Development of Halofluorochromic Polymer Nanoassemblies for the Potential Detection of Liver Metastatic Colorectal Cancer Tumors Using Experimental and Computational Approaches.

PURPOSE: To develop polymer nanoassemblies (PNAs) modified with halofluorochromic dyes to allow for the detection of liver metastatic colorectal cancer (CRC) to improve therapeutic outcomes. METHODS: We combine experimental and computational approaches to evaluate macroscopic and microscopic PNA distributions in patient-derived xenograft primary and orthotropic liver metastatic CRC tumors. Halofluorochromic and non-halofluorochromic PNAs (hfPNAs and n-hfPNAs) were prepared from poly(ethylene glycol), fluorescent dyes (Nile blue, Alexa546, and IR820), and hydrophobic groups (palmitate), all of which were covalently tethered to a cationic polymer scaffold [poly(ethylene imine) or poly(lysine)] forming particles with an average diameter < 30 nm. RESULTS: Dye-conjugated PNAs showed no aggregation under opsonizing conditions for 24 h and displayed low tissue diffusion and cellular uptake. Both hfPNAs and n-hfPNAs accumulated in primary and liver metastatic CRC tumors within 12 h post intravenous injection. In comparison to n-hfPNAs, hfPNAs fluoresced strongly only in the acidic tumor microenvironment (pH < 7.0) and distinguished small metastatic CRC tumors from healthy liver stroma. Computational simulations revealed that PNAs would steadily accumulate mainly in acidic (hypoxic) interstitium of metastatic tumors, independently of the vascularization degree of the tissue surrounding the lesions. CONCLUSION: The combined experimental and computational data confirms that hfPNAs detecting acidic tumor tissue can be used to identify small liver metastatic CRC tumors with improved accuracy.

PKD prevents H2O2-induced apoptosis via NF-kappaB and p38 MAPK in RIE-1 cells.

Previously, we demonstrated that protein kinase D (PKD) plays a protective role during H(2)O(2)-induced intestinal cell death. Here, we sought to determine whether this effect is mediated by nuclear factor-kappaB (NF-kappaB) and mitogen-activated protein kinases (MAPKs). Treatment with H(2)O(2) activated NF-kappaB in RIE-1 cells; H(2)O(2) also induced the translocation of NF-kappaB p65 as well as phosphorylation of IkappaB-alpha. PKD1 siRNA inhibited H(2)O(2)-induced activation, translocation of NF-kappaB, and phosphorylation of IkappaB-alpha. We also found that overexpression of wild type PKD1 attenuated H(2)O(2)-induced phosphorylation of p38 MAPK and its upstream activator, MAPK kinase (MKK) 3/6, whereas the phosphorylation was increased by PKD1 siRNA or kinase-dead PKD1. Phosphorylation of neither extracellular signal-regulated kinases (ERK) 1/2 nor c-Jun N-terminal kinases (JNK) was altered by PKD1 plasmids or siRNA. Our findings suggest that PKD protects intestinal cells through up-regulation of NF-kappaB and down-regulation of p38 MAPK.

Colorectal cancer lung metastasis treatment with polymer-drug nanoparticles.

Colorectal cancer (CRC) is the second leading cause of cancer deaths in the United States; the predominant cause for mortality is metastasis to distant organs (e.g., lung). A major problem limiting the success of chemotherapy in metastatic CRC is the inability to target tumor tissues selectively and avoid severe side effects to normal tissues and organs. Here, we demonstrate polymeric nanoparticles (PNPs) entrapping chemotherapeutic agents provide a new therapeutic option for treating CRC that has metastasized to the lung. PNPs assembled from FDA approved biocompatible block copolymer accumulated predominantly in lung tissue. PNPs showed negligible accumulation in liver, spleen and kidneys, which was confirmed by fluorescent nanoparticle imaging and analysis of PI3K inhibition in the organs. PNPs entrapping PI3K inhibitors (i.e., wortmannin and PX866) suppressed CRC lung metastasis growth, and SN-38-loaded PNPs completely eliminated CRC lung metastasis. Our results demonstrate that polymer-drug nanoparticles offer a new approach to reduce toxicity of cancer therapy and has the potential to improve outcomes for patients with lung metastasis.

Adipocytes activate mitochondrial fatty acid oxidation and autophagy to promote tumor growth in colon cancer.

