Current Cancer Drug Targets - Volume 14, Issue 2, 2014

PIM1 kinase is a serine/threonine kinase that has been shown to be overexpressed in multiple human malignancies, including prostate cancer. PIM1 phosphorylates multiple cellular substrates to inhibit apoptosis and promote cell cycle progression. Increased PIM1 can also facilitate genomic instability to promote neoplastic processes. PIM1 kinase is overexpressed in high-grade prostate intraepithelial neoplasia and in prostate cancer compared to normal prostatic tissue and benign prostate hyperplasia. Elevated PIM1 levels have been shown to be the direct result of oncogenic fusion proteins and active signal transduction pathways. In vitro and in vivo mouse studies indicate that PIM1 is weakly tumorigenic but synergizes dramatically when coexpressed with MYC. PIM1 kinase can also phosphorylate the androgen receptor (AR), thereby regulating AR degradation and function, in a low androgen environment. This finding implicates PIM1 in castration -resistant prostate cancer. Furthermore, expression of PIM1 has been shown to be increased in prostate tissue after docetaxel exposure, conferring partial resistance to docetaxel. Correlatively, decreased PIM1 levels sensitize prostate cancer cells to docetaxel treatment. Thus, PIM1 may be a target in docetaxel resistant disease. In summary, PIM1 kinase is involved in prostate tumorigenesis, castration resistance, and docetaxel resistance. Several PIM1 kinase inhibitors have been reported and are in varied stages of drug development. PIM1 is involved in multiple processes in the development and propagation of prostate cancer, thus a PIM1 kinase inhibitor may serve as an effective therapeutic agent in this prevalent disease.

Background: The prognosis of the oral squamous cell carcinoma (OSCC) patients remains very poor, mainly due to their high propensity to invade and metastasize. E-cadherin reduced expression occurs in the primary step of oral tumour progression and gene methylation is a mode by which the expression of this protein is regulated in cancers. In this perspective, we investigated E-cadherin gene (CDH1) promoter methylation status in OSCC and its correlation with Ecadherin protein expression, clinicopathological characteristics and patient outcome. Methods: Histologically proven OSCC and paired normal mucosa were analyzed for CDH1 promoter methylation status and E-cadherin protein expression by methylation-specific polymerase chain reaction and immunohistochemistry. Colocalization of E-cadherin with epidermal growth factor (EGF) receptor (EGFR) was evidenced by confocal microscopy and by immunoprecipitation analyses. Results: This study indicated E-cadherin protein down-regulation in OSCC associated with protein delocalization from membrane to cytoplasm. Low E-cadherin expression correlated to aggressive, poorly differentiated, high grade carcinomas and low patient survival. Moreover, protein down-regulation appeared to be due to E-cadherin mRNA downregulation and CDH1 promoter hypermethylation. In an in vitro model of OSCC the treatment with EGF caused internalization and co-localization of E-cadherin with EGFR and the addition of demethylating agents increased E-cadherin expression. Conclusion: Low E–Cadherin expression is a negative prognostic factor of OSCC and is likely due to the hypermethylation of CDH1 promoter. The delocalization of E-cadherin from membrane to cytoplasm could be also due to the increased expression of EGFR in OSCC and the consequent increase of E-cadherin co-internalization with EGFR.

BRAF is a major oncoprotein and oncogenic mutations in BRAF are found in a significant number of cancers, including melanoma, thyroid cancer, colorectal cancer and others. Consequently, BRAF inhibitors have been developed as treatment options for cancers with BRAF mutations which have shown some success in improving patient outcomes in clinical trials. Development of resistance to BRAF kinase inhibitors is common, however, overcoming this resistance is an area of significant concern for clinicians, patients and researchers alike. In this review, we identify the mechanisms of BRAF kinase inhibitor resistance and discuss the implications for strategies to overcome this resistance in the context of new approaches such as multi-kinase targeted therapies and emerging RNA interference based technologies.

