1. G0S2 Represses PI3K/AKT/mTOR Signaling and Increases Sensitivity to PI3K/mTOR Pathway Inhibitors in Estrogen Receptor-Positive Breast Cancer Cells Christina Y. Yim, Emmanuel Bikorimana, Ema Khan, Jennifer Rodriguez, Michael J. Spinella, and Sarah J. Freemantle. Department of Comparative Biosciences, University of Illinois at Urbana-Champaign, Urbana, IL, USA Other collaborators: Dr. Ethan Dmitrovsky, MD Anderson, Houston, Texas Drs Michael Cole, Todd Miller and Manabu Kurokowa, Dartmouth Medical School NH

2. What is G0S2?
Why breast cancer?
How does G0S2 impact cancer treatment response?
Where do we go from here?

3. G0S2 is a retinoic acid target Gene
NB4
Primary APL
Tamayo et al. PNAS (1999)
Ma et al. Onocogene (2003)
Kitareewan et al. Int J Oncol (2008)

4. What do we think G0S2 does?
Go-G1 switch gene 2 (G0S2): originally identified at transiently induced in blood mononuclear cells during Go to G1 transition.
Small basic protein of 12 KD, no homology with other proteins
Implicated in immunoregulation based on increased expression in peripheral blood cells of patients with autoimmune diseases.
G0S2 promoter is methylated in head and neck, lung cancer, leukemia
G0S2 associated with induced terminal differentiation, cell cycle withdrawal of adipocytes, quiescence of hematopoietic cells and senescence of fibroblasts
G0S2 decreased proliferation and induce apoptosis in leukemia, colon and lung cancer cells.

5. G0S2 is a negative regulator of Adipose Triglyceride Lipase (ATGL)
G0S2 role in fat homeostasis due to the direct interaction with ATGL, can regulate lipid droplet size in adipocytes
Yang et al Cell Metab :

6. G0S2 role in adiposity, energy balance, thermogenesis and lactation
G0S2 female mice cannot support their newborn pups in the first 2 days of life.
Pups can be successfully fostered to wild-type females.
Ma et al. Cancer Biology&Therapy (2014)

7. G0S2 role in adiposity, energy balance and thermogenesis
Ma et al. Cancer Biology&Therapy (2014)

8. G0S2 May Function as a Tumor Suppressor
G0S2 is epigenetically silenced by gene promoter methylation in several types of solid tumors and cancer cell lines.
Lung
Head and Neck
Adrenocortical Carcinoma
Cisplatin-resistant cell lines
G0S2 promotes apoptosis in certain cell contexts.
G0S2 decreases proliferation of leukemia cells both in vitro and in vivo.

9. G0S2-Null MEFs Have an Increased Susceptibility to Undergo Oncogene-Induced Transformation

10. To compare global gene expression profiles of G0S2-null vs. WT MEFs

11. G0S2-Null Cells Have Upregulated Signatures Associated with Transformation and MYC

12. G0S2 Ablation Induces c-MYC Expression at Transcript and Protein Levels

13. Repression of MYC Opposes Oncogene-Induced Transformation of G0S2-Null MEFs
The absence of G0S2 promotes oncogene- induced cellular transformation that is closely associated with a basal increase in MYC pathway activation

14. G0S2 Expression is Repressed in Breast Cancer Compared to Normal Breast
Data obtained through the Oncomine Database
> than 4-fold decline in G0S2 expression in breast cancer vs. normal
P <

15. G0S2 Expression in Breast Cancer is Associated with Decreased Recurrence Rate

16. Association Between G0S2 Expression and Low Recurrence Within the Stratified Subgroups of Breast Cancer Patients

17. G0S2-Null MEFs are Enriched in PI3K/mTOR Activated Gene Signatures
mTORC1
signaling
Leucine
deprivation
Glutamine
deprivation
Rapamycin
response

18. PI3K/AKT/mTOR Inhibitors
Rapamycin
Slomovitz and Coleman, Clinical Cancer Research (2012)

19. G0S2-Null MEFs Exhibit Decreased Sensitivity to mTOR Inhibitors Rapamycin and Everolimus

20. G0S2 Overexpression Represses and G0S2 Depletion Induces Basal mTOR Signaling
BT474
MCF7
P-p70S6K
G0S2
Actin
V5-G0S2
Empty
Relative Gene Expression
G0S2 WT
G0S2 Null *
RRM2
UCHL5
PDK1
RDH1 1 3 5 7 A B
P-p70S6K
actin
Drug rap eve rap eve
G0S2 wt
G0S2 KO
Yim et al. Cell Cycle (2017)

21. Conclusions
G0S2 loss is associated with enhanced oncogenic transformation
G0S2 loss in associated with activation of MYC and PI3K/mTOR pathways
G0S2 is repressed in breast cancer, which is associated with increased recurrence (ER+)
G0S2 loss is associated with resistance to PI3K/mTOR inhibitors
Restoring G0S2 in breast cancer cells decreased proliferation and sensitizes to PI3K/mTOR inhibitors.

22. Implications of G0S2 in ER+ Breast Cancer
G0S2 as a New Therapeutic Target
Candidate tumor suppressor
Potential biomarker for predicting recurrence and drug response to PI3K/mTOR pathway inhibitors in ER+ breast cancer

23. Future directions
What is the normal function of G0S2 in breast epithelia?
Is G0S2 loss associated with MYC and PI3K/mTOR activation in breast cancer patients?
Are G0S2 knockout mice prone to breast cancer and other cancers G0S2-/-, MMTV-HRas; G0S2- /-,MMTV-PyMT
Mechanism by which G0S2 silencing mediates MYC induced oncogenesis and PI3K/mTOR activation in breast cancer/other tumors.
Is G0S2 methylated in breast cancer? Can G0S2 be targeted/restored in breast/other cancers?

24. Thank You