Novel dual cyclooxygenase and lipoxygenase inhibitors targeting hyaluronan-CD44v6 pathway and inducing cytotoxicity in colon cancer cells.

Cyclooxygenase-2 (COX-2) and 5-lipoxygenase (5-LOX) enzyme have been found to play a role in promoting growth in colon cancer cell lines. The di-tert-butyl phenol class of compounds has been found to inhibit both COX-2 and 5-LOX enzymes with proven effectiveness in arresting tumor growth. In the present study, the structural analogs of 2,6 di-tert-butyl-p-benzoquinone (BQ) appended with hydrazide side chain were found to inhibit COX-2 and 5-LOX enzymes at micromolar concentrations. Molecular docking of the compounds into COX-2 and 5-LOX protein cavities indicated strong binding interactions supporting the observed cytototoxicities. The signaling interaction between endogenous hyaluronan and CD44 has been shown to regulate COX-2 activities through ErbB2 receptor tyrosine kinase (RTK) activation. In the present studies it has been observed for the first time, that three of our COX/5-LOX dual inhibitors inhibit proliferation upon hydrazide substitution and prevent the activity of pro-angiogenic factors in HCA-7, HT-29, Apc10.1 cells as well as the hyaluronan synthase-2 (Has2) enzyme over-expressed in colon cancer cells, through inhibition of the hyaluronan/CD44v6 cell survival pathway. Since there is a substantial enhancement in the antiproliferative activities of these compounds upon hydrazide substitution, the present work opens up new opportunities for evolving novel active compounds of BQ series for inhibiting colon cancer.

Synthesis, characterization and anti-tumor activity of moxifloxacin-copper complexes against breast cancer cell lines.

Novel moxifloxacin-copper complexes were synthesized, characterized and screened for anti-proliferative and apoptosis-inducing activity against multiple human breast cancer cell lines (hormone-dependent MCF-7 and T47D as well as hormone-independent MDA-MB-231 and BT-20). The results indicated that the parent compound moxifloxacin (1) does not exert any inhibitory activity against breast cancer cell lines examined. On the other hand, the copper conjugate 2 and its nitrogen adducts 3-5 exerted growth inhibitory and apoptosis-inducing activity against breast cancer cell lines without any substantial effect on non-tumorigenic breast epithelial cells MCF-10A at equimolar concentration, suggesting a cancer cell-specific activity. BT-20 cells were more sensitive to compounds 2 and 3, while compounds 4 and 5 exerted significant anti-proliferative and apoptosis-inducing effects on T47D, MDA-MB-231 and BT-20 cell lines. Our results suggest that these novel compounds could be useful for the treatment of breast cancer in the future.

Hybrid anticancer agents: isothiocyanate-progesterone conjugates as chemotherapeutic agents and insights into their cytotoxicities.

New hybrid molecules of isothiocyanate and progesterone and their metal complexes were synthesized exhibiting promising anti-proliferative and pro-apoptotic activity against breast and prostate cancer cells. These metal complex compounds exploited an existing cellular transport pathway for delivery of cytotoxic isothiocyanate moiety across cell membrane resulting in the inhibition of cell viability and inducing apoptosis. The highest apoptotic action was shown by the copper complex, which was mediated through the inhibition of Akt signaling similar to the one shown by isothiocyanate compounds. Our results underscore the possible role of metal redox cycling, and thus it is likely will open newer avenues for further optimization for the synthesis of novel active compounds through appropriate isothiocyanate pharmacophores.

Back to the future: COX-2 inhibitors for chemoprevention and cancer therapy.

