Sex hormone control of cell proliferationChapter 5(Book : The Society of CelIsCancer and Control ofCell Proliferation

1. Sex hormone control
of cell proliferation
Chapter 5
(Book : The Society of
CelIs
Cancer and Control of
Cell Proliferation)
Presented by:
MAHAM ABBASI (1)
SADAQAT BIBI (12)
UROOJ BIBI (28)
HMNA RASHID(29)
HUMA PARVEEN (30)

2. Sex Hormone-mediated
Control of Cell Proliferation

3. "It is also a good rule not to put too much confidence in the
observational results
that are put forward until they are confirmed by theory."
-Sir Arthur Eddington (1934), quoted in: Horace F. Judson
(1979)
The Eighth Day of Creation. Penguin Books, London, p. 93

4. " ... both the ideas that science generates and the
way in which science is carried
out are entirely counter-intuitive and against
common sense .... Science does not fit
with our natural expectations."
-Lewis Wolpert (1992) The Unnatural Nature of
Science. Faber & Faber, London, p. 1

5. Introduction
• The study of the control of cell proliferation in metazoa
requires the selection of a suitable experimental model.
• The cells of the lining of the accessory sex organs- most
promising tool (due to several reasons).
1. Sex hormones are acknowledged to be
physiologically relevant.
2. Sex steroids reach all tissues of the body but only
specific cells recognize them as signals.

6. 3. Target cell lines mimic many of the properties of
their 'normal' counterparts and they can be studied in
culture.
Introduction
 Results from these experiments helped us in
formulating hypotheses on the control of cell
proliferation in the animal.

7. Control of cell proliferation by estrogens:
• In rodents, ovarian cycle is 4-5 days long during which
estrogen levels in blood vary- leads to histological and
physiological changes in estrogen target cells.
• Changes in epithilial lining of uterus and vagina:
 Hyperplasia.
 Hypertrophy.
 Apoptosis.

9.  Schematic representation (shown in previous
slide) of the control of cell proliferation by estrogens
and androgens. In the absence of sex hormones (by
gonadectomy), these target cells are prevented from
proliferating.
Step 1: a single injection of the relevant sex hormone
is followed by the proliferation of their specific
target cells (e.g. uterine cells for estradiol, or
prostate cells for androgens; --, cell number).
Step 2: if the hormone concentration (-----) is kept
high for several days by implanting a pellet with the
pertinent hormone, the proliferative response is
followed by a period of proliferative arrest.

10. Estrogen Receptors:
• Until momentous experiments by Jensen and Jacobson in the
1950s, little was known about the fate of estrogens in the
organism.
• It is now understood that estrogen receptors operate as
transcription factors, which are necessary in the process of
estrogen-induced gene expression.

12. DIRECT AND INDIRECT
POSITIVE HYPOTHESIS

13. Hypothesis
• Direct-positive hypothesis.
 In the 1950s, Furth administrated estrogen doses in rats which
results pituitary tumors.
 Tumors were transplantable.
 Tumors were not grew in ovariectomized (surgical removal of
ovaries)
 Cell lines were established from these tumors.
 Cell grew depending on hormones having estrogen
receptors(regulates cell proliferation growth)

14. Establishment of estrogen-target
pituitary cell lines
 The establishment of estrogen-target pituitary cell lines.
In the 1970s, all research programs on estrogen action
on cell proliferation were conducted
 Estrogens were induced cell proliferation.
 Estrogen stimulates via the estrogen receptor, by
inducing the entry of these cells into the cell cycle
(direct-positive hypothesis)

15. Paradox
• These cells developed into estrogen-dependent
tumors when inoculated into animals, in culture
they proliferated at the same rate regardless of the
addition of estrogens

16. Indirect-positive hypothesis. Evaluation of cell
proliferation as a discrete marker
• In the mid-1970s, we became convinced that estradiol was the proximate
and not the ultimate cause of the proliferative event described above. This
conclusion was based on the following facts:
• first, estradiol administration to animals did not increase cell proliferation
in some of the normal tissues and neoplastic cells that carried estrogen
receptors. This implied that the presence of estrogen receptors might have
been necessary but not sufficient for the proliferative response to estradiol
to occur.
• Second, neither our data nor those of other scientists showed a direct
proliferative effect of estradiol on target cells in culture. Hence, we
concluded that estradiol affected the proliferation of its target cells
indirectly . Hypothetically, there was an intermediary step requiring the
intervention of growth factors secreted by estrogen target organs under
estradiol stimulation

17. Three variations of this hypothesis
• The endocrine hypothesis
• The paracrine hypothesis
• Autocrine hypothesis

18. Data produced in support of these
hypotheses
• There, we called attention to the fact that data claimed to demonstrate
effects of growth factors and estrogens were not gathered by counting
cells during the exponential phase of proliferation.
Further, we suggested the rigorous application of the rule that cell
proliferation should be estimated by measuring the doubling time of
cell populations during the exponential phase of proliferation.
The data we gathered on the role of the pituitary gland as a source of
estrogen-induced growth factors, presumably acting on the uterus,
were inconsistent with the indirect positive endocrine hypothesis

19. Data produced in support of these
hypotheses
 estrogen treatment resulted in the increase of the uterine
weight.
this suggested that the pituitary gland did not have a
crucial role in estrogen-mediated induction of cell
proliferation. in sum, the overall data were inconclusive in
regard to the positive hypothesis.

