Cell Cycle Regulation and Cancer Biology
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Questions and Answers

What is the primary characteristic that defines cancer?

  • Controlled cell growth
  • Uncontrolled cell growth (correct)
  • Cell death
  • Normal cell division

What does malignancy refer to in the context of cancer?

  • The mechanism of apoptosis in cells
  • The potential to spread and invade nearby tissues (correct)
  • The ability to undergo normal mitosis
  • The stage of early tumor formation

Which factor is NOT associated with uncontrolled cell division leading to cancer?

  • Balanced internal stimuli (correct)
  • Disruption of normal cell cycle regulation
  • Lack of homeostasis
  • Response to external stimuli

Which statement best explains carcinogenesis?

<p>It arises from a lack of control in cell division leading to tumor formation. (C)</p> Signup and view all the answers

What can be a consequence of uncontrolled cell division?

<p>Metastasis of tumor cells (B)</p> Signup and view all the answers

What is the role of cyclins in cell cycle control?

<p>They are the regulatory subunit that activates cdks. (A)</p> Signup and view all the answers

How do cyclin-dependent kinases (cdks) become activated?

<p>By binding to a specific cyclin. (B)</p> Signup and view all the answers

What is the primary function of the active cyclin-cdk complex?

<p>To phosphorylate other proteins leading to their activation or inactivation. (B)</p> Signup and view all the answers

What commonly happens to cyclins during the cell cycle?

<p>Their concentration fluctuates. (C)</p> Signup and view all the answers

What occurs when cdks are inactive?

<p>They are unable to activate transcription factors for DNA replication. (C)</p> Signup and view all the answers

What is the primary role of ubiquitin in the regulation of cyclins?

<p>To tag proteins for degradation (A)</p> Signup and view all the answers

Which protein complex is responsible for degrading short-lived proteins like cyclins?

<p>Proteasome (A)</p> Signup and view all the answers

What is one of the consequences of loss of cell cycle control?

<p>Carcinogenesis may take place (B)</p> Signup and view all the answers

What does MPF consist of in the context of cell cycle regulation?

<p>Mitotic cyclin and cdk-1 (B)</p> Signup and view all the answers

What is the effect of MPF on the Anaphase promoting complex (APC)?

<p>It phosphorylates and inactivates APC (A)</p> Signup and view all the answers

Which of the following best describes the function of E3 ligases?

<p>To add ubiquitin to proteins for degradation (C)</p> Signup and view all the answers

What triggers the progression from G2 to M phase in the cell cycle?

<p>Activation of MPF through phosphorylation (C)</p> Signup and view all the answers

What happens to the nuclear envelope during mitosis as a result of MPF activity?

<p>It undergoes fragmentation (D)</p> Signup and view all the answers

What function does the p53 protein perform in cells?

<p>Detects DNA damage (B)</p> Signup and view all the answers

Which statement is true about the TP53 gene?

<p>Mutations in TP53 occur in over 50% of cancers. (A)</p> Signup and view all the answers

What role do internal signals play at cell cycle checkpoints?

<p>They control progression based on cell conditions. (B)</p> Signup and view all the answers

What is a common effect of PDGF on fibroblast cells?

<p>Stimulates fibroblast growth. (D)</p> Signup and view all the answers

Which checkpoint monitors the separation of sister chromatids?

<p>M phase checkpoint (A)</p> Signup and view all the answers

Which factor is NOT a consideration for internal signals controlling the cell cycle?

<p>Environmental conditions (B)</p> Signup and view all the answers

What is the primary role of growth factors like PDGF in cell biology?

<p>Stimulating cell division (C)</p> Signup and view all the answers

Which of the following statements about p53 is true?

<p>It induces cell cycle arrest. (C)</p> Signup and view all the answers

What is density-dependent inhibition?

<p>Crowded cells stop dividing. (A)</p> Signup and view all the answers

What is anchorage dependence?

<p>Cells can only divide when attached to a substratum. (D)</p> Signup and view all the answers

How do normal mammalian cells behave when they form a complete layer?

<p>They stop dividing due to density-dependent inhibition. (A)</p> Signup and view all the answers

What characteristic distinguishes cancer cells from normal cells?

<p>Cancer cells do not stop dividing when crowded. (B)</p> Signup and view all the answers

What happens when normal cells are scraped away from a surface?

