[Show abstract][Hide abstract] ABSTRACT: Background:Isolation of colorectal cancer (CRC) cell populations enriched for cancer stem cells (CSCs) may facilitate target identification. There is no consensus regarding the best methods for isolating CRC stem cells (CRC-SCs). We determined the suitability of various cellular models and various stem cell markers for the isolation of CRC-SCs.Methods:Established human CRC cell lines, established CRC cell lines passaged through mice, patient-derived xenograft (PDX)-derived cells, early passage/newly established cell lines, and cells directly from clinical specimens were studied. Cells were FAC-sorted for the CRC-SC markers CD44, CD133, and aldehyde dehydrogenase (ALDH). Sphere formation and in vivo tumorigenicity studies were used to validate CRC-SC enrichment.Results:None of the markers studied in established cell lines, grown either in vitro or in vivo, consistently enriched for CRC-SCs. In the three other cellular models, CD44 and CD133 did not reliably enrich for stemness. In contrast, freshly isolated PDX-derived cells or early passage/newly established CRC cell lines with high ALDH activity formed spheres in vitro and enhanced tumorigenicity in vivo, whereas cells with low ALDH activity did not.Conclusions:PDX-derived cells, early passages/newly established CRC cell lines and cells from clinical specimen with high ALDH activity can be used to identify CRC-SC-enriched populations. Established CRC cell lines should not be used to isolate CSCs.British Journal of Cancer advance online publication, 23 December 2014; doi:10.1038/bjc.2014.620 www.bjcancer.com.
British Journal of Cancer 12/2014; 112(3). · 4.82 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Purpose: We hypothesized that chemotherapy synergizes with VEGF/VEGFR (VEGF/R) inhibitors in patients with advanced solid malignancies. Patients and Methods: Patients treated on phase I protocols between December 2004 and July 2013 (n=1,498) were included in this analysis. The primary outcome was clinical benefit, defined as stable disease ≥6 months, complete response, or partial response. Two odds ratios (ORs) for achieving clinical benefit were calculated: one for patients treated with a VEGF/R inhibitors (OR with VEGF/R) and another for patients treated without (OR without VEGF/R). To compare these two ORs, an interaction term was included in the multivariate model: (chemotherapy/factor of interest)×(VEGF/R). We took significant interaction terms (interaction P<0.05) to suggest effect modification (either synergy or antagonism) with VEGF/R inhibitors. Results: All patients treated with VEGF/R inhibitors exhibited higher OR for clinical benefit than those who were not (OR=1.9 ([95% confidence interval [CI] 1.5-2.4], P<0.0001). Use of chemotherapy agents concomitant with VEGF/R inhibitors was associated with significantly higher OR for clinical benefit compared to chemotherapy use without VEGF/R inhibitors (OR with VEGF/R=1.6 [95% CI 1.1-2.5] v. OR without VEGF/R=0.4 [95% CI 0.3-0.6], interaction P=0.02). Specifically, the anti-metabolite class was associated with the greatest increase in OR for clinical benefit (OR with VEGF/R=2.7 [95% CI 1.5-4.7] v. OR without VEGF/R=0.2 [95% CI 0.1-0.3], interaction P=0.004). Conclusions: VEGF/R inhibitor was found to synergize with chemotherapeutics. This effect was most pronounced with the anti-metabolite class.