20. Indirect negative
hypothesis

21. The indirect-negative hypothesis
 The indirect-negative hypothesis assumes that the default state of all
cells is proliferation. In the absence of serum/plasma (in culture
conditions only), estrogen-target cells proliferate.
 In the presence of serum/plasma (in culture or in animals) and in the
absence of estrogens, these same cells are prevented from
proliferating.
 Estradiol would increase the proliferation of its target cells by blocking
either of the two following mechanisms.
• Estradiol would neutralize the effect of a blood-borne inhibitor by
• Estradiol would inhibit the synthesis or release of the inhibitor at its source

22. MCF7 cells: the foremost human breast
estrogen-target established cell line
 The first estrogen-target cell line established from a breast cancer was
called MCF7.
 Established at the Michigan Cancer Foundation in Detroit in the early
1970s.

23. Uses for MCF-7 Cell Line
 MCF-7 cells are useful for in vitro breast cancer studies as a result of
the cell line retaining several ideal characteristics particular to the
mammary epithelium.
 These include the ability for MCF-7 cells to process estrogen in the
form of estradiol via estrogen receptors in the cell cytoplasm.
 This results in the MCF-7 cell line being an estrogen receptor (ER)
positive cell line.

24. MCF7 cells
 Cells from this line grew as tumors when inoculated into athymic
nude mice (these mice tolerate grafts from species other than their
own
 Major obstacle to testing the effect of estrogens on the proliferation
of MCF7 cells in culture was the presence of estrogens in serum
 There is considerable variation in the ability of different sublines of
MCF7 cells to become inhibited by estrogen less serum

25. There was indeed a plasma-borne
inhibitor
 In 1983, for purification purposes, we adopted an experimental
human model.
 Putative inhibitor would be less effective or abundant in the serum of
women at midcycle, when the levels of estradiol are high
 The degree of inhibition of MCF7 cell proliferation would be
proportional to the amount of serum in the culture medium.
 Addition of estradiol reversed the inhibitory activity of serum from
men and from women on the first day of their cycle.

26. Removal of estrogens from serum
 These experiments could not discern whether the lack of
inhibition by serum from women at midcycle was due to low
inhibitor levels or high estrogen levels
 The degree of inhibition was, again, proportional to the
amount of serum in the medium Estradiol reversed this
inhibitory effect
 we named this serum-borne inhibitor of the proliferation of
estrogen-target cells with a shortened name known as
estrocolyone-I

27. The final identification of the plasma-borne
inhibitor (estrocolyone-1)
 published a paper claiming that commercial preparations of bovine
serum albumin inhibited the proliferation of MCF7 cells and that
estradiol reversed this inhibition
 Recombinant albumin is produced by yeast cells grown in a synthetic
medium devoid of animal proteins
 It was concluded that albumin was the long-sought estrocolyone-1,
the inhibitor of the proliferation of estrogen-target cells
 Serum albumin is a protein characterized by a three domain
structure that must have evolved from the duplication of an ancestral
gene

28. ROLE OF EGF IN CELL PROLIFERATION

29. Role of EGF in endometrial cells proliferation
 EGF implants induced both cell proliferation and
estrogen-regulated genes in uterine and vaginal
epithelia in mice.
 There is a lack of this effect in ERKO mice.
 The stimulatory effect of EGF was seen in normal
mice.

30. Stroma-epithelium interaction and cell
proliferation:
 It was formulated to explain induction of cell
proliferation by sex hormones.
Sex steroids
Stroma-epithelium cells
Growth factors
Proliferation of adjacent epithelial cells

31. – Endometrial epithelial cells
( from ERKO mouse)
Proliferate on estrogen treatment
When recombined with stroma cell from wild
type mouse having normal estrogen receptor

32. Stroma-epithelium interaction and cell
proliferation:
If the contact between stroma and epithelium remains
intact in culture
Epithelial cells proliferate even in the absence of
estrogen and growth factors.

33. Inhibitory pathways controlling the
proliferation:
Two inhibitory pathways are controlling this
process.
1. That act directly on epithelial cells.
2. That is mediated by inhibitory factors
produced in stromal cells.

34. PROLONGED ESTROGEN
TREATMENT

35. Prolonged estrogen administration
and proliferation:
• Repeated estrogen administration lead to:
Proliferation shutoff.
Stopping of proliferation
Hyperplasia
Over production and increase in cell size and
number.
Dysplasia.
Presence of abnormal cell within tissue or organ.
Both of these subsequent stages than lead to
neoplasia( new uncnotrolled growth of cell,
subclassified as malignant or benign tumor).

37. Control of cell proliferation by androgens:
 Administration of androgen in castrated rat results in:
 Inhibition of cell death.
 Increase in proliferation.
 Inhibition of cell proliferation.
 Androgen affect the proliferation of their target cell in
culture.
 Androgen role on their target cell is comparable to estrogen.
 Androgen bind to androgen receptor to form complex that
bind to DNA And regulates androgen activity.

38. How androgen affect proliferation of their
target cell?
 Androgen affect proliferation of their target cell in two
steps.
 Step 1:
 Promoting proliferation by cancelling inhibition.
 Step 2:
 Inhibiting proliferation by producing inhibitory protein.
 AR/catenin B complex

39. Conclusion
• Estrogen play role in cell proliferation either
directly or indirectly.
• EGF induce proliferation by binding to its
receptor.
• Three hypothesis are formulated to evaluate
estrogen role.
• Serum albumin act as a inhibitor of
proliferation.
• Estrogen act as inhibitor of serum albumin by
blocking its inhibition activity.
• Androgen also increase proliferation of its target
cell in same manner as that of estrogen.