The document is a lecture on molecular pharmacology focusing on the cell cycle, DNA, and cancer. It discusses key concepts such as the structure of eukaryotic cells, the phases of mitosis, cell cycle checkpoints, and the role of cyclins and kinases in regulating cell division. It also highlights the implications of these processes in cancer development and treatment, emphasizing how various anti-cancer drugs target specific cell cycle defects.

1. Molecular Pharmacology course
lecture No.1
Cell Cycle
Dr.Omer Yahia Elhussein
B.sc. Pharmacy.
M.sc. Molecular Medicine.

2. Where do we find DNA?

3. Peter J. Russell, iGenetics: Copyright © Pearson Education, Inc., publishing as Benjamin Cummings.

4. Eukaryotes: (meaning “true nucleus”)
are organisms with cells within
which the genetic material
(DNA)is located in the nucleus.
Nucleus: is a discrete structure
bounded by a nuclear envelope .
It is selectively permeable and
has pores about 20 to 80 nm in
diameter that allow certain
materials to move between the
nucleus and the cytoplasm
Chromatin is the stainable material
in a cell nucleus: DNA and
proteins.
Cell and Molecular Biology concepts and experiments 6 edition page 10

5. What do you now about epigenetic ?

6. Histones and nonhistones are two major
types of proteins associated with DNA
in chromatin.
Histones: are small basic proteins with a net
positive charge that facilitates their
binding to the negatively charged DNA.
Five main types of histones are associated
with eukaryotic nuclear DNA: H1, H2A,
H2B, H3, and H4.
Nonhistones : Include proteins that play a
role in the processes of DNA replication,
DNA repair, transcription (including
gene regulation), and recombination.
o A number of anti-cancer drugs
(e.g., Zolinza) are currently being
tested that act by inhibiting HDAC
enzymes .
Cell and Molecular Biology concepts and experiments 6 edition page 520

7. Ploidy
• Ploidy : is the number of copies of
chromosomes.
• Diploidy: Presence of two copies of
genes per cell, one from each
parent.
• Haploidy: one copy of each gene
per cell rather than two as in most
eukaryotic cells
• Aneuploidy: A condition in which a
cell has an abnormal number of
chromosomes that is not a multiple
of the haploid number.
Diploid
MEIOSIS
Haploid
Aneuploidy (Photo) chromosome 21 trisomy in Down syndrome)
Cell and Molecular Biology concepts and experiments 6 edition page 596

8. What do you know a bout mitochonderia?

9. Mitochondrion
• Mitochondrion is inherited
maternally.
• It has an Important role in
sequestering and releasing
Ca++.
• It is responsible for cellular
respiration and energy
production.
• It carries important biochemical
reactions (e.g. aerobic glycolysis)
• It mediates intrinsic apoptotic
path way
• (Picture)A premature-aging
phenotype caused by increased
mutations in mtDNA.
Mitochondrial DNA
T. Strachan, A. Read - Human Molecular Genetics 4ed(2011) page 258

10. Mitochonderial DNA vs. Nuclear DNA
T. Strachan, A. Read - Human Molecular Genetics 4ed(2011) page 260

11. When do cell divide?

12. …... •G1 Phase: cell growth and
progress for mitosis.
• S Phase: DNA replication and
chromosome duplication.
•G2 Phase: cell grows and
carries out normal
metabolism;
organelles duplicate.
M Phase: Mitosis.
Cell and Molecular Biology concepts and experiments 6 edition page 261
How cell cycle work

13. Stages of mitosis
• Interphase: Technically not part
of mitosis, but rather
encompasses stages G1, S, and
G2 of the cell cycle which prepare
the cell for mitosis.
• Prophase: Chromatin in nucleus
condense; nucleolus disappears.
Centrioles begin moving to
opposite ends of the cell and
fibers extend from the
centromeres.
• Metaphase: Spindle fibers align
the chromosomes along the
middle of the cell nucleus. This
line is referred to as the
‘metaphase plate.’
• Anaphase: The paired
chromosomes separate at the
kinetochores and move to
opposite sides of the cell. Motion
results from the physical
interaction of polar microtubules.

