Antiproliferative effect of sulindac in colonic neoplasia prevention: role of COOH-terminal Src kinase

Celecoxib repurposing in cancer therapy: molecular mechanisms and nanomedicine-based delivery technologies

While cancer remains a significant global health problem, advances in cancer biology, deep understanding of its underlaying mechanism and identification of specific molecular targets allowed the development of new therapeutic options. Drug repurposing poses several advantages as reduced cost and better safety compared with new compounds development. COX-2 inhibitors are one of the most promising drug classes for repurposing in cancer therapy. In this review, we provide an overview of the detailed mechanism and rationale of COX-2 inhibitors as anticancer agents and we highlight the most promising research efforts on nanotechnological approaches to enhance COX-2 inhibitors delivery with special focus on celecoxib as the most widely studied agent for chemoprevention or combined with chemotherapeutic and herbal drugs for combating various cancers.

Fractal Characterization of Chromatin Decompaction in Live Cells

Chromatin organization has a fundamental impact on the whole spectrum of genomic functions. Quantitative characterization of the chromatin structure, particularly at submicron length scales where chromatin fractal globules are formed, is critical to understanding this structure-function relationship. Such analysis is currently challenging due to the diffraction-limited resolution of conventional light microscopy. We herein present an optical approach termed inverse spectroscopic optical coherence tomography to characterize the mass density fractality of chromatin, and we apply the technique to observe chromatin decompaction in live cells. The technique makes it possible for the first time, to our knowledge, to sense intracellular morphology with length-scale sensitivity from ∼30 to 450 nm, thus primarily probing the higher-order chromatin structure, without resolving the actual structures. We used chromatin decompaction due to inhibition of histone deacytelases and measured the subsequent changes in the fractal dimension of the intracellular structure. The results were confirmed by transmission electron microscopy and confocal fluorescence microscopy.

Nonsteroidal anti-inflammatory drug sulindac sulfide suppresses structural protein Nesprin-2 expression in colorectal cancer cells

BACKGROUND

Nonsteroidal anti-inflammatory drugs (NSAIDs) are well known for treating inflammatory disease and have been reported to have anti-tumorigenic effects. Their mechanisms are not fully understood, but both cyclooxygenase (COX) dependent and independent pathways are involved. Our goal was to shed further light on COX-independent activity.

METHODS

Human colorectal cancer cells were observed under differential interference contrast microscopy (DICM), fluorescent microscopy, and micro-impedance measurement. Microarray analysis was performed using HCT-116 cells treated with sulindac sulfide (SS). PCR and Western blots were performed to confirm the microarray data and immunohistochemistry was performed to screen for Nesprin-2 expression. Micro-impedance was repeating including Nesprin-2 knock-down by siRNA.

RESULTS

HCT-116 cells treated with SS showed dramatic morphological changes under DICM and fluorescent microscopy, as well as weakened cellular adhesion as measured by micro-impedance. Nesprin-2 was selected from two independent microarrays, based on its novelty in relation to cancer and its role in cell organization. SS diminished Nesprin-2 mRNA expression as assessed by reverse transcriptase and real time PCR. Various other NSAIDs were also tested and demonstrated that inhibition of Nesprin-2 mRNA was not unique to SS. Additionally, immunohistochemistry showed higher levels of Nesprin-2 in many tumors in comparison with normal tissues. Further micro-impedance experiments on cells with reduced Nesprin-2 expression showed a proportional loss of cellular adhesion.

CONCLUSIONS

Nesprin-2 is down-regulated by NSAIDs and highly expressed in many cancers.

GENERAL SIGNIFICANCE

Our data suggest that Nesprin-2 may be a potential novel oncogene in human cancer cells and NSAIDs could decrease its expression.

