Self-renewal of human epithelial stem cells versus their commitment to differentiation are closely linked. Understanding this process is of great potential impact for new therapeutic approaches to human tumors, which are mostly of epithelial origin. Our main interest is the interplay between intra- and inter-cellular signaling pathways involved in control of epithelial tissue homeostasis and tumor development. Our present research is focused on two main topics : (i) intrinsic control mechanisms underlying the balance between epithelial stem cell renewal and differentiation; (ii) role of underlying mesenchymal cells in control of epithelial cell fate determination and tumorigenesis. For a general overview of our research efforts and their impact, see the enclosed interview article
i) The gene regulatory network involved in intrinsic keratinocyte growth/differentiation control.
Keratinocytes and skin provide an attractive experimental system to study the connection between growth/differentiation potential of epithelial cells and transformation. Notch signalling is an important form of cell-cell communication with a function that is highly context-dependent. A substantial body of evidence (reviewed in1) has confirmed and expanded our original findings that this pathway plays a key role in promoting epidermal cell differentiation and suppressing tumor development 2,3. We showed that the Notch1 gene, which plays the most critical function in keratinocytes, is a direct target of p53 and that down-modulation of Notch1 expression in keratinocyte-derived tumors can be explained by mutation of p53 4 or down-modulation of p53 expression by increased EGFR activation 5 or calcineurin inhibition 6. Notch activation, in turn, suppresses p63, a p53-related transcription factor with an essential role in maintenance of keratinocyte self renewing populations 7. The cross-talk between Notch, p53/EGFR and p63 is at the core of a genetic network with key role in keratinocyte growth/differentiation control and tumor development. Another components of this network with an essential role in epidermal development and differentiation is IRF6, a transcription factor of the IRF (Interferon Responsive Factors) family that we have recently established as Notch target 8. Importantly, deep sequencing analysis of oral, skin and lung squamous cell carcinomas (SCCs) by a number of other laboratories has revealed that one or more components of the Notch/p53/p63 network can be inactivated by mutations in human SCCs, confirming their key role in the disease 9-12. We are currently further exploring regulation and function of this gene network in the skin.
Summary diagram of the Notch-connected network involved in keratinocyte differentiation and tumor suppression. A set of representative genes with a known or likely role in keratinocyte differentiation and Notch signalling is indicated. For explanation and more complete specification of network elements and connections, see the text above and indicated references.
ii) The dermal fibroblast gene regulatory network involved in skin field cancerization.
While great attention has been paid to the role of Notch signalling in the epithelial compartment of the skin, we have started to explore the role of this pathway in the underlying mesenchyme. We have developed a genetic mouse model with loss of Notch signalling in the mesenchymal compartment of the skin, finding that this pathway is essential for cell fate maintenance of overlying hair follicle keratinocytes 13. More importantly, by combined analysis of the mouse model and clinically-derived skin samples, we have uncovered a novel essential role of mesenchymal Notch signalling in field cancerization in the skin 14. Epithelial tumours are usually thought to result from genetic changes in a discrete group of cells, originating from a single initial progenitor, and of changes in immediately surrounding normal cells. The field cancerization process refers instead to pro-tumourigenic changes, in both epithelial cells and surrounding stromal cells, that occur in larger areas, or "fields", of target organs like the skin, oral cavity, lung, prostate and breast. The widespread changes help explaining the frequent multifocality of epithelial tumors and the fact that, after removal, these tumors often recur. Field cancerization has been linked to the presence of genetic pro-tumourigenic changes in apparently normal ‘patches’ of epithelial cells that expand over time. Our recent findings indicate that compromised Notch signalling in the underlying dermal fibroblasts is likely to play an equally important primary role, resulting in tissue alterations (stromal atrophy and inflammation) that precede premalignant and malignant epithelial tumor development 14. Mechanistically, Notch signaling in dermal fibroblasts of both murine and human origin results in intrinsically increased expression of diffusible growth factors and inflammatory cytokines, cancer-associated matrix components and matrix remodeling enzymes, which are amenable to up-regulation of AP1 levels and activity 14. The findings are of likely clinical significance, as suppression of Notch/CSL signaling and associated gene expression events occur in stromal fields adjacent to cutaneous premalignant lesions (actinic keratosis), and can be induced by UVA exposure, a major cause of skin chronic and cancer-predisposing alterations 14. We have established an intensive research effort to further explore the molecular and cellular basis of field cancerization in the skin.
