Christopher O. McGovern

Targeted Indocyanine-Green-Loaded Calcium Phosphosilicate Nanoparticles for In Vivo Photodynamic Therapy of Leukemia

Leukemia is one of the most common and aggressive adult cancers, as well as the most prevalent childhood cancer. Leukemia is a cancer of the hematological system and can be divided into a diversity of unique malignancies based on the onset of the disease as well as the specific cell lineages involved. Cancer stem cells, including recently identified leukemia stem cells (LSCs), are hypothesized to be responsible for cancer development, relapse, and resistance to treatment, and new therapeutics targeting these cellular populations are urgently needed. Nontoxic and nonaggregating calcium phosphosilicate nanoparticles (CPSNPs) encapsulating the near-infrared fluoroprobe indocyanine green (ICG) were recently developed for diagnostic imaging and drug delivery as well as for photodynamic therapy (PDT) of solid tumors. Prior studies revealed that specific targeting of CPSNPs allowed for enhanced accumulation within breast cancer tumors, via CD71 targeting, or pancreatic cancer tumors, via gastrin receptor targeting. In the present study, ICG-loaded CPSNPs were evaluated as photosensitizers for PDT of leukemia. Using a novel bioconjugation approach to specifically target CD117 or CD96, surface features enhanced on leukemia stem cells, in vitro ICG-CPSNP PDT of a murine leukemia cell line and human leukemia samples were dramatically improved. Furthermore, the in vivo efficacy of PDT was dramatically enhanced in a murine leukemia model by utilizing CD117-targeted ICG-CPSNPs, resulting in 29% disease-free survival. Altogether, this study demonstrates that leukemia-targeted ICG-loaded CPSNPs offer the promise to effectively treat relapsing and multidrug-resistant leukemia and to improve the life of leukemia patients.

Bioconjugation of calcium phosphosilicate composite nanoparticles for selective targeting of human breast and pancreatic cancers in vivo.

The early diagnosis of cancer is the critical element in successful treatment and long-term favorable patient prognoses. The high rate of mortality is mainly attributed to the tendency for late diagnoses as symptoms may not occur until the disease has metastasized, as well as the lack of effective systemic therapies. Late diagnosis is often associated with the lack of timely sensitive imaging modalities. The promise of nanotechnology is presently limited by the inability to simultaneously seek, treat, and image cancerous lesions. This study describes the design and synthesis of fluorescent calcium phosphosilicate nanocomposite particles (CPNPs) that can be systemically targeted to breast and pancreatic cancer lesions. The CPNPs are a approximately 20 nm diameter composite composed of an amorphous calcium phosphate matrix doped with silicate in which a near-infrared imaging agent, indocyanine green (ICG), is embedded. In the present studies, we describe and validate CPNP bioconjugation of human holotransferrin, anti-CD71 antibody, and short gastrin peptides via an avidin-biotin or a novel PEG-maleimide coupling strategy. The conjugation of biotinylated human holotransferrin (diferric transferrin) and biotinylated anti-CD71 antibody (anti-transferrin receptor antibody) to avidin-conjugated CPNPs (Avidin-CPNPs) permits targeting of transferrin receptors, which are highly expressed on breast cancer cells. Similarly, the conjugation of biotinylated pentagastrin to Avidin-CPNPs and decagastrin (gastrin-10) to PEG-CPNPs via PEG-maleimide coupling permits targeting of gastrin receptors, which are overexpressed in pancreatic cancer lesions. These bioconjugated CPNPs have the potential to perform as a theranostic modality, simultaneously enhancing drug delivery, targeting, and imaging of breast and pancreatic cancer tumors.

Growth of human pancreatic cancer is inhibited by down-regulation of gastrin gene expression.

