BIOM 503
LIBERTY UNIVERSITY
FALL 2020
BIOM 503
HUMAN GENETICS
LECTURE ASSIGNMENT 9 INSTRUCTIONS
Compose a paragraph-style response for the essay topics listed below. The assignment must
reflect your own understanding of the course material.
1. Describe an example of a disease that is caused by an imbalance of estrogen signaling.
2. How do SERMs alter the actions of the estrogen receptor? Focus your answer on the
specific interactions between the receptor and SRC.
1. When estrogens bound to estrogen receptors, they allow the estrogen receptors to dimerize
and bind to the DNA and cause transcriptional outcomes that are different. This leads to an
increase in expression. However, there are some instances in which estrogen has been shown
to repress expression of genes. Overall, estrogen is seen as a mitogen because it promotes the
overall cell function and proliferation.
In the normal endometrium, estrogens play a mitogenic function, driving tissue growth during
the menstrual cycle as part of pregnancy anticipation. Estrogens are released during the late
follicular phase of the menstrual cycle by the developing follicle, leading to the growth of
endometrium. The development of estrogen peaks at ovulation, the end of the follicular process,
but the corpus luteum produces it at lower levels during the mid- to late-luteal period until fallinfg
until menstruation.
The second wave of estrogens does not contribute to endometrial cell proliferation, and this is
due to the presence of progestogens, especially progesterone. Progesterone levels are low
during the menstrual cycle's follicular period, but increase in the mid- to late-luteal process due
to the development of corpus luteum. During the luteal process, progesterone prevents
estrogen-induced endometrial growth while also transforming the endometrium to a receptive
state ready for implantation of blastocysts. During cancer development, this balance between
the pro-growth estrogens and anti-growth progestogens is also regulated by estrogens.
High levels of estrogens unopposed by progesterone can result in the formation of endometrial
cancer.1 This suggests that the imbaalance of estrogen and progesterone levels can cause
endometrial cancer development. This can happen because of women taking estrogen drugs
like in hormone replacement therapy where the estrogen levels are high in their body. Normally
when estrogen levels are high in a woman, progesterone levels are also high, and this goes with
the menstrual cycle, but high levels of estrogen without progesterone leads to unopposed
estrogen signaling, causing endometrial cancer.
BIOM 503
References
1. Rodriguez AC, Blanchard Z, Maurer KA, Gertz J. Estrogen Signaling in Endometrial
Cancer: a Key Oncogenic Pathway with Several Open Questions. Horm Cancer.
2019;10(2-3):51-63. doi:10.1007/s12672-019-0358-9
