Regulation of lung stem cells in homeostasis and tumorigenesis. Role of Stress-Activated Protein Kinases

Lung diseases and specially lung cancer, are among the more prevalent and one of the first causes of mortality in humans. Dysruption of lung homeostasis is underlying these pathologies. The alveolar epithelium is the area where gas exchange takes place. Thus the maintenance of the proper morphology and cellular composition is a key event for lung function. The turnover of lung epithelia is responsibility of a small group of cells named lung stem/ progenitor cells that have the potentiality to differentiate into any of the cell types of the alveolar epithelia. However, very little is known about lung stem cells and only recently have been isolated. I have been able to isolate lung stem/progenitor cells and culture them. Using this system I plan to study the mechanisms involved in the regulation of lung stem cell homeostasis. I will also search for markers that may be used for the detection and spotting of these cells in vitro and in vivo.
In-depth characterisation of the mechanisms regulating lung stem cells will make possible controlling their fate to self-renewal or production of alveolar epithelia by manipulation of some specific proteins. Transferring of these findings to humans will open new ways in the study and therapy of lung diseases.

In the lung there is a population of stem/progenitor cells able to produce Alveolar type-II and Clara cells that constitute lung epithelia. I have developed a modified protocol to culture these lung stem/progenitor cells and induce their differentiation in vitro. I have demonstrated that a member of the Stress-Activated Protein Kinases (SAPKs), p38a, is essential in the regulation of the lung stem cell homeostasis.
I aim to study and characterise the mechanisms underlying the control of lung stem cells by p38a and the crosstalk with other pathways that may be also involved in lung stem cell homeostasis. I will use a double approach using tissue cultured lung stem cells and examined their in vivo properties with animal experimentation.
Lung cancer is among the most prevalent and fatal in western countries. Currently, a new body of research focuses on stem cells as the origin of cancer. It remains controversial the existence of cancer stem cells and the connection of these cells to normal stem cells. I have recently found the regulation of lung stem cell homeostasis by the stress-activated protein kinase (SAPK) p38a and the consequences of losing this control to the lung tumorigenesis induced by K-RasV12.

To that purpose I will
1. delineate the phenotypic and molecular attributes of lung stem/progenitor cells,
2. dissect the signaling networks that collaborate with p38a to regulate these cells in vitro and in vivo.
3. study the lung stem cell contribution to tumorigenesis and the role of p38a in this process.
I will examine these working hypotheses:

(i) There is a specific population of lung stem/progenitor cells with the potential to differentiate into all alveolar cell types. As I have isolated cells that act in vitro as potential alveolar stem cells. We need to assay that potentiality in vivo.
(ii) SAPKs are essential regulators of the intracellular mechanisms involved in lung stem cell regulation. Molecular and phenotypical characterisation of lung stem cells and their regulation. Use of a double promoter system to trace lung stem cells searching for specific markers that allow differential localization and isolation.
(iii) Lung stem cells are the origin for cancer stem cells. Using tissue culture and animal injections I will characterise genetically, biochemically and functionally putative cancer stem cells isolated from lung tumors (K-Ras) using cancer (TTF-1) and stem cell markers (Side Population, CD133+, CD44, alpha2beta1 integrin). I will examine the potentiality of lung stem cells to be transformed and become cancer stem cells.