A novel platform for attenuating immune hyperactivity using EXO-CD24 in Covid-19 and beyond

A small but significant proportion of Covid19 patients develop life-threatening cytokine storm. We have developed a new anti-inflammatory drug, EXO-CD24, a combination of an immune checkpoint (CD24) and a delivery platform (exosomes). CD24 inhibits the NF-kB pathway and the production of cytokines/chemokines. EXO-CD24 discriminates Damage- from Pathogen-Associated Molecular Patterns (DAMPs and PAMPs) therefore does not interfere with viral clearance. EXO-CD24 was produced and purified from CD24-expressing 293-TREx™ cells. Exosomes displaying murine CD24 (mCD24) were also created. EXO-CD24/mCD24 were characterized and examined, for safety and efficacy, in vitro and in vivo. In a phase Ib/IIa study, 35 patients with moderate-high severity COVID-19 were recruited and given escalating doses, 10⁸ -10¹⁰ , of EXO-CD24 by inhalation, QD, for five days. No adverse events related to the drug were observed up to 443-575 days. EXO-CD24 effectively reduced inflammatory markers and cytokine/chemokine, though randomized studies are required. EXO CD24 may be a treatment strategy to suppress the hyper-inflammatory response in the lungs of Covid-19 patients and further serve as a therapeutic platform for other pulmonary and systemic diseases characterized by cytokine storm.

Feasibly of CD24/CD11b as a Screening Test for Hematological Malignancies

An estimated 1.24 million blood cancer cases occur annually worldwide, accounting for approximately 6% of all cancer cases. Currently, there are no standardized hematology cancer screening tests that are recommended for the general population. CD24 is a mucin-like cell surface molecule and P-selectin ligand, which plays a significant role in the maturation of B-lymphocytes and was found to be overexpressed in a number of hematological malignancies. Our primary aim was to assess the sensitivity and specificity of the CD24/CD11b-based blood test for the detection of hematological malignancies. Our cohort included 488 subjects with positive hematological cancer diagnosis (n = 122) and healthy subjects (n = 366). CD24/CD11b expression in peripheral blood leukocytes (PBLs) obtained from blood samples of participants was analyzed by flow cytometry. Our results demonstrated that the average levels of CD24/CD11b in healthy patients (21.7 ± 9.0) were statistically significantly lower compared to levels of CD24/CD11b in cancer patients (29.5 ± 18.7, p < 0.001). The highest levels of CD24/CD11b were found in multiple myeloma (39.1 ± 23.6), followed by chronic myeloid leukemia (33.0 ± 13.7) and non-Hodgkin lymphoma (32.3 ± 13.3). The test had an overall sensitivity for hematologic cancers of 78.5% (95% CI, 70.7-86.3%) and specificity of 80.2% (95% CI, 76.1-84.3%). In conclusion, our findings indicate the feasibility of a CD24/CD11b-based blood test as a screening test of hematological malignancies.

Innovative dual system approach for selective eradication of cancer cells using viral-based delivery of natural bacterial toxin-antitoxin system

The inactivation of p53, a tumor suppressor, and the activation of the RAS oncogene are the most frequent genetic alterations in cancer. We have shown that a unique E. coli MazF-MazE toxin–antitoxin (TA) system can be used for selective and effective eradication of RAS-mutated cancer cells. This out of the box strategy holds great promise for effective cancer treatment and management. We provide proof of concept for a novel platform to selectively eradicate cancer cells using an adenoviral delivery system based on the adjusted natural bacterial system. We generated adenoviral vectors carrying the mazF toxin (pAdEasy-Py4-SV40mP-mCherry-MazF) and the antitoxin mazE (pAdEasy-RGC-SV40mP-MazE-IRES-GFP) under the regulation of RAS and p53, resp. The control vector carries the toxin without the RAS-responsive element (pAdEasy-ΔPy4-SV40mP-mCherry-MazF). In vitro, the mazF-mazE TA system (Py4-SV40mP-mCherry-MazF+RGC-SV40mP-MazE-IRES-GFP) induced massive, dose-dependent cell death, at 69% compared to 19% for the control vector, in a co-infected HCT116 cell line. In vivo, the system caused significant tumor growth inhibition of HCT116 (KRAS^mut/p53^mut) tumors at 73 and 65% compared to PBS and ΔPY4 control groups, resp. In addition, we demonstrate 65% tumor growth inhibition in HCT116 (KRAS^mut/p53^wt) cells, compared to the other two control groups, indicating a contribution of the antitoxin in blocking system leakage in WT RAS cells. These data provide evidence of the feasibility of using mutations in the p53 and RAS pathway to efficiently kill cancer cells. The platform, through its combination of the antitoxin (mazE) with the toxin (mazF), provides effective protection of normal cells from basal low activity or leakage of mazF.

Integrase-derived peptides together with CD24-targeted lentiviral particles inhibit the growth of CD24 expressing cancer cells

The integration of viral DNA into the host genome is mediated by viral integrase, resulting in the accumulation of double-strand breaks. Integrase-derived peptides (INS and INR) increase the number of integration events, leading to escalated genomic instability that induces apoptosis. CD24 is a surface protein expressed mostly in cancer cells and is very rarely found in normal cells. Here, we propose a novel targeted cancer therapeutic platform based on the lentiviral integrase, stimulated by integrase-derived peptides, that are specifically delivered to cancerous cells via CD24 antigen-antibody targeting. INS and INR were synthesized and humanized and anti-CD24 antibodies were fused to the lentivirus envelope. The activity, permeability, stability, solubility, and toxicity of these components were analyzed. Cell death was measured by fluorescent microscopy and enzymatic assays and potency were tested in vitro and in vivo. Lentivirus particles, containing non-functional DNA led to massive cell death (40–70%). Raltegravir, an antiretroviral drug, inhibited the induction of apoptosis. In vivo, single and repeated administrations of INS/INR were well tolerated without any adverse effects. Tumor development in nude mice was significantly inhibited (by 50%) as compared to the vehicle arm. In summary, a novel and generic therapeutic platform for selective cancer cell eradication with excellent efficacy and safety are presented.

High Expression Level of PPARγ in CD24 Knockout Mice and Gender-Specific Metabolic Changes: A Model of Insulin-Sensitive Obesity

Background: The heat-stable HSA/CD24 gene encodes a protein that shows high expression levels in adipocyte precursor cells but low levels in terminally differentiated adipocytes. Its high expression in many types of human cancer suggests an association between cancer, diabetes, and obesity, which is currently unclear. In addition, peroxisome proliferator-activated receptor gamma (PPARγ) is a regulator of adipogenesis that plays a role in insulin sensitivity, lipid metabolism, and adipokine expression in adipocytes. Aim: To assess gender-dependent changes in CD24 KO and its association with PPARγ expression. Experimental approach: WT and CD24 KO mice were monitored from birth up to 12 months, and various physiological and molecular characteristics were analysed. Mean body weight and adipose mass were higher in KO mice than in WT mice. Male, but not female, KO mice showed increased insulin sensitivity, glucose uptake, adipocyte size, and PPARγ expression than WT mice. In addition, enteric bacterial populations, assessed through high-throughput sequencing of stool 16S rRNA genes, were significantly different between male KO and WT mice. Conclusions: CD24 may negatively regulate PPARγ expression in male mice. Furthermore, the association between the CD24 and insulin sensitivity suggests a possible mechanism for diabetes as a cancer risk factor. Finally, CD24 KO male mice may serve as a model of obesity and insulin hyper-sensitivity.

The dark age of single organ screening is over: CD24 is a novel universal simple blood test for early detection of cancer

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Background: More than 1.8 million new cancer cases are expected to be diagnosed in 2020. Only in the U.S, about 606,520 Americans are expected to die this year, which translates to about 1,660 deaths per day. However, when found early, in the asymptomatic phase, cancer is often effectively treated or even cured. The few cancer screens available today, including mammograms and colonoscopies, each look for a single type of cancer. CD24 is hardly expressed in normal cells (but to B-lymphocytes, differentiating neuroblasts and neutrophils) but is overexpressed in numerous human cancers. Aim: To establish a universal cancer screening blood test. Methods: Blood samples were obtained from consecutive patients and healthy volunteers. 1x106 leukocytes were stained using anti-CD11b-PerCp-Cy5.5 and anti-CD24-FITC and analyzed by flow cytometry (CyFlow Cube 6, Sysmex, Germany). Percentage of positive cells was determined by subtracting the percentage of CD24 and CD11b-positive cells (dual stain) from CD24-positive cells (single stain). The cut off for cancer detection was 25. Healthy subjects underwent a thorough evaluation at the health promotion center and integrated cancer prevention center. All cancers were verified histologically. Results: CD24/CD11b expression in the healthy population was evaluated in 337 women and 408 men, ages 20-85. There were 222 cancer patients. After excluding thyroid and bladder cancers, the assay detected 146 out of 196 (75%) cancers at all stages and even in 31 out of colonic adenomas (table). The levels of CD24 drop back to near normal level following successful surgery/chemotherapy. The test score was not affected by age, gender, fasting and the time of the day that the blood sample is taken. In 55 cases the test was performed twice, with similar results, as well as when the test was performed in another flow cytometry, after 1d, 1w, 1m after freezing . Conclusions: 1. CD24 is a universal cancer screening. 2. It can detect pre malignant lesions like adenomas in the colon. 3. Preliminary results suggest that it can serve as a predictive marker. [Table: see text]