14. Stages of mitosis (cont.)
• Telophase: Chromatids arrive at
opposite poles of cell, and new
membranes form around the
daughter nuclei. The
chromosomes disperse.
• Cytokinesis: Results when a fiber
ring composed of a protein called
actin around the center of the
cell contracts, pinching the cell
into two daughter cells, each with
one nucleus.

15. Mitosis
• Mitosis is the process by which a cell duplicates the chromosomes in its cell
nucleus in order to generate two, identical, daughter nuclei.
• It is followed immediately by cytokinesis, which divides the nuclei, cytoplasm,
organelles and cell membrane into two daughter cells containing roughly equal
shares of these cellular components.
• Mitosis and cytokinesis together define the mitotic (M) phase of the cell cycle.
• Mitosis is a normal cellular process necessary to sustain life, but its deregulation in
one form or another is found in all cancer cells.
• Mitosis can often become abnormal by the change in, or absence of, the normal
cell cycle checkpoints.

16. Cell Cycle regulation

17. Cell cycle checkpoints
• Cell cycle checkpoints are points in the cell cycle which act to ensure correct
transmission of genetic information during cell division. These checkpoints
look for abnormalities within the cycle, specifically chromosomal aberrancy.
• Checkpoints take place towards the end of each phase of mitosis and must be
passed before the cell can get clearance to enter into the next stage of mitosis.
• If errors are found during checkpoints, the cell acts quickly to correct them,
arresting cell growth and not proceeding with mitosis until the error has been
fixed.
• If these errors cannot be fixed, the cell normally undergoes apoptosis, or
programmed cell death.

18. Cell cycle check points
• Cell cycle shows 3 major check
points :
a) G1 / S check point : (restriction
point)
Is environment favorable ?
B) G2 / M check point:
Is all DNA replicated ?
Is environment favorable ?
C) Metaphase to Anaphase
transition :
Are all chromosomes attached
to spindle ?
Peter J. Russell, iGenetics: Copyright © Pearson Education, Inc., publishing as Benjamin Cummings.
Cell cycle control

19. Factors regulate cell cycle
• Cyclin - dependent kinases (CDK): enzymes that control progression of
cells through cell cycle.
• Cyclins : are proteins required to activate cyclin dependent kinases to
form an active cyclin-CDK complex (e.g. MPF )
• APC/SCF: complexes: they are two classes of multi subunits complexes
that function as ubiquitin ligasis . These complexes recognizes the
protein to be degraded and linked it to the polyubiquitin chain , that
ensure their destruction by Proteosome
Cyclins:(named because their concentration increases and decreases in a regular pattern through the cell cycle)

20. Check Point Regulation
At the G1toS checkpoint,
two different G1 cyclin
Cdk complexes form,
resulting in activation of
the kinases.
The kinases catalyze a
series of Phosphorylations
of cell cycle Control
proteins, affecting
the functions of those
proteins and leading,
therefore, to transition
into the S phase.
PRB: Retino Plastoma Protein. It is a tumor suppressor
protein associated with a familial (inherited) eye’s
cancer
.Peter J. Russell, iGenetics: Copyright © Pearson Education, Inc., publishing as Benjamin Cummings.

21. How do check points prevent
cancer ?
Entry into S phase is blocked
when there is unrepaired DNA
damage. Irreparable damage
leads to apoptosis.
Within S phase there are
additional checkpoints at which
DNA damage prevents new
origins of replication from
becoming active.
Peter J. Russell, iGenetics: Copyright © Pearson Education, Inc., publishing as Benjamin Cummings.
P53 is a tumor suppressor protein; have a molecular
importance in many cancers

22. To BE CONTINUED…….
15 MIN. BREAK

23. Cell Cycle and cancer

24. What is Cancer?
• Cancer is the deregulation of normal cellular processes. Cells that have
been transformed tend to proliferate in an uncontrolled and deregulated
way and, in some cases, to metastasize (spread).
• Cancer is not one disease, but a group of more than 100 different and
distinctive diseases.
• Cancer can involve any tissue of the body and take on many different
forms in each area.