Clinical Cancer Research 10/2014; · 8.19 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Despite being amongst the most common oncogenes in human cancer, to date there are no effective clinical options for inhibiting KRAS activity. We investigated whether systemically delivered KRAS siRNAs have therapeutic potential in KRAS mutated cancer models. We identified KRAS siRNA sequences with notable potency in knocking-down KRAS expression. Using lung and colon adenocarcinoma cell lines, we assessed anti-proliferative effects of KRAS silencing in vitro. For in vivo experiments, we used a nano-liposomal delivery platform, DOPC, for systemic delivery of siRNAs. Various lung and colon cancer models were utilized to determine efficacy of systemic KRAS siRNA based on tumor growth, development of metastasis and down-stream signaling. KRAS siRNA sequences induced >90% knock-down of KRAS expression, significantly reducing viability in mutant cell lines. In the lung cancer model, KRAS siRNA treatment demonstrated significant reductions in primary tumor growth and distant metastatic disease, while the addition of CDDP was not additive. Significant reductions in Ki-67 indices were seen in all treatment groups, while significant increases in caspase-3 activity was only seen in the CDDP treatment groups. In the colon cancer model, KRAS siRNA reduced tumor KRAS and pERK expression. KRAS siRNAs significantly reduced HCP1 subcutaneous tumor growth, as well as outgrowth of liver metastases. Our studies demonstrate a proof-of-concept approach to therapeutic KRAS targeting using nanoparticle delivery of siRNA. This study highlights the potential translational impact of therapeutic RNA interference, which may have broad applications in oncology, especially for traditional "undruggable" targets.
Molecular Cancer Therapeutics 10/2014; · 5.60 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Metastasis and drug resistance are the major limitations in the survival and management of cancer patients. This study aimed to identify the mechanisms underlying HT29 colon cancer cell chemoresistance acquired after sequential exposure to 5-fluorouracil (5FU), a classical anticancer drug for treatment of epithelial solid tumors. We examined its clinical relevance in a cohort of colon cancer patients with liver metastases after 5FU-based neoadjuvant chemotherapy and surgery.
We show that a clonal 5F31 cell population, resistant to 1μM 5FU, express a typical cancer stem cell-like phenotype and enter into a reversible quiescent G0-state upon re-exposure to higher 5FU concentrations. These quiescent cells overexpressed the tyrosine kinase c-Yes that became activated and membrane-associated upon 5FU exposure. This enhanced signaling pathway induced the dissociation of the Yes/YAP (Yes-associated protein) molecular complex and depleted nuclear YAP levels. Consistently, c-Yes silencing decreased nuclear YAP accumulation and induced cellular quiescence in 5F31 cells cultured in 5FU-free medium. Importantly, c-Yes and YAP transcript levels were higher in liver metastases of colon cancer patients after 5FU-based neoadjuvant chemotherapy. Moreover, the c-Yes and YAP levels positively correlated with colon cancer relapse and shorter patient survival (p<0.05 and p<0.025, respectively).
We identified c-Yes and YAP as potential molecular targets to eradicate quiescent cancer cells and dormant micrometastases during 5FU chemotherapy and resistance and as predictive survival markers for colon cancer.
Clinical Cancer Research 12/2013; · 8.19 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: LGR4 is an R-spondin receptor with strong positive effect on Wnt signaling. It plays a critical role in development as its ablation in the mouse led to total embryonic/neonatal lethality with profound defects in multiple organs. Haplotype insufficiency of LGR4 in human was associated with several diseases, including increased risk of squamous cell carcinoma of the skin, reduced birth weights, electrolyte imbalance, and decreased levels of testosterone, which are similar to the phenotypes of LGR4-hypomorphic mice. Tissue distribution of LGR4 was extensively analyzed in the mouse using gene-trap reporter enzyme alleles. However, its expression pattern in human tissues remained largely unknown. We have developed LGR4-specific monoclonal antibodies and used them to examine the expression of LGR4 in selected adult human and mouse tissues by immunohistochemical analysis. Intense LGR4-like immunoreactivity was observed in the epidermis and hair follicle of the skin, pancreatic islet cells, and epithelial cells in both the male and female reproductive organs. Of particular interest is that LGR4 is highly expressed in germ cells and pancreatic islet cells, which have important implications given the role of R-spondin-LGR4 signaling in the survival of adult stem cells. In addition, the majority of colon tumors showed elevated levels of LGR4 receptor. Overall, the expression pattern of LGR4 in human tissues mapped by this IHC analysis is similar to that in the mouse as revealed from gene trap alleles. Importantly, the pattern lends strong support to the important role of LGR4 in the development and maintenance of skin, kidney, reproductive systems, and other organs.
