Franco O. Ranelletti

FLAVONOIDS APIGENIN AND QUERCETIN INHIBIT MELANOMA GROWTH AND METASTATIC POTENTIAL

Flavonoids are a class of polyphenolic compounds widely distributed in the plant kingdom, which display a variety of biological activities, including chemoprevention and tumor growth inhibition. Our aim was to investigate the effects of several polyphenols on the growth and metastatic potential of B16‐BL6 melanoma cells in vivo. Intraperitoneal administration of quercetin, apigenin, (–)‐epigallocathechin‐3‐gallate (EGCG), resveratrol, and the anti‐estrogen tamoxifen, at the time of i.m. injection of B16‐BL6 cells into syngeneic mice, resulted in a significant, dose‐dependent delay of tumor growth, without toxicity. The relative descending order of potency was EGCG > apigenin = quercetin = tamoxifen > resveratrol > control. Furthermore, polyphenols significantly potentiated the inhibitory effect of a non‐toxic dose of cisplatin. When tested for the ability to inhibit lung colonization, quercetin, apigenin, and tamoxifen (but not EGCG or resveratrol) significantly decreased the number of B16‐BL6 colonies in the lungs in a dose‐dependent manner, with quercetin and apigenin being more effective than tamoxifen. Interestingly, quercetin, apigenin, and tamoxifen (but not EGCG or resveratrol) significantly decreased the invasion of B16‐BL6 cells in vitro, with quercetin and apigenin being more effective than tamoxifen. This suggests that anti‐invasive activity is one of the mechanisms underlying inhibition of lung colonization by quercetin and apigenin. In conclusion, quercetin and apigenin inhibit melanoma growth and invasive and metastatic potential; therefore, they may constitute a valuable tool in the combination therapy of metastatic melanoma. Int. J. Cancer 87:595–600, 2000.

Cyclooxygenase-2 expression is induced during human megakaryopoiesis and characterizes newly formed platelets

Cyclooxygenase (COX)-1 or -2 and prostaglandin (PG) synthases catalyze the formation of various PGs and thromboxane (TX) A2. We have investigated the expression and activity of COX-1 and -2 during human megakaryocytopoiesis. We analyzed megakaryocytes from bone marrow biopsies and derived from thrombopoietin-treated CD34+ hemopoietic progenitor cells in culture. Platelets were obtained from healthy donors and patients with high platelet regeneration because of immune thrombocytopenia or peripheral blood stem cell transplantation. By immunocytochemistry, COX-1 was observed in CD34+ cells and in megakaryocytes at each stage of maturation, whereas COX-2 was induced after 6 days of culture, and remained detectable in mature megakaryocytes. CD34+ cells synthesized more PGE2 than TXB2 (214 ± 50 vs. 30 ± 10 pg/106 cells), whereas the reverse was true in mature megakaryocytes (TXB2 8,440 ± 2,500 vs. PGE2 906 ± 161 pg/106 cells). By immunostaining, COX-2 was observed in <10% of circulating platelets from healthy controls, whereas up to 60% of COX-2-positive platelets were found in patients. A selective COX-2 inhibitor reduced platelet production of both PGE2 and TXB2 to a significantly greater extent in patients than in healthy subjects. Finally, we found that COX-2 and the inducible PGE-synthase were coexpressed in mature megakaryocytes and in platelets. We conclude that both COX-isoforms contribute to prostanoid formation during human megakaryocytopoiesis and that COX-2-derived PGE2 and TXA2 may play an unrecognized role in inflammatory and hemostatic responses in clinical syndromes associated with high platelet turnover.

Quercetin potentiates the effect of adriamycin in a multidrug-resistant MCF-7 human breast-cancer cell line: P-glycoprotein as a possible target

This study demonstrates that the flavonoid quercetin (Q), a plant-derived compound with low toxicity in vivo, greatly potentiates the growth-inhibitory activity of Adriamycin (ADR) on MCF-7 ADR-resistant human breast cancer cells. The effect of Q was dose-dependent at concentrations ranging between 1 and 10 μM. Since ADR resistance in these cells is associated with the expression of high levels of P-glycoprotein (Pgp), we evaluated the effect of Q and related flavonoids of Pgp activity in cytofluorographic efflux experiments with the fluorescent dye rhodamine 123 (Rh 123). Our results indicate that Q and 3-OMe Q (3′,4′,7-trimethoxyquercetin) but not the 3-rhamnosylglucoside of Q (rutin) inhibit the Pgp pump-efflux activity in a dose-related manner. Moreover, 10 μM Q reduces the expression of the immunoreactive Pgp in MCF-7 ADR-resistant cells as evaluated by cytofluorimetric assay. In conclusion, these findings provide a further biological basis for the potential therapeutic application of Q as an anticancer drug either alone or in combination with ADR in multidrug-resistant breast tumor cells.

