Stem-like and non-stem human pancreatic cancer cells distinguished by morphology and metastatic behavior

Color-Coded Imaging of Cancer and Stromal-Cell Interaction in the Pancreatic-Cancer Tumor Microenvironment (TME)

The tumor microenvironment (TME) contains stromal cells in a complex interaction with cancer cells. This relationship has become better understood with the use of fluorescent proteins for in vivo imaging, originally developed by our laboratories. Spectrally-distinct fluorescent proteins can be used for color-coded imaging of the complex interaction of the tumor microenvironment in the living state using cancer cells expressing a fluorescent protein of one color and host mice expressing another-color fluorescent protein. Cancer cells engineered in vitro to express a fluorescent protein were orthotopically implanted into transgenic mice expressing a fluorescent protein of a different color. Confocal microscopy was then used for color-coded imaging of the TME. Color-coded imaging of the TME has enabled us to discover that stromal cells are necessary for metastasis. Patient-derived orthotopic xenograft (PDOX) tumors were labeled by first passaging them orthotopically through transgenic nude mice expressing either green, red, or cyan fluorescent protein in order to label the stromal cells of the tumor (Yang et al., Cancer Res 64:8651-8656, 2004; Yang et al. J Cell Biochem 106: 279-284, 2009). The colored stromal cells become stably associated with the PDOX tumors through multiple passages in transgenic colored nude mice or non-colored nude mice. The fluorescent protein-expressing stromal cells included cancer-associated fibroblasts and tumor-associated macrophages. Color-coded imaging enabled the visualization of apparent fusion of cancer and stromal cells. Color-coded imaging is a powerful tool visualizing the interaction of cancer and stromal cells during cancer progression and treatment.

Comparison of tumor biology of two distinct cell sub-populations in lung cancer stem cells

Characterization of the stem-like properties of cancer stem cells (CSCs) remain indirect and qualitative, especially the ability of CSCs to undergo asymmetric cell division for self renewal and differentiation, a unique property of cells of stem origin. It is partly due to the lack of stable cellular models of CSCs. In this study, we developed a new approach for CSC isolation and purification to derive a CSC-enriched cell line (LLC-SE). By conducting five consecutive rounds of single cell cloning using the LLC-SE cell line, we obtained two distinct sub-population of cells within the Lewis lung cancer CSCs that employed largely symmetric division for self-renewal (LLC-SD) or underwent asymmetric division for differentiation (LLC-ASD). LLC-SD and LLC-ASD cell lines could be stably passaged in culture and be distinguished by cell morphology, stem cell marker, spheroid formation and subcutaneous tumor initiation efficiency, as well as orthotopic lung tumor growth, progression and survival. The ability LLC-ASD cells to undergo asymmetric division was visualized and quantified by the asymmetric segregation of labeled BrdU and NUMB to one of the two daughter cells in anaphase cell division. The more stem-like LLC-SD cells exhibited higher capacity for tumorigenesis and progression and shorter survival. As few as 10 LLC-SD could initiate subcutaneous tumor growth when transplanted to the athymic mice. Collectively, these observations suggest that the SD-type of cells appear to be on the top of the hierarchical order of the CSCs. Furthermore, they have lead to generated cellular models of CSC self-renewal for future mechanistic investigations.

Activation of endogenous human stem cell-associated retroviruses (SCARs) and therapy-resistant phenotypes of malignant tumors

Recent reports revealed consistent activation of specific endogenous retroviral elements in human preimplantation embryos and embryonic stem cells. Activity of stem cell associated retroviruses (SCARs) has been implicated in seeding thousands of human-specific regulatory sequences in the hESC genome. Activation of specific SCARs has been demonstrated in patients diagnosed with multiple types of cancer, autoimmune diseases, and neurodegenerative disorders, and appears associated with clinically lethal therapy resistant death-from-cancer phenotypes in a sub-set of cancer patients diagnosed with different types of malignant tumors. A hallmark feature of human-specific SCAR integration sites is deletions of ancestral DNA. Analysis of human-specific genetic loci of SCARs' stemness networks in tumor samples of TCGA cohorts representing 29 cancer types suggests that this approach may facilitate identification of pan-cancer genomic signatures of clinically-lethal disease defined by the presence of somatic non-silent mutations, gene-level copy number changes, and transcripts and proteins' expression of SCAR-regulated host genes. Present analyses indicate that multiple lines of strong circumstantial evidence support the hypothesis that activation of SCARs' networks may play an important role in cancer progression and metastasis, perhaps contributing to the emergence of clinically-lethal therapy-resistant death-from-cancer phenotypes.

