Isoprenylation Inhibition Suppresses FcεRI-mediated Mast Cell Function and Allergic Inflammation

Allergic disease is driven by cell signaling cascades that activate immune cells. One key player is mast cells, which is activated by IgE antibodies signaling through the high affinity IgE receptor, FceRI. Therefore, targeting FceRI-mediated cascades can offer for novel treatments for allergic disease. Statins have been demonstrated to reduce the severity of asthma, a common allergic airway disease. Statins are an FDA approved class of drugs with the intended purpose of lowering blood cholesterol. We previously found that while statins inhibit mast cell function in allergic disease, these anti-inflammatory effects vary widely amongst differing mouse strains and human donors, suggesting genetic variability. This project sought to overcome statin resistance by acting “downstream” in the cholesterol synthesis pathway on protein isoprenylation pathways. The logic is that isoprenylated proteins are critical for FceRI signaling, thus blocking this step of protein modification should reduce FceRI-mediated mast cell function. The novel FGTI-2734 drug was used to suppress the isoprenylation enzymes farnesyl transferase and geranylgeranyl transferase. FGTI-2734 reduced IgE-mediated mast cell degranulation and cytokine and chemokine secretion. Additional work found that both transferases must be targeted to produce these anti-inflammatory effects. Furthermore, we revealed that the K-Ras protein is an isoprenylation target that is essential for IgE-mediated mast cell function. Collectively, these studies demonstrate the translational potential of the novel drug FGTI-2734 and suggest it acts by suppressing isoprenylation of proteins critical for mast cell function, including K-Ras.https://scholarscompass.vcu.edu/uresposters/1455/thumbnail.jp

Vitamin E δ-tocotrienol Sensitizes Human Pancreatic Cancer Cells to TRAIL-induced Apoptosis Through Proteasome-Mediated Down-Regulation of c-FLIP

Background: Vitamin E δ-tocotrienol (VEDT), a vitamin E compound isolated from sources such as palm fruit and annatto beans, has been reported to have cancer chemopreventive and therapeutic effects. Methods: We report a novel function of VEDT in augmenting tumor necrosis factor-related apoptosis-inducing ligand- (TRAIL-) induced apoptosis in pancreatic cancer cells. The effects of VEDT were shown by its ability to trigger caspase-8-dependent apoptosis in pancreatic cancer cells. Results: When combined with TRAIL, VEDT significantly augmented TRAIL-induced apoptosis of pancreatic cancer cells. VEDT decreased cellular FLICE inhibitory protein (c-FLIP) levels without consistently modulating the expression of decoy death receptors 1, 2, 3 or death receptors 4 and 5. Enforced expression of c-FLIP substantially attenuated VEDT/TRAIL-induced apoptosis. Thus, c-FLIP reduction plays an important part in mediating VEDT/TRAIL-induced apoptosis. Moreover, VEDT increased c-FLIP ubiquitination and degradation but did not affect its transcription, suggesting that VEDT decreases c-FLIP levels through promoting its degradation. Of note, degradation of c-FLIP and enhanced TRAIL-induced apoptosis in pancreatic cancer cells were observed only with the anticancer bioactive vitamin E compounds δ-, γ-, and β-tocotrienol but not with the anticancer inactive vitamin E compounds α-tocotrienol and α-, β-, γ-, and δ-tocopherol. Conclusions: c-FLIP degradation is a key event for death receptor-induced apoptosis by anticancer bioactive vitamin E compounds in pancreatic cancer cells. Moreover, VEDT augmented TRAIL inhibition of pancreatic tumor growth and induction of apoptosis in vivo. Combination therapy with TRAIL agonists and bioactive vitamin E compounds may offer a novel strategy for pancreatic cancer intervention

Selective chemical probe inhibitor of Stat3, identified through structure-based virtual screening, induces antitumor activity