Innovative dual system for selective eradication of cancer cells using exosomes carrying natural bacterial toxin-antitoxin (TA)

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Background: Inactivation of P53 and activation of ras are frequent genetic alterations in cancer. We have shown in vitro and in vivo, that the TA system can selectively and effectively eradicate RAS-mutated cancer cells. Aim: Selective killing of cancer cells while sparing the normal cells based on tumor genetic signature. Methods: A “first generation” ΔE1/ΔE3 human type-5 adenoviral-vectors for gene delivery were designed and constructed to specifically target cancer cells. They are designated as "PY4-mazF-mCherry" (PY4, ras responsive element), "ΔPY4-mazF-mCherry" (control viruses) and "RGC-mazE-IRES-GFP" (RGC, P53 responsive element). Their potency was tested in vitro, by the enzymatic MTT assay, microscopic observation, colony formation assay and FACS analysis, and in a xenograft model of CRC. Next, we generated, small natural vesicles, exosomes, that directly targeted cancer through specific small antibody fragments against CD24 that is expressed in most cancer cells and rarely on normal cells. Results: The TA system ("PY4-mazF-mCherry"+"RGC-mazE-IRES-GFP") induced a massive cell death, in a dose-dependent manner in vitro, 69% as compared to 19% in control co-infected ("ΔPY4-mazF-mCherry"+"RGC-mazE-IRES-GFP") HCT116 CRC cells (mutated RAS and p53). In vivo, growth of HCT116-/- ( KRASmutand P53mut) and HCT116+/+ ( KRASmut and P53wt) tumors were significantly inhibited (70% and 65%, respectively). Conclusions: 1. Abusing the P53 genetic status and the activated Ras pathway holds promising effective and safe strategy to target tumor cells while sparing normal tissues. 2. It is a proof of concept for personalized cancer therapy based on the tumor genetic profile.

The chick embryo chorioallantoic membrane assay: In ovo model for personalized assessment and evaluation of the most effective therapeutic approach in cancer therapy

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Background: "Personalized medicine,” is the tailoring of medical treatment to a single person aiming to maximize efficacy and minimize toxicity. Currently there is no good prediction for response to therapy. The Chick Chorioallantoic Membrane (CAM) is naturally immuno-deficient and rich in vascularity therefore an ideal system, allowing generate 3D cancerous “organoids” in a very efficient, reproducible and cost-effective manner and translates basic research to the clinic. Aims: Generate a “personalized” HTP system for a quick, reliable and effective evaluation of different therapeutic options using 3D tumors in a "humanized egg" instead of mouse PDX model. Methods: Fertilized eggs were incubated until day 3 (37°C, 75-90% humidity). Then, 2ml of albumin was pulled out to separate the CAM from the eggshell and a small window in the eggshell has been made. To destroy the chicken immune system development, the eggs were irradiated at day 5 and human immune cells were then inoculated onto the CAM. On day 7, single cells suspension or tissues, derived from cancer patients, were transplanted onto the CAM and visible tumors were performed ("CAM-PDX"). Drugs, mAbs and chemotherapy, were applied via the yolk sac. Tumor growth was measured, weighted and monitored by caliper and IVIS fluorescent imaging platform. IHC was performed and confirmed the response of the particular specimens to the tested regiment. Results: Histology and IHC analysis confirmed that the established tumors retained their characteristics. Positive Ki-67 staining confirmed that cancer cells proliferate while the treated tumors showed reduced staining. Anti-CD24 mAb, FOLFOX, cetuximab, Foflorinox and Gemcitabine, given as single agent or combinations, successfully inhibited CR and pancreatic tumors (by 70-75%). Detection of active caspase 3 confirmed those results. Biopsies from human specimens, were successfully established and expanded by serial passages allows generation of bio-bank. The stimulated human PBMCs demonstrated enhanced proliferation in vitro and in ovo, even after 5 days in the egg. Irradiated eggs showed no functional immune system even after 2 weeks of development. Conclusions: The CAM is an ideal, effective, economical and powerful avatar-based precision medicine approach to predict the best protocol for cancer therapy.

Of mice and men: a novel dietary supplement for the treatment of ulcerative colitis

BACKGROUND

Curcumin, green tea polyphenols and selenium possess anti-inflammatory and anti-oxidant properties. Individually they have demonstrated some efficacy in animal models and human subjects with inflammatory bowel disease (IBD). To evaluate the efficacy and safety of Coltect [Curcumin (500 mg), green tea (250 mg) and selenium (100 µg)] in vivo and in patients with ulcerative colitis (UC).

METHODS

Each component was compared to placebo in a DSS mice colitis model. The efficacy was validated in a 2,4,6-trinitrobenzenesulfonic acid (TNBS) rat colitis model. Twenty patients with mild-to-moderate UC received two Coltect tablets twice daily for 8 weeks. Enrollees underwent sigmoidoscopy at study entrance and closure, and physical and laboratory evaluation at baseline, 4 and 8 weeks.

RESULTS

Coltect showed a synergistic therapeutic effect in the DSS and TNBS models. Disease activity was significantly higher in the placebo versus the treated group (p < 0.05). Selenium was the more active component. The contribution of green tea was minor. In the TNBS model, the Wallace scores for macroscopic lesions were 4.8 ± 1.5 (treatment) and 8.2 ± 0.5 (placebo) (p = 0.01). In humans, Coltect was well tolerated and effective. Fourteen subjects (70%) improved: nine (45%) went into complete remission, four (20%) experienced marked improvement and one (5%) experienced moderate improvement at the end of the trial. Clinical activity index decreased significantly at 4 and 8 weeks (p < 0.001). Two patients had no change in their symptoms, and one withdrew after 4 weeks. Flare-up in four subjects caused three to withdraw from the study after less than 4 weeks. Endoscopic improvement was observed in 11 (69%) patients, and four patients (25%) achieved complete remission.

CONCLUSIONS

Coltect may serve as a first-line or add-on therapy in patients with mild-to-moderate UC.

Abstract 3854: Successful selective eradication of colorectal cancer cells by adenovirus-based delivery of toxins

Background: K-Ras gene mutation is an early event in the development of colorectal cancer (CRC) and occurs in ∼50% of CRC cases. We propose a strategy that exploits the Ras hyperactive pathway, rather than inhibiting it as was tried and failed many times. We have previously reported that recombinant adenovirus, carrying a pro-apoptotic gene under the regulation of Ras-responsive elements (Ets/AP1), suppressed the growth of cancer cells displaying hyperactive K-Ras (Biomed Pharm, 2005,Cancer Gene Ther,2012, Exp Cell Res,2012). TA systems are evolutionarily successful entities that are prevalent in lower organisms and play important roles in a diverse range of cellular activities.

im: To establish a tight control and improved ras responsive element based on the bacterial MazEF system

Methods: Efficient vectors for cancer-directed gene delivery were constructed and cloned into a “first generation” ΔE1/ΔE3 human type-5 adenoviral-vector. Virus particles were produced, their titer was calculated by the End-Point Dilution Assay (EPDA) and their potency was tested. Cell death was measured qualitatively by using the fluorescent microscopy and colony formation assay, and was quantified by MTT. FACS analysis using annexin V and RedDot2 dyes was performed for measuring apoptosis and dead cells, respectively. In vivo tumor formation was measured in xenograft model. Ad-Py4-SV40-MazEF and Ad-ΔPY4-CMV-MazEF viruses (1×109pfu) or PBS were administrated intraperitoneal twice with a 3-day interval between injections.

Results: Adenovirus therapy induced massive cell death, in a dose-dependent manner; 73% with a titer of 10 MOI in cells with activated K-Ras as compared to 22% in tumor cells having the WT K-Ras. The cytotoxic effect was confirmed qualitatively by colony formation assay. In the absence of K-ras-responsive DNA element increase expression of MazE, the anti-toxin, protected normal cells from any possible internal or external leakage of the system and confirmed the selectivity, specificity and safety of the targeting system. FACS analysis confirmed massive cell death, 55% apoptosis and 82% dead cells, following infection with the full toxin-antitoxin encoding viruses.

Control viruses lacking the K-ras responsive element a modest toxicity was seen (18% and 10%, respectively). Impressive tumor shrinkage was demonstrated in vivo following treatment with Ad-Py4-SV40-MazEF-encoding adenovirus (61%) without any toxic or side effects. Ad-ΔPY4-SV40-MazEF treated mice (control group) tumor volume was reduced only by 27% (P&lt;0.05). No growth inhibition was seen following injection of PBS.