Methods for Tumor Targeting with Salmonella typhimurium A1-R

Salmonella typhimurium A1-R (S. typhimurium A1-R) has shown great preclinical promise as a broad-based anti-cancer therapeutic (please see Chapter 1 ). The present chapter describes materials and methods for the preclinical study of S. typhimurium A1-R in clinically-relevant mouse models. Establishment of orthotopic metastatic mouse models of the major cancer types is described, as well as other useful models, for efficacy studies of S. typhimurium A1-R or other tumor-targeting bacteria, as well. Imaging methods are described to visualize GFP-labeled S. typhimurium A1-R, as well as GFP- and/or RFP-labeled cancer cells in vitro and in vivo, which S. typhimurium A1-R targets. The mouse models include metastasis to major organs that are life-threatening to cancer patients including the liver, lung, bone, and brain and how to target these metastases with S. typhimurium A1-R. Various routes of administration of S. typhimurium A1-R are described with the advantages and disadvantages of each. Basic experiments to determine toxic effects of S. typhimurium A1-R are also described. Also described are methodologies for combining S. typhimurium A1-R and chemotherapy. The testing of S. typhimurium A1-R on patient tumors in patient-derived orthotopic xenograft (PDOX) mouse models is also described. The major methodologies described in this chapter should be translatable for clinical studies.

Tumor imaging technologies in mouse models

In this chapter, we describe protocols for tumor imaging technologies in mouse models. These models utilize human cancer cell lines which have been genetically engineered to selectively express high levels of green fluorescent protein (GFP) or red fluorescent protein (RFP). Tumors with fluorescent genetic reporters are established subcutaneously in nude mice, and fragments of the subcutaneous tumors are then surgically transplanted onto the orthotopic organ. Locoregional tumor growth and distant metastasis of these orthotopic implants occur spontaneously and rapidly throughout the abdomen in a manner consistent with clinical human disease. Highly specific, high-resolution, real-time quantitative fluorescence imaging of tumor growth and metastasis may be achieved in vivo without the need for contrast agents, invasive techniques, or expensive imaging equipment. Transplantation of RFP-expressing tumor fragments onto the pancreas of GFP- or cyan fluorescent protein (CFP)-expressing transgenic nude mice was used to facilitate visualization of tumor-host interaction between the pancreatic cancer cells and host-derived stroma and vasculature. Such in vivo models have enabled us to visualize in real time and acquire images of the progression of pancreatic cancer in the live animal, and to demonstrate the real-time antitumor and antimetastatic effects of several novel therapeutic strategies on a variety of malignancies. We discuss studies from our laboratory that demonstrate that fluorescence imaging in mice is complementary to other modalities such as magnetic resonance imaging (MRI) or ultrasound. These fluorescent models are powerful and reliable tools with which to investigate metastatic human cancer and novel therapeutic strategies directed against it.

Neoplastic spindle cells are an independent prognostic factor in pancreatic cancer

OBJECTIVE

Several reports showed that neoplastic spindle cells (NSCs) may be strongly involved in the invasion, metastasis, and poor prognosis, as well as in epithelial-mesenchymal transition (EMT). It has not yet been investigated that NSCs relate to the recurrence and prognosis in various cancers. Furthermore, NSCs participate in EMT in pancreatic cancer (PC) too. We clinicopathologically investigated the association between NSCs and the recurrence, prognosis, and EMT in PC.

METHODS

We studied 68 PC patients. Cancer cells with a spindle or oval shape that do not exhibit luminal structures were defined as NSCs. We graded NSCs regarding to an area of NSCs at hematoxylin and eosin stain (NSC grade) and examined the participation in NSCs and EMT by immunohistostaining of snail antibody and E-cadherin antibody.

RESULTS

In multivariate analysis, NSC grade was an independent risk factor for disease-free survival and overall survival. This was independent of TNM stage and histological grade. Neoplastic spindle cells were related to EMT pattern in immunohistostaining significantly.

CONCLUSIONS

Neoplastic spindle cell grade significantly related to the recurrence and prognosis of PC. The NSC grade assessment can be not only performed inexpensively and conveniently, but also used to guide future individualized therapeutic approaches. Furthermore, NSCs were found to relate to EMT profoundly.

Back to the Future: Are Tumor-Targeting Bacteria the Next-Generation Cancer Therapy?