Summary diagram of the Notch-connected network involved in dermal fibroblast activation and skin field cancerization. The genes in the network are partially overlapping with those involved in the keratinocyte network illustrated above. The diagram is based on our recent findings that UVA exposure of human skin / dermal fibroblasts induces down-modulation of Notch expression and activity through specific mechanisms like increased DNA methylation of the Notch2 promoter 14. Notch suppression leads to up-regulated expression of AP1 family members and of AP1 target genes with a role in inflammation, promotion of cancer development and/or aging 14.
|1.||Dotto, G.P. Notch tumor suppressor function. Oncogene 27, 5115-5123 (2008).|
|2.||Nicolas, M., et al. Notch1 functions as a tumor suppressor in mouse skin. Nat Genet 33, 416-421 (2003).|
|3.||Rangarajan, A., et al. Notch signaling is a direct determinant of keratinocyte growth arrest and entry into
differentiation. Embo J 20, 3427-3436 (2001).
|4.||Lefort, K., et al. Notch1 is a p53 target gene involved in human keratinocyte tumor suppression through
negative regulation of ROCK1/2 and MRCKalpha kinases. Genes Dev 21, 562-577 (2007).
|5.||Kolev, V., et al. EGFR signalling as a negative regulator of Notch1 gene transcription and function in
proliferating keratinocytes and cancer. Nat Cell Biol 10, 902-911 (2008).
|6.||Wu, X., et al. Opposing roles for calcineurin and ATF3 in squamous skin cancer. Nature 465, 368-372(2010).|
|7.||Nguyen, B.C., et al. Cross-regulation between Notch and p63 in keratinocyte commitment to differentiation.
Genes Dev 20, 1028-1042 (2006).
|8.||Restivo, G., et al. IRF6 is a mediator of Notch pro-differentiation and tumour suppressive function in
keratinocytes. EMBO J 30, 4571-4585 (2011).
|9.||Agrawal, N., et al. Exome sequencing of head and neck squamous cell carcinoma reveals inactivating mutations in NOTCH1. Science 333, 1154-1157 (2011).|
|10.||Durinck, S., et al. Temporal Dissection of Tumorigenesis in Primary Cancers. Cancer Discov 1, 137-143 (2011).|
|11.||Stransky, N., et al. The mutational landscape of head and neck squamous cell carcinoma. Science 333, 1157-
|12.||Wang, N.J., et al. Loss-of-function mutations in Notch receptors in cutaneous and lung squamous cell
carcinoma. Proc Natl Acad Sci U S A 108, 17761-17766 (2011).
|13.||Hu, B., et al. Control of hair follicle cell fate by underlying mesenchyme through a CSL-Wnt5a-FoxN1 regulatory
axis. Genes Dev 24, 1519-1532 (2010).
|14.||Hu, B., et al. Loss of mesenchymal CSL signaling leads to multifocal epithelial tumors and field cancerization.
cell 149, 1207–1220 (2012).