Conclusions: A proof-of-concept for a novel cancer gene therapy by exploiting aberrant K-Ras hyperactive pathway was successfully demonstrated. The lack of toxicity holds promise for effective and safe therapy of human cancers carrying K-Ras mutations.

Citation Format: Shiran Shapira, Assaf Shapira, Dina Kazanov, Ilana Nabiochtchikov, Sarah R. Kraus, Nadir Arber. Successful selective eradication of colorectal cancer cells by adenovirus-based delivery of toxins. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3854.

Abstract 3805: A novel anti-CD24 monoclonal antibody, humanized and affinity maturated for targeting gastrointestinal cancers

Background: CD24 is a cell-surface heavily glycosylated GPI-anchored protein. We had previously shown that CD24 in an important player in the multistep process of GI carcinogenesis (Gastro 2006, Clin Can Res 2007, Can Res 2008). The creation of chimeric, humanized or fully human antibodies was a major breakthrough and led to a wave of US FDA-approved antibodies.

Aim: To further improve the efficacy of the humanized anti-CD24 mAb by increasing its binding strength and thereby generating a novel therapy tool for GI malignancy

Methods: From murine to humanized, unarmed and conjugated, small derivatives and full IgG antibodies were recombinantly engineered. The antibody genes were recovered, amplified and cloned into appropriate vectors. Then the vectors were introduced into a host (mammalian and E.coli) and adequate amounts of functional antibody were achieved. Sequence analysis of the CDR loops was the base for library designing. Affinity maturation was performed in two-steps selection (CDR walking) and by using phage display technique. The binding of the different derivatives were evaluated on full Glycan array in which more than 70 sugar moieties were printed.

Results: In vivo antibody targeting and accumulation within a CD24 positive tumor and its excess clearance was clearly demonstrated using live imaging device (Maestro Cri device). High-affinity antibodies were selected and created from combinatorial phage-displayed antibody libraries that contain varying degrees of diversity at randomized positions. A chosen matured clone was isolated and showed higher binding strength (1.8×10-8), compared to the parental murine and humanized Abs. The matured antibody showed selective recognition and binding to the CD24 antigen which proves that the genetic manipulations carried out did not affect its properties. Its stability was enhanced following the maturation process,as well as its pharmacokinetics parameters which showed a long serum half-life.The matured antibody mediates ADCC (antibody-dependent cell cytotoxicity), 75% of target cell lysis was demonstrated. Combined treatment with standard chemotherapy and natural products, such as monoterpenes (terpinen-4-ol), showed significant reduction in cell viability (90% cell death). Binding of anti-CD24 Ab to glycan microarray could not be detected while high binding intensities were observed where the whole CD24 protein was printed, indicating that the antibodies bind to the core peptide and not to its sugar residues.

Conclusion: Targeting CD24 may be a promising treatment for GI malignancies in combination with chemotherapy and natural agents. The resulted matured humanized anti-CD24 mAb proved to be more effective than the murine parental Ab. The long serum half-life is desirable as it would decrease the need for repetitive injections.

Citation Format: Shiran Shapira, Dina Kazanov, Vered Padler Karavani, Itai Benhar, Nadir Arber. A novel anti-CD24 monoclonal antibody, humanized and affinity maturated for targeting gastrointestinal cancers. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3805.

Delayed Wound Healing in Heat Stable Antigen (HSA/CD24)-Deficient Mice

Background

Healthy individuals rarely have problems with wound healing. Most skin lesions heal rapidly and efficiently within one to two weeks. However, many medical and surgical complications can be attributed to deficiencies in wound repair. Open wounds have lost the barrier that protects tissues from bacterial invasion and allows the escape of vital fluids. Without expeditious healing, infections become more frequent. The CD24 gene encodes a heavily-glycosylated cell surface protein anchored to the membrane by phosphatidylinositol. CD24 plays an important role in the adaptive immune response and controls an important genetic checkpoint for homeostasis and autoimmune diseases in both mice and humans. We have previously shown that overexpression of CD24 results in increased proliferation and migration rates.

Aim

To examine the role of CD24 in the wound healing process.

Methods

An excisional model of wound healing was used and delayed wound healing was studied in genetically modified heat stable antigen (HSA/CD24)-deficient mice (HSA^-/-) compared to wild-type (WT) mice.

Results

Large full-thickness skin wounds, excised on the back of mice, exhibited a significant delay in the formation of granulation tissue, and in wound closure when compared to their WTHSA^+/+ littermates. Wounds were histologically analyzed and scored, based on the degree of cellular invasion, granulation tissue formation, vascularity, and re-epithelialization. Additionally, in stitched wounds, the HSA^-/- mice failed to maintain their stitches; they did not hold and fell already 24 hours, revealing erythematous wound fields. Re-expression of HSA, delivered by lentivirus, restored the normal healing phenotype, within 24 hours post-injury, and even improved the healing in WT, and in BalbC mice.

Conclusions

Delayed wound-healing in the absence of HSA/CD24 suggests that CD24 plays an important role in this process. Increased expression of CD24, even in the normal state, may be used to enhance wound repair.

Abstract 3532: Selective eradication of colorectal cancer cells by adenovirus-based delivery of toxins

Background: K-Ras gene mutation is an early event in the development of colorectal cancer (CRC) and occurs in ∼50% of CRC cases. We propose a strategy that exploits the Ras hyperactive pathway, rather than inhibiting it. We have previously shown that recombinant adenovirus, carrying a pro-apoptotic gene under the regulation of Ras-responsive elements (RREs; Ets/AP1), suppressed the growth of tumor cells displaying hyperactive K-Ras (Naumov, 2012; Lisiansky, 2012). Toxin-antitoxin (TA) systems are evolutionarily successful entities, prevalent in lower organisms that play important roles in a diverse range of cellular activities

Aim: To establish an improved tightly regulated RRE-cassette based on the bacterial MazEF TA system.

Methods: Efficient vectors for targeted gene delivery were constructed and cloned into a “1st generation” ΔE1/ΔE3 human type-5 adenoviral vector. Virus particles were produced their titer was calculated, by the end-point dilution assay, and tested for their potency. Cell death was measured qualitatively by fluorescent microscopy and colony formation assay, and quantified by MTT. Apoptosis was determined by FACS using annexin V and RedDot2 dyes. In vivo tumor formation was examined in xenografts. Ad-Py4-SV40-MazEF and Ad-ΔPY4-CMV-MazEF viruses (1×109pfu) or PBS were administrated i.p. twice with a 3-day interval between injections.

Results: Adenovirus treatment induced massive cell death, in a dose-dependent manner; 73% in K-Ras-mutated compared to 22% in WT K-Ras tumor cells, at 10 MOI. The cytotoxic effect was confirmed qualitatively by colony formation assay. In the absence of RRE, MazE anti-toxin expression was increased, protecting normal cells from any possible system leakage and confirming the selectivity, specificity, and safety of the targeting system. FACS analysis showed massive cell death, 55% apoptosis and 82% dead cells, following infection with the full TA-encoding viruses. In control RRE-lacking viruses a modest toxicity was seen (18% and 10%, respectively). Impressive tumor shrinkage was demonstrated in vivo following treatment with Ad-Py4-SV40-MazEF-encoding adenovirus (61%) without any toxic side effects. The tumor volume in the Ad-ΔPY4-SV40-MazEF-treated mice (control group) was reduced only by 27% (p&lt;0.05). No growth inhibition was seen following injection of PBS.

Conclusions: A proof-of-concept for a novel cancer gene therapy by exploiting aberrant K-Ras hyperactive pathway was successfully demonstrated. The lack of toxicity holds promise for effective and safe therapy of human cancers carrying K-Ras mutations.

Note: This abstract was not presented at the meeting.

Citation Format: Shiran Shapira, Assaf Shapira, Dina Kazanov, Ilana Nabiochtchikov, Nadir Arber, Sarah R. Kraus. Selective eradication of colorectal cancer cells by adenovirus-based delivery of toxins. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3532. doi:10.1158/1538-7445.AM2015-3532

Abstract 3645: CD24 polymorphisms and susceptibility to inflammatory bowel disease and colorectal cancer risk

Background: Inflammatory bowel diseases (IBD), including ulcerative colitis (UC) and Crohn's disease (CD), are chronic inflammatory disorders of the gastrointestinal tract probably resulting from an aberrant immune response to luminal microbial antigens in a genetically predisposed host. Despite significant progress in the understanding and treatment of IBD, patients have an increased risk of colorectal cancer. We have previously shown that CD24 plays an important role in the multistep process of colorectal carcinogenesis and that it may be a target for chemoprevention and antitumor therapy (Sagiv, Gastroenterol, 2006; Sagiv, Can Res, 2008; Shapira, Gastroenterol 2011). However, the role of CD24 in mediating colitis has not been elucidated. Recently, single nucleotide polymorphisms (SNPs) in the CD24 gene have been associated with disease risk and progression in autoimmune diseases and may impact breast cancer prognosis.