Obesity has been associated with increased incidence and mortality of a wide variety of human cancers including colorectal cancer. However, the molecular mechanism by which adipocytes regulate the metabolism of colon cancer cells remains elusive. In this study, we showed that adipocytes isolated from adipose tissues of colon cancer patients have an important role in modulating cellular metabolism to support tumor growth and survival. Abundant adipocytes were found in close association with invasive tumor cells in colon cancer patients. Co-culture of adipocytes with colon cancer cells led to a transfer of free fatty acids that released from the adipocytes to the cancer cells. Uptake of fatty acids allowed the cancer cells to survive nutrient deprivation conditions by upregulating mitochondrial fatty acid ß-oxidation. Mechanistically, co-culture of adipocytes or treating cells with fatty acids induced autophagy in colon cancer cells as a result of AMPK activation. Inhibition of autophagy attenuated the ability of cancer cells to utilize fatty acids and blocked the growth-promoting effect of adipocytes. In addition, we found that adipocytes stimulated the expression of genes associated with cancer stem cells and downregulated genes associated with intestinal epithelial cell differentiation in primary colon cancer cells and mouse tumor organoids. Importantly, the presence of adipocytes promoted the growth of xenograft tumors in vivo. Taken together, our results show that adipocytes in the tumor microenvironment serve as an energy provider and a metabolic regulator to promote the growth and survival of colon cancer cells.

The role of NF-kappaB/IkappaB proteins in cancer: implications for novel treatment strategies.

The nuclear factor-kappaB (NF-kappaB) family of transcription factors are involved in multiple cellular processes, including cytokine gene expression, cellular adhesion, cell cycle activation, apoptosis and oncogenesis. Constitutive activation of NF-kappaB has been described in a number of solid tumors and this activation appears to affect cancer cell survival. Inhibition of NF-kappaB has been shown to enhance the sensitivity of some cancer cell lines to antineoplastic- or radiation-induced apoptosis. Furthermore, suppression of NF-kappaB results in attenuation of cancer cachexia in a mouse tumor model. Studies are underway to further delineate the role of NF-kappaB in cancer cell survival, growth and resistance to standard chemotherapy and radiation regimens. Moreover, the effects of novel therapeutic agents which specifically target NF-kappaB proteins are currently being assessed in experimental models of cancer cell growth both in vitro and in vivo. In this review, we discuss the possible involvement of NF-kappaB in the growth of various solid tumors and potential future treatment strategies based on NF-kappaB inhibition.

Current management of gastrointestinal carcinoid tumors.

Gastrointestinal carcinoid tumors are rare neuroendocrine tumors arising from the embryologic primitive gut. Depending on the location in the gastrointestinal tract, these tumors may secrete a variety of hormonally active substances. However, many of these tumors are found incidentally, or the diagnosis is made postoperatively. Also, there is a significant incidence of multicentric carcinoid tumors and synchronous noncarcinoid malignancies in these patients. Treatment is usually based on the size of the tumor. Surgical resection remains the cornerstone of therapy. For advanced metastatic disease, somatostatin analog therapy and surgical debulking provide the best symptomatic relief and may improve survival. Recent studies have demonstrated a benefit from radiolabeled somatostatin analogs for carcinoid tumor localization. In contrast, radiolabeled somatostatin analogs have shown little therapeutic benefit. Future directions include somatostatin receptor profiling of carcinoid tumors, with somatostatin analog therapy targeting the specific receptors.

Oxidative stress-induced intestinal epithelial cell apoptosis is mediated by p38 MAPK.

Free oxygen radicals are involved in the pathogenesis of necrotizing enterocolitis (NEC) in premature infants. The stress-activated p38 mitogen-activated protein kinase (MAPK) has been implicated in gut injury. Here, we found that phosphorylated p38 was detected primarily in the villus tips of normal intestine, whereas it was expressed in the entire mucosa in NEC. H(2)O(2) treatment resulted in a rapid phosphorylation of p38 MAPK and subsequent apoptosis of rat intestinal epithelial (RIE)-1 cells; this induction was attenuated by treatment with SB203580, a selective p38 MAPK inhibitor, or transfection with p38alpha siRNA. Moreover, SB203580 also blocked H(2)O(2)-induced PKC activation. In contrast, the PKC inhibitor (GF109203x) did not affect p38 activation, indicating that p38 MAPK activation occurs upstream of PKC activation in H(2)O(2)-induced apoptosis. H(2)O(2) treatment also decreased mitochondrial membrane potential; pretreatment with SB203580 attenuated this response. Our study demonstrates that the p38 MAPK/PKC pathway plays an important role as a pro-apoptotic cellular signaling during oxidative stress-induced intestinal epithelial cell injury.