S31-201 (NSC 74859) is a chemical probe inhibitor of Stat3 activity, which was identified from the National Cancer Institute chemical libraries by using structure-based virtual screening with a computer model of the Stat3 SH2 domain bound to its Stat3 phosphotyrosine peptide derived from the x-ray crystal structure of the Stat3 beta homodimer. S31-201 inhibits Stat3-Stat3 complex formation and Stat3 DNA-binding and transcriptional activities. Furthermore, S31-201 inhibits growth and induces apoptosis preferentially in tumor cells that contain persistently activated Stat3. Constitutively climerized and active Stat3C and Stat3 SH2 domain rescue tumor cells from S31-201-induced apoptosis. Finally, S31-201 inhibits the expression of the Stat3-regulated genes encoding cyclin D1, BcI-xL, and survivin and inhibits the growth of human breast tumors in vivo. These findings strongly suggest that the antitumor activity of S31-201 is mediated in part through inhibition of aberrant Stat3 activation and provide the proof-of-concept for the potential clinical use of Stat3 inhibitors such as S31-201 in tumors harboring aberrant Stat3

Ack1 Mediated AKT/PKB Tyrosine 176 Phosphorylation Regulates Its Activation

The AKT/PKB kinase is a key signaling component of one of the most frequently activated pathways in cancer and is a major target of cancer drug development. Most studies have focused on its activation by Receptor Tyrosine Kinase (RTK) mediated Phosphatidylinositol-3-OH kinase (PI3K) activation or loss of Phosphatase and Tensin homolog (PTEN). We have uncovered that growth factors binding to RTKs lead to activation of a non-receptor tyrosine kinase, Ack1 (also known as ACK or TNK2), which directly phosphorylates AKT at an evolutionarily conserved tyrosine 176 in the kinase domain. Tyr176-phosphorylated AKT localizes to the plasma membrane and promotes Thr308/Ser473-phosphorylation leading to AKT activation. Mice expressing activated Ack1 specifically in the prostate exhibit AKT Tyr176-phosphorylation and develop murine prostatic intraepithelial neoplasia (mPINs). Further, expression levels of Tyr176-phosphorylated-AKT and Tyr284-phosphorylated-Ack1 were positively correlated with the severity of disease progression, and inversely correlated with the survival of breast cancer patients. Thus, RTK/Ack1/AKT pathway provides a novel target for drug discovery

Phase II study of the farnesyltransferase inhibitor R115777 in advanced melanoma (CALGB 500104)

BACKGROUND: Multiple farnesylated proteins are involved in signal transduction in cancer. Farnesyltransferase inhibitors (FTIs) have been developed as a strategy to inhibit the function of these proteins. As FTIs inhibit proliferation of melanoma cell lines, we undertook a study to assess the impact of a FTI in advanced melanoma. As farnesylated proteins are also important for T cell activation, measurement of effects on T cell function was also pursued. METHODS: A 3-stage trial design was developed with a maximum of 40 patients and early stopping if there were no responders in the first 14, or fewer than 2 responders in the first 28 patients. Eligibility included performance status of 0–1, no prior chemotherapy, at most 1 prior immunotherapy, no brain metastases, and presence of at least 2 cutaneous lesions amenable to biopsy. R115777 was administered twice per day for 21 days of a 28-day cycle. Patients were evaluated every 2 cycles by RECIST. Blood and tumor were analyzed pre-treatment and during week 7. RESULTS: Fourteen patients were enrolled. Two patients had grade 3 toxicities, which included myelosuppression, nausea/vomiting, elevated BUN, and anorexia. There were no clinical responses. All patients analyzed showed potent inhibition of FT activity (85-98%) in tumor tissue; inhibition of phosphorylated ERK and Akt was also observed. T cells showed evidence of FT inhibition and diminished IFN-γ production. CONCLUSIONS: Despite potent target inhibition, R115777 showed no evidence of clinical activity in this cohort of melanoma patients. Inhibition of T cell function by FTIs has potential clinical implications. Clinicaltrials.gov number NCT0006012

Candida dubliniensis: An Appraisal of Its Clinical Significance as a Bloodstream Pathogen