Aim: Evaluate whether CD24 SNPs are associated with a risk for IBD.

Methods: The CD24 polymorphisms: C170T (rs8734), TG1527del (rs3838646), A1626G (rs1058881) and A1056G (rs1058818) were assessed in a case-control study of an Israeli cohort comprising 138 IBD patients and 105 age- and gender-matched healthy controls. Restriction fragment length polymorphism (RFLP) analysis was performed using BstX1, Bsr1, Mfe1, and BstU1 restriction enzymes, respectively. Odds ratio (OR) and 95% confidence interval (CI) were estimated by logistic regression models.

Results: C170T carriers had more IBD (OR=3.022, 95% CI: 1.748-5.223, p=0.001): UC (OR=3.002, 95% CI: 1.661-5.427, p=0.001) and CD (OR=3.077, 95% CI: 1.334-7.095 p=0.008). Carrying the A1626G and A1056G SNPs was a risk factor for IBD: OR=2.460, 95% CI: 1.420-4.259, p=0.001 and OR=1.856, 95%: 1.011-3.405, p=0.01, respectively, specifically UC: OR=2.218, 95% CI: 1.207-4.075, p=0.01 and OR=1.944, 95% CI: 0.995-3.798, p=0.01, respectively, but not for CD (p=0.086, p=0.299). A1626G and TG1527del were associated with a younger age of IBD onset (p=0.022, p=0.027, respectively).

Conclusions:

1. The CD24 C170T polymorphism is associated with IBD risk.

2. CD24 A1626G and A1056G SNPs might be specifically associated with UC risk.

3. CD24 SNPs associated with an earlier onset of IBD (A1626G and TG1527del) may have a protective role.

4. CD24 may be a new IBD genetic susceptibility factor, with clinical implications in the prediction of IBD phenotype, the course of the disease, and colitis-associated cancer.

Citation Format: Victoria Lisiansky, Sarah R. Kraus, Inna Naumov, Dina Kazanov, Ilana Nabiochtchikov, Ohad Toledano, Moshe Leshno, Doran Avivi, Menachem Moshkowitz, Iris Dotan, Nadir Arber. CD24 polymorphisms and susceptibility to inflammatory bowel disease and colorectal cancer risk. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3645. doi:10.1158/1538-7445.AM2014-3645

Aspirin but not meloxicam attenuates early atherosclerosis in apolipoprotein E knockout mice

BACKGROUND

Atherosclerosis is a complex vascular inflammatory disease. In the last decade it was suggested that nonsteroidal anti-inflammatory drugs (NSAIDs) and in particular inhibition of cyclooxygenase (COX)-2 are associated with an increase in cardiovascular morbidity and mortality. Aspirin is known to reduce the incidence and mortality from ischemic heart disease and is a mainstay in the prevention of vascular complications of atherosclerosis.

OBJECTIVES

To examine the effect of meloxicam, a selective COX-2 inhibitor, or low dose aspirin on the development of experimental atherosclerosis in apoE knockout (KO) compared to wild-type (WT) mice. We aimed to test the hypothesis that meloxicam, a potential vasculitis inducer, would exacerbate atherosclerotic lesions while aspirin, which is known to reduce the incidence of thrombosis occlusive events, would increase protection in this model.

METHODS

We randomly divided 36 male apoE KO and 36 WT mice, 8 weeks old. Mice were treated for 10 weeks with 0.1 mg/ml aspirin, or 0.05 mg/ml meloxicam, dissolved in their drinking water. Control groups received regular drinking water. At sacrifice, the hearts were removed for histochemical staining and plaque size and composition were examined.

RESULTS

Aspirin-treated animals displayed a decreased atherosclerotic lesion area compared to the untreated control mice, while meloxicam had a null effect on the extent of atherosclerosis in Apo E KO mice.

CONCLUSIONS

These results suggest that low dose aspirin reduces early atherosclerosis, while inhibition of COX-2 by meloxicam is not associated with an increase in atherosclerotic plaque size in this mouse model.

CD24 knockout prevents colorectal cancer in chemically induced colon carcinogenesis and in APC(Min)/CD24 double knockout transgenic mice

Increased expression of CD24 is seen in a large variety of solid tumors, including up to 90% of gastrointestinal (GI) tumors. Stable derivatives of SW480 colorectal cancer (CRC) cells that overexpress CD24 proliferate faster, and increase cell motility, saturation density, plating efficiency, and growth in soft agar. They also produce larger tumors in nude mice as compared to the parental SW480 cells. Most significantly, even depletion of one copy of the CD24 allele in the APC(Min/+) mice of a transgenic mouse model led to a dramatic reduction in tumor burden in all sections of the small intestine. Homozygous deletion of both CD24 alleles resulted in complete abolishment of tumor formation. Moreover, CD24 knockout mice exhibited resistance to chemically induced inflammation-associated CRC. Finally, a new signal transduction pathway is suggested: namely, CD24 expression downstream to COX2 and PGE2 synthesis, which is directly regulated by β-catenin. CD24 is shown in vitro and in vivo as being an important oncogene in the gut, and one that plays a critical role in the initiation and progression of carcinogenesis.

Abstract 3303: Selective eradication of cancer cells by adenovirus-based delivery of cytotoxic agents: an alternative method for targeting pancreatic cancer

Background: Most cases of pancreatic cancer (PC) are diagnosed at the metastatic stage and current therapies are inefficient. K-Ras mutations are present in 95% of the cases. Ras is a difficult target to inhibit thus, we propose an alternative strategy which does not inhibit the Ras pathway but exploits it. We have previously shown that recombinant adenovirus, which carries the pro-apoptotic PUMA gene under the control of Ets and AP1/Ras- responsive elements (RREs; Py2-SV40-PUMA), suppressed the growth of cancer cells expressing mutated Ras. We have constructed additional vectors; Py4-; Py5-SV40-PUMA containing several RREs repeats, which were proven effective in selectively targeting Ras-mutated tumor cells (Naumov et al., 2012; Lisiansky et al., 2012). In this study, we utilized a MazE-MazF (MazEF) unique toxin-antitoxin (TA) system encoded from the E. coli genome. Under silent conditions the antitoxin (antidote) inhibits the toxin and the toxin-antidote complex acts as a repressor for the TA operon, whereas in activation conditions, proteolytic degradation of the antidote outpaces its synthesis.

Aim: Improve the therapeutic efficacy and specificity of the adenoviral vectors by substituting the lethal gene with more toxic agents that are highly regulated.

Methods: To achieve efficient DNA delivery into mammalian cells; the ribonuclease MazF-mCherry fusion gene, truncated derivative of Pseudomonas exotoxin (PE38), the full regulated cassette encoding for the MazEF TA system, and the corresponding control vectors were cloned into a “first generation” ΔE1/ΔE3 human type-5 adenoviral-vector under the control of RRE or SV40 minimal promoter. Virus particles were propagated in HEK293 toxin-resistant packaging cells. Tumor cells harboring wild type (WT) and mutated K-Ras were used to test inhibition of cell proliferation, viability, and toxin-expression upon treatment. Apoptosis was detected by FACS using the RedDot 2 and Annexin V stains, measuring the fraction of dead cells.

Results: Two modified helper cell lines and efficient vectors for targeted gene delivery were established. Virus particles were produced and their potency was tested. Specific massive cell death (&gt;50%) at low MOIs was induced in cells exhibiting activated K-Ras upon treatment, compared to WT-K-Ras cells. Induction of cell death was measured qualitatively by fluorescent microscopy and quantified by the MTT assay. Viral infection induced a marked inhibition of cell growth and induction of apoptosis in cells expressing high levels of Ras activity whereas WT-K-Ras cells remained unaffected.

Conclusions: These novel adenoviral vectors carrying either, PE38, MazF or MazEF genes targeting the K-Ras pathway can serve to selectively and efficiently kill PC cells harboring K-Ras mutations while sparing normal cells with WT Ras, thereby improving the outcome of this devastating disease.

Citation Format: Shiran Shapira, Dina Kazanov, Nadir Arber, Sarah R. Kraus. Selective eradication of cancer cells by adenovirus-based delivery of cytotoxic agents: an alternative method for targeting pancreatic cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3303. doi:10.1158/1538-7445.AM2013-3303

The APC I1307K polymorphism as a significant risk factor for CRC in average-risk Ashkenazi Jews

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Background: The I1307K adenomatous polyposis coli gene variant, prevalent among Ashkenazi Jews, may increase risk for colorectal neoplasia. We studied the clinical importance of screening for this polymorphism in 3305 Israelis undergoing colonoscopic assessment. Methods: Blood samples and risk factor information were collected from individuals undergoing colonoscopic examination at our medical center. Germline genetic analysis for the APC I1307K variant was performed using real-time PCR for DNA extracted from peripheral mononuclear cells. Results: The overall prevalence of the I1307K polymorphism was 8.0% (10.1% among Ashkenazi while only 2.7% among Sephardic Jews, p<0.001). The overall adjusted odds ratio (OR) for CR neoplasia among carriers was 1.51(95% CI, 1.16 –1.98). Among average risk Ashkenazi Jews, the OR was 1.76 (95% CI 1.26-2.45). On the contrary, among Sephardi subjects the OR was 0.996 (95% CI, 0.51-1.93). A multiplicative interaction was identified between Ashkenazi ethnicity and APC I1307K carrier status (PINTERACTION=0.055). The histopathological features of adenomas and cancers did not differ between carriers and non-carriers. Conclusions: The APC I1307K gene variant is an important risk factor for CRC in average risk Ashkenazi jews and should be considered for screening in this population.

