Cancer genetics of breast cancer based on Progesterone receptor

1. Role of Progesterone
Receptor in Breast Cancer
PRESENTED BY:
Aleena Haqqi
COURSE : CANCER GENETICS

2. Introduction To Breast Cancer
Every 1 in 8 women
It effects about 12%
women worldwide
Signs of breast cancer
• A lump in the breast
• A change in shape
• Dimpling of the skin
Cancer that develops
from breast tissue

3. TYPES OF BREAST CANCER
 Cancers developing from the ducts are known
as ductal carcinomas, while those developing
from lobules are known as lobular carcinomas
 non-invasive breast cancer (carcinoma in situ) –
found in the ducts of the breast (ductal carcinoma
in situ, or DCIS) which has not spread into the
breast tissue surrounding the ducts.
 invasive breast cancer – where the cancer cells
have spread through the lining of the ducts into the
surrounding breast tissue. This is the most
common type of breast cancer.
Lobule
Duct cells
Duct
Lobular cells

4. Altered cellular pathways in BC
A number of cellular pathways are altered in it including. These pathways are altered due to alteration in oncogenes; HER2, c-MYC, and
RAS, the ER and PR genes, and the genes for cell cyclin D1 and E, and the tumor suppressor genes RB, TP53, and PTEN, and the breast
cancer susceptibility genes BRCA1 and BRCA2.
MAPK
RB/E2F
PI3K AKT
mTOR
TP53

5. Progesterone
Introduction
Members of the steroid
hormone receptor family
Act as ligand-activated
transcription factors
Function as direct activators of
cytoplasmic signal
transduction molecules.
Including regulation of
metabolism, cell-cycle
progression, and survival
Master regulator in
female reproductive
tissues
It Controls developmental
processes
Proliferation
Differentiation during
the reproductive cycle and
pregnancy.
Role in BC
PR also plays a role in
progression of endocrine-
dependent breast cancer
the main action of PR is to
regulate networks of target gene
expression in response to
binding its cognate steroid
hormone, Progesterone

6. The isoforms PR-A and PR-B are
the products of a single gene.
the two principle PR isoforms PR-A
(94 kDa) and PR-B (118 kDa).
The isoforms contain a DNA
binding domain and a ligand
binding domain. N-terminal to the
DBD is an AF-1 (activation function
-1) and in the C-terminal direction a
nuclear localisation signal and the
LBD containing AF-2.
It is believed that AF-1 is thought to
mediate ligand-independent
activity, whilst AF-2 is attributed
wih ligand-dependent PR
activation.
The third isoform is the splice
variant PR-C. PR-C can bind the
ligand, but in the absence of the
DBD would not be able to bind to
PREs of target genes

7. Hormone Receptor Status in BC

8. Signalling Pathways

9. Conventional
Pathway
Nuclear Receptor
PR (Transcript
Regulator)
Ligand binding
PR-A & PR-B
Dimerization of
PR
Conformational
Changes
Translocation
to Nucleus
Binding to PRE

10. PG activation of progesterone receptor

11. Non-Classical Pathway

12. Non-Classical Pathway
 Non-classical signaling has been shown to affect several processes including
 Oocyte development
 The growth of breast cancer cells, production of inflammatory cytokines
 Extracellular matrix (ECM) protein production induced by mechanical stimulation
of myocytes

13. Routes of PGR signalling and the
crosstalk with the ER signalling pathways

15. Progesterone Concenteration in BC
 Although both PRA and PRB are highly expressed in normal tissues, PRB protein
concentrations reportedly are elevated in breast carcinoma. This results in a
 Decrease in the PRA:PRB ratio, which appears to be an important parameter for
progesterone-mediated functions.
 The transcription of the PR gene is regulated by estrogen in breast and
reproductive tissues.

16. Importance of PR in Hormone Therapy
for BC
 Similar to ER‐α, PR status is a good predictor of tumor responsiveness to
therapy.
 Nearly 50% of all ER+ tumors also are reported to be PR+ and approximately 75%
of these ER/PR+ tumors respond positively to endocrine therapy.
 ER+, PR‐ tumors are reported to be less responsive to therapy,
 perhaps suggesting that PR may be necessary for positive therapeutic outcomes with
hormone therapy.
 Alternatively, because ER is a key transcription factor for the activation of PR, lack
of PR expression in these ER+/PR‐ cells also could suggest that the estrogen
response pathway may not be functional in these tumors.
 Only a small fraction of tumors are ER‐/PR+ (< 5%) and they demonstrate an
intermediate response to endocrine therapy.

17. Hormone Receptor-positive Or Hormone
Receptor-negative
Breast cancers can be classified based on receptor status or histology,
 HER2+
 ER+/PR+ (about 70% of breast cancers)
 triple-negative breast cancer,(HR negative)
 Harmone receptor negative refers to the absence of these receptor proteins on
tumor cells.
 Invasive lobular carcinomas.

18. Hormone Receptor
HR+
 Normal breast cells and some breast cancer cells have receptors that attach to the hormones
estrogen and progesterone, and depend on these hormones to grow.
 These breast cancers can be treated with hormone therapy drugs.
 these cancers can sometimes come back many years after treatment.
HR-
 have neither estrogen nor progesterone receptors.
 Treatment with hormone therapy drugs is not helpful for these cancers.
 These cancers tend to grow faster than hormone receptor-positive cancer

19. Estrogen Priming
Estrogen is required for early breast development rather than progesterone/PR.
Increased estrogen levels induce PR expression; this is known as ‘estrogen
priming’ and PR-B plays role in latter stage of breast development.
During pregnancy, progesterone signaling via PR in the epithelial compartment
is required for branching and alveolar proliferation and differentiation.

