per week, and 2) control animals, which received IP saline injections. Exponential growth and decay and tumor doubling time were calculated. Also, serum IL-10 levels were measured. One hundred percent of treated rats showed tumor regression versus 0% of control rats. The increase of tumor-induced IL-10 levels was reverted by the treatment with Cy. On the other hand, there were no tumor regressions, in treated or control nude mice. However, the tumor doubling times of treated nude mice were significantly higher than those of control mice, implying that other antitumor mechanism(s), independent of the adaptive immune response, might be taking place. Our present results indicate that modulation of the immune response would be involved in the antitumor effect of MCT with Cy, because the absence of the specific immune response impairs, at least in part, its therapeutic effect in a lymphoma tumor model.

Lovastatin enhances the antitumoral and apoptotic activity of doxorubicin in murine tumor models.

Despite its effectiveness as an antineoplastic drug, doxorubicin (DOX) is usually associated with cardiotoxicity. Lovastatin (LOV), a hypolipidemic agent used in the clinic, has been demonstrated to have antitumoral and antimetastatic effects in murine models. Since the two agents arrest tumor cells in different phases of the cell cycle and induce apoptosis, the goal of this study was to examine the efficacy of a combination therapy with LOV and low doses of DOX, in an attempt to obtain an improved antitumoral effect devoid of toxicity, by using a rat B-cell lymphoma and a mouse mammary tumor. In the two models, the combined treatment showed a synergistic antitumoral effect, which is mainly ascribed to an increased apoptotic response elicited by a LOV/DOX combination than either agent alone. The therapeutic benefit demonstrated by the combination treatment is further emphasized by the lack of toxicity.

Angiogenic and antiangiogenic balance regulates concomitant antitumoral resistance.

Concomitant antitumoral resistance (CAR), the phenomenon by which the growth of distant secondary tumor implants or metastases in some tumor-bearing hosts is inhibited by the presence of a primary tumor, has been previously ascribed to an antiangiogenic process. Here, we investigated vascular endothelial growth factor (VEGF) and endostatin serum levels in nude or BALB/c mice bearing human lung tumors (Calu-6 and H460) or murine mammary tumors (M3MC, M-234p and M-234m), respectively. In these experimental models we previously found an association between in vivo generation of CAR and in vitro conversion of plasminogen into angiostatin. Serum endostatin level in CAR+ Calu-6-bearing mice was significantly higher than in CAR- H460 counterpart. Sera from mammary tumor-bearing mice showed similar levels of endostatin, regardless of their ability to induce CAR. Conversely, serum VEGF levels in mice bearing CAR+ tumors were lower than those found in CAR- tumor-bearing hosts. Immunostaining with an anti-CD31 antibody revealed that secondary tumors subjected to CAR were significantly less vascularized than primary tumors, while this difference was not observed in CAR- tumors. In vitro studies showed an inhibitory effect of sera from CAR-inducing tumors on endothelial cell proliferation as compared to normal sera, whereas sera from non-CAR-inducing tumors did not alter endothelial proliferation and, in some instances, even caused stimulation of endothelial proliferation. These data suggest that the antiangiogenic mechanism operating in concomitant antitumoral resistance is the result of an increase in the ratio of antiangiogenic/proangiogenic regulators. The levels of the factors involved in this phenomenon can vary in the different tumor models, but the trend favoring the inhibition of angiogenesis is always conserved.

Hsp25 and Hsp70 in rodent tumors treated with doxorubicin and lovastatin.

Heat shock protein 27 (Hsp27) and Hsp70 have been involved in resistance to anticancer drugs in human breast cancer cells growing in vitro and in vivo. In this study, we examined the expression of Hsp25 (the rodent homologue to human Hsp27) and Hsp70 in 3 different rodent tumors (a mouse breast carcinoma, a rat sarcoma, and a rat lymphoma maintained by subcutaneous passages) treated in vivo with doxorubicin (DOX) and lovastatin (LOV). All tumors showed massive cell death under control untreated conditions, and this massive death increased after cytotoxic drug administration. In this study, we show that this death was due to classic apoptosis. The tumors also showed isolated apoptotic cells between viable tumor cells, and this occurred more significantly in the lymphoma. The tumor type that was more resistant to cell death was the sarcoma, and this was found in sarcomas growing both under control conditions and after cytotoxic drug administration. Moreover, sarcomas showed the highest expression levels of Hsp25 in the viable tumor cells growing under untreated conditions, and these levels increased after DOX and LOV administration. After drug treatment, only sarcoma tumor cells showed a significant increase in Hsp70. In other words, sarcomas were the tumors with lower cell death, displayed a competent Hsp70 and Hsp25 response with nuclear translocation, and had the highest levels of Hsp25. In sarcomas, Hsp25 and Hsp70 were found in viable tumor cells located around the blood vessels, and these areas showed the most resistant tumor cell phenotype after chemotherapy. In addition, Hsp25 expression was found in endothelial cells as unique feature revealed only in lymphomas. In conclusion, our study shows that each tumor type has unique features regarding the expression of Hsp25 and Hsp70 and that these proteins seem to be implicated in drug resistance mainly in sarcomas, making these model systems important to perform more mechanistic studies on the role of Hsps in resistance to certain cytotoxic drugs.

Differential production of angiostatin by concomitant antitumoral resistance-inducing cancer cells.

The phenomenon by which tumor-bearing hosts are capable of inhibiting secondary tumor implants or metastases, known as concomitant antitumoral resistance (CAR), is presumably due to antiangiogenesis at places distant from the primary tumor. Although angiostatin, a potent inhibitor of angiogenesis, has been reported to be one of the factors responsible for suppressing the growth of secondary tumors in mice bearing previous tumors, it has not been definitively proven yet. With the aim of investigating whether CAR-inducing cancer cells display a differential angiostatin production and to support the role ascribed to that molecule concerning the inhibition of secondary tumor implants, 5 tumor models with different CAR-inducing capacities were studied herein. One of the 2 human lung cancer cell lines analyzed revealed a strong CAR against secondary s.c. tumor implants in nude mice, and 2 of 3 of the murine mammary tumors used exhibited inhibitory effect on secondary s.c. and i.v. tumor inoculations in syngeneic hosts. Since angiostatin is a proteolytic fragment from plasminogen, we examined by Western blot the ability of all conditioned media collected from the tumor cells studied to convert plasminogen to angiostatin. An association between in vivo generation of CAR and in vitro conversion of plasminogen into angiostatin was found. Since different enzymatic mechanisms were described to explain the generation of angiostatin, we also studied gelatinase and urokinase-type plasminogen activator secretion in conditioned media by zymography. The conversion of plasminogen into angiostatin by conditioned media was mainly inhibited by broad-spectrum serine proteinase inhibitors, suggesting a possible role for 1 or more enzymes of that group in the process. These findings suggest the existence of a differential angiostatin generation by CAR-inducing cancer cells, providing additional support to previous data obtained by other authors.