PLoS ONE 10/2013; 8(10):e78144. · 3.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Combination chemotherapy is standard for metastatic colorectal cancer (CRC); however, nearly all patients develop drug resistance. Understanding the mechanisms that lead to resistance to individual chemotherapeutic agents may enable identification of novel targets and more effective therapy. Irinotecan is commonly used in first- and second-line therapy for patients with metastatic CRC, with the active metabolite being SN38. Emerging evidence suggests that altered metabolism in cancer cells is fundamentally involved in the development of drug resistance. Using Oncomine and unbiased proteomic profiling, we found that ATP citrate lyase (ACLy), the first-step rate-limiting enzyme for de novo lipogenesis, was upregulated in CRC compared to its levels in normal mucosa and in chemoresistant CRC cells compared to isogenic chemo-naïve CRC cells. Overexpression of exogenous ACLy by lentivirus transduction in chemo-naïve CRC cells led to significant chemoresistance to SN38 but not to 5-fluorouracil or oxaliplatin. Knockdown of ACLy by siRNA or inhibition of its activity by a small-molecule inhibitor sensitized chemo-naïve CRC cells to SN38. Furthermore, ACLy was significantly increased in cancer cells that had acquired resistance to SN38. In contrast to chemo-naïve cells, targeting ACLy alone was not effective in re-sensitizing resistant cells to SN38, due to a compensatory activation of the AKT pathway triggered by ACLy suppression. Combined inhibition of AKT signaling and ACLy successfully re-sensitized SN38-resistant cells to SN38. We conclude that targeting ACLy may improve the therapeutic effects of irinotecan and that simultaneous targeting of ACLy and AKT may be warranted to overcome SN38 resistance.
Molecular Cancer Therapeutics 10/2013; · 5.60 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Therapeutic antibody development is one of the fastest growing areas of the pharmaceutical industry. Generating high-quality monoclonal antibodies against a given therapeutic target is crucial for successful drug development. However, due to immune tolerance, making it difficult to generate antibodies using conventional approaches.
Mixed four human gastric cancer (GC) cell lines were used as the immunogen in A/J mice; sixteen highly positive hybridoma colonies were selected via fluorescence-activated cell sorting-high throughput screening (FACS-HTS) using a total of 20,000 colonies in sixty-seven 96-well plates against live cells (mixed human GC cells versus human PBMC controls). MS17-57 and control commercial Alkaline Phosphatase (ALP) mAbs were used to confirm the target antigens (Ags), which were identified as ALPs expressed on the GC cell surface through a combination of western blot, immunoprecipitation and mass spectrometry (MS). MS identified the Ags recognized by MS17-57 to be two variants of a secreted ALP, PALP and IALP (Placental and intestinal ALP). These proteins belong to a hydrolase enzyme family responsible for removing phosphate groups from many types of molecules. Immunofluorescence staining using MS17-57 demonstrated higher staining of gastrointestinal (GI) cancer tissues compared to normal GI tissues (P<0.03), and confirmed binding of MS17-57 to be restricted to a functional epitope expressed on the cancer cell surface. Proliferation assays using the PALP/IALP-expressing GC cell lines demonstrated that MS17-57 inhibited cell growth by 32±8%. Transwell cell migration assays documented that MS17-57 can inhibit PALP/IALP-expressing GI cancer cell migration by 25±5%. MS17-57 mAb inhibited tumor growth in nude mice.
Our findings indicate that PALP and IALP can be ectopically expressed on extracellular matrix of GI cancers, and that MS17-57 directed against PALP/IALP can inhibit GI cancer cells growth and migration in vitro and in vivo. This investigation provides an example of identification of cancer biomarkers representing promising therapeutic targets using mAb generated through a novel HTS technology.
