8 research outputs found
Mechanisms of confluence-dependent expression of CD26 in colon cancer cell lines
<p>Abstract</p> <p>Background</p> <p>CD26 (dipeptidyl peptidase IV, DPPIV) is a 110 kDa surface glycoprotein expressed in most normal tissues, and is a potential novel therapeutic target for selected cancers. Our work evaluates the mechanism involved in confluence-dependent CD26 expression in colon cancer.</p> <p>Methods</p> <p>Colon adenocarcinoma cells were grown to confluence, and expression of CD26 and transcription factors implicated in its regulation was confirmed by immunofluorescence and Western blotting. Real-time PCR was also performed to evaluate CD26 upregulation at the transcriptional level. The influence of c-Myc on CD26 expression during different growth conditions was further evaluated following transient transfection of a c-Myc-expressing plasmid and a c-Myc specific siRNA.</p> <p>Results</p> <p>We found that the colon cancer cell lines HCT-116 and HCT-15 exhibited a confluence-dependent increase in CD26 mRNA and protein, associated with decreased expression of c-Myc, increased USF-1 and Cdx 2 levels, and unchanged HNF-1α expression. Meanwhile, ectopic expression of c-Myc in both cell lines led to decreased CD26 expression. In contrast, transfection of a siRNA targeted to Cdx2 resulted in decreased CD26 level. Importantly, culturing of cells in serum-depleted media, but not acidic conditions, upregulated CD26. While HIF-1α level also increased when cells were cultured in serum-depleted media, its expression was required but not sufficient for CD26 upregulation.</p> <p>Conclusions</p> <p>CD26 mRNA and protein levels increase in a confluence-dependent manner in colon carcinoma cell lines, with c-Myc acting as a repressor and Cdx2 acting as an enhancer of CD26 expression. The enhanced expression of CD26 in serum-depleted media and a requirement for HIF-1α suggest a role for nutrients or growth factors in the regulation of CD26 protein expression.</p
Combination therapy for renal cell cancer: what are possible options?
Antiangiogenic therapy has shown promise in the treatment of patients with renal cell carcinoma (RCC). Two classes of antiangiogenic drugs, the anti-vascular endothelial growth factor antibody bevacizumab and the tyrosine kinase inhibitors sorafenib, sunitinib and pazopanib, have shown efficacy in patients with RCC and are approved by the US Food and Drug Administration for treatment of this cancer. In practice, the clinical benefit of antiangiogenic drugs in RCC has been heterogeneous, and in patients who do respond, benefits are modest and/or short-lived. To improve efficacy, combination targeted therapy has been attempted, but with either very limited additional efficacy or nontolerable toxicities. Recent advances in the molecular understanding of tumor angiogenesis and mechanism of resistance, along with the rapid development of targeted drug discovery, have made it possible to further explore novel combination therapy for RCC
Multidimensional Screening Platform for Simultaneously Targeting Oncogenic KRAS and Hypoxia-Inducible Factors Pathways in Colorectal Cancer
Colorectal cancer (CRC) is a genetic
disease, due to progressive accumulation of mutations in oncogenes
and tumor suppressor genes. Large scale genomic sequencing projects
revealed >100 mutations in any individual CRC. Many of these mutations
are likely passenger mutations, and fewer are driver mutations. Of
these, activating mutations in RAS proteins are essential for cancer
initiation, progression, and/or resistance to therapy. There has been
significant interest in developing drugs targeting mutated cancer
gene products or downstream signaling pathways. Due to the number
of mutations involved and inherent redundancy in intracellular signaling,
drugs targeting one mutation or pathway have been either ineffective
or led to rapid resistance. We have devised a strategy whereby multiple
cancer pathways may be simultaneously targeted for drug discovery.
For proof-of-concept, we targeted the oncogenic KRAS and HIF pathways,
since oncogenic KRAS has been shown to be required for cancer initiation
and progression, and HIF-1α and HIF-2α are induced by
the majority of mutated oncogenes and tumor suppressor genes in CRC.
We have generated isogenic cell lines defective in either oncogenic
KRAS or both HIF-1α and HIF-2α and subjected them to multiplex
genomic, siRNA, and high-throughput small molecule screening. We have
identified potential drug targets and compounds for preclinical and
clinical development. Screening of our marine natural product library
led to the rediscovery of the microtubule agent dolastatin 10 and
the class I histone deacetylase (HDAC) inhibitor largazole to inhibit
oncogenic KRAS and HIF pathways. Largazole was further validated as
an antiangiogenic agent in a HIF-dependent manner in human cells and <i>in vivo</i> in zebrafish using a genetic model with activated
HIF. Our general strategy, coupling functional genomics with drug
susceptibility or chemical-genetic interaction screens, enables the
identification of potential drug targets and candidates with requisite
selectivity. Molecules prioritized in this manner can easily be validated
in suitable zebrafish models due to the genetic tractability of the
system. Our multidimensional platform with cellular and organismal
components can be extended to larger scale multiplex screens that
include other mutations and pathways