For more than a century, inhibition of prostaglandin biosynthesis via inhibition of the fatty acid cyclooxygenase (COX) has been achieved by non-steroidal anti-inflammatory drugs (NSAIDs), which targets both COX-1 and COX-2 and as such could be responsible for causing gastrointestinal (GI) toxicity. COX-2 is an inducible enzyme produced by many cell types in response to multiple stimuli. Recently, COX-2 over-expression has been found in several types of human cancers such as colon, breast, prostate and pancreas and appears to control many cellular processes. Because of its role in carcinogenesis, apoptosis, and angiogenesis, it is an excellent target for developing new drugs with selectivity for prevention and/or treatment of human cancers. Development of selective COX-2 inhibitors has been successfully documented and as such showed less toxicity to GI tract as compared to conventional NSAIDs. However, the long term use of COX-2 selective inhibitors showed cardiovascular toxicity, and thus their utilization for cancer prevention and therapy is currently questionable, suggesting that further development of novel COX-2 selective agents are needed. Among many solid tumors, pancreatic cancer has the worst prognosis, and inflammation has been identified as a significant factor in the development of pancreatic malignancy. Several cytokines, reactive oxygen species (ROS) and mediators of inflammatory pathway such as activation of nuclear factor-kappaB (NF-kappaB) and COX-2 leads to an increase in cell proliferation, survival, and inhibition of pro-apoptotic pathway, ultimately resulting in tumor angiogenesis, invasion and metastasis. In this brief review, we summarize the role of COX-2 and discuss some of the experimental data linking inflammation with the development of pancreatic cancer. In addition, we provide further evidence regarding the state of our knowledge toward the development of novel COX-2 targeting agents for the prevention and/or treatment of human cancers especially pancreatic cancer.

Copper conjugates of nimesulide Schiff bases targeting VEGF, COX and Bcl-2 in pancreatic cancer cells.

Copper conjugates of Schiff base derivatives of nimesulide (1), a well-known cyclooxygenase-2 (COX-2) inhibitor, were synthesized, structurally characterized and evaluated for their COX selectivity indices and cytotoxicities on pancreatic tumor, BxPC-3 (COX-2 positive) and MiaPaCa (COX-2 negative) cell lines. Copper conjugates exhibit distorted square planar geometries as revealed by the single crystal X-ray structure determination of Cu(L1)(2) and show significant growth inhibition in both cell lines (IC50 values 3-26 microM for COX-2 positive and 5-9 microM for COX-2 negative cell line) than the parent nimesulide (35 microM for COX-2 positive and >100 microM for COX-2 negative cell line). The mechanistic pathway for the biological activity involves inhibition of vascular endothelial growth factor (VEGF) and COX inhibition, as well as down regulation of antiapoptotic Bcl-2 and Bcl-(XL) proteins.

Novel Schiff base copper complexes of quinoline-2 carboxaldehyde as proteasome inhibitors in human prostate cancer cells.

We report the synthesis of novel 1:1 Schiff base copper complexes of quinoline-2-carboxaldehyde showing dose-dependent, antiproliferative, and proapoptotic activity in PC-3 and LNCaP prostate cancer cells. We found that quinoline thiosemicarbazone 2 (FPA-137) was the most potent and inhibited proteosome activity in intact human prostate cancer PC-3 and LNCaP cells (IC50 of 4 and 3.2 microM, respectively) compared to clioquinol and pyrrolidine dithiocarbamate (IC50 of 10 and 20 microM), supporting the novelty of 2.

Synthesis, molecular characterization, and biological activity of novel synthetic derivatives of chromen-4-one in human cancer cells.

The synthesis and characterization of Schiff base derivatives of 3-formylchromone 3-6 (FPA-120 to FPA-123), the minimal biologically active structural motif of soy isoflavone, genistein, and their copper(II) complexes 7-10 (FPA-124 to FPA-127) are reported here. These copper complexes possess distorted square-planar geometries capable of stabilizing Cu2+/Cu+ redox forms. The molecular modeling study revealed that the key interaction of the metal complexes was with amino acids in the pleckstrin homology (PH) and the kinase domain of the PKB (Akt) protein. Copper complex 7 significantly forms stronger charge interactions in the kinase domain than genistein, leading to better stabilization in the active pocket. In vitro evaluation of copper complexes against hormone-independent and metastatic breast (BT20), prostate (PC-3), and K-ras mutant (COLO 357) and K-ras wild-type (BxPC-3) pancreatic cancer cells revealed that 7 was the most potent compound which exhibited PKB (Akt protein) inhibitory activities and caused NF-kappaB inactivation in a well-established orthotopic pancreatic tumor model using COLO 357 cells. An inverse relationship was observed between IC50 values of the anti-proliferative activities and the Cu2+/Cu+ redox couple for these compounds, which may provide a rapid screen for evaluating the efficacy of active metallodrugs affecting redox-sensitive transcription factors such as NF-kappaB and its upstream target, the PKB (Akt) pathway, in multiple cancers.