20.  Mutations in DNA repair genes such as BRCA1, BRCA2, CHEK2, PALB2, ATM, P53
and others are associated with elevated risk for breast cancers.
 Some gene mutations are linked to triple negative breast cancers (eg, BRCA1) others
are linked to ER+ breast cancer (eg, CHEK2) while PR+ breast cancer is linked with
BRCA2.
 BRCA1 mutation carriers have deregulated progesterone signaling leading to
higher proliferation and DNA damage in a progesterone-sensitive RANK+ luminal
progenitor subsets.
 Long-duration exposure to pharmacologic progestogen levels combined with estrogen,
either through use of contraceptives or menopausal hormone therapy (primarily with
estrogen+progestin formulations increases breast cancer risk.

21. Treatment Strategies for BC
BRCA replacement
gene therapy.
reintroduction of
BRCA genes into
breast cancer cells
have resulted in cell
cycle arrest and
apoptosis
Another strategy
involves BRCA1
overexpression in a
breast cancer cell
line, which confers
resistance to
chemotherapy.
Utilization of BRCA1
antisense
oligonucleotides
restored drug
sensitivity
second generation
platinum-based
chemotherapeutic
s.

22. Anti – RANKL Therapy
 The tumor necrosis factor (TNF) receptor RANK (TNFRSF11A) and its ligand
RANKL (TNFSF11) regulate bone metabolism and control stem cell expansion
and proliferationof mammary epithelial cells via the sex hormone progesterone
 RANKL and RANK have been implicated in the onset of hormone-induced
breast cancer.
 RANK/RANKL are regulators for BRCA1 mutation-driven breast cancer.
 anti-RANKL therapy should be pursued as a preventative strategy for breast
cancer.

23. Endocrine Therapy
 Endocrine Therapy
 If breast cancer is harmone receptor positive.
 Surgery

24. Endocrine therapy
 Endocrine therapy is the treatment of choice for patients with breast cancer
expressing ER and/or PR
 The clinical usefulness of endocrine therapy has been proven in the Prevention,
adjuvant and metastatic settings
 Postoperative adjuvant endocrine therapy provides approximately a 50%
reduction in the development of recurrent disease
 metastatic breast cancer, which initially responds to endocrine therapy, always
acquires endocrine resistance
 Which conclude half of breast cancers expressing hormone receptors (HR) are de
novo resistant to endocrine therapy

25.  Both de novo and acquired resistance to endocrine therapy are important
problems in the management of breast cancer patients
 A number of classes of antiestrogen agents are approved for patients with early,
advanced, or metastatic BC
 Selective Estrogen Receptor Modulators (Serms)
 Aromatase Inhibitors (Ais)
 A Selective Estrogen Receptor Degrader (SERD)

26. Mechanism of Resistance
 The estrogen receptor acts as a ligand dependent transcription factor and has two
forms:
 Erα, encoded by ESR1 gene
 Erβ, encoded by ESR2 gene
 In 15–20% of cases, the resistance is associated with the activation of an ERα-
independent proliferation mechanism
 It may be accompanied by a phenotypic change in cells, from ERα + to ERα−

27. Mechanism of Resistance
As luminal B breast cancers are characterized by the lower expression of
ERα than luminal A breast cancers
there is a higher probability of ERα expression loss in luminal B breast
cancers
luminal B breast cancers are considered to have a higher risk of acquiring
endocrine resistance than luminal A breast cancers

28. Mechanism of Resistance
 According to recent studies, several mechanisms are important in
acquiring resistance to endocrine therapy, including;
 Molecular mechanisms of estrogen-independence
 ER switch
 The role of miRNA
 Autophagy
 Stemness (cancer stem like cells)

29. Ways to overcome Resistance
The tumor cells have estrogen receptors and grow when exposed to this hormone
Most of these cancers will respond to drugs that target the activity of the receptor
E.g. selective estrogen receptor modulators (SERMs) work by competing with estrogen
Selective estrogen receptor downregulators (SERDs) behave in a similar way, but they
can also trigger the degradation of the receptors

30.  Drugs that inhibit the production of estrogen have fewer side effects and are usually
the first choice when treating patients with post-menopausal breast cancer
 The mutations in estrogen receptors can reduce the effectiveness of these drugs
 A hybrid SERM/SERD drug can overcome the resistance conferred by mutant
receptors
 Hybrid SERM/SERD molecules, such as the drug bazedoxifene, display exceptional
inhibitory activities in tumor models, but they degrade estrogen receptors very
inefficiently
 Intense efforts are underway to identify new drugs that target estrogen receptors and
also safe and tolerable

31. References
 http://atlasgeneticsoncology.org/Genes/GC_PGR.html
 Garg, D., Ng, S. S. M., Baig, K. M., Driggers, P., & Segars, J. (2017). Progesterone-mediated non-
classical signaling. Trends in Endocrinology & Metabolism, 28(9), 656-668.
 Henry NL, Shah PD, Haider I, Freer PE, Jagsi R, Sabel MS. Chapter 88: Cancer of the Breast. In:
Niederhuber JE, Armitage JO, Doroshow JH, Kastan MB, Tepper JE, eds. Abeloff’s Clinical
Oncology. 6th ed. Philadelphia, Pa: Elsevier; 2020.
 Brufsky, A. M., & Dickler, M. N. (2018). Estrogen Receptor‐Positive Breast Cancer: Exploiting
Signaling Pathways Implicated in Endocrine Resistance. The oncologist, theoncologist-2017
 Szostakowska, M., Trębińska-Stryjewska, A., Grzybowska, E. A., & Fabisiewicz, A. (2019).
Resistance to endocrine therapy in breast cancer: Molecular mechanisms and future goals. Breast
cancer research and treatment, 173(3), 489-497