<p>Remaining cells proliferate to fill the gap. (D)</p> Signup and view all the answers

Which statement regarding cancer cells is incorrect?

<p>Cancer cells adhere strongly to substratum. (B)</p> Signup and view all the answers

Which of the following factors is NOT associated with normal cell division?

<p>Unrestricted cell density (A)</p> Signup and view all the answers

What occurs in terms of cell proliferation in cancerous tissues?

<p>They exhibit uncontrolled growth regardless of contact inhibition. (D)</p> Signup and view all the answers

What is the primary focus of precision oncology?

<p>Employing a patient’s genetics to tailor treatment plans (B)</p> Signup and view all the answers

Which checkpoint controls the transition from the G1 phase to the S phase in the cell cycle?

<p>G1 checkpoint (B)</p> Signup and view all the answers

What characteristic contributes to the heterogeneity of tumors?

<p>Diverse physiological pathways (C)</p> Signup and view all the answers

Which of the following cellular components are involved in cell cycle regulation?

<p>Cyclin-cdks (A)</p> Signup and view all the answers

What is a significant challenge in cancer treatment?

<p>Accumulate multiple mutations in cancer cells (B)</p> Signup and view all the answers

Which checkpoint is responsible for controlling the transition through the stages of mitosis?

<p>M checkpoint (B)</p> Signup and view all the answers

How does precision oncology differ from traditional cancer treatment approaches?

<p>It tailors therapies based on the specific molecular characteristics of a patient’s cancer (B)</p> Signup and view all the answers

What phenomenon describes the accumulation of different mutations within cancer cells?

<p>Heterogeneity of tumors (A)</p> Signup and view all the answers

Flashcards

Normal Cell Division

When cells divide in a normal, controlled way, creating two identical daughter cells from one parent cell.

Uncontrolled Cell Division

Uncontrolled cell division happens when cells keep multiplying without any regulation. This can lead to the formation of cancer.

Carcinogenesis

This term refers to the overall process of cancer development and refers to a lack of homeostasis within the cells.

What is Cancer?

Cancer is defined as the uncontrolled growth and spread of abnormal cells. These cells multiply out of control and sometimes spread to other parts of the body (metastasis).

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What is Malignancy?

Malignancy refers to the ability of a tumor to invade nearby tissues and spread to other areas of the body (metastasis). This is the key characteristic of cancer.

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Cyclin-CDK complex

A protein complex crucial for cell cycle regulation, composed of two subunits: a regulatory cyclin and a catalytic cyclin-dependent kinase.

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Cyclins

Regulatory subunits of the cyclin-CDK complex that control the activity of CDKs by binding to them.

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Cyclin-dependent kinases (CDKs)

Catalytic subunits of the cyclin-CDK complex that are responsible for phosphorylating target proteins.

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Phosphorylation

The process of adding a phosphate group to a molecule, often altering its activity.

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G1/S transcription factors

Proteins that control the progression of the cell cycle by regulating DNA replication through phosphorylation.

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Cdk regulation

The activity of cyclin-dependent kinases (cdks) is regulated by the destruction of cyclins.

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Proteasome

A large protein complex in cells that breaks down proteins marked for destruction.

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Ubiquitin

A small protein that tags proteins destined for breakdown by the proteasome.

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Ubiquitin ligases (E3 ligases)

Enzymes that add ubiquitin tags to proteins.

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Unregulated cell proliferation

Uncontrolled cell division, often leading to cancer.

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MPF

Mitosis Promoting Factor, a complex of a mitotic cyclin and a cdk that triggers the transition from G2 to M phase.

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Anaphase Promoting Complex (APC)

A protein complex regulated by MPF that controls progression through the cell cycle.

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Nuclear Lamina

A structure that surrounds the nucleus and breaks down during mitosis.

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Density-dependent inhibition

A phenomenon where crowded cells stop dividing due to limited space and resources.

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Anchorage dependence

The need of most animal cells to be attached to a surface in order to divide.

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How do normal cells regulate growth?

Cells divide until they form a single layer, then they stop, preventing uncontrolled growth.

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How do cancer cells differ from normal cells?

These cancer cells continue to divide even when they are crowded and despite lacking attachment to a surface.

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Characteristic of cancer cells

Cancer cells can form a clump of overlapping cells, indicating uncontrolled growth.

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What does it mean when cancer cells lack density-dependent inhibition?

Cancer cells ignore the signals that normally stop cell division, allowing them to multiply uncontrollably.

