An Oleocanthal-Enriched EVO Oil Extract Induces the ROS Production in Gastric Cancer Cells and Potentiates the Effect of Chemotherapy.

Oleocanthal, a minor polar compound in extra-virgin olive (EVO) oil, contains anticancer properties, which should be encouraged in its use in oncology. Gastric Cancer (GC), a very aggressive human cancer, is often diagnosed at advanced stages, when surgery is substituted or supported by chemotherapy (CT). However, CT frequently fails due to the patient's resistance to the treatment. Thus, the aim of this study is to verify whether an OC-enriched EVO oil extract fraction (OCF) may be useful in order to overcome a resistance to GC. We evaluated the OCF effects on an AGS gastric adenocarcinoma cell line wild type (AGS wt) and on its subpopulations resistant to 5-fluorouracil (5FUr), Paclitaxel (TAXr) or cisplatin (CISr). We found that a 60 µM dose of the OCF acts on the AGS wt, 5FUr and TAXr, leading to the cell cycle inhibition and to a ROS production, but not on CISr cells. Resistance of CISr to the OCF seems to be due to higher levels of antioxidant-enzymes that can counteract the OCF-induced ROS production. Moreover, using the OCF plus 5-fluorouracil, Paclitaxel or cisplatin, we found a potentiating effect compared with a mono-treatment in all resistant GC cells, including CISr. In conclusion, the use of the OCF in the management of GC has shown very interesting advantages, opening-up the possibility to evaluate the efficacy of the OCF in vivo, as a valid adjuvant in the treatment of resistant GC.

uPAR Controls Vasculogenic Mimicry Ability Expressed by Drug-Resistant Melanoma Cells.

Malignant melanoma is a highly aggressive skin cancer characterized by an elevated grade of tumor cell plasticity. Such plasticity allows adaptation of melanoma cells to different hostile conditions and guarantees tumor survival and disease progression, including aggressive features such as drug resistance. Indeed, almost 50% of melanoma rapidly develop resistance to the BRAFV600E inhibitor vemurafenib, with fast tumor dissemination, a devastating consequence for patients outcomes. Vasculogenic mimicry (VM), the ability of cancer cells to organize themselves in perfused vascular-like channels, might sustain tumor spread by providing vemurafenib-resistant cancer cells with supplementary ways to enter into circulation and disseminate. Thus, this research aims to determine if vemurafenib resistance goes with the acquisition of VM ability by aggressive melanoma cells, and identify a driving molecule for both vemurafenib resistance and VM. We used two independent experimental models of drug-resistant melanoma cells, the first one represented by a chronic adaptation of melanoma cells to extracellular acidosis, known to drive a particularly aggressive and vemurafenib-resistant phenotype, the second one generated with chronic vemurafenib exposure. By performing in vitro tube formation assay and evaluating the expression levels of the VM markers EphA2 and VE-cadherin by Western blotting and flow cytometer analyses, we demonstrated that vemurafenib-resistant cells obtained by both models are characterized by an increased ability to perform VM. Moreover, by exploiting the CRISPR-Cas9 technique and using the urokinase plasminogen activator receptor (uPAR) inhibitor M25, we identified uPAR as a driver of VM expressed by vemurafenib-resistant melanoma cells. Thus, uPAR targeting may be successfully leveraged as a new complementary therapy to inhibit VM in drug-resistant melanoma patients, to counteract the rapid progression and dissemination of the disease.

Oleuropein, the Main Polyphenol of Olea europaea Leaf Extract, Has an Anti-Cancer Effect on Human BRAF Melanoma Cells and Potentiates the Cytotoxicity of Current Chemotherapies.

Oleuropein (Ole), a secoiridoid glucoside present in Olea europaea leaves, gained scientific interest thanks to its several biological properties, including the anticancer one. We verified whether Ole might potentiate the cytotoxicity of conventional drugs used to treat melanoma, disclosing a potentially new therapeutic strategy. We tested the cytotoxic action of Ole alone or in combination with chemotherapeutics on A375 human melanoma cells. We found that Ole was able, at a dose of 500 µM, to stimulate apoptosis, while at a non-toxic dose of 250 µM, it affected cell proliferation and induced the downregulation of the pAKT/pS6 pathway. A dose of 250 µM Ole did not potentiate the effect of Vemurafenib (PLX4032), but it succeeded in increasing the cytotoxic effect of Dacarbazine (DTIC). The major effect was found in the association between Ole and Everolimus (RAD001), also on PLX4032-resistant BRAF melanoma cells, which possibly cooperate in the inhibition of the pAKT/pS6 pathway. Of interest, an olive leaf extract enriched in equimolar Ole was more effective and able to further improve DTIC and RAD001 efficacy on BRAF melanoma cells with respect to Ole alone. Therefore, Ole represents a natural product able to potentiate a wide array of chemotherapeutics against BRAF melanoma cells affecting the pAKT/pS6 pathway.