Nano-architectural alterations in mucus layer fecal colonocytes in field carcinogenesis: potential for screening

Current fecal tests (occult blood, methylation, DNA mutations) target minute amounts of tumor products among a large amount of fecal material and thus have suboptimal performance. Our group has focused on exploiting field carcinogenesis as a modality to amplify the neoplastic signal. Specifically, we have shown that endoscopically normal rectal brushings have striking nano-architectural alterations which are detectable using a novel optical technique, partial wave spectroscopic microscopy (PWS). We therefore wished to translate this approach to a fecal assay. We examined mucus layer fecal colonocytes (MLFC) at preneoplastic and neoplastic time points (confirmed with rat colonoscopy) in the azoxymethane (AOM)-treated rat model and conducted PWS analysis to derive the nano-architectural parameter, disorder strength (Ld). We confirmed these results with studies in a genetic model (the Pirc rat). We showed that MLFC appeared microscopically normal, consistent with field carcinogenesis. Ld was elevated at an early time point (5 weeks post-AOM injection, effect size = 0.40, P = 0.024) and plateaued before adenoma formation (10 weeks post-AOM, effect size = 0.66, P = 0.001), with no dramatic increase once tumors developed. We replicated these data in the preneoplastic Pirc rat with an effect size in the MLFC that replicated the rectal brushings (increase vs. age-matched controls of 62% vs. 74%, respectively). We provide the first demonstration of a biophotonics approach to fecal assay. Furthermore, targeting the nano-architectural changes of field carcinogenesis rather than the detection of tumor products may provide a novel paradigm for colorectal cancer screening.

COX-Independent Mechanisms of Cancer Chemoprevention by Anti-Inflammatory Drugs

Epidemiological and clinical studies suggest that non-steroidal anti-inflammatory drugs (NSAIDs), including cyclooxygenase (COX)-2 selective inhibitors, reduce the risk of developing cancer. Experimental studies in human cancer cell lines and rodent models of carcinogenesis support these observations by providing strong evidence for the antineoplastic properties of NSAIDs. The involvement of COX-2 in tumorigenesis and its overexpression in various cancer tissues suggest that inhibition of COX-2 is responsible for the chemopreventive efficacy of these agents. However, the precise mechanisms by which NSAIDs exert their antiproliferative effects are still a matter of debate. Numerous other studies have shown that NSAIDs can act through COX-independent mechanisms. This review provides a detailed description of the major COX-independent molecular targets of NSAIDs and discusses how these targets may be involved in their anticancer effects. Toxicities resulting from COX inhibition and the suppression of prostaglandin synthesis preclude the long-term use of NSAIDs for cancer chemoprevention. Furthermore, chemopreventive efficacy is incomplete and treatment often leads to the development of resistance. Identification of alternative NSAID targets and elucidation of the biochemical processes by which they inhibit tumor growth could lead to the development of safer and more efficacious drugs for cancer chemoprevention.

HDAC up-regulation in early colon field carcinogenesis is involved in cell tumorigenicity through regulation of chromatin structure

Normal cell function is dependent on the proper maintenance of chromatin structure. Regulation of chromatin structure is controlled by histone modifications that directly influence chromatin architecture and genome function. Specifically, the histone deacetylase (HDAC) family of proteins modulate chromatin compaction and are commonly dysregulated in many tumors, including colorectal cancer (CRC). However, the role of HDAC proteins in early colorectal carcinogenesis has not been previously reported. We found HDAC1, HDAC2, HDAC3, HDAC5, and HDAC7 all to be up-regulated in the field of human CRC. Furthermore, we observed that HDAC2 up-regulation is one of the earliest events in CRC carcinogenesis and observed this in human field carcinogenesis, the azoxymethane-treated rat model, and in more aggressive colon cancer cell lines. The universality of HDAC2 up-regulation suggests that HDAC2 up-regulation is a novel and important early event in CRC, which may serve as a biomarker. HDAC inhibitors (HDACIs) interfere with tumorigenic HDAC activity; however, the precise mechanisms involved in this process remain to be elucidated. We confirmed that HDAC inhibition by valproic acid (VPA) targeted the more aggressive cell line. Using nuclease digestion assays and transmission electron microscopy imaging, we observed that VPA treatment induced greater changes in chromatin structure in the more aggressive cell line. Furthermore, we used the novel imaging technique partial wave spectroscopy (PWS) to quantify nanoscale alterations in chromatin. We noted that the PWS results are consistent with the biological assays, indicating a greater effect of VPA treatment in the more aggressive cell type. Together, these results demonstrate the importance of HDAC activity in early carcinogenic events and the unique role of higher-order chromatin structure in determining cell tumorigenicity.