Abstract 1338: Knockdown of CD24 prevents colorectal polyp formation in APCmin/CD24 double knockout transgenic mice

Background: Previous studies in our lab have shown that CD24 is a potential oncogene in the colon. CD24, a mucin-like glycoprotein, is overexpressed in 90% of colorectal cancer (CRC) tumors at a fairly early stage in the multistep process of CR carcinogenesis (Sagiv et al., Gastroenterology, 2006). We have also shown that CD24 downregulation by shRNA interference (Sagiv et al., Can Res, 2008) or anti-CD24 mAb targeting (Shapira et al., Gastroenterology, 2011) retarded tumorigenicity of human CRC cell lines and/or reduced tumor volume in nude mice. The APCmin/+ is a popular animal model for studies of human colon carcinogenesis and the molecular changes associated with neoplasia in this system have been partially characterized. These mice have a germline nonsense mutation at codon 850 of the APC gene and spontaneously develop hundreds of polyps, mostly in the small intestine at the age of 10-12 weeks. Aim: To validate the importance of CD24 in intestinal carcinogenesis using a transgenic mouse model with a double knockout (KO) of CD24−/+ /CD24+/− and APCMin/+ alleles. Methods: We generated the CD24−/+/APCMin/+ double KO by crossing the mice with each of the single gene knockouts, in order to obtain both CD24+/−/APCMin/+ and CD24−/+ APCMin/+ genotypes. The double KO mice were followed up thrice a week and sacrificed at 12 weeks of age. Tumors from the entire small and large intestine were counted and verified by histological analysis Results: There was almost a complete absence of polyps in the small intestine in APCMin/+/CD24+/− double heterozygotes compared to that of the parental APCMin/+, CD24+/+ animals: 273±55.4 vs. 6±1.7 polyps, respectively (P=0.0001). APCMin/+and CD24−/+ homozygotes showed a striking lack of polyps (P&lt; 0.0001). This reduction occurred in all sections of the small intestine. Histophatological analysis confirmed the absence of malignant lesions in the double KO mice as compared to the parental mice. Conclusions: 1. A deficiency of only one CD24 allele is sufficient to suppress almost completely polyp formation in the APCMin/+ mice that normally develop hundreds of polyps. 2. Although the mechanism/s underlying the pathophysiologic role of CD24 in the development of CRC are still unknown, these studies suggest that CD24 plays a critical role in the proliferation and progression of CRC and is a potential important target for the prevention and treatment of intestinal neoplasia.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1338. doi:1538-7445.AM2012-1338

Abstract 1004: Impact of genetic polymorphisms on colorectal adenoma recurrence and toxicity in a COX-2 inhibitor trial (Celecoxib): Results from a pilot study

Background: Chemoprevention trials have shown that Celecoxib, a selective COX-2 inhibitor can reduce adenoma recurrence but can also increase risk of cardiac toxicity. Therefore, in this pilot study, we evaluated the associations between genetic variation in several candidate pathways (e.g. prostaglandin, arachidonic acid and leukotriene synthesis), the incidence of adenoma recurrence as well as toxicity (any, gastrointestinal, cardiac, and non-gastrointestinal/non-cardiac toxicities). Methods: This analysis includes 119 Israeli patients with colorectal adenoma who participated in the Prevention of Colorectal Sporadic Adenomatous Polyps (PreSAP) trial. Reassessment followed after ∼3 years on Celecoxib, followed by 2 years off drug. Incidence of colorectal adenomas was measured by colonoscopy at years 1, 3, and 5. The presence of any, gastrointestinal, cardiac and non-gastrointestinal/non-cardiac toxicities was assessed by investigators for the on-treatment period and collected by patient self-report after treatment. A linkage-disequilibrium-based tagSNP selection algorithm (r2≥0.90, MAF≥4%) identified tagSNPs in candidate pathways. Genotyping was performed using IlluminaTM GoldenGate bead-based genotyping technology. Results: Multiple variants were associated with adenoma recurrence and toxicities. Variability, particularly in COX-1 (rs10306164, rs1236913, rs1330344, rs3119773), COX- 2 (rs4648268), and ALOX12 (rs2073438, rs2292350) played a major role in adenoma recurrence risk among patients on placebo compared to patients on Celecoxib. The highest risk was observed for the COX-1 rs3119773 variant (1890 G&gt;A intron 2) (HR=4.65, 95%CI 1.71-12.64, p=0.0026). Variants in COX2 (rs2206593, rs2745557), EGFR (rs1558544, rs17336919), ALOX15 (rs2619112, rs2619118, rs4796535), SRC (rs6018027, rs7269342), SEPP1 (rs230819, rs230820), and WNT6 (rs6747776, rs6754599) genes were associated with any toxicity. In contrast to gastrointestinal toxicity, a larger number of gene variants (especially variants in PGES, CRP, SRC and GPX3) were associated with increased risk of cardiac toxicity. The increased risk of cardiac toxicity associated with the SRC gene variants (rs6017996, rs6018256, rs6018257) ranged from 7- to 11-fold. Conclusion: Genetic polymorphisms in multiple inflammation-related genes appear to mediate the effect of Celecoxib on adenoma recurrence and the resultant toxicity, particularly cardiac toxicity. Identification of these genetic variants can potentially help in the provision of tailored and optimum care for colorectal adenoma patients. Larger studies validating these pharmacogenetic relationships are warranted.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1004. doi:1538-7445.AM2012-1004

The CD24 protein inducible expression system is an ideal tool to explore the potential of CD24 as an oncogene and a target for immunotherapy in vitro and in vivo

CD24 is a cell surface, heavily glycosylated glycosylphosphatidylinositol-anchored mucin-like protein that is overexpressed in various human malignancies. To accurately analyze CD24 function and dissect its biological role in a defined genetic background, it is critical to tightly regulate its expression and be able to turn it on/off in a restricted environment and at a specific time. The tetracycline-induced expression system is most promising as it exhibits such regulation, lack of pleiotropic effects, and high and rapid induction levels. To evaluate the oncogenic and immunotherapeutic potential of CD24 by applying the Tet-On system, the human CD24 gene was cloned downstream to two tetracycline operator sequences, resulting in pCDNA4/TO-CD24, which was then transfected into tetracycline (Tet) repressor-expressing cells (293T-REx), allowing tight on/off regulation, thereby resulting in a very low background or leaky CD24 expression. Selected clones were chosen for further studies and characterized in vitro and in vivo, and several treatment modalities were examined. In addition, the role of CD24 in promoting cell proliferation and tumor growth was studied. The tetracycline-dependent system was successfully implemented. Tetracycline treatment induced CD24 expression in a dose- and time-dependent fashion, which was abrogated following treatment with anti-CD24 monoclonal antibodies (mAbs). CD24-induced expression led to an increased proliferation rate that was inhibited by mAb treatment. In vivo, significantly larger tumors were developed in tetracycline-fed mice. The CD24 Tet-On system is a good model to unravel the role and underlying CD24 pathogenesis in vivo. This valuable tool allows the successful study of novel treatment options, whose effectiveness depends on the CD24 expression level. This set of experiments supports CD24 oncogenic properties.

An immunoconjugate of anti-CD24 and Pseudomonas exotoxin selectively kills human colorectal tumors in mice

BACKGROUND & AIMS

Effective and selective treatment options are needed for patients with colorectal cancer (CRC). The CD24 mucin-like glycoprotein is overexpressed in CRCs; monoclonal antibodies (mAbs) against CD24 inhibit tumor cell growth in vitro and in vivo. Based on the tumor-specific expression of CD24, we investigated the potential of anti-CD24 SWA11 mAb, to deliver a cytotoxic agent into CRC cells.

METHODS

We conjugated SWA11 to a Pseudomonas exotoxin derivative (PE38) via an Fc-binding ZZ domain from Staphylococcal protein A (which binds the Fc domain of mouse IgG2a immunoglobulins) to generate the immunotoxin SWA11-ZZ-PE38; IgG-ZZ-PE38 was used as control. Human HT-29 and COLO320 (CD24-positive) and HCT116 (CD24-negative) CRC cell lines were assayed for immunotoxin binding, cytotoxicity, viability, and apoptosis. Toxicity and antitumor efficacy were tested in mice.