22 : 6n-3 DHA inhibits differentiation of prostate fibroblasts into myofibroblasts and tumorigenesis.

Prostate cancer is one of the most common malignancies in men. Epidemiological and experimental studies have revealed that stromal cells of the tumour microenvironment contribute to the development of prostate cancers, while long-chain n-3 PUFA-enriched diets reduce the risk of this tumour histotype. These findings prompted us to investigate whether DHA, an n-3 PUFA, may abrogate differentiation of prostate fibroblasts into myofibroblasts, the activated form of fibroblasts generally involved in prostate cancer progression. We used the human prostate carcinoma cell line (PC3) as a prostate adenocarcinoma model and found that DHA (1) inhibits α-smooth muscle actin (α-SMA) expression, a typical marker of myofibroblast differentiation, in prostate fibroblasts stimulated in vitro with transforming growth factor-ß (TGF-ß), (2) blocks the matrix metalloproteinase-2-dependent enhanced invasiveness of PC3 prostate adenocarcinoma cells migrated in a medium conditioned by TGF-ß-stimulated prostate fibroblasts, (3) prevents epithelial-mesenchymal transition (EMT) and invasiveness of PC3 cells promoted by a medium conditioned by TGF-ß-stimulated prostate fibroblasts, and (4) reduces the growth rate of tumours obtained in immunodeficient animals injected with PC3 cells plus TGF-ß-stimulated prostate fibroblasts. Moreover, DHA was found to revert α-SMA expression and the invasiveness-promoting activity exerted in PC3 cells by tumoral-activated fibroblasts. Thus, DHA represents a suitable agent to inhibit prostate myofibroblast differentiation, invasiveness and EMT, two most important tumour-promoting activities involved in the progression of prostate cancer cells.

Dietary n-3 polyunsaturated fatty acids enhance metastatic dissemination of murine T lymphoma cells.

Epidemiological investigation and animal studies have shown that dietary n-3 PUFA prevent the development and progression of certain types of cancer. However, conflicting results have been reported by the few studies that focused on the effect of dietary n-3 PUFA on the development of metastases. In the present study, we investigated the metastatic dissemination of murine T lymphoma lines with different metastatic potential transplanted into mice fed a fish oil diet, compared with mice fed a maize oil diet. Transplantation of highly metastatic S11 cells into animals fed a fish oil diet induced a large lymphomatoid infiltration in the spleen, associated with an eight-fold increase in spleen weight, compared with normal animals on the same diet. In contrast, only a limited increase in spleen weight was found in animals transplanted with S11 cells while fed a maize oil diet. No significant increase in spleen weight was found in animals transplanted with low-metastatic 164T2 cells regardless of whether they were fed a fish oil or a maize oil diet. At the end of experiment, an overt cachexia was shown by animals fed a fish oil diet transplanted with S11 cells, but not by those transplanted with 164T2 cells. The particularly high pro-metastatic effect of dietary n-3 PUFA on S11 cells rules out the generalisation that dietary n-3 PUFA inhibit tumour growth and progression.

An enhanced apoptosis and a reduced angiogenesis are associated with the inhibition of lung colonisation in animals fed an n-3 polyunsaturated fatty acid-rich diet injected with a highly metastatic murine melanoma line.

Both epidemiological and experimental studies indicate that dietary n-3 PUFA inhibit carcinogenesis and tumour growth. Metastatic diffusion has also been found to be affected in animals fed diets containing purified n-3 PUFA or fish oil. In the present study, we investigated whether the metastatic diffusion of a highly metastatic variant (F10-SR cells) isolated from the B16 melanoma F10 line was affected by feeding host animals a diet containing 5 % fish oil. In these animals, compared with those fed a diet containing 5 % maize oil, there was a reduced number of metastatic pulmonary colonies. The immunohistochemical analysis of appropriate markers revealed that the antimetastatic effect of dietary n-3 PUFA was not related to a reduction of proliferation, but rather to an enhanced apoptotic activity. The reduction of von Willebrand factor immunoreactivity found in pulmonary colonies of F10-SR cells grown in fish oil-fed animals indicates that a decrease of angiogenesis contributes to the antimetastatic effect of dietary n-3 PUFA. This conclusion stands in spite of the higher expression of vascular endothelial growth factor observed in pulmonary colonies grown in fish oil-fed animals.