Synergistic cytotoxic effect of sulindac and pyrrolidine dithiocarbamate against ovarian cancer cells

Sulindac, a non-steroidal anti-inflammatory drug, suppresses carcinogenesis and inhibits growth of tumor cells. Pyrrolidine dithiocarbamate (PDTC), a potent NF-κB inhibitor, has been also identified as a potential anti-neoplastic agent. We hypothesized that combination of sulindac and PDTC could result in augmentation of cytotoxicity against ovarian cancer cells. The effect of sulindac and PDTC was examined on several ovarian cancer lines. Tumor cell viability was assessed using the MTT assay. Annexin-V/PI staining was used to detect apoptosis, cell cycle distribution was analyzed in FACS, and expression of cellular proteins was detected by Western blotting. Incubation of OVA-14, OVP-10 and CAOV-1 ovarian cancer cells with sulindac and PDTC resulted in significantly greater inhibition of cell viability compared to either compound alone. In a model of OVA-14 cells it was evident that this effect was not related to the expression of COX enzymes since both active (sulindac sulfide) and inactive (sulindac) in vitro compounds affected the growth of tumor cells to a similar extent and synergized in cytotoxicity with PDTC. Combination of sulindac and PDTC lead to G0 arrest and massive apoptosis in co-treated cultures. Western blotting analysis argued for induction of the mitochondrial apoptotic pathway. These data demonstrate the synergistic cytotoxic effect of sulindac and PDTC on ovarian cancer cells through apoptosis and cell cycle arrest and prompt to test the efficacy of this combination in animal models.

Intervening in β-catenin signaling by sulindac inhibits S100A4-dependent colon cancer metastasis

Colon cancer metastasis is often associated with activation of the Wnt/β-catenin signaling pathway and high expression of the metastasis mediator S100A4. We previously demonstrated the transcriptional regulation of S100A4 by β-catenin and the importance of the interconnection of these cellular programs for metastasis. Here we probe the hypothesis that the nonsteroidal anti-inflammatory drug sulindac sulfide can inhibit colon cancer metastasis by intervening in β-catenin signaling and thereby interdicting S100A4. We treated colon cancer cell lines heterozygous for gain-of-function and wild-type β-catenin with sulindac. We analyzed sulindac's effects on β-catenin expression and subcellular localization, β-catenin binding to the T-cell factor (TCF)/S100A4 promoter complex, S100A4 promoter activity, S100A4 expression, cell motility, and proliferation. Mice intrasplenically transplanted with S100A4-overexpressing colon cancer cells were treated with sulindac. Tumor growth and metastasis, and their β-catenin and S100A4 expressions, were determined. We report the expression knockdown of β-catenin by sulindac, leading to its reduced nuclear accumulation. The binding of β-catenin to TCF was clearly lowered, resulting in reduced S100A4 promoter activity and expression. This correlated well with the inhibition of cell migration and invasion, which could be rescued by ectopic S100A4 expression. In mice, sulindac treatment resulted in reduced tumor growth in the spleen (P = .014) and decreased liver metastasis in a human colon cancer xenograft model (P = .025). Splenic tumors and liver metastases of sulindac-treated mice showed lowered β-catenin and S100A4 levels. These results suggest that modulators of β-catenin signaling such as sulindac offer potential as antimetastatic agents by interdicting S100A4 expression.

Interruption of mitochondrial complex IV activity and cytochrome c expression activated O₂·⁻-mediated cell survival in silibinin-treated human melanoma A375-S2 cells via IGF-1R-PI3K-Akt and IGF-1R-PLC γ-PKC pathways