PLoS ONE 10/2013; 8(10):e77398. · 3.53 Impact Factor
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[Show abstract][Hide abstract] ABSTRACT: Circulating angiogenic factors are altered in patients with mCRC receiving bevacizumab. Evaluation of alterations in levels of VEGF ligands may provide insights into possible resistance mechanisms.
PlGF, VEGF-A, VEGF-C, and VEGF-D were measured from two cohorts of patients. Sequential plasma samples were obtained from a discovery cohort of 42 patients treated with chemotherapy and bevacizumab. A validation cohort included plasma samples from a cross-sectional of 403 patients prior to chemotherapy, or after progression on a regimen with or without bevacizumab.
In the discovery cohort, VEGF-C was increased prior to progression and at progression (+49% and +95%, respectively, p<0.01), consistent with previously reported elevations in PlGF. Levels of VEGF-D were increased (+23%) at progression (p=0.05). In the validation cohort, samples obtained from patients after progression on a regimen with bevacizumab had higher levels of PlGF and VEGF-D (+43% and +6%, p=0.02, p=0.01, respectively) compared to untreated patients, but failed to validate the increase in VEGF-C seen in the first cohort. Patients who progressed on chemotherapy with bevacizumab had significantly elevated levels of PlGF (+88%) but not VEGF-C and VEGF-D compared to patients treated with chemotherapy alone. Elevations of PlGF and VEGF-D appeared transient and returned to baseline with a half-life of 6 weeks.
Increases in PlGF and VEGF-D were observed after progression on chemotherapy with bevacizumab. These changes appear to be reversible after discontinuing therapy. These ligands are associated with resistance to bevacizumab-containing chemotherapy in mCRC, but causation remains to be established.
PLoS ONE 10/2013; 8(10):e77117. · 3.53 Impact Factor
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[Show abstract][Hide abstract] ABSTRACT: Chemotherapy for patients with metastatic colorectal cancer (CRC) is the standard of care, but ultimately nearly all patients develop drug resistance. Understanding the mechanisms that lead to resistance to individual chemotherapeutic agents may help identify novel targets and drugs that will, in turn, improve therapy. Oxaliplatin is a common component combination therapeutic regimen for use in patients with metastatic CRC, but is also used as a component of adjuvant therapy for patients at risk for recurrent disease. In this study, unbiased microRNA array screening revealed that the miR-203 microRNA is up-regulated in three of three oxaliplatin-resistant CRC cell lines, and therefore we investigated the role of miR-203 in chemoresistance. Exogenous expression of miR-203 in chemo-naïve CRC cells induced oxaliplatin resistance. Knockdown of miR-203 sensitized chemoresistant CRC cells to oxaliplatin. In silico analysis identified ataxia telangiectasia mutated (ATM), a primary mediator of the DNA damage response, as a potential target of miR-203. ATM mRNA and protein levels were significantly down-regulated in CRC cells with acquired resistance to oxaliplatin. Using TCGA database, we identified a significant reverse correlation of miR-203 and ATM expression in CRC tissues. We validated ATM as a bona fide target of miR-203 in CRC cells. Mutation of the putative miR-203 binding site in the 3' untranslated region (3'UTR) of the ATM mRNA abolished the inhibitory effect of miR-203 on ATM. Furthermore, stable knockdown of ATM induced resistance to oxaliplatin in chemo-naïve CRC cells. This is the first report of oxaliplatin resistance in CRC cells induced by miR-203-mediated suppression of ATM.