Objectives: This study evaluated the effects of gastrin messenger RNA (mRNA) down-regulation on growth of human pancreatic cancer. Methods: Gastrin expression was examined in human pancreatic cancer cell lines by reverse transcriptase-polymerase chain reaction, and peptide expression was assessed by immunocytochemistry. Gastrin was down-regulated using either stable transfection of an antisense gastrin cDNA or 1 of 3 shRNA (short hairpin RNA) constructs. Tumor formation was evaluated after either subcutaneous or orthotopic injections into nude mice. The effect of nanoliposomes loaded with gastrin siRNA (small interfering RNA) was tested in mice bearing pancreatic tumors. Results: Stable transfection of gastrin antisense or shRNAs into BxPC-3 cells resulted in clones with more than 90% reduction in gastrin mRNA. Tumor growth rate and incidence of metastases in both wild-type and transfected pancreatic cancer cells were directly proportional to the degrees of gastrin mRNA expression. Immunofluorescence analysis confirmed that gastrin peptide levels were decreased in antisense and shRNA tumors. Gastrin knockdown clones had lower Ki-67 and increased cleaved caspase-3 staining, consistent with known effects of gastrin on proliferation and apoptosis. Tumors in mice treated with gastrin siRNA were smaller than controls. Conclusions: These results suggest that RNAi targeting of gastrin could serve as an effective treatment for pancreatic cancer.

Downregulation of the CCK-B receptor in pancreatic cancer cells blocks proliferation and promotes apoptosis.

Gastrin stimulates the growth of pancreatic cancer cells through the activation of the cholecystokinin-B receptor (CCK-BR), which has been found to be overexpressed in pancreatic cancer. In this study, we proposed that the CCK-BR drives growth of pancreatic cancer; hence, interruption of CCK-BR activity could potentially be an ideal target for cancer therapeutics. The effect of CCK-BR downregulation in the human pancreatic adenocarcinoma cells was examined by utilizing specific CCK-BR-targeted RNA interference reagents. The CCK-BR receptor expression was both transiently and stably downregulated by transfection with selective CCK-BR small-interfering RNA or short-hairpin RNA, respectively, and the effects on cell growth and apoptosis were assessed. CCK-BR downregulation resulted in reduced cancer cell proliferation, decreased DNA synthesis, and cell cycle arrest as demonstrated by an inhibition of G(1) to S phase progression. Furthermore, CCK-BR downregulation increased caspase-3 activity, TUNEL-positive cells, and decreased X-linked inhibitor of apoptosis protein expression, suggesting apoptotic activity. Pancreatic cancer cell mobility was decreased when the CCK-BR was downregulated, as assessed by a migration assay. These results show the importance of the CCK-BR in regulation of growth and apoptosis in pancreatic cancer. Strategies to decrease the CCK-BR expression and activity may be beneficial for the development of new methods to improve the treatment for patients with pancreatic cancer.

Role of endogenous cholecystokinin on growth of human pancreatic cancer

Cholecystokinin (CCK) and gastrin stimulate growth of pancreatic cancer. Although down-regulation of gastrin inhibits growth of pancreatic cancer, the contribution of endogenous CCK to tumor growth is unknown. The purpose of this study was to evaluate the role of endogenous CCK on autocrine growth of pancreatic cancer. Pancreatic cancer cell lines were analyzed for CCK mRNA and peptide expression by real-time RT-PCR and radioimmunoassay, respectively. The effect of endogenous CCK on growth was evaluated by treating cancer cells with CCK neutralizing antibodies and by down-regulating CCK mRNA by RNAi. Wild-type pancreatic cancer cells expressed significantly lower CCK mRNA and peptide levels than gastrin. Neither treatment of pancreatic cancer cells with CCK antibodies nor the down-regulation of CCK mRNA and peptide by shRNAs altered growth in vitro or in vivo. Conversely, when gastrin mRNA expression was down-regulated, the same cells failed to produce tumors in spite of having sustained levels of endogenous CCK. Pancreatic cancer cells produce CCK and gastrin; however, the autocrine production of gastrin is more important for stimulating tumor growth.