The role of genistein and synthetic derivatives of isoflavone in cancer prevention and therapy.

Genistein, one of the predominant soy isoflavones, has been shown to compete with 17beta-estradiol for estrogen receptor binding because of its structural similarity, resulting in agonistic or antagonistic activity. It causes inhibition of cell growth in breast and prostate cancers in vivo and in vitro. From gene expression profiles, genistein has been found to regulate the genes that are critical for the control of cell proliferation, cell cycle, apoptosis, oncogenesis, transcription regulation, and cell signal transduction pathways. It has been reported that genistein induces apoptosis and inhibits activation of NF-kappaB and Akt signaling pathways, both of which are known to maintain a balance between cell survival and apoptosis. Recently, we found that genistein sensitized cancer cells to apoptosis induced by chemotherapeutic agents including docetaxel, gemcitabine and cisplatin through inactivation of NF-kappaB in multiple cancer cell lines. To enhance the anti-cancer activity of genistein, we have synthesized structurally-modified derivatives of isoflavone based on the structural requirements for optimal anti-cancer effect. We found that these synthetic derivatives of isoflavone exerted higher anti-cancer activity with lower IC50. These derivatives of isoflavone also induced more apoptosis compared to genistein. These results suggest that genistein and synthetic structurally-modified derivatives of isoflavone may be promising agents for cancer chemoprevention and therapy either alone or in combination with existing chemotherapeutic agents.

Rad6 is a Potential Early Marker of Melanoma Development.

Melanoma is the leading cause of death from skin cancer in industrialized countries. Several melanoma-related biomarkers and signaling pathways have been identified; however, their relevance to melanoma development/progression or to clinical outcome remains to be established. Aberrant activation of Wnt/ß-catenin pathway is implicated in various cancers including melanoma. We have previously demonstrated Rad6, an ubiquitin-conjugating enzyme, as an important mediator of ß-catenin stability in breast cancer cells. Similar to breast cancer, ß-catenin-activating mutations are rare in melanomas, and since ß-catenin signaling is implicated in melanoma, we examined the relationship between ß-catenin levels/activity and expression of ß-catenin transcriptional targets Rad6 and microphthalmia-associated transcription factor-M (Mitf-M) in melanoma cell models, and expression of Rad6, ß-catenin, and Melan-A in nevi and cutaneous melanoma tissue specimens. Our data show that Rad6 is only weakly expressed in normal human melanocytes but is overexpressed in melanoma lines. Unlike Mitf-M, Rad6 overexpression in melanoma lines is positively associated with high molecular weight ß-catenin protein levels and ß-catenin transcriptional activity. Double-immunofluorescence staining of Rad6 and Melan-A in melanoma tissue microarray showed that histological diagnosis of melanoma is significantly associated with Rad6/Melan-A dual positivity in the melanoma group compared to the nevi group (P=.0029). In contrast to strong ß-catenin expression in normal and tumor areas of superficial spreading malignant melanoma (SSMM), Rad6 expression is undetectable in normal areas and Rad6 expression increases coincide with increased Melan-A in the transformed regions of SSMM. These data suggest a role for Rad6 in melanoma pathogenesis and that Rad6 expression status may serve as an early marker for melanoma development.

-(-)Gossypol promotes the apoptosis of bladder cancer cells in vitro.

