1. Hedgehog (Hh) Signaling Pathway
Daniel Soria, P. Garrett Candelaria, Savannah Salazar, Hannah Williams, Jet Murphy, Gabriel Ruja, and Humberto Colunga

2. Presentation Outline Hedgehog and Cancer
Basal Cell Carcinoma Connection to Hedgehog
Signaling Pathway
Advances in Research
Gaps in Knowledge/Limitations
Conclusion

3. Hedgehog Gene is Involved With Development of Cancers
Example: Triple Negative Breast Cancer (TNBC)
Missing estrogen, progesterone, and human epidermal growth factor receptor 2 (HER2) receptor
Basal-like cancer with poor outcomes
More aggressive
Higher grade
Finding effective treatments is imperative to improve patient outcome
Dysregulation Hedgehog signaling pathway found to be documented in development of breast cancers

4. What is the Role of the Hh Signaling Pathway in Basal Cell Carcinoma (BCC)?
Patched 1 (Ptch1) Receptor
Activation Effects
Loss of Function
Ligand Dependencies
However, activation of the pathway has been shown to be a factor in the development of a number of human malignancies and inhibition of the pathway is being investigated as a potential treatment for multiple cancers.
In the absence of Hh, PTCH, located on the cell membrane at the base of the primary cilium, suppresses the activation of SMO, located on the membrane of intracellular endosomes, by blocking it from entering the cilium. Gli proteins are converted by proteosomes to the repressor form (GliR), which represses transcription to the target genes.
Hh signaling and activation of the pathway seems to be significantly reduced or absent in adults.
Hh signaling may be of importance in adults, e.g., the proliferation of stem cells in the hemopoietic system, the neural system, and mammary glands
When PTCH1 is unable to do its job leads to constitutive upregulation of Hh signaling and and that is what leads to the development of the Basal Cell Nevus Syndrome BCNS with multiple skin tumors
Activation = initiating certain cancers, for example BCC
With loss of function of PTCH1, SMO is no longer suppressed and the Hh pathway is activated. PTCH1 sequences identified it as the homolog of the Hh signaling inhibitor in Drosophila and it functions as a tumor suppressor gene.
Aberrant activation of the Hh pathway in cancer may also be ligand dependent.
The Hh ligand from these cell types has been shown to activate the Hh pathway in neighboring stromal cells, which seem to be of myofibroblast lineage (14, 15). This paracrine activation of stromal cells may support the tumor microenvironment.
Caro, I., & Low, J. A. (2010, July 01). The Role of the Hedgehog Signaling Pathway in the Development of Basal Cell Carcinoma and Opportunities for Treatment. Retrieved from

5. How does Hedgehog Signaling occur?
Hh- segment polarity proteins
Very regulated pathway
Why?
Graded Signaling
Certain genes activated by different levels of Hh
Hh signaling in animals. (A) Hh production is highly conserved between Drosophila and mammals (middle). Autocatalytic cleavage of the Hh precursor protein yields a cholesterol- modified signaling peptide (HhN), which is further palmitoylated by Skinny Hedgehog (Ski), then released from the cell by Disp (Drosophila) or Disp1 (mammals). In Drosophila (left), the released lipophilic HhN is incorporated into lipophorin complexes (not shown) and distributed to other cells with the help of heparan sulfate proteoglycans (Dally and Dlp; also not shown). The suppressive action of Ptc or Ptch1 on Smo is conserved in Hh- responsive cells from Drosophila (left) and mammals (right). Members of the CDO receptor family (not shown), including Ihog, facilitate Hh binding and inhibition of Ptc or Ptch1, allowing activation of Smo. In Drosophila, Dlp also appears to facilitate Hh response. Smo- mediated regulation of Ci (Drosophila) or Gli (mammals) nuclear localization and proteolytic processing into a repressor (CiR or Gli3R) depends on Cos2, Fu, and Su(fu) in Drosophila, and proteins that function in the primary cilium in mammals. The mechanism by which Smo inhibits the pathway suppressor Su(fu) in mammals is unknown. (B) Tumors with aberrant Hh pathway activity in Gorlin’s syndrome, as well as their sporadic counterparts, frequently harbor mutations in Ptch1. Other tumors for which molecular lesions have not been defined also exhibit aberrant Hh pathway response. References for most of the tumors described here can be found in (16).

6. How does Hedgehog Signaling occur? (con.)
Hh signaling in animals. (A) Hh production is highly conserved between Drosophila and mammals (middle). Autocatalytic cleavage of the Hh precursor protein yields a cholesterol- modified signaling peptide (HhN), which is further palmitoylated by Skinny Hedgehog (Ski), then released from the cell by Disp (Drosophila) or Disp1 (mammals). In Drosophila (left), the released lipophilic HhN is incorporated into lipophorin complexes (not shown) and distributed to other cells with the help of heparan sulfate proteoglycans (Dally and Dlp; also not shown). The suppressive action of Ptc or Ptch1 on Smo is conserved in Hh- responsive cells from Drosophila (left) and mammals (right). Members of the CDO receptor family (not shown), including Ihog, facilitate Hh binding and inhibition of Ptc or Ptch1, allowing activation of Smo. In Drosophila, Dlp also appears to facilitate Hh response. Smo- mediated regulation of Ci (Drosophila) or Gli (mammals) nuclear localization and proteolytic processing into a repressor (CiR or Gli3R) depends on Cos2, Fu, and Su(fu) in Drosophila, and proteins that function in the primary cilium in mammals. The mechanism by which Smo inhibits the pathway suppressor Su(fu) in mammals is unknown. (B) Tumors with aberrant Hh pathway activity in Gorlin’s syndrome, as well as their sporadic counterparts, frequently harbor mutations in Ptch1. Other tumors for which molecular lesions have not been defined also exhibit aberrant Hh pathway response. References for most of the tumors described here can be found in (16).