25. Continue…..
• Cancer cells become deregulated in many different ways.
• One way: Mutations in one or more mitotic checkpoints allow the cell to
move from one phase of mitosis to another unchecked.
• Another way: Mutations in cellular machinery itself so that mitotic errors
are not properly detected/repaired, and the cell is allowed to move
through mitosis unchecked.

26. Continue…..
• The cell is allowed to move through the cell cycle and grow unchecked,
and more mutations are accumulated over time that extend past the cell
cycle to the cellular machinery itself.
• These mutations, in combination with the genetic mutations accrued
through abnormal mitotic progression, eventually cause the cell to be
completely deregulated in its growth and proliferation.
• It becomes unstoppable and even immortal.

27. Molecular Pharmacology

28. Molecular Pharmacology
• Check points defects as
anticancer target:
1. Spindle defects: (by using anti-
microtubule drugs)
2. growth conditions: (by using
anti proliferative factors e.g.
DNA damage, ionizing
radiation and UV)
3. Replication faults: (by using
anti-metabolites) .
4. Chromosome catenation: (by
using topoisomerase
inhibitors )

29. Antimitotic Agents
• Antimitotic agents: Anti-tumor
agents that inhibit the function of
microtubules through the binding of
their subunits or through direct
cessation of their growth.
• What are microtubules (MTs)?
Protein polymers formed by a-Tubulin
and B-tubulin heterodimers that play
an important role in critical cell
functions such as movement,
phagocytosis and axonal
transport. They also play a key role in
the formation of the mitotic spindle
apparatus and cytokinesis at the end
of mitosis.
• In normal cells, microtubules are
formed when a cell starts dividing
during mitosis. Once the cell
stops dividing, microtubules are
broken down or destroyed.
• The crucial involvement of MTs in
mitosis makes them a prime
target for anti-cancer agents.

31. Spindle defects
sciencedirect.com

32. Spindle defects

36. • Prevent the growth of cancer cells by affecting
microtubules.
• Overall, they encourage microtubule formation, then
they stop the microtubules from being broken down
so that the cells become so clogged with
microtubules that they cannot continue to grow and
divide. This results in the cell’s arrest in mitosis.
• Eventually, cell DEATH by apoptosis.
Taxol

37. Complicating Factors
• B-tubulin mutations which inhibit the binding of taxanes to
the correct place on the microtubules; this renders the drug
ineffective.
• In addition, some resistant cells also display increased aurora
kinase, an enzyme that promotes completion of mitosis .

38. Spindle defects
Vinca alkaloids and its
role in cancer treatment

39. Catharanthus roseus is known as the
common or Madagascar periwinkle
Originally native to island of
Madagascar.
Spindle defects

40. Vincristine and Vinblastine Inhibit
mitosis in metaphase by binding
tubulin
Spindle defects

41. Vinca Alkaloids
• The Vincas work through their ability to bind to the
B- tubulin subunit of microtubules, blocking their
ability to polymerize with the a- tubulin subunit to
form complete microtubules.
• This causes the cell cycle to arrest in metaphase
because, in absence of an intact mitotic spindle,
duplicated chromosomes cannot align along the
division plate.
• The ultimate fate of such cells is to undergo
apoptosis.

42. Complicating Factors
• Resistance to the Vinca alkaloids comes in the form of cross-
resistance due to the structural similarity of the compounds
(multidrug resistance)
• Because of the heavy concentration of microtubules in the brain
and the drug’s disruption of this, patients treated with Vinca
alkaloids can experience severe neurotoxicity.

43. Another examples :
• Colchicine :Colchicine is an alkaloid derived from the autumn crocus
(Colchicum autumnale). It inhibits mitosis by inhibiting microtubule
polymerization. While colchicine is not used to treat cancer in humans, it is
commonly used to treat acute attacks of gout . It poison (PMN; Polymorph
nuclear Leukocytes ) that mediate joint inflammation .
• Podophyllotoxin: Podophyllotoxin and Podophyllin, derived from the may
apple plant, are used to treat viral skin infections.
• Griseofulvin: derived from a Penicillium mold, is an antifungal drug.
Spindle defects

44. discussion

45. Thank you

46. Three
apples;
Adam’s,
Newton’s,
And
Steve Jobs