Silibinin was reported to have high cyto-toxicity in many malignant cell lines, however, it showed low cyto-toxicity in treatment of human melanoma A375-S2 cells and even protected these cells against certain stress insults. Reactive oxygen species was reported to have controversial effects on cancer chemotherapy. In this study we investigated the mechanism of reactive oxygen species generation and the role of reactive oxygen species in protecting cells against silibinin induced cyto-toxicity in A375-S2 cells. We found that silibinin induced the generation of large amount of superoxide anion (O(2)(∙-)) and small amount of hydrogen peroxide (H(2)O(2)) through down-regulating the activity of mitochondrial complex IV and the protein level of cytochrome c. We also discovered that O(2)(∙-) generation activated insulin like growth factor-1 receptor (IGF-1R) and its down-stream phosphatidylinositol 3-kinases-Akt (PI3K-Akt) and phospholipase C γ-protein kinase C (PLC γ-PKC) signaling pathways, which were augmented by H(2)O(2) scavenger catalase. Scavenging O(2)(∙-) by superoxide dismutase (SOD) or inhibition of IGF-1R-PI3K-Akt and IGF-1R-PLC γ-PKC signaling pathways increased cell apoptosis. Therefore, O(2)(∙-) mediated cell resistance to silibinin via activating IGF-1R-PI3K-Akt and IGF-1R-PLC γ-PKC pathways in silibinin treated A375-S2 cells.

c-Src dependency of NSAID-induced effects on NF-κB-mediated apoptosis in colorectal cancer cells

Long-term aspirin or related non-steroidal anti-inflammatory drugs (NSAIDs) ingestion can protect against colorectal cancer (CRC). NSAIDs have a pro-apoptotic activity and we have shown that stimulation of the nuclear factor-kappaB (NF-κB) pathway is a key component of this pro-apoptotic effect. However, the upstream pathways have yet to be fully elucidated. Here, we demonstrate that aspirin activates the c-Src tyrosine kinase pathway in CRC cells. We show that c-Src activation occurs in a time- and dose-dependent manner, preceding aspirin-mediated degradation of IκBα, nuclear/nucleolar translocation of NF-κB/RelA and induction of apoptosis. Furthermore, inhibition of c-Src activity, by chemical inhibition or expression of a kinase dead form of the protein abrogates aspirin-mediated degradation of IκBα, nuclear translocation of RelA and apoptosis, suggesting a causal link. Expression of constitutively active c-Src mimics aspirin-induced stimulation of the NF-κB pathway. The NSAIDs sulindac, sulindac sulphone and indomethacin all similarly activate a c-Src-dependent NF-κB and apoptotic response. These data provide compelling evidence that c-Src is an upstream mediator of aspirin/NSAID effects on NF-κB signalling and apoptosis in CRC cells and have relevance to the development of future chemotherapeutic/chemopreventative agents.

Neo-angiogenesis and the premalignant micro-circulatory augmentation of early colon carcinogenesis

Spectroscopic techniques have demonstrated that in the microscopically normal mucosa, there is an increase in mucosal micro-circulation in patients harboring neoplasia elsewhere in the colon (i.e. marker of field carcinogenesis). However, the physiological and molecular basis of this early increase in blood supply (EIBS) has not been elucidated. We, therefore, investigated the microvessel density (MVD) and angiogenic gene expression in the premalignant colonic mucosa from the well-validated azoxymethane (AOM)-treated rat experimental model of colon carcinogenesis. Fisher 344 rats were treated with AOM (15 mg/kg i.p.) or saline and euthanized 14 weeks later (a time-point that precedes carcinoma development). Colon sections were studied for MVD via immunohistochemical assessment for CD31 and location was compared with optical assessment of mucosal hemoglobin with low-coherence enhanced backscattering spectroscopy (LEBS). Finally, we performed a pilot real-time PCR angiogenesis microarray (84 genes) from the microscopically normal colonic mucosa of AOM and age-matched saline treated rats. AOM treatment increased MVD in both the mucosa and submucosa of the rats (125% increase in mucosa; p<0.007, and 96% increase in submucosa; p<0.02) but the increase was most pronounced at the cryptal base consistent with the LEBS data showing maximal hemoglobin augmentation at 200-225 μm depth. Microarray analysis showed striking dysregulation of angiogenic and anti-angiogenic factors. We demonstrate, for the first time, that neo-angiogenesis occurs in the microscopically normal colonic mucosa and was accentuated at the bottom of the crypt. This finding has potential implications as a biomarker for risk-stratification and target for chemoprevention.