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What does it mean when cancer cells lack anchorage dependence?

Cancer cells can grow and spread even without being anchored to a surface, allowing them to invade new tissues.

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Why are density-dependent inhibition and anchorage dependence important?

The cellular processes of density-dependent inhibition and anchorage dependence are critical in preventing uncontrolled growth, like that of cancer.

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TP53 gene

A gene encoding the p53 protein, which plays a critical role in regulating cell cycle progression and preventing uncontrolled cell growth.

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p53 protein

A protein encoded by the TP53 gene. It acts as a tumor suppressor by detecting DNA damage, halting cell cycle progression if necessary, and triggering apoptosis to eliminate damaged cells.

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G1 checkpoint

A checkpoint in the cell cycle where the cell checks for DNA damage before entering the S phase for DNA replication. If damage is detected, the cell cycle is halted until repairs are made.

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M phase checkpoint

A checkpoint in the cell cycle where the cell inspects the duplicated chromosomes and ensures they are properly aligned before entering mitosis.

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Apoptosis

A form of programmed cell death where cells self-destruct to prevent uncontrolled growth or spreading of damaged cells.

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Growth factors

Factors produced by cells that stimulate other cells to divide. They act as signals for cell growth and proliferation.

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G2 checkpoint

A checkpoint in the cell cycle where the cell checks for damaged or incompletely replicated DNA before entering the M phase. If issues are found, the cell cycle is paused until repairs are completed.

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Internal signals

Signals originating from within the cell itself that regulate the cell cycle. These signals can include factors like cell size or the proper alignment of chromosomes.

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What are the characteristics of cancer cells?

Cancer cells divide uncontrollably, invading surrounding tissues and potentially spreading to distant sites (metastasis).

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Why are cancer cells so challenging to treat?

Cancer cells accumulate multiple mutations, leading to diverse physiological pathways and tissue-specific variations. These factors contribute to the difficulty in effectively targeting cancerous cells.

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What is precision oncology?

Precision oncology utilizes a patient's genetic information to create a tailored treatment plan based on the specific molecular characteristics of their cancer.

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What are the key cell cycle checkpoints?

The G1 checkpoint regulates the transition from the G1 to the S phase (DNA replication). The G2 checkpoint controls the transition from the G2 to the M phase (mitosis). The M checkpoint ensures proper chromosome alignment during mitosis.

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What are cyclin-dependent kinases (CDKs)?

Cyclin-dependent kinases (CDKs) are enzymes that add phosphate groups (phosphorylation) to proteins, regulating their activity.

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What are cyclins?

Cyclins are regulatory proteins that bind to CDKs, activating them and driving the cell through different stages of the cycle.

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How do cyclins and CDKs work together?

The combination of a cyclin and a CDK forms a complex responsible for regulating the cell cycle.

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What role does phosphorylation play in cell cycle regulation?

Phosphorylation, the addition of a phosphate group to a protein, is a key mechanism by which CDKs regulate cell cycle progression.

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Study Notes

Cell Cycle Regulation

  • Cell cycle control is crucial for normal cell function and preventing diseases like cancer
  • The cell cycle is a series of events that lead to cell duplication, involving checkpoints for regulation
  • Learning objectives include understanding cell cycle control, checkpoints, the role of cyclin-cdks, tumor suppressor genes (Rb and p53), and cdk inhibitors (CKIs)
  • Cancer is characterized by uncontrolled cell growth, proliferation, and potential metastasis
  • Learning the difference between benign and malignant tumors is key
  • Recommended reading includes chapters 12 of Campbell Biology and 17 of Alberts et al.'s Molecular Biology of the Cell (2008 7th Edition)

Phases of the Cell Cycle

  • The cell cycle consists of interphase (G1, S, and G2 phases) and the mitotic phase (M phase) which includes mitosis and cytokinesis
  • Interphase: the period of growth and DNA replication before mitosis
  • G1 phase: cell growth and preparation for DNA replication
  • S phase: DNA replication occurs
  • G2 phase: final preparation for cell division
  • Mitotic phase (M phase): the division of the nucleus and cytoplasm
  • Mitosis: nuclear division
  • Cytokinesis: cytoplasmic division

Importance of Cell Cycle Regulation

  • Cell division must be tightly controlled
  • Uncontrolled cell division leads to carcinogenesis
  • Homeostasis in normal tissue is maintained by the balance between mitosis (creation of new cells) and apoptosis is death of cells
  • Imbalance results in disease
  • Understanding cell cycle regulation is essential to understand how and why cancer occurs

What is Cancer?

