icamp: Cancer biology tutorial II: recent developments in tumor biology, experimental methodology, and reference identification

Transcription

1 icamp: Cancer biology tutorial II: recent developments in tumor biology, experimental methodology, and reference identification Stem cells and the environment in the adenoma-carcinoma sequence (Medema, 2011) Anna Konstorum 7/17/12

2 Purpose of tutorial II: we try to answer (or at least introduce the questions): What are cancer stem cells, and how are they 'organized' in tumors? How do microenvironmental interactions impact tumor development? What are some methods that biologists use to better understand cancer in the laboratory? What are the methods that were used to produce the experimental results that we are currently analyzing?

3 Review: what is cancer? Normal cells are subject to signals that dictate whether the cell should divide, differentiate into another cell, or die. Cancer can be defined as a disease in which a group of abnormal cells grow uncontrollably by disregarding the normal rules of cell division.

4 Actually, neither normal nor cancerous tissue is as homogenous as we have shown. Schematic representation of the colon crypt illustrates stem cells residing at the crypt bottom immediately above the Paneth cell compartment. The (red) slowly-dividing immature stem cells divide asymmetrically to yield a (green) population of TA cells and replacement stem cells (red arrows). TA cells gradually commit to differentiation during bipolar migration (yellow arrows). The fully differentiated epithelial cells are represented in green, purple and blue at the crypt-villus junction, and in orange at the base of the crypt. (Pinto and Clevers, 2005)

5 Histology of normal crypt Chemical and immunohistochemical detection of the four principal cell lineages of the small intestine (arrowheads): villusassociated absorptive cells (alkaline phosphatase), Goblet mucus-secreting cells (periodic acid/schiff), enteroendocrine cells (synaptophysin), and Paneth cells (lysozyme) The upper small panels show the entire crypt-villus axis while the lower large panels show magnifications of the crypts. (Pinto and Clevers, 2005)

6 Medema, 2011 Normal, multispecies tissue, is highly regulated via interactions within the tissue and with the microenvironment.

7 Medema, 2011 Current studies implicate the microenvironment in driving tumor progression. Histological sample to the right represents (a)->(b) in diagram above.

8 (a) Normal crypt. (b,c ) A mutation in a stem cell is thought to initiate the premetastatic lesion. Newly mutated cancer stem cells (CSCs) secrete factors to the stroma that 'activate' stromal cells (myofibroblasts) to facilitate division and spread of CSCs (more on this in subsequent slides). CSCs also secrete factors that attract immune cells into the stroma that then promote cancer progression and stromal activation. Activated myofibroblasts produce, among other factors, large amounts of hepatocyte growth factor (HGF), which promotes dedifferentiation.

9 a. (a) Simple schematic of a positive feedback between cancer and stromal cells, Note that there is potential here for a positive feedback loop to be created (Matsumoto, 2006). (b) Experimental result that implicates stromal factors in promoting cancer cell stemness and dedifferentiation: α-sma is a marker for stroma (pink) and β-catenin (brown) is a marker for stem cells. Note that this histological slide of a human colon carcinoma has stronger staining for β-catenin at the border of the tumor and the stroma (Vermeulen, 2010).

10 Towards a quantification of HGF action on cancerous colon. There is now a good amount of evidence that activated stroma secretes HGF near the tumor and causes cells in the tumor to become dedifferentiated, and many of the molecular details of this action are being worked out. Our group wanted to know an important question that falls out from the above studies: how does behavior of the tumor, at the tissue level, change with increased HGF signal? This is an important question as studies on HGF have focused on molecular, cellular, and clinical correlation data, which cannot fully describe the spatio-temporal aspects of HGF action, and how this action coincides with the heterogeneous spatial distribution of tumor cell types.

11 Experimental cancer biology: mammalian cell culture. Introduction to animal cell culture (Bjanka, 2009).

12 Experimental cancer biology: mammalian cell culture. Introduction to animal cell culture (Bjanka, 2009).

13 Experimental cancer biology: mammalian cell culture. Introduction to animal cell culture (Bjanka, 2009).

14 Experimental cancer biology: mammalian cell culture. Introduction to animal cell culture (Bjanka, 2009).

15 Experimental cancer biology: mammalian cell culture. Introduction to animal cell culture (Bjanka, 2009).

16 Experimental cancer biology: mammalian cell culture. Introduction to animal cell culture (Bjanka, 2009).

17 Experimental cancer biology: tumor spheroids and co-culture. Schematic protocols of tissue preparation (derived from primary brain tumor) for in vitro experimentation.

18 CCIC tumor spheroid growth in increasing [HGF]. Cell line used: primary, 'colon cancer initiating cells' (CCICs). CCICs cultured in ultra-low attachment flasks with DMEM + supplement. Cultured CCICs were trypsinized (to break down cell-cell contacts) and spun down (to remove old media). Single cells were plated in 96 well ultra-low attachment plates with media and with or without HGF at various concentrations. CCICs were images at 10x resolution once each day for 12 days. Spheroid grown in media + 50ng/ml HGF, day 8.

19 CCIC tumor spheroid growth in increasing [HGF]. In upcoming experiments, plan to incorporate markers for cell stemness and differentiation, to directly probe the hypothesis that HGF causes cells at the tumor/host boundary to take on a stem-cell phenotype. Spheroid grown in media + 50ng/ml HGF, day 8. Spheroids on the right have been fixed and stained for GLUT1 (marker of hypoxia, brown) and Ki67 (marker for proliferation). (Vinci et al., 2012)

20 References Pinto D, Clevers H. Wnt, stem cells and cancer in the intestine. Biol Cell Mar;97(3): Review. Medema JP, Vermeulen L. Microenvironmental regulation of stem cells in intestinal homeostasis and cancer. Nature Jun 15;474(7351): doi: /nature Review. "Introduction to animal cell culture" (Bjanka, 2009) %20Tissue%20Culture%20Lecture%202%20combinedBjanka.pdf Corcoran A, De Ridder LI, Del Duca D, Kalala OJ, Lah T, Pilkington GJ, Del Maestro RF. Evolution of the brain tumour spheroid model: transcending current model limitations. Acta Neurochir (Wien) Sep;145(9): Review. Vinci M, Gowan S, Boxall F, Patterson L, Zimmermann M, Court W, Lomas C, Mendiola M, Hardisson D, Eccles SA. Advances in establishment and analysis of three-dimensional tumor spheroid-based functional assays for target validation and drug evaluation. BMC Biol Mar 22;10:29.