The Opioid Antagonist Naltrexone Improves Murine Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is a condition of the intestine with significant morbidity. Although hereditary, environmental, immunologic, and bacterial factors have been implicated, the etiology of IBD remains unknown. Since opioid peptides modulate inflammatory cytokine production and opioid antagonists promote tissue growth and repair, we hypothesized the opioid antagonist naltrexone could reduce inflammation of the bowel. Using a chemically-induced mouse model of IBD, C57BL/6J mice received either untreated drinking water or water containing 2% dextran sulfate sodium (DSS) in two parallel regimens modeling moderate and severe colitis. After colitis was established, animals in the moderate colitis study were administered either saline (control) or naltrexone (NTX; 8 or 400 μ g/kg) daily, while those in the severe colitis study received 0.1 or 10 mg/kg NTX. DSS-treated animals had significant weight loss (p = 0.006) and higher disease activity index (DAI) scores (p < 0.001) compared to water controls. However, NTX treatment of mice with moderate colitis resulted in less weight loss, lower DAI scores, and less histologic evidence of inflammation compared to controls. Significantly, elevated levels of colonic RNA for pro-inflammatory cytokines interleukin (IL)-6 and IL-12 were also decreased toward normal with NTX. Similar to patients with severe and unresponsive disease, animals in the severe colitis study did not significantly respond to treatment. Thus, NTX therapy reverses physical symptoms, histologic evidence, and molecular markers of inflammation in moderate colitis. The mechanism by which NTX acts to reverse colitis is related in part to the decreased expression of pro-inflammatory cytokines.

PhotoImmunoNanoTherapy Reveals an Anticancer Role for Sphingosine Kinase 2 and Dihydrosphingosine-1-Phosphate

Tumor-associated inflammation mediates the development of a systemic immunosuppressive milieu that is a major obstacle to effective treatment of cancer. Inflammation has been shown to promote the systemic expansion of immature myeloid cells which have been shown to exert immunosuppressive activity in laboratory models of cancer as well as cancer patients. Consequentially, significant effort is underway toward the development of therapies that decrease tumor-associated inflammation and immunosuppressive cells. The current study demonstrated that a previously described deep tissue imaging modality, which utilized indocyanine green-loaded calcium phosphosilicate nanoparticles (ICG-CPSNPs), could be utilized as an immunoregulatory agent. The theranostic application of ICG-CPSNPs as photosensitizers for photodynamic therapy was shown to block tumor growth in murine models of breast cancer, pancreatic cancer, and metastatic osteosarcoma by decreasing inflammation-expanded immature myeloid cells. Therefore, this therapeutic modality was termed PhotoImmunoNanoTherapy. As phosphorylated sphingolipid metabolites have been shown to have immunomodulatory roles, it was hypothesized that the reduction of immature myeloid cells by PhotoImmunoNanoTherapy was dependent upon bioactive sphingolipids. Mechanistically, PhotoImmunoNanoTherapy induced a sphingosine kinase 2-dependent increase in sphingosine-1-phosphate and dihydrosphingosine-1-phosphate. Furthermore, dihydrosphingosine-1-phosphate was shown to selectively abrogate myeloid lineage cells while concomitantly allowing the expansion of lymphocytes that exerted an antitumor effect. Collectively, these findings revealed that PhotoImmunoNanoTherapy, utilizing the novel nontoxic theranostic agent ICG-CPSNP, can decrease tumor-associated inflammation and immature myeloid cells in a sphingosine kinase 2-dependent manner. These findings further defined a novel myeloid regulatory role for dihydrosphingosine-1-phosphate. PhotoImmunoNanoTherapy holds the potential to be a revolutionary treatment for cancers with inflammatory and immunosuppressive phenotypes.