HSF1 (Heat Shock transcription Factor 1) is the main transcription factor activated in response to proteotoxic stress. Once activated, it induces an expression of heat shock proteins (HSPs) which enables cells to survive in suboptimal conditions. HSF1 could be also activated by altered kinase signaling characteristic for cancer cells, which is a probable reason for its high activity found in a broad range of tumors. There is rapidly growing evidence that HSF1 supports tumor initiation and growth, as well as metastasis and angiogenesis. It also modulates the sensitivity of cancer cells to therapy. Functions of HSF1 in cancer are connected with HSPs’ activity, which generally protects cells from apoptosis, but also are independent of its classical targets. HSF1-dependent regulation of non-HSPs genes plays a role in cell cycle progression, glucose metabolism, autophagy and drug efflux. HSF1 affects the key cell-survival and regulatory pathways, including p53, RAS/MAPK, cAMP/PKA, mTOR and insulin signaling. Although the exact mechanism of HSF1 action is still somewhat obscure, HSF1 is becoming an attractive target in anticancer therapies, whose inhibition could enhance the effects of other treatments.

Curcumin, a polyphenol isolated from the plant Curcuma longa, displays chemotherapeutic and chemopreventive effects in diverse cancers, including colorectal cancer. A mono-carbonyl analogue B63 was synthesized through several chemical modifications of the basic structure of curcumin to increase its biological activity and bioavailability. In vitro assays showed potent anti-proliferative effects of B63 on colon cancer cells (about 2 fold more effective than curcumin based on IC50). B63 treatment also induced significant necrosis, apoptosis, and S phase cell cycle arrest in SW620 colon cancer cells. The pro-apoptotic proteins Bad and Bim were up-regulated, and cytochrome c release from the mitochondria into the cytosol was enhanced, resulting in pro-caspase-3 and PARP-1 cleavage. Furthermore, the anticancer activity of B63 was dependent on intracellular ROS from damaged mitochondrial function and induced endoplasmic reticulum (ER) stress. In vivo, 50 mg/kg of B63 inhibit tumor growth similarly to 100 mg/kg curcumin in a mouse xenograft model using SW620 cells. These results suggest that the curcumin derivative B63 has a greater anticancer capacity than the parent curcumin in colon cancer cells and that the necrotic and apoptotic effects of B63 are mediated by ROS resulting from ER stress and mitochondrial dysfunction.

FUS1 is one of the most important tumor suppressor genes in lung cancer, as well as an important immunomodulatory molecule. Interleukin (IL)-12 has attracted considerable interest as a potential anti-tumor cytokine. Cationic liposome has been shown to effectively deliver therapeutic genes to the lungs and control metastatic lung tumors when administered intravenously. Here we evaluated the enhanced efficacy of cationic liposome-mediated delivery of FUS1 and human IL (hIL)-12 eukaryotic coexpression plasmid (pVITRO2-FUS1-hIL-12) against the human lung cancer in HuPBL-NOD/SCID mice model by local and systemic administration, and explored the related molecular mechanism. Our study demonstrated that FUS1-hIL-12 coexpression could more sufficiently inhibit tumor growth and experimental lung metastasis, significantly prolong the survival of experimental lung metastasis mice. Moreover, FUS1-hIL-12 coexpression performed higher antitumor activity and lower toxicity in the inhibition of experimental lung metastatic tumor compared to cisplatin. We further identified that FUS1-hIL-12 coexpression could induce strong antitumor immune response by secreting much higher levels of human interferon-γ (hIFN-γ) and hIL-15, enhancing expression of MHC-I and Fas, increasing infiltration of activated human CD4+ and CD8+ T lymphocytes. FUS1-hIL-12 coexpression could also obviously induce tumor cell apoptosis and inhibit tumor cell proliferation partly by higher activation of STAT1 signal pathway and upregulation of p53. In addition, FUS1-hIL-12 coexpression also superiorly reduced the angiogenesis in tumors, which might be associated with downregulation of VEGF and VEGFR, and upregulation of human IP-10. Our results therefore suggest that cationic liposome-mediated FUS1-hIL-12 coexpression may be a new promising strategy for lung cancer treatment in clinical studies.