7. What are some of the recent advances in medicine?
Hh dysregulation has has been implicated with multiple forms of malignant cancers
Ovarian, Breast, Gastrointestinal, Hepatic, Pancreatic, and Lung
Treatment involving the target of the Hh pathway has proven to be an effective treatment of cancer.
Vismodegib
Basal-Cell Carcinoma
Treatment involving the target of the Hh pathway has proven to be an effective treatment of cancer.
Drugs that target multiple steps in the Hh pathway have been tested but of the most tested is Vismodegib which targets the SMO protein. This drug inhibits the pathway and promotes cell cycle arrest and eventual apoptosis.
Hh dysregulation has has been implicated with multiple forms of malignant cancers.

8. What are the limitations of Shh research?
Complexity of breast cancer (BC)
Shh independent determinant?
Shh in relation to BC
Shh Examination in humans
Cancer stem cell self renewal
Mechanism not understood
Key limitations
Model organism, mechanism, confounding variables
-High levels of Shh linked to breast cancer
- Breast cancer is a complex disease with multiple associated variables. While Shh has been found to correlate positively with BC, it is not known how significant overregulation is. It is just known that Shh overregulation is + coorilated with BC. (Norman)
-Examination of Shh in human breast tissue is recent, promising, but recent. The mouse model has been examined further and shown that Shh could be a novel target to reduce BC with downstream effects. (Kasper) -Another study has found that the over expression of Shh leads to the process of cancer stem cell self renewal. This has shown to leave chemotherapy treatments less effective. (Heiden)
Veira-McTierman F. Funding research to fill the gaps in cancer knowledge. World Cancer Fund Research International. July 21, Accessed October 8, 2018.

9. The take home message: Hh pathway is implicated in carcinogenesis.
Understanding Hh pathway and its dysregulation may lead to improved cancer treatments.
The most well studied is basal cell carcinoma.
Ligand-dependencies in certain cancers
Take home point: overexpression of hedgehog pathway has been implicated in carcinogenesis like basal cell carcinoma
Humberto: talk about gaps in research-->start off the conclusion a major gap in terms of breast CA is that we don’t know if Shh is an independent factor or if there is cross-talk between other ligands and molecules. Further, limited data on how Shh affects CA progression, proliferation, and cancer stem cell maintenance.
Both BCC and medulloblastoma are Hh-ligand independent, mutation-driven cancers.
As discussed, the overexpression of Hh pathway has been implicated in certain cancers. Understanding the dysregulation of sonic hedgehog pathway can lead to improved cancer treatments
Even just one ligand and receptor mishap can lead to detrimental effects like we saw in Patched 1 playing a key role in the development of cancers. Further, certain tumors secrete more Hh ligand than their corresponding normal tissue. All of these factors can lead to the development of certain cancers, but these results are still preliminary and further research is needed.

10. References:
Noman AS, Uddin M, Rahman MZ, et al. Overexpression of sonic hedgehog in the triple negative breast cancer: clinicopathological characteristics of high burden breast cancer patients from Bangladesh. Scientific Reports. 2016;6:18830.
Kasper M, Jaks V, Fiaschi M, Toftgard R. Hedgehog signalling in breast cancer. Carcinogenesis. 2009;30(6): doi: /carcin/bgp048
Heiden KB, Williamson AJ, Doscas ME, et al. The Sonic Hedgehog Signaling Pathway Maintains the Cancer Stem Cell Self-Renewal of Anaplastic Thyroid Cancer by Inducing Snail Expression. The Journal of Clinical Endocrinology and Metabolism. 2014;99(11):E2178-E2187. doi: /jc
Veira-McTierman F. Funding research to fill the gaps in cancer knowledge. World Cancer Fund Research International. July 21, Accessed October 8, 2018.
Tigerstar1324. Breast cancer awareness month sonic. Accessed Oct 8, 2018.
Caro, I., & Low, J. A. (2010, July 01). The Role of the Hedgehog Signaling Pathway in the Development of Basal Cell Carcinoma and Opportunities for Treatment. Retrieved from
Jacob, L., & Lum, L. (2007). Deconstructing the Hedgehog Pathway in Development and Disease. Science (New York, N.Y.), 318(5847), 66–68.
Li H, Li J, Feng L. Hedgehog signaling pathway as a therapeutic target for ovarian cancer. Cancer Epidemiology. 2016;40: doi: /j.canep