A single nucleotide polymorphism of the cholecystokinin-B receptor predicts risk for pancreatic cancer

There currently are no tests available for early diagnosis or for the identification of patients at risk for development of pancreatic cancer. We report the discovery of single nucleotide polymorphism (SNP) in the cholecystokinin B receptor (CCKBR) gene predicts survival and risk of pancreatic cancer. Growth of human pancreatic cancer is stimulated by gastrin through the CCKBR and an alternatively spliced isoform of the CCKBR gene called CCKCR. One hundred and ten surgically resected benign and malignant pancreatic tissues as well as normal pancreas were prospectively evaluated for CCKBR genotype and protein expression. Analysis demonstrated the expression of the spliced isoform, CCKCR, was associated with a (SNP) (C > A) at position 32 of the intron 4 (IVS 4) of the CCKBR gene. Since the SNP is within an intron, it has not previously been identified in the GWAS studies. Only patients with the A/A or A/C genotypes, exhibited immunoreactivity to a selective CCKCR antibody. Survival among pancreatic cancer patients with the A-SNP was significantly shorter (p = 0.0001, hazard ratio = 3.63) compared with individuals with C/C genotype. Other variables such as surgical margins, lymph node status, histologic grade or adjuvant chemotherapy were not associated with survival. Furthermore, having one or two of the A-alleles was found to increase the risk of pancreatic adenocarcinoma by 174% (p = 0.0192) compared with the C/C wild type. Cancer cells transfected to overexpress the CCKCR demonstrated increased proliferation over controls. Genetic screening for this SNP may aid in early detection of pancreatic cancer in high risk subjects.

Cholecystokinin receptor antagonist halts progression of pancreatic cancer precursor lesions and fibrosis in mice.

Objectives Exogenous administration of cholecystokinin (CCK) induces hypertrophy and hyperplasia of the pancreas with an increase in DNA content. We hypothesized that endogenous CCK is involved in the malignant progression of pancreatic intraepithelial neoplasia (PanIN) lesions and the fibrosis associated with pancreatic cancer. Methods The presence of CCK receptors in early PanIN lesions was examined by immunohistochemistry in mouse and human pancreas. Pdx1-Cre/LSL-KrasG12D transgenic mice were randomized to receive either untreated drinking water or water supplemented with a CCK receptor antagonist (proglumide, 0.1 mg/mL). Pancreas from the mice were removed and examined histologically for number and grade of PanINs after 1, 2, or 4 months of antagonist therapy. Results Both CCK-A and CCK-B receptors were identified in early stage PanINs from mouse and human pancreas. The grade of PanIN lesions was reversed, and progression to advanced lesions arrested in mice treated with proglumide compared with the controls (P = 0.004). Furthermore, pancreatic fibrosis was significantly reduced in antagonist-treated animals compared with vehicle (P < 0.001). Conclusions These findings demonstrate that endogenous CCK is in part responsible for the development and progression of pancreatic cancer. The use of CCK receptor antagonists may have a role in cancer prophylaxis in high-risk subjects and may reduce fibrosis in the microenvironment.

A Cholecystokinin B Receptor-Specific DNA Aptamer for Targeting Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinomas (PDACs) constitutively express the G-protein-coupled cholecystokinin B receptor (CCKBR). In this study, we identified DNA aptamers (APs) that bind to the CCKBR and describe their characterization and targeting efficacy. Using dual SELEX selection against “exposed” CCKBR peptides and CCKBR-expressing PDAC cells, a pool of DNA APs was identified. Further downselection was based on predicted structures and properties, and we selected eight APs for initial characterizations. The APs bound specifically to the CCKBR, and we showed not only that they did not stimulate proliferation of PDAC cell lines but rather inhibited their proliferation. We chose one AP, termed AP1153, for further binding and localization studies. We found that AP1153 did not activate CCKBR signaling pathways, and three-dimensional Confocal microscopy showed that AP1153 was internalized by PDAC cells in a receptor-mediated manner. AP1153 showed a binding affinity of 15 pM. Bioconjugation of AP1153 to the surface of fluorescent NPs greatly facilitated delivery of NPs to PDAC tumors in vivo. The selectivity of this AP-targeted NP delivery system holds promise for enhanced early detection of PDAC lesions as well as improved chemotherapeutic treatments for PDAC patients.