Inflammatory mechanisms contributing to pancreatic cancer development.

OBJECTIVE: Pancreatic cancer is the most deadly of all gastrointestinal (GI) malignancies, yet relatively little is known regarding mechanisms of tumor development including the role of inflammation. SUMMARY BACKGROUND DATA: Chronic pancreatitis (CP) increases the risk of developing cancer by 10- to 20-fold; mediators of the chronic inflammatory process and the surrounding fibrotic stroma likely support a transformation to malignancy, yet the exact mechanisms remain undefined. The purpose of our present study was to determine potential inflammatory components in epithelial and stromal cells that may contribute to both CP and pancreatic cancers. METHODS: Specimens of normal pancreas, CP, and pancreatic cancer were examined using laser-capture microdissection (LCM), gene array, and immunohistochemistry. RESULTS: Gene array analysis from LCM-dissected tissues demonstrated: (i) increased expression of interleukin-8 (IL-8), an activator of the inflammatory factor nuclear factor-kappaB (NF-kappaB), and (ii) decreased expression of IkappaB (an inhibitor of NF-kappaB) in CP ductal cells compared with normal ducts. Compared with CP, cancers demonstrated: (i) increased expression of tumor related genes including S100A4, cyclin E1, and epidermal growth factor (EGF) receptor, and (ii) expression of matrix metalloproteinase 2, a pro-invasive factor for tumor cells, which was not present in the CP stroma. Increased staining of both the p50 NF-kappaB subunit and IKKalpha kinase (a protein that allows activation of NF-kappaB) was noted in CP and cancers. CONCLUSIONS: Our results demonstrate that similar inflammatory components and downstream effectors are present in CP and pancreatic cancers. Importantly, these findings suggest that a common pathway for pancreatic cancer development may be through a chronic inflammatory process including stroma formation. These findings may lead to novel strategies for pancreatic cancer prophylaxis based on inhibition of inflammatory mediators.

Gut peptide receptor expression in human pancreatic cancers.

OBJECTIVE: To determine the prevalence of gastrointestinal (GI) peptide receptor expression in pancreatic cancers, and to further assess signaling mechanisms regulating neurotensin (NT)-mediated pancreatic cancer growth. SUMMARY BACKGROUND DATA: Pancreatic cancer remains one of the leading causes of GI cancer death; novel strategies for the early detection and treatment of these cancers is required. Previously, the authors have shown that NT, an important GI hormone, stimulates the proliferation of an NT receptor (NTR)-positive pancreatic cancer. METHODS: A total of 26 human pancreatic adenocarcinomas, obtained after resection, and 5 pancreatic cancer xenografts were analyzed for expression of NTR, vasoactive intestinal peptide receptor (VIPR), substance P receptor (SPR), and gastrin-releasing peptide receptor (GRPR). In addition, NTR expression, [Ca2+]i mobilization, and growth in response to NT was determined in L3.6, a metastatic pancreatic cancer cell line. RESULTS: Neurotensin receptor was expressed in 88% of the surgical specimens examined and all five of the pancreatic cancer xenografts. In contrast, VIPR, SPR, and GRPR expression was detected in 31%, 27%, and 8% of pancreatic cancers examined, respectively. Expression of NTR, functionally coupled to the Ca2+ signaling pathway, was identified in L3.6 cells; treatment with NT (10 micromol/L) stimulated proliferation of these cells. CONCLUSIONS: The authors demonstrated NTR expression in most of the pancreatic adenocarcinomas examined. In contrast, VIPR, SPR, and GRPR expression was detected in fewer of the pancreatic cancers. The expression of NTR and other peptide receptors suggests the potential role of endocrine manipulation in the treatment of these cancers. Further, the presence of GI receptors may provide for targeted chemotherapy or radiation therapy or in vivo scintigraphy for early detection.