  • Cancer is uncontrolled cell growth
  • Abnormal cell growth, proliferation, and often metastasis
  • Characterized by the loss of cell cycle checkpoints and controls

Carcinogenesis

  • Cancer development involves environmental and genetic predisposition
  • Carcinogens are substances that can lead to cancer, categorized as chemical, physical, and viral
  • Mutations leading to uncontrolled proliferation and inhibited apoptosis contribute to carcinogenesis
  • Activation of oncogenes and inactivation of tumor suppressor genes are key factors in carcinogenesis

Cell Cycle Checkpoints

  • Checkpoints are control points in the cell cycle to ensure proper progression
  • G1 checkpoint: evaluates cell size, correct DNA, nutrients and factors before DNA replication
  • G2 checkpoint: ensures that DNA replication has been properly completed and any damage is repaired
  • M checkpoint: verifies correct chromosome attachment to mitotic spindle before separation

G1 Checkpoint

  • Checks for cell size, nutrients, growth factors and DNA damage
  • If conditions favorable, the cell commits to entering the S (DNA replication) phase

G2 Checkpoint

  • Monitors if the DNA replication is complete and free of damage before mitosis
  • Ensures accurate DNA replication before cell division
  • Regulates the transition from G2 phase to M phase

M (Metaphase) Checkpoint

  • Checks for accurate chromosome alignment on mitotic spindle for correct chromosome segregation during mitosis
  • Prevents the separation of sister chromatids if alignment is incorrect

Molecules for Cell Cycle Control

  • Cyclins and cyclin-dependent kinases (Cdks) are crucial parts of the cell cycle control system
  • Cdks are present at a constant concentration to maintain control of the cycle. They only become active upon binding to cyclins
  • Cyclins fluctuate in concentration, activating and inactivating Cdks.
  • The activity of Cdks is regulated by the proteasome, which targets cyclins for degradation.
  • Tight regulation of Cdks is imperative to normal cell function, loss of regulation triggers unregulated cell proliferation and carcinogenesis

Cell Cycle Regulation by Cyc-Cdks

  • Different classes of cyclins associate with distinct classes of Cdks at different times in the cell cycle to regulate the phases.
  • (Early G1), (Late G1), (S phase), (G2/M phase)

Cell Cycle Regulation by Tumor Suppressor Genes

  • Crucial for controlling cell growth and preventing uncontrolled cell proliferation
  • Examples include RB1 and TP53 -RB1: involved in controlling the progression from G1 to S by controlling E2F
  • TP53: called the "guardian of the genome" plays a role in DNA repair and apoptosis to prevent damaged cells from dividing.

Internal and External Signals

  • Internal signals, such as cell size and chromosome alignment, trigger checkpoints
  • External signals, like growth factors, allow cell-to-cell communication and promote cell division
  • Signals trigger cell cycle progression via specific signaling pathways

External Signals

  • Growth factors promote cell division
  • Density-dependent inhibition: crowded cells stop dividing, ensuring cells don't excessively proliferate
  • Anchorage dependence: animal cells must attach to a surface to divide

Cancer Cells: Loss of Cell Cycle Control

  • Cancer cells do not respond to density-dependent inhibition or anchorage dependence
  • They make their own growth factors, keep the growth promoting signaling pathways turned "on", and demonstrate abnormal cell cycle control
    • Benign tumors: not invasive, contained at the site of origin
    • Malignant tumors: invasive, can spread to other organs

Malignant Tumors

  • Malignant tumors invade surrounding tissues and spread (metastasis)
  • Key characteristics include uncontrolled proliferation and loss of cell cycle checkpoints, allowing for cancer spread

Precision Oncology

  • This is the science of using a patient's genetics to tailor treatment plans for cancer
  • Aims to target the specific molecular characteristics of the cancer, ensuring effective and efficient treatment

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Related Documents

Cell Cycle Regulation PDF

Description

This quiz explores the essential concepts of cell cycle regulation and the mechanisms leading to cancer. It covers topics such as cyclins, cyclin-dependent kinases, carcinogenesis, and the implications of uncontrolled cell division. Test your knowledge on how these elements interrelate in the context of cancer biology.

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