Session 7: cancer

Cancer

Cancer is a group of diseases in which abnormal cells grow uncontrollably and can spread to other parts of the body. If not treated, it can be life-threatening.

• exact causes remain unclear, but there are modifiable and non-modifiable risks; they can act alone or together

Modifiable cancer risk

include things like tobacco use, excess body weight, poor diet, and certain infections.

Non modifiable cancer risk

include inherited genetic mutations and age

carcinogen

any substance or agent that can cause cancer in humans.

natural carcinogens

Aflatoxin: produced by a fungus found on improperly stored grains and nuts

man-made carcinogens

• Asbestos, tobacco smoke, and certain industrial chemicals

• Carcinogens can damage a cell’s DNA, leading to genetic mutations that drive cancer development.

endocrine disrupters

• chemicals that interfere with the body’s hormone (endocrine) system.

• They may cause harmful developmental, reproductive, neurological, and immune effects in both humans and animals

sources of endocrine disrupters

• Pharmaceuticals

• Dioxins, PCBs (polychlorinated biphenyls)

• DDT and other pesticides

• Plasticizers like bisphenol A (BPA

endocrine disrupters can be found in

• Plastic bottles, metal food cans

• Detergents, flame retardants ▪ Cosmetics, toys, food, and pesticides

how does a cell become a cancer cell

1. Self-Sufficiency in Growth Signals

   1. Cancer cells can divide without the usual signals that tell normal cells to grow.

2. Insensitivity to Anti-Growth Signals

   1. They ignore external cues that normally tell cells to stop dividing.

3. Evasion of Apoptosis

   1. They resist programmed cell death—even when damaged or abnormal.

4. Unlimited Replicative Potential

   1. Cancer cells can divide indefinitely, bypassing normal aging and senescence (deterioration with age)

5. Sustained Angiogenesis

   1. They stimulate the growth of new blood vessels to supply nutrients and oxygen to tumors.

6. Tissue Invasion & Metastasis

   1. Cancer cells can invade surrounding tissue and spread to distant organs, forming secondary tumors.

Grade

Describes how abnormal (or undifferentiated) the cancer cells look under a microscope.

• Low grade = cells look more like normal cells

• High grade = cells look more abnormal and may grow/spread faster

Stage

Refers to how far the cancer has spread in the body.

• Takes into account tumor size, lymph node involvement, and spread to other organs (metastasis)

Carcinoma

Cancer that begins in epithelial tissues (e.g., skin, glands, lining of organs)

• Most common type; often invasive and capable of metastasis

Sarcoma

Arises from mesenchymal tissue such as bone, cartilage, fat, or muscle

Lymphomas, leukemias, myelomas

Cancers that begin in blood-forming tissues or the immune system

metastasis

The process by which cancer cells break away from the original tumor, travel through blood or lymph, and form new tumors in other parts of the body.

How does cancer form

Cancer is a disease caused when cells divide uncontrollably and spread to surrounding tissues

What causes Cancer (DNA)

Cancer is caused by changes to DNA. Most cancer-causing DNA changes occur in sections of DNA called genes. These changes are also called genetic changes.

Oncogenes

A DNA change can cause genes involved in normal cell growth to become oncogenes. Unlike normal genes, oncogenes cannot be turned off, so they cause uncontrolled cell growth.

Tumor suppressor genes

In normal cells, tumor suppressor genes prevent cancer by slowing or stopping the cell growth. DNA changes that inactivate tumor suppressor genes can lead to uncontrolled cell growth and cancer.

tumor microenvironment

W/I a tumor, cancer cells are surrounded by a variety of immune cells, fibroblasts, molecules, and blood vessels – what’s known as the tumor microenvironment. Cancer cells can change the microenvironment, which in turn can affect how cancer grows and spreads

how immune system interacts with cancer

Immune system cells can detect and attach cancer cells. But some cancer cells can avoid detection or thwart an attack. Some cancer treatments can help the immune system better detect and kill cancer cells

how genetic changes affect cancer treatment

Each person’s cancer has a unique combination of genetic changes. Specific genetic changes may make a person’s cancer more or less likely to respond to certain treatments.

what causes genetic changes

Genetic changes that cause cancer can be inherited or arise from certain environmental exposures. Genetic changes can also happen because of errors that occur as cells divide.

how age relates to cancer

Most often, cancer-causing genetic changes accumulate slowly as a person ages, leading to a higher risk of cancer later in life.

environmental exposures linked to cancer

• combustible tobacco: lung, kidney

• UV radiation: skin, melanoma

• HIV: Anal Cancer

• X Rays: Leukemia, lymphoma

lifestyle factors that increase cancer risk

• Low Fruit & Vegetable Consumption

  • Lack of protective nutrients and antioxidants may increase risk for several cancers.