RESULTS

The immunotoxin preserved the affinity and specificity of SWA11, bound and selectively killed CD24-expressing CRC cells via apoptosis. IC(50) values ranged from 20 to 50 ng/mL-several orders of magnitude lower than that of the mAb alone. The immunotoxins were not toxic to mice at the maximum dose of 0.75 mg/kg. Growth of HT-29 xenograft tumors was significantly reduced in mice given SWA11-ZZ-PE38 (by 78%) compared to untreated mice.

CONCLUSIONS

Anti-CD24 SWA11 mAb can deliver a PE exotoxin derivative to CRC cells and cause them to undergo apoptosis, without toxicity to normal tissues. This immunotoxin might be developed as a therapeutic treatment for patients with CRC.

Chemopreventive effects of Coltect, a novel dietary supplement, alone and in combination with 5-aminosalicylic acid in 1,2-dimethylhydrazine-induced colon cancer in rats

OBJECTIVES

Coltect is a novel dietary supplement containing curcumin, green tea and selenomethionine. Previous reports have suggested that these agents can prevent colorectal cancer (CRC). The present study examined the chemopreventive effect of Coltect alone or combined with 5-aminosalicylic acid (5-ASA) using the 1,2-dimethylhydrazine (DMH) model in rats.

METHODS

The effect of Coltect was examined on HT-29 CRC cells by growth inhibition assay. Apoptosis was determined by annexin V-FITC/PI staining. Male rats were injected with DMH in vivo and treated with Coltect 150 mg/kg, 5-ASA 50 mg/kg or their combination, by oral gavage. Aberrant crypt foci (ACF) were identified by methylene blue staining.

RESULTS

HT-29 cells exhibited a dose-dependent response to Coltect. Part of the growth inhibition can be explained by the induction of mild-moderate apoptosis in cancer cells (28%) compared with the untreated cells (10%). In the in vivo model, the average number of ACF was divided into small (1-3 crypts) or large (≥4 crypts). The Coltect compound reduced the number of small and large ACF similarly to 5-ASA (40% reduction). This reduction was amplified by combining the two agents (70% reduction).

CONCLUSION

Coltect inhibits the growth of colon cancer cells, induces apoptosis and inhibits ACF development. Furthermore, it augments the growth inhibitory effect of 5-ASA in vivo. This may be clinically important since this safe dietary supplement-drug combination can be administered as a chemopreventive regimen for the treatment of CRC.

Abstract 5333: Novel Ab treatment tool for CRC

Background: We have shown that CD24, a cell surface molecule, is overexpressed early in the multistep process of colorectal neoplasia (Gastroenterology, 2006) hence, it can serve as a target for early detection and immunotherapy. The anti-CD24 murine SWA11 Mab (generous gift from Prof. Sthal, Zurich University) binds to CD24 and inhibits tumor cell growth, in vitro and in vivo, in a time- and dose-dependent manner (Cancer Research, 2008). However, murine Mabs have limitations because of their xenogeneic nature and due to the human anti-mouse antibody (HAMA) response.

Aim: To produce an improved, chimeric form of the SWA11 Mab.

Methods: Mammalian vector pMAZ-IgH for human γ1 heavy-chain and pMAZ-IgL for human κ light chain expression were designed. The variable region genes encoding the murine anti-CD24 SWA11 MAb were cloned for expression as chimeric γ1/kappa antibody into the mammalian pMAZ-IgH and pMAZ-IgL expression vectors and co-transfected into HEK293 cells. Stable clones were screened and selected for IgG production, analyzed by whole-cell and antigen-based ELISA, and Western blotting.

Results: The new chimeric IgG derivative of the anti-CD24 SWA11 Mab possesses similar affinity and specificity (ELISA and Western blot), but has improved activity in inhibiting cell growth.

The chimeric Mabs also have the ability to induce complement-dependent cytotoxicity, causing up to 60% cell lysis in the presence of complement. Conclusions: We had successfully generated a chimeric IgG derivative of the anti-CD24 SWA11 Mab that can serve as a novel therapeutic tool for cancer cells harboring CD24.

Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5333.

Abstract 2902: A simple blood test, evaluating the level of CD24 protein, can detect subjects with colorectal adenomas and adenocarcinomas

Background: CD24 is a cell surface protein involved in cell adhesion and metastasis. Using gene expression array we have shown that CD24 expression is associated with colorectal cancer (CRC) [1,2]. The data was confirmed by IHC staining showing expression of CD24 in ∼90% of CR adenomas and adenocarcinomas.

Two genetic variants of CD24, a C to T single nucleotide polymorphism (SNP), leading to an Ala/Val exchange (A57V) and a TG deletion in the 3’-UTR have been described, may have functional relevance, and affect CD24 protein level and stability.

Objectives: To evaluate CD24 protein expression in peripheral blood leukocytes (PBLs) from normal, adenoma and CRC subjects, and score the associations of CD24 genetic variants and CRC risk.

Methods: The calibration trial included 150 consented subjects (CRC=63, Adenomas=19, Normal=68) attending Tel Aviv Medical Center that underwent colonoscopy. PBLs were isolated and analyzed by Western blotting using anti-CD24. The samples were externally evaluated at the Technion, Haifa. The validation trial included 73 subjects. Additional 83 subjects were recently examined. Band intensities were scanned and tested for statistical significance. Sensitivity and specificity for CD24 was determined using receiver operating characteristic (ROC) curves. The study was approved by the Israel Ministry of Health.

Results: The sensitivity and specificity of the CD24 test for distinguishing CRC from normal subjects was 70.5% (95% CI, 54.8-83.2%) and 83.8% (95% CI, 74.6-92.7%), respectively, and for advanced adenomas 84.2% (95% CI, 60.4-96.4%) and 73.5% (95% CI, 61.4-83.5%), respectively. The external evaluation study varied slightly. Improved values were achieved in the validation trial. Thus, the sensitivity for the detection of CRC was 92.3% (95% CI, 63.9-98.7%), with similar specificity, whereas the specificity for detecting adenomas was higher, 89.2% (95% CI, 74.6-96.9%). No significant correlations were found between the expression of CD24 and the two SNPs examined. However, preliminary data shows that the P170 C/T variant may increase susceptibility to CR adenomas (p=0.048) while the TG/del CD24 SNP may have a protective role (NS).

Conclusions: The CD24 blood test is the first of its kind to be able to detect adenomas. It can also successfully distinguish CRC from healthy subjects. CD24 may serve as a potential and promising biomarker for the early detection of CRC. Larger studies are warranted to establish the future potential of this promising test.

References:

1. Sagiv E., Gastroenterology 2006

2. Sagiv E., Can Res, 2008

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2902.

Abstract 593: Abusing oncogenic RAS to selectively target colorectal and pancreatic cancer cells

Background: RAS mutations are present in 40-60% of human colorectal (CRC) and 75-95% of pancreatic (PC) tumors leading to the activation of downstream target genes. The pro-apoptotic PUMA protein interacts with Bcl-XL and Bcl-2 to induce the release of mitochondrial cytochrome C and apoptosis.

Aim: To selectively kill RAS transformed cells by overexpressing the PUMA gene under the control of a RAS-responsive promoter.

Materials and methods: Four CRC and three PC cell lines were used. Six of them harboring KRAS mutations; SW480, HCT116, DLD1, Colo357, Panc1 and MiaPaca, whereas HT29 cells, harboring wt KRAS, served as control. In addition, normal rat enterocytes, IEC18 and RIE and their KRAS (R1), HRAS (RIE-RAS) transformed counterparts, were tested. We constructed two adenoviral vectors with the wt PUMA sequence, one containing RAS-responsive elements as an upstream promoter (PY4-PUMA) and a second lacking these elements which served as control (SV40-PUMA). Prior to the infections, RAS activity was determined by pull-down assay using GST-RBD. Inhibition of proliferation was determined on a Coulter counter; cell viability by MTT assay, apoptosis by FACS and protein expression by Western blotting. The effect of the adenoviruses was evaluated in vivo following injection of 106 cells into two flanks of nude mice (n=30).

Results: As expected, SW480, HCT116, DLD1, Colo357, Panc1, R1 and RIE-RAS showed increased RAS activity compared to HT29, IEC18 and RIE cells which had no activity. Infection with PY4-PUMA induced a marked inhibition of cell growth, up to 40-50% and spontaneous apoptosis, in all cells exhibiting high levels of RAS activity whereas HT29, IEC18 and RIE were unaffected by PY4-PUMA. The SV40-PUMA had no effect. Selective and high expression of PUMA was detected in PY4-PUMA affected cells.

In xenograft models of CRC in nude mice, PY4-PUMA injected i.p twice during a period of 4 weeks, suppressed de novo tumor formation and inhibited by ∼35% the growth of established tumors compared to the control virus.

Conclusions: Selective expression of PUMA in RAS transformed cells can induce cancer cell death. The minimal quantity of only two adenoviral injections in our in vivo model showed no toxicity and holds promise for its future application in humans that, unlike immunodeficient mice, are immunocompetent. Gene therapy may become a useful, effective and safe approach to target RAS mutated tumors while sparing the normal surrounding tissue. It might be applicable not only to GI tumors but to other tumors harboring KRAS or HRAS mutations.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 593.