Honors and Awards
1982 Grant-in-Aid of Research of the Sigma Xi, The Scientific Research Society, New Haven, CT;
1984 Fellow; The Jane Coffin Childs Memorial Fund, New Haven CT
1987 Hull Cancer Research Award
1988 Swebilius Cancer Research Award
2001 Honorary Masters’ degree, Harvard University
2002-2003 NIH study section member (GMA-1)
2005/2007 Vice Chair/Chair Gordon Conference on Epithelial Differentiation
2010 Lecturing Professor, “Oncology at the Limits”, Cape Town, South Africa
2010 “Irwin Blank Symposium Lecture”, Society of Investigative Dermatology Meeting, Atlanta, Georgia
2011 Elected EMBO membership
2012 American Skin Association Lifetime Achievement Award
2013 European Research Council Panel Member, in “Physiology, Pathophysiology and Endocrynology”.
Present Group Members:
Bach Cuc Nguyen - firstname.lastname@example.org
Yang Brooks - email@example.com
Jun Dai - firstname.lastname@example.org
Stefania Gastaldi - email@example.com
Seunghee Jo - firstname.lastname@example.org
Recent Publications: Full List of Publications
Directions to Charlestown Navy Yard MGH East - Building 149
From Storrow Drive
From 93 North
- From the end of Storrow Drive (Leverett Circle) keep to the far right and take a sharp right (do not go up the ramp), and continue beneath the underpass one quarter mile to the light.
- Turn left onto Causeway street under the elevated subway tracks. The Fleet Center will be on your left, the North Station T station on your right.
- One block past the Garden, turn left on to N. Washington Street, passing over the Charlestown Bridge.
- At the first light after the bridge, take a right. Go through three traffic control lights.
- At the fourth light, turn right into Navy Yard (Gate 5 - 13th Street). To park, take first left onto Fifth Avenue. Building 149 is one block on the right.
- The parking garage entrance is on the right about half way down the block.
From 93 South
- Take the Mass Pike (I-90) to I-93 North (Exit 24B)
- Take the Storrow Drive Exit (Exit 26)Stay in the left lane once getting on the exit ramp. Follow signs for North Station/Leverett Circle Go through 1 light and take left at the 2nd light (almost immediately after the first)
- Get immediately into the right lane
- Take a right at the light onto Route 28N
- The Museum of Science will be on your left
- Take a right at the 3rd light (there is a sign at the corner for Charlestown)
- Go over the bridge and get in the right lane (City Square)
- Take your 1st right and get into the left lane
- Turn left at the 2nd light (immediately before Charlestown Bridge, at City Square) onto Chelsea Street (If you go over bridge, you've gone too far).
- Go through three traffic control lights
- At the 4th light, turn right into the Navy Yard (Gate 5 - 13th Street).
- To park, take first left onto Fifth Avenue. Parking Garage entrance is on the right above half way down the block. Building 149 is one block on the right once you turn into Gate 5. Building 149 is also connected to the parking garage.
- Take Exit 28 (Charlestown/Sullivan Square).
- At the end of the exit where the read forks stay to the right and proceed past the bus terminal to the rotary at Sullivan Square.
- Go halfway around the rotary towards Charlestown (the Schrafts building with a large American flag on top of it will be on your left).
- Cross the railroad tracks and take a left at the fire station onto Medford Street.
- At the end of Medford street turn left onto Chelsea Street and make an immediate right into the Navy Yard.
- The MGH East Research Building (Bldg. 149) will be on the right and is connected to the parking garage by overhead walkways.
By Public Transportation & the MGH/Partners Shuttle
- Direct the driver to the MGH East, Building 149 in the Charlestown Navy Yard.
- The CBRC is on the 3rd Floor of Building 149.
- Take the T (Green Line) to North Station
- Take the MGH/Partners Shuttle bus to the Charlestown Navy Yard MGH East Research Building (Building 149).
- The CBRC is on the 3rd Floor.
- The MGH/Partners Shuttle bus leaves MGH on Blossom Street and stops at North Station on Canal Street by the Green Line T stop. The shuttle goes every 15 minutes during working hours. (Less often on the weekends and holidays).
- To get to the CBRC, take the first set of elevators to the left of the main entrance by the Security Desk to the third floor. You may need to check in with security on the main level of Building 149.
- From the elevator, exit to the East to the CBRC offices, or in the opposite direction for the laboratories.