A nine-year prospective study (2002–2010) on the prevalence of Candida dubliniensis among Candida bloodstream isolates is presented. The germ tube positive isolates were provisionally identified as C. dubliniensis by presence of fringed and rough colonies on sunflower seed agar. Subsequently, their identity was confirmed by Vitek2 Yeast identification system and/or by amplification and sequencing of the ITS region of rDNA. In all, 368 isolates were identified as C. dubliniensis; 67.1% came from respiratory specimens, 11.7% from oral swabs, 9.2% from urine, 3.8% from blood, 2.7% from vaginal swabs and 5.4% from other sources. All C. dubliniensis isolates tested by Etest were susceptible to voriconazole and amphotericin B. Resistance to fluconazole (≥8 µg/ml) was observed in 2.5% of C. dubliniensis isolates, 7 of which occurred between 2008–2010. Of note was the diagnosis of C. dubliniensis candidemia in 14 patients, 11 of them occurring between 2008–2010. None of the bloodstream isolate was resistant to fluconazole, while a solitary isolate showed increased MIC to 5-flucytosine (>32 µg/ml) and belonged to genotype 4. A review of literature since 1999 revealed 28 additional cases of C. dubliniensis candidemia, and 167 isolates identified from blood cultures since 1982. In conclusion, this study highlights a greater role of C. dubliniensis in bloodstream infections than hitherto recognized

RhoB as a suppressor of cancer cell growth, cell transformation, and metastasis

The present invention concerns the use of the protein RhoB and its variants to inhibit cancer cell growth, migration, invasion, metastasis, malignant cell transformation, and/or to modulate oncogenic signaling, wherein introducing RhoB directly, or indirectly via a nucleic acid sequence encoding RhoB, into a malignantly transformed cell or a cancerous cell decreases phosphorylation of Erk and Akt proteins inhibiting the PI3-kinase/Akt cell survival pathway and promoting apoptotic cell death. In one aspect, the compositions and methods of the present invention are used to inhibit the malignant transformation of cells by the oncogenes H-Ras, N-Ras, K-Ras, EGFR, or ErbB2, or to inhibit the growth of cancer cells transformed by such oncogenes. The compositions and methods of the present invention may be used to inhibit cancer cell growth, inhibit malignant cell transformation, and modulate oncogenic signaling in vivo or in vitro

RHoB as a suppressor of cancer cell growth, cell transformation, and metastasis

The present invention concerns the use of the protein RhoB and its variants to inhibit cancer cell growth, migration, invasion, metastasis, malignant cell transformation, and/or to modulate oncogenic signaling, wherein introducing RhoB directly, or indirectly via a nucleic acid sequence encoding RhoB, into a malignantly transformed cell or a cancerous cell decreases phosphorylation of Erk and Akt proteins inhibiting the PI3-kinase/Akt cell survival pathway and promoting apoptotic cell death. In one aspect, the compositions and methods of the present invention are used to inhibit the malignant transformation of cells by the oncogenes H-Ras, N-Ras, K-Ras, EGFR, or ErbB2, or to inhibit the growth of cancer cells transformed by such oncogenes. The compositions and methods of the present invention may be used to inhibit cancer cell growth, inhibit malignant cell transformation, and modulate oncogenic signaling in vivo or in vitro

Inhibition of the Raf/Mek/P-Erk pathway for treating cancer

The invention disclosed herein provides for methods of treating cancer using inhibitors of the Raf/Mek/P-Erk 1/2 pathway. These inhibitors include B2AR agonists (such as ARA-211 (pirbuterol) and isoproterenol), adenylyl cyclase activators, cAMP analogs and Epac activators. The invention also provides methods for diagnosing cancer in an individual

RhoB variants and methods of use

In one aspect, the present invention concerns RhoB variant polypeptides and isolated degenerate polynucleotides encoding the RhoB variant polypeptides. In another aspect, the present invention concerns nucleic acid constructs containing a polynucleotide encoding a RhoB variant polypeptide, and host cells genetically modified to express such polynucleotides. In another aspect, the present invention provides a method of inhibiting the growth of, and inducing apoptosis in, cancerous cells by contacting the cells with an effective amount of a RhoB variant