Effect of the I1307K polymorphism in APC confers a higher risk for polyp recurrence in Jewish Ashkenazi carriers

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Background: The I1307K adenomatous polyposis coli gene variant, prevalent among Ashkenazi Jews, may increase risk for colorectal neoplasia [colorectal cancer (CRC) and CR adenoma]. We studied the clinical importance of this polymorphism in 3283 Israelis undergoing colonoscopic assessment. Methods: Blood samples and risk factor information were collected from individuals undergoing colonoscopic examination at our medical center. Germline genetic analysis for the APC I1307K variant was performed using real-time PCR for DNA extracted from peripheral mononuclear cells. Results: The overall prevalence of the I1307K polymorphism was 8.1% (10.2% among Ashkenazi while only 2.5% among Sephardic Jews, p=0.001). The overall adjusted odds ratio (OR) for CR neoplasia among carriers was 1.3 (1.0 -1.7, p=0.049). Among Ashkenazi Jews, the I1307K variant was significantly more prevalent among persons with a personal or family history (1st degree) of CR neoplasia (p=0.01) as compared to Ashkenazi Jews with no family history. The histopathological features of adenomas and cancers did not differ between carriers and non-carriers. No interactions were found between the I1307K variant and demographic, lifestyle, or dietary modifiers that independently modulated the risk for CR neoplasia. Conclusions: In the general population, the APC I1307K variant does not change the risk or prognosis of colorectal neoplasia in carriers and does not necessarily change their clinical practice. Nevertheless, the variant, which is more prevalent among high risk individuals of Ashkenazi Jewish origin, is an important risk factor for the assessment of recurrence of neoplasia as it confers a higher risk for polyp recurrence in this population.

No significant financial relationships to disclose.

The APC E1317Q and I1307K polymorphisms in non-colorectal cancers

Mutation of the adenomatous polyposis coli (APC) gene is an important initiating factor in the early stages of the multi-step colorectal cancer (CRC) carcinogenesis. APC E1317Q and I1307K variants have been linked to CRC. The aim of this study was to examine the association of these variants with non-colorectal cancers. Mutation screening was performed using real-time PCR. The APC E1317Q variant was detected in 1.25% individuals undergoing testing. Among 2076 patients that were analyzed for this mutation, 404 had cancer outside of the colon. None of the non-colorectal cancer patients was a carrier of the E1317Q polymorphism. The I1307K variant was found in 32 subjects with non-CRC (7.9%). We conclude herein that the E1317Q gene variant in the APC gene is not found in cancers outside of the colon. The prevalence of the more common I1307K variant is similar to that of CRC.

Down-regulation of PGE2 by physiologic levels of celecoxib is not sufficient to induce apoptosis or inhibit cell proliferation in human colon carcinoma cell lines

This study was performed to evaluate whether down-regulation of prostaglandin E(2) (PGE(2)) synthesis by celecoxib treatment is associated with inhibition of cell growth in human colon carcinoma cell lines. Physiologic concentrations of celecoxib (5-10 microM) inhibited 80% to 90% of PGE(2) production in HT-29 cells that express high levels of COX-2 protein. In these concentrations, celecoxib had a minor inhibitory effect (20-30%) on cell growth. There was a significant change in induction of apoptosis only at higher concentrations of celecoxib (>20 microM). Treatment by low concentrations of celecoxib did not alter the levels of COX-1, beta-catenin, P(27), Bcl-2, and Bcl-x proteins. The effect of celecoxib on cell growth inhibition was higher on the COX-2-positive HT-29 cell line (IC(50)=20 microM) than on the COX-2 deficient SW-480 cell line (IC(50)=35 microM). In conclusion, inhibition of PGE(2) synthesis is an early, but not sufficient, step in the mechanism of celecoxib-mediated cell growth inhibition. These results support the need for additional evaluation of independent COX-2 pathways of celecoxib in chemoprevention of CRC.

CD24 plays an important role in the carcinogenesis process of the pancreas

Patients with pancreatic adenocarcinoma have a doom prognosis these tumors were previously proved to express high level of CD24. The current study was aimed to demonstrate that the treatment with monoclonal antibodies to CD24 is effective, in vitro, in pancreatic cancer cells, similar to what we had previously shown in the setting of colorectal cancer. Three human pancreatic cancer cell lines, Colo357, Panc1 and MIA-PaCa, were analyzed for their expression levels of CD24 by Western blot analysis. The correlation for the protein available on the cytoplasmic membrane was assessed by ELISA assay to plates coated with fixed cells using anti-CD24 Ab as the first binder. Human cancer cell lines were tested for their response to two different anti-CD24 monoclonal antibodies and a control antibody (mouse anti-GFP). Human pancreatic adenocarcinomas cell lines that express CD24 (Colo357 and Panc1 cells) showed growth inhibition in dose and time dependent manners. These results were repetitive for the two different antibodies. Growth rate was not affected in MIA-PaCa cells that do not express CD24, or when cells were treated with a control antibody. CD24 may play an important role in the carcinogenesis process of pancreatic cancer. It may serve as a useful target in the therapy of pancreatic cancer.

Ha-ras(val12) induces HSP70b transcription via the HSE/HSF1 system, but HSP70b expression is suppressed in Ha-ras(val12)-transformed cells

Heat shock proteins (Hsps) are overexpressed in many tumors, but are downregulated in some tumors. To check for a direct effect of Ha-Ras(val12) on HSP70 transcription, we transiently expressed the oncoprotein in Rat1 fibroblasts and monitored its effect on HSP70b promoter-driven reporter gene. We show that expression of Ha-Ras(val12) induced this promoter. Promoter analysis via systematic deletions and point mutations revealed that Ha-Ras(val12) induces HSP70b transcription via heat shock elements (HSEs). Also, Ha-Ras(val12) induction of HSE-mediated transcription was dramatically reduced in HSF1-/- cells. Yet, residual effect of Ha-Ras(val12) that was still measured in HSF1-/- cells suggests that some of the Ha-Ras(val12) effect is Hsf1-independent. When HSF1-/- cells, stably expressing Ha-Ras(val12), were grown on soft agar only small colonies were formed suggesting a role for heat shock factor 1 (Hsf1) in Ha-Ras(val12)-mediated transformation. Although Ha-ras(Val12) seems to be an inducer of HSP70's expression, we found that in Ha-ras(Val12-)transformed fibroblasts expression of this gene is suppressed. This suppression is correlated with higher sensitivity of Ha-ras(val12)-transformed cells to heat shock. We suggest that Ha-ras(Val12) is involved in Hsf1 activation, thereby inducing the cellular protective response. Cells that repress this response are perhaps those that acquire the capability to further proliferate and become transformed clones.

Gene targeting approach to selectively kill colon cancer cells, with hyperactive K-Ras pathway

BACKGROUND

Ras mutations are present in approximately 50% of human colorectal tumors. We have previously shown that transfection of a non-tumorigenic rat intestinal epithelial cell line, IEC18, by the K-Ras oncogene (R1 cells), resulted in malignant cell transformation. Utilizing the constantly active Ras signaling pathway to selectively target transformed but not normal cells is a plausible goal.

AIM

To selectively kill Ras transformed cells by over expressing a lethal gene using a Ras-responsive promoter.

MATERIAL AND METHODS

IEC18, R1 and a number of colon cancer cell lines were transfected with luciferase (Luc) reporter gene under the control of different Ras-responsive elements. The Ras-responsive promoter Py2 contains two copies of adjacent Ets and AP I binding sites followed by a minimal promoter. Apoptotic genes (bax, caspase-8 and PKG) were cloned into the Py2 plasmids. RI cells co-transfected with expression constructs and a selected vector and then grown for 3 weeks under selection.

RESULTS

R1, SW480 and HCT116 with mutated c-K-Ras expressed high level of Luc activity following transfection with the Py2 element. IEC18 cell lines that do not contain this mutation expressed negligible low Luc activity. Following transfection of SW480 and R1 cells with Py2-bax, caspase-8 and PKG, there was a significant reduction in the number of colony formation.

CONCLUSIONS

1. Selective over-expression of pro-apoptotic genes, inhibits the growth of Ras transformed cells, and not normal cells. 2. This gene approach therapy may become a useful, effective and safe to target Ras mutated tumor cells with sparing of the normal cells.

Curcumin synergistically potentiates the growth inhibitory and pro-apoptotic effects of celecoxib in pancreatic adenocarcinoma cells

BACKGROUND AND AIM

Adenocarcinoma of the Pancreas is a leading cause of cancer-related mortality, accounting for an estimated 30,000 deaths per year in the United States. Multiple studies have indicated that specific cyclooxygenase-2 (COX-2) inhibitors may serve in the prevention and treatment of a variety of malignancies including pancreatic adenocarcinoma. Recent studies had shown that the long-term use of high concentration of COX-2 inhibitors is not toxic free and may be limited due to serious gastrointestinal and cardiovascular side effects. The chemopreventive efficacy of the phytochemical, curcumin has been demonstrated in several in vitro and animal models. In this study we investigated whether curcumin potentiates the growth inhibition effect of a COX-2 inhibitor (celecoxib, Pfizer, NY, USA) in human pancreatic cancer cells.