[Show abstract][Hide abstract] ABSTRACT: Expression of microRNAs (miRNAs) involves transcription of miRNA genes and maturation of the primary transcripts. Recent studies have shown that posttranscriptional processing of primary and precursor miRNAs is induced after DNA damage through regulatory RNA-binding proteins in the Drosha and Dicer complexes, such as DDX5 and KSRP. However, little is known about the regulation of nuclear export of pre-miRNAs in the DNA-damage response, a critical step in miRNA maturation. Here, we show that nuclear export of pre-miRNAs is accelerated after DNA damage in an ATM-dependent manner. The ATM-activated AKT kinase phosphorylates Nup153, a key component of the nucleopore, leading to enhanced interaction between Nup153 and Exportin-5 (XPO5) and increased nuclear export of pre-miRNAs. These findings define an important role of DNA-damage signaling in miRNA transport and maturation.
[Show abstract][Hide abstract] ABSTRACT: The pharmaceutical and biotechnology industries depend on findings from academic investigators prior to initiating programs to develop new diagnostic and therapeutic agents to benefit cancer patients. The success of these programs depends on the validity of published findings. This validity, represented by the reproducibility of published findings, has come into question recently as investigators from companies have raised the issue of poor reproducibility of published results from academic laboratories. Furthermore, retraction rates in high impact journals are climbing.
To examine a microcosm of the academic experience with data reproducibility, we surveyed the faculty and trainees at MD Anderson Cancer Center using an anonymous computerized questionnaire; we sought to ascertain the frequency and potential causes of non-reproducible data. We found that ∼50% of respondents had experienced at least one episode of the inability to reproduce published data; many who pursued this issue with the original authors were never able to identify the reason for the lack of reproducibility; some were even met with a less than "collegial" interaction.
These results suggest that the problem of data reproducibility is real. Biomedical science needs to establish processes to decrease the problem and adjudicate discrepancies in findings when they are discovered.
PLoS ONE 05/2013; 8(5):e63221. · 3.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Therapy targeting VEGF has become the standard of care in several solid malignancies. Early investigations attempting to identify predictive markers for the efficacy of therapy failed to identify any predictive markers that could help oncologist decide who should, and more importantly, who should not receive VEGF-targeted therapies. However, there has been renewed interest in predictive biomarkers for VEGF-targeted therapies especially in light of the fact that the US Food and Drug Administration withdrew approval for use of bevacizumab, an antibody to VEGF, in patients with metastatic breast cancer. In a recent publication in the Journal of Clinical Oncology, investigators identified circulating VEGF and tumor neuropilin-1 expression as potential predictive biomarkers for bevacizumab. In this perspective, we provide a critical evaluation of the utility of these markers, and the need for validation in prospective clinical trials.
Clinical Cancer Research 04/2013; · 8.19 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We report a paracrine effect whereby endothelial cells (ECs) promote the cancer stem cell (CSC) phenotype of human colorectal cancer (CRC) cells. We showed that, without direct cell-cell contact, ECs secrete factors that promoted the CSC phenotype in CRC cells via Notch activation. In human CRC specimens, CD133 and Notch intracellular domain-positive CRC cells colocalized in perivascular regions. An EC-derived, soluble form of Jagged-1, via ADAM17 proteolytic activity, led to Notch activation in CRC cells in a paracrine manner; these effects were blocked by immunodepletion of Jagged-1 in EC-conditioned medium or blockade of ADAM17 activity. Collectively, ECs play an active role in promoting Notch signaling and the CSC phenotype by secreting soluble Jagged-1.
[Show abstract][Hide abstract] ABSTRACT: Bone marrow-derived cells have a potent impact on the formation and progression of tumor metastasis. This study demonstrates that bone marrow directly promotes metastasis to distant sites from tumor cells residing in the bone marrow in multiple types of tumors and multiple tumor cell lines. The bone marrow environment requires less tumor cells for inducing distant metastasis and overcomes the inhibition of metastasis resulting from engineering the tumor cells with reporter genes. This discovery provides an effective approach to generate spontaneous-like metastatic tumor models which will satisfy the urgent need for studying metastasis biology and discovering novel therapeutics.