Cancer patients infected with various bacteria were reported, for at least two centuries, to have spontaneous remission. W.B. Coley, of what is now the Memorial Sloan-Kettering Cancer Center, pioneered bacterial therapy of cancer in the clinic with considerable success beginning in the late nineteenth century. After Coley died in 1936, bacterial therapy of cancer essentially ended. Currently there is much excitement in developing bacterial therapy for treating cancer using either obligate or facultative anaerobic bacteria. This chapter will demonstrate the potential and strategy of Salmonella typhimurium A1-R, an engineered tumor-targeting variant for the systemic treatment of metastatic cancer. A new concept using Salmonella typhimurium A1-R for cell cycle "decoy" chemotherapy of metastatic cancer is also described.

Electrokinetics and Rare-Cell Detection

Lab-on-a-chip devices perform functions which are not feasible or difficult to achieve with macroscale devices. Importantly, isolating and enriching rare cells is key in health and environmental applications, such as detecting circulating tumor cells from body fluid biopsies, or pathogens from water. Within a microdevice, the dominant mechanical force on a suspended particle is the drag force as it flows through the fluid. Electrokinetic forces such as dielectrophoresis - the motion of a particle due to its polarization in the presence of a non-uniform electric field - may also be applied to manipulate particles. For instance, separation of particles can be achieved using a combination of drag and dielectrophoretic forces to precisely manipulate a particle. Understanding the interaction of electrokinetic forces, particles, and fluid flow is critical for engineering novel microsystems used for cell sorting. Determining this interaction is even more complicated when dealing with bioparticles, especially cells, due to their intrinsic complex biological properties which influence their electrical and mechanical behaviors. In order to design novel and more practical microdevices for medical, biological, and chemical applications, it is essential to have a comprehensive understanding of the mechanics of particle-fluid interaction and the dynamics of particle movement. This chapter will describe the role of electrokinetic techniques in rare cell detection and the behavior of electrokinetic microsystems.

The tumor-educated-macrophage increase of malignancy of human pancreatic cancer is prevented by zoledronic acid

We previously defined macrophages harvested from the peritoneal cavity of nude mice with subcutaneous human pancreatic tumors as “tumor-educated-macrophages” (Edu) and macrophages harvested from mice without tumors as “naïve-macrophages” (Naïve), and demonstrated that Edu-macrophages promoted tumor growth and metastasis. In this study, Edu- and Naïve-macrophages were compared for their ability to enhance pancreatic cancer malignancy at the cellular level in vitro and in vivo. The inhibitory efficacy of Zoledronic acid (ZA) on Edu-macrophage-enhanced metastasis was also determined. XPA1 human pancreatic cancer cells in Gelfoam co-cultured with Edu-macrophages proliferated to a greater extent compared to XPA1 cells cultured with Naïve-macrophages (P = 0.014). XPA1 cells exposed to conditioned medium harvested from Edu culture significantly increased proliferation (P = 0.016) and had more migration stimulation capability (P<0.001) compared to cultured cancer cells treated with the conditioned medium from Naïve. The mitotic index of the XPA1 cells, expressing GFP in the nucleus and RFP in the cytoplasm, significantly increased in vivo in the presence of Edu- compared to Naïve-macrophages (P = 0.001). Zoledronic acid (ZA) killed both Edu and Naïve in vitro. Edu promoted tumor growth and metastasis in an orthotopic mouse model of the XPA1 human pancreatic cancer cell line. ZA reduced primary tumor growth (P = 0.006) and prevented metastasis (P = 0.025) promoted by Edu-macrophages. These results indicate that ZA inhibits enhanced primary tumor growth and metastasis of human pancreatic cancer induced by Edu-macrophages.

Comparison of efficacy of Salmonella typhimurium A1-R and chemotherapy on stem-like and non-stem human pancreatic cancer cells

The XPA1 human pancreatic cancer cell line is dimorphic, with spindle stem-like cells and round non-stem cells. We report here the in vitro IC 50 values of stem-like and non-stem XPA1 human pancreatic cells cells for: (1) 5-fluorouracil (5-FU), (2) cisplatinum (CDDP), (3) gemcitabine (GEM), and (4) tumor-targeting Salmonella typhimurium A1-R (A1-R). IC 50 values of stem-like XPA1 cells were significantly higher than those of non-stem XPA1 cells for 5-FU (P = 0.007) and CDDP (P = 0.012). In contrast, there was no difference between the efficacy of A1-R on stem-like and non-stem XPA1 cells. In vivo, 5-FU and A1-R significantly reduced the tumor weight of non-stem XPA1 cells (5-FU; P = 0.028; A1-R; P = 0.011). In contrast, only A1-R significantly reduced tumor weight of stem-like XPA1 cells (P = 0.012). The combination A1-R with 5-FU improved the antitumor efficacy compared with 5-FU monotherapy on the stem-like cells (P = 0.004). The results of the present report indicate A1-R is a promising therapy for chemo-resistant pancreatic cancer stem-like cells.