Increased Cyclooxygenase-2 Expression Is Associated With Chemotherapy Resistance and Poor Survival in Cervical Cancer Patients

PURPOSE To investigate the expression of cyclooxygenase (COX-2) and its association with clinicopathologic parameters and clinical outcome in patients with cervical cancer. PATIENTS AND METHODS The study included 84 patients with stage IB to IVA cervical cancer. Patients with early-stage cases (n = 21) underwent radical surgery, whereas patients with locally advanced cervical cancer (LACC) (n = 63) were first administered neoadjuvant cisplatin-based treatment and subjected to surgery in case of response. Immunohistochemical analysis was performed on paraffin-embedded sections with rabbit antiserum against COX-2. RESULTS COX-2--integrated density values in the overall population ranged from 1.2 to 82.3, with mean plus minus SE values of 27.4 plus minus 2.4. According to the chosen cutoff value, 36 (42.9%) of 84 patients were scored as COX-2 positive. COX-2 levels were shown to be highly associated with tumor susceptibility to neoadjuvant treatment. COX-2 showed a progressive increase from mean plus minus SE values of 19.9 plus minus 8.0 in complete responders through 31.5 plus minus 3.5 in partial responses to 44.8 plus minus 3.9 in patients who were not responsive (P =.0054). When logistic regression was applied, only advanced stage and COX-2 positivity retained independent roles in predicting a poor chance of response to treatment. COX-2--positive patients had a shorter overall survival (OS) rate than COX-2--negative patients. In patients with LACC, the 2-year OS rate was 38% in COX-2--positive versus 85% in COX-2--negative patients (P =.0001). In the multivariate analysis, only advanced stage and COX-2 positivity retained independent negative prognostic roles for OS. CONCLUSION The assessment of COX-2 status could provide additional information to identify patients with cervical cancer with a poor chance of response to neoadjuvant treatment and unfavorable prognosis.

Quercetin inhibits the growth of a multidrug-resistant estrogen-receptor-negative MCF-7 human breast-cancer cell line expressing type II estrogen-binding sites

SummaryIt has been demonstrated that the flavonoid quercetin (3,3′,4′,5,7-pentahydroxyflavone; Q) inhibits the growth of several cancer cell lines. There is evidence suggesting that the antiproliferative activity of this substance is mediated by the so-called type II estrogen-binding, site (type II EBS). We looked for the presence of type II EBS and the effect of Q on the proliferation of an Adriamycinresistant estrogen-receptor-negative human breast-cancer cell line (MCF-7 ADRr). By whole-cell assay using estradiol labelled with 6,7-tritium ([3H]-E2) as a tracer, we demonstrated that MCF-7 ADRr cells contain type II EBSs. Competition analysis revealed that diethylstilbestrol (DES) and Q competed with similar potency for [3H]-Es binding to type II EBSs. The antiestrogen tamoxifen (TAM) competed for type II EBSs, albeit to a lesser extent than either DES or Q. Growth experiments demonstrated that Q and DES exerted a dose-dependent inhibition of cell proliferation in the range of concentrations between 10 nM and 10 μm, whereas TAM was less effective. Q could also inhibit colony formation in a clonogenic assay. Our results indicate that multidrug-resistant estrogen-receptor-negative MCF-7 cells express, type II EBSs and are sensitive to the inhibitory effect of Q. This substance could be the parent compound of a novel class of anticancer agents.

Inhibitory effect of quercetin on OVCA 433 cells and presence of type II oestrogen binding sites in primary ovarian tumours and cultured cells

We investigated the effect of the flavonoid quercetin (Q) on the proliferation of the ovarian cancer cell line OVCA 433. Growth experiments demonstrated that Q exerted a reversible dose-dependent inhibition of cell proliferation in the range of concentrations between 10 nM and 10 microM. Two other flavonoids tested, rutin and hesperidin, were ineffective in inhibiting cell growth. Cell cycle analysis showed that the growth inhibitory effect of Q was due to a blocking effect in the GO/G1 phase. Using a whole cell assay with (6.7-3H) oestradiol (3H-E2) as tracer we demonstrated that OVCA 433 cells contain type II oestrogen binding sites (type II EBS). Competition analysis showed that Q competed for 3H-E2 binding to type II EBS while both rutin and hesperidin did not. Appreciable amounts of type II EBS were also detected in seven primary ovarian tumours. Our results suggest that Q may regulate ovarian cancer cell growth through a mechanism involving a binding interaction with type II EBS. This mechanism could also be active in vivo since primary ovarian tumours contain type II EBS.