There is an emerging paradigm shift in oncology that seeks to emphasize molecularly targeted approaches for cancer prevention and therapy. Chalcones (1,3-diphenyl-2-propen-1-ones), naturally-occurring compounds with widespread distribution in spices, tea, beer, fruits and vegetables, consist of open-chain flavonoids in which the two aromatic rings are joined by a three-carbon α, β-unsaturated carbonyl system. Due to their structural diversity, relative ease of chemical manipulation and reaction of α, β-unsaturated carbonyl moiety with cysteine residues in proteins, some lead chalcones from both natural products and synthesis have been identified in a variety of screening assays for modulating important pathways or molecular targets in cancers. These pathways and targets that are affected by chalcones include MDM2/p53, tubulin, proteasome, NF-kappa B, TRIAL/death receptors and mitochondria mediated apoptotic pathways, cell cycle, STAT3, AP-1, NRF2, AR, ER, PPAR-γ and β-catenin/Wnt. Compared to current cancer targeted therapeutic drugs, chalcones have the advantages of being inexpensive, easily available and less toxic; the ease of synthesis of chalcones from substituted benzaldehydes and acetophenones also makes them an attractive drug scaffold. Therefore, this review is focused on molecular targets of chalcones and their potential implications in cancer prevention and therapy.

The ends of chromosomes in mammals are composed of telomeric DNA containing TTAGGG repeats, which bind specific proteins called shelterins. This telomeric DNA together with shelterins form a cap that protects the ends of chromosomes from being recognized as sites of DNA damage and from chromosomal fusions. Many very successful antitumor drugs used in the treatment of cancer patients bind to DNA, some of them with a prominent sequence specificity leads to changes in DNA structure and integrity. We propose a new target for antitumor drugs where small molecule ligands can bind to telomeric DNA and induce specific structural changes. These changes would lead to a selective interference with the formation of telomeric DNA-shelterin complexes, especially involving TRF1 and TRF2 proteins, as these proteins bind double-stranded telomeric DNA in a sequence- and structure-dependent manner. The rationale of the proposed therapeutic strategy is further justified by the fact that tumor cells have relatively short telomeres and frequently de-regulated shelterin expression and/or functionality. Thus uncapping of chromosome ends by DNA binding compounds which disrupt DNA-shelterin complexes can ultimately induce selective cytotoxic effect in tumor cells. Possible implications for rational design of new antitumor drugs which interfere with telomeric DNA structure and formation of DNA-shelterin complexes are discussed.

Mutation status of Kirsten rat sarcoma viral oncogene homolog (KRAS) may serve as a negative predictive marker of Cetuximab in treating colorectal cancer. The present study was to determine the role of KRAS status in EGFR antibody treatment for gastric cancer. KRAS status was clarified in SGC-7901 (wild type) and YCC-2 (G→A mutation) gastric cancer cell lines. Anti-proliferative and pro-apoptotic effects of Cetuximab were tested both in vitro and in vivo, the expression of phosphorylated (p) ERK, a downstream protein in EGFR-RAS-MEK pathway, was also analyzed. No significant in vitro anti-proliferative or pro-apoptotic effects of Cetuximab were observed in both cell lines. The growth of either SGC-7901 or YCC-2 gastric cancer xenograft was significantly inhibited by Cetuximab. Apoptosis was induced in SGC-7901 but not in YCC-2 xenografts after Cetuximab treatment. The expression of pERK was up-regulated in YCC-2 but not SGC-7901 xenografts after Cetuximab treatment. In conclusion, KRAS (G→A) mutation does not affect in vivo anti-cancer efficacy of Cetuximab.