• High Body Mass Index (BMI)

  • Excess body fat is linked to cancers such as breast (postmenopausal), colorectal, pancreatic, and more.

• Physical Inactivity

  • Regular exercise helps regulate hormones and immune function—reducing cancer risk.

• Alcohol Consumption

  • Even moderate drinking increases risk for cancers of the mouth, liver etc

• Tobacco Use

  • The leading preventable cause of cancer and cancer deaths worldwide.

  • Strongly linked to lung, throat cancer.

  • Lung cancer is the most preventable cancer type.

infectious diseases as cause of cancer

• ~16%

• HBV and HCV linked to liver cancer

• HPV cause nearly all cervical cancers and genital, anal, or throat cancers

What is HPV

• HPV infections, especially in younger people, are usually cleared by the immune system without symptoms or lasting effects.

• However, chronic HPV infections can persist and increase the risk of developing cancer.

• HPV infections are localized to basal cells and stratified epithelial tissue (such as skin and mucous membranes).

• Once inside the cell, HPV takes 12–24 hours to begin viral gene transcription, starting its replication cycle.

facts about HPV

• HPV refers to a group of about 200 viruses

• Most people don’t have problems from HPV, but some high-risk types can cause genital warts or cancer.

• In 90% of cases, the body clears the infection on its own.

• Persistent infection with high-risk HPV types causes cervical cancer and is linked to cancers of the vulva, vagina, mouth/throat, penis, and anus.

• In 2019, HPV was responsible for about 620,000 cancer cases in women and 70,000 in men worldwide.

• Vaccination can prevent many HPV-related cancers.

• Screening and treating precancerous changes is an effective way to prevent cervical cancer

HPV vaccine

Who should get vaccinated?

• Recommended for males to age 21 and females to age 26

• All children ages 11-12 should receive 2 doses, spaced about 6 months apart Impact of Vaccine

Impact of Vaccine

• HPV causes around 30,700 cancer cases annually in the U.S.

• Vaccination could prevent about 28,000 cases each year (about 81%)

Why Is it not required in schools

• School-entry vaccine mandates exist but are controversial in many states

• Concerns include parental rights, misinformation, and political debates

breast cancer is linked to

• Increases in excess body weight

• Changes in reproductive patterns such as:

  • Higher age at first childbirth

  • Fewer number of births

breast cancer mortality trends

Death Rate Decline

• Female breast cancer death rates peaked in 1989

• Since then, death rates have dropped by 42% as of 2021

Reasons for decline

• Earlier detection through screening mammography

• Increased breast cancer awareness

• Advances in treatment options

Impact

• Approximately 490,500 fewer deaths than expected if death rates had stayed at their peak From 2012 to 2021, death rates continued to decline by 1% per year

environmental exposures linked to breast cancer

• smoking

• drinking

• weight

preventing cancer techniques

• UV protection

  • avoiding excessive sun exposure, wear sunscreen

• Immunization against carcinogenic viruses such as HPV and Hepatitis B vaccine

• condom use reduces transmission of HPV and HIV

• Regulation of carcinogenic chemicals

  • environmental policies

• early detection

  • recognizing breast lumps, persistent cough

• cancer screening programs

targeted therapy

• A treatment that targets specific genetic mutations in cancer cells

• Unlike chemotherapy, it focuses only on cancer cells with certain changes — sparing more healthy cells

how targeted therapy works

• Cancer forms when genes mutate and cause uncontrolled cell growth

• Doctors use genetic testing (next-generation sequencing) to identify mutations in a tumor 3.

• If a known mutation is found, a targeted drug can be used to block or slow the cancer

• Only ~5–10% of cancers are due to inherited mutations (e.g., BRCA1/2) Most mutations are acquired during life (from aging, smoking, sun exposure, etc.)

Chemotherapy vs targeted therapy

• chemotherapy:

  • attacks all fast growing cells

  • more side effects

  • one size fits all

• Targeted therapy

  • targets cells with specific mutations

  • usually fewer side effects

  • personalized to the patients tumor

targeted therapy example with breast cancer

• ~20% of breast cancers have HER2 gene amplification

• This leads to aggressive tumor growth

• Trastuzumab (Herceptin) is a targeted therapy that blocks HER2 signals

• Improves survival and reduces recurrence compared to chemotherapy alone

remaining challenges in cancer prevention and control

• for many cancers, exact causes remain unknown or multifactorial

• detecting individuals with elevated genetic or environmental risk

• some cancers remain resistant to treatment (e.g., pancreatic, brain)

• affecting behavioral and policy change

• identifying and mitigating risks; many exposures have uncertain or emerging risks to cancer

• improving prevention strategies