Dysregulation of Bcl2 family member proteins has been associated with poor chemotherapeutic response in bladder cancer, suggesting that agents targeting these crucial proteins may provide an interventional strategy to slow or halt bladder cancer progression and metastasis. In this study, we investigated whether the cottonseed polyphenol, -(-)gossypol, a BH3 mimetic, can reduce the expression of pro-survival, or increase the expression of pro-apoptotic, Bcl2 family proteins and thereby effectively sensitize otherwise resistant bladder cancer cells to the standard chemotherapeutic drugs gemcitabine, paclitaxel and carboplatin. These studies show that gossypol induced apoptosis in both chemosensitive UM-UC2 and chemoresistant resistant UM-UC9 bladder cancer cells in vitro in a dose and time dependent manner via a caspase mediated death signaling pathway. Moreover, in combined treatments, gossypol synergized with gemcitabine and carboplatin to induce apoptosis in chemoresistant bladder cancer cells. This effect was associated with the down-regulation the Bcl-xl and Mcl-1 pro-survival Bcl2 family proteins and up-regulation of the Bim and Puma BH3-only Bcl2 family proteins. Overall, these studies show that gossypol sensitizes bladder cancer cells to standard chemotherapeutic drugs and may provide a promising new strategy for bladder cancer treatment.

CXCL5 promotes prostate cancer progression.

CXCL5 is a proangiogenic CXC-type chemokine that is an inflammatory mediator and a powerful attractant for granulocytic immune cells. Unlike many other chemokines, CXCL5 is secreted by both immune (neutrophil, monocyte, and macrophage) and nonimmune (epithelial, endothelial, and fibroblastic) cell types. The current study was intended to determine which of these cell types express CXCL5 in normal and malignant human prostatic tissues, whether expression levels correlated with malignancy and whether CXCL5 stimulated biologic effects consistent with a benign or malignant prostate epithelial phenotype. The results of these studies show that CXCL5 protein expression levels are concordant with prostate tumor progression, are highly associated with inflammatory infiltrate, and are frequently detected in the lumens of both benign and malignant prostate glands. Exogenous administration of CXCL5 stimulates cellular proliferation and gene transcription in both nontransformed and transformed prostate epithelial cells and induces highly aggressive prostate cancer cells to invade through synthetic basement membrane in vitro. These findings suggest that the inflammatory mediator, CXCL5, may play multiple roles in the etiology of both benign and malignant proliferative diseases in the prostate.

A novel copper complex of 3-benzoyl-alpha methyl benzene acetic acid with antitumor activity mediated via cyclooxygenase pathway.

Pancreatic cancer (PC) is characterized as one of the deadliest malignancies and its treatment is a great challenge to clinical oncologists. Expression of COX-2 is detectable in 75% of PCs among which 50% showed overexpression, suggesting the importance of COX-2 enzyme and its metabolic product prostaglandin E2 (PGE(2)) in PC. Here the authors report the synthesis and biological activity of a novel COX-2 inhibitor, FPA-306, and its effects on PC cells with different levels of COX-2 expression. Using MTT assay, the authors found a significant growth inhibition of BxPC-3 cells treated by FPA-306 with an IC(50) of 10 micromol/L, which was lower than that of ketoprofen (IC(50) = 35.4 micromol/L) and celecoxib (IC(50) > 100 micromol/L). There was no such effect found in MIAPaCa cell line, which does not express COX-2. The authors also found dose dependent reduction in cell survival and induction of apoptosis by FPA-306 treatment in BxPC-3 cells but not in MIAPaCa cells. These results were correlated with apoptosis data and secreted PGE(2) levels. The molecular modeling of FPA-306 in the COX-2 active site showed that FPA-306 is potentially able to inhibit the activity of enzyme by blocking the active site, thereby resulting in decreased PGE(2) production. The authors also found a significant reduction of COX-2 at the mRNA and protein levels together with downregulation of NF-kappaB DNA binding activity and its downstream genes, Bcl-2 and survivin. These results suggest that FPA-306 is an effective and potent agent in inhibiting the growth of PC cells.