Quercetin inhibits p21‐RAS expression in human colon cancer cell lines and in primary colorectal tumors

Immunocytochemical studies have revealed that 10 μM quercetin reduced the steady state levels of p21‐ras proteins in both colon cancer cell lines and primary colorectal tumors. These findings were confirmed by Western blot and flow cytometric analysis showing that the inhibition of p21‐ras expression by quercetin was time‐ and concentration‐dependent. Twenty‐four‐hour treatment with 10 μM quercetin reduced p21‐ras levels to about 50% of control values. Quercetin was similarly effective in inhibiting the expression of K‐, H‐, and N‐ras proteins. Moreover, the effect of quercetin on ras oncogene expression was not dependent on the cell cycle position of colon cancer cells and appeared to be specific and not merely a consequence of overall inhibition of protein synthesis. Northern blot analysis revealed that quercetin produced in colon cancer cells an early (30 min) reduction of the steady state levels of K‐, H‐, and N‐ras mRNAs. This reduction was also present after 6 hr of flavonoid treatment. These effects of quercetin suggest a possible chemopreventive role for this compound in colorectal carcinogenesis. Int. J. Cancer 85:438–445, 2000. ©2000 Wiley‐Liss, Inc.

Cyclooxygenase-2 expression in endometrial carcinoma: correlation with clinicopathologic parameters and clinical outcome.

Cyclooxygenase‐2 (COX‐2) is overexpressed in endometrial hyperplasia and carcinoma, but no data have been reported until now about the expression of COX‐2 and its possible clinical significance in endometrial carcinoma. We investigated by immunohistochemistry the expression of COX‐2 in a single institutional series of primary untreated endometrial carcinoma patients. The relationship between COX‐2 expression and microsatellite instability (MI) status was also analyzed.

beta-carotene at high concentrations induces apoptosis by enhancing oxy-radical production in human adenocarcinoma cells.

This is the first report demonstrating a relationship between apoptosis induction and changes of intracellular redox potential in the growth-inhibitory effects of high concentrations of beta-carotene in a tumor cell line. beta-Carotene inhibited the growth of human WiDr colon adenocarcinoma cells in a dose- and time-dependent manner, induced apoptosis, and blocked Bcl-2 expression. These effects were accompanied by an enhanced production of intracellular reactive oxygen species (ROS). The addition of the antioxidant alpha-tocopherol blocked both the pro-oxidant and the growth-inhibitory effects of the carotenoid. These findings suggest that beta-carotene may act as an inductor of apoptosis by its pro-oxidant properties.

Lycopene induces cell growth inhibition by altering mevalonate pathway and Ras signaling in cancer cell lines.

Several evidences suggest that cancer cells have abnormal cholesterol biosynthetic pathways and prenylation of small guanosine triphosphatase proteins. Tomato lycopene has been suggested to have beneficial effects against certain types of cancer, including that of prostate, although the exact molecular mechanism(s) is unknown. We tested the hypothesis that lycopene may exert its antitumor effects through changes in mevalonate pathway and in Ras activation. Incubation of the Ras-activated prostatic carcinoma LNCaP cells with a 24 h lycopene treatment (2.5-10 μM) dose dependently reduced intracellular total cholesterol by decreasing 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase expression and by inactivating Ras, as evidenced by its translocation from cell membranes to cytosol. Concomitantly, lycopene reduced the Ras-dependent activation of nuclear factor-kappaB (NF-κB). Such a reduction was parallel to an inhibition of reactive oxygen species production and to a decrease in the phosphorylation ofc-jun N-terminal kinase, extracellular signal-regulated kinase 1/2 and p38. These effects were also accompanied by an arrest of cell cycle progression and by apoptosis induction, as evidenced by a decrease in cyclin D1 and phospho-AKT levels and by an increase in p21, p27 and p53 levels and in Bax:Bcl-2 ratio. The addition of mevalonate prevented the growth-inhibitory effects of lycopene as well as its increase in Ras cytoplasmatic accumulation and the subsequent changes in NF-κB. The ability of lycopene in inhibiting HMG-CoA reductase expression and cell growth and in inactivating Ras was also found in prostate PC-3, colon HCT-116 and HT-29 and lung BEN cancer cells. These findings provide a novel mechanistic insight into the growth-inhibitory effects of lycopene in cancer.