METHODS

P-34 (expressing high levels of COX-2), and MIAPaCa (expressing low levels of COX-2) and Panc-1 (no expression of COX-2) evaluated cell lines were exposed to different concentrations of celecoxib (0-40 microM), curcumin (0-20 microM) and their combination. Cell viability was by XTT assay. Apoptosis was assessed by flow cytometry and COX-2 expression was measured by Western blotting analysis.

RESULTS

In P-34 cells, curcumin synergistically potentiated the inhibitory effect of celecoxib on cell growth. The growth inhibition was associated with inhibition of proliferation and induction of apoptosis. Western blot analysis showed that COX-2 expression was down-regulated by the combination therapy.

CONCLUSION

Curcumin synergistically augments the growth inhibition inserted by celecoxib in pancreatic cancer cells expressing COX-2. The synergistic effect was mediated through inhibition of COX-2. This may enable the use of celecoxib at lower and safer concentrations and may pave the way for a more effective treatment in this devastating disease.

Down-regulation of prostaglandin E2 by curcumin is correlated with inhibition of cell growth and induction of apoptosis in human colon carcinoma cell lines

Several in vitro and in vivo studies have demonstrated an association between curcumin, a diferuloylmethane derived from the plant Curcuma longa, and colorectal cancer (CRC) prevention. Nevertheless, the molecular mechanism responsible for the chemopreventive effect of curcumin is not well understood and most probably involves several pathways. Several studies indicate that curcumin may exert its effect by specifically inhibiting the cyclooxygenase-2 (COX-2) isoenzyme, which is up-regulated in 40 to 50% of colorectal polyps and in up to 85% of CRCs. However, other studies have suggested that curcumin may also inhibit polyps formation by COX-2 independent mechanisms (eg, inhibition of ErbB-1, AkT). The aim of this study was to evaluate whether curcumin's effect on the inhibition of cell growth and induction of apoptosis in human colon carcinoma cell lines is correlated with inhibition of PGE2 synthesis and down-regulation of COX-2. HT29 cells (expressing COX-2) and SW480 (deficient of COX-2) were exposed to different concentrations (0-50 microM) of curcumin for 72 hours. Growth inhibition was assessed by Coulter counter. Cell viability was assessed by the ability of metabolically active cells to reduce tetrazolium salt to colored formazan compounds (tetrazolium salt assay). Apoptosis was measured by two independent methods: flow cyto-metric analysis and 4'-6-Diamidino-2-phenylindole (DAPI) staining. Activity of COX-2 was evaluated by measuring prostaglandin E2 (PGE2) concentration using a specific enzyme-linked immunoassay. COX-1 and COX-2 expressions were measured by Western blot analysis. There was a significant difference between curcumin effect on COX-2-expressing (HT29: inhibitory concentration 50% [IC50] = 15 microM) and COX-2-deficient (SW480: IC50 = 40 microM) cells. Similarly, induction of apoptosis was higher in cells expressing COX-2. Western blot analysis and PGE2 immunoassay showed that curcumin inhibited COX-2 protein activity and expression in a dose-dependent manner. In conclusion, inhibition of cell survival and induction of apoptosis by curcumin in colorectal adenocarcinoma cell lines is associated with the inhibition of PGE2 synthesis and down-regulation of COX-2.

Curcumin synergistically potentiates the growth-inhibitory and pro-apoptotic effects of celecoxib in osteoarthritis synovial adherent cells

OBJECTIVES

Osteoarthritis (OA) is the Western world's leading cause of disability. Cyclo-oxygenase-2 (COX-2) inhibitors are efficient anti-inflammatory agents commonly used in the treatment of osteoarthritis. However, recent studies have shown that their long-term use may be limited due to cardiovascular toxicity. The anti-inflammatory efficacy of the phytochemical curcumin has been demonstrated in several in vitro and animal models. This study was undertaken to investigate whether curcumin augments the growth-inhibitory and pro-apoptotic effects of celecoxib in OA synovial adherent cells.

METHODS

OA synovial adherent cells were prepared from human synovial tissue collected during total knee replacement surgery. The cells were exposed to different concentrations of celecoxib (0-40 mum), curcumin (0-20 mum) and their combination. Flow cytometric analysis was used to measure the percentage of cells with a subdiploid DNA content, the hallmark of apoptosis. COX-2 activity was assessed by measuring production of prostaglandin E(2) by enzyme-linked immunoassay.

RESULTS

A synergistic effect was observed in inhibition of cell growth when the cells were exposed to various concentrations of celecoxib combined with curcumin. The inhibitory effect of the combination on cell growth was associated with an increased induction of apoptosis. The synergistic effect was mediated through a mechanism that involves inhibition of COX-2 activity.

CONCLUSIONS

This effect may enable the use of celecoxib at lower and safer concentrations, and may pave the way for a novel combination treatment in osteoarthritis and other rheumatological disorders.

The I1307K adenomatous polyposis coli gene variant does not contribute in the assessment of the risk for colorectal cancer in Ashkenazi Jews

Ashkenazi Jews with the I1307K adenomatous polyposis coli gene variant were suggested to confer a higher risk for colorectal cancer (CRC). We assessed the clinical importance of this polymorphism in Israeli Jews at average and elevated risk for CRC. Among 1,370 consecutive subjects that were examined, 975 Ashkenazi Jews were stratified into those at average risk (no personal or family history of colorectal neoplasia) and those at high risk. DNA was obtained from peripheral leukocytes and amplified by PCR, with primers designed to detect the I1307K variant. Overall, I1307K polymorphism was found in 7.1% (9.1% among Ashkenazi and 1.7% among non-Ashkenazi Jews). The carrier rate was 8.3 and 9.3% in average and high-risk Ashkenazim, respectively (P = 0.65). The overall odds ratio for neoplasia in carriers was 1.43 (95% confidence interval, 0.89-2.30). Age, gender, and the histopathological features of adenomas and cancers did not differ between carriers and noncarriers. No interaction on the CRC risk was found between I1307K variant and lifestyle modifiers (such as cigarette smoking, alcohol consumption, high body mass index, low physical activity, and vitamins/antioxidant intake). The I1307K adenomatous polyposis coli gene variant is not an important marker for increased risk for CRC. It confirms previous reports of a slight nonsignificant increase (OR, 1.4) in the risk of CRC in these carriers. There is no interaction effect on the risk of colorectal neoplasia between the I1307K variant and various lifestyle risk factors. The usual recommended screening and surveillance strategies should be used for carriers of this polymorphism.

Prospective assessment of microsatellite instability in gastrointestinal neoplasia in Ashkenazi and non-Ashkenazi Jews

BACKGROUND

Microsatellite instability (MSI) is a useful marker of replication errors in neoplasia, resulting from mutations in the mismatch repair (MMR) genes. Nearly all hereditary non-polyposis colorectal cancer (HNPCC) and about 15% of sporadic colorectal cancers (CRC) exhibit high MSI (MSI-H). The use of the Amsterdam criteria for HNPCC diagnosis may fail to identify many HNPCC cases. Genetic screening of mutations in the MMR genes is laborious, time-consuming, expensive and limited by a low detection rate. Hence, MSI testing is a feasible and cost-effective method to select suspected HNPCC patients for genetic analysis. MSI has not been used routinely or prospectively in the assessment of newly diagnosed CRC.

AIMS

To prospectively evaluate MSI status in a cohort of patients seen at the Gastrointestinal Oncology Unit of the Tel Aviv Medical Center.

METHODS

Ninety-eight consecutive patients with colonic or gastric neoplasia were included. Samples from neoplastic and normal mucosa were obtained at the time of diagnostic endoscopy. MSI was determined based on five Bethesda markers using standard polymerase chain reaction procedures.

RESULTS

The overall incidence of MSI was 20.4%. MSI-H was detected in 22.2% of CRC, 20% of colonic adenomas and 18.2% of gastric neoplasia. MSI-positive neoplasia tended to display multiple colonic sites, moderate-well differentiated tumors, and a higher rate of familial gastrointestinal neoplasia.

CONCLUSIONS

MSI may be involved in the early stages of some colorectal tumorigenesis pathways since it may be detected in adenomas. MSI may serve as a cost-effective, reliable and important tool in the selection of HNPCC-suspected families for genetic testing. A small study population, referral bias or ethnic variation might explain the higher MSI rate. It is suggested that, similar to familial adenomatous polyposis, a state of attenuated HNPCC may exist. Hence, the clinical approach in positive patients, and their family members, should be conducted as for families with genetically proven HNPCC.