​Developing Cancer

Cancer Progress Report 2015: Contents

In this section you will learn:

  • Cancer is not one disease; it is a collection of many diseases characterized by the uncontrolled growth of cells.

  • Changes in the genetic material in a normal cell underpin cancer initiation and development in most cases.

  • A cancer cell’s surroundings influence the development and progression of disease.

  • The most advanced stage of cancer, metastatic disease, accounts for more than 90 percent of cancer deaths.

  • The more we know about the biology of cancer, the more precisely we can prevent, detect, diagnose, and treat it.

  • Cancer is not one disease; it is a collection of many diseases that arise when the processes that control the multiplication and life span of normal cells go awry.


As humans develop, we grow, through extensive cell multiplication, from a single cell to an estimated 37.2 trillion cells in an adult body (20). When a person matures, the pace of cell multiplication slows. In adults, normal cells primarily multiply only to replace cells that die either due to exposure to a variety of external factors or naturally as a result of normal cellular wear and tear, which is related to the number of times the cell has multiplied.

When the processes that control the multiplication and life span of normal cells go awry, the cells start multiplying uncontrollably, fail to die when they should, and begin to accumulate. In body organs and tissues, these cancerous cells form a tumor mass, and in the blood or bone marrow, they crowd out the normal cells.

Without medical intervention, over time, some cancerous cells gain the ability to invade local tissues, and some spread, or metastasize, to distant sites. The progression of a cancer to metastatic disease is the cause of most cancer-related deaths.

Changes, or mutations, in the genetic material of the cells are the primary cause of cancer initiation and development. Not all mutations contribute to cancer development, but the greater the chance that a cell will acquire a mutation, the greater the chance that one of these mutations will cause cancer. The identity, order, and speed at which a cell acquires genetic mutations determine the length of time it takes for a cancer to develop and are influenced by numerous interrelated factors (see sidebar on Why Me? Why This Cancer?).

CancerDevelopment: Influ​ences​ Inside the Cell

Cancer develops largely as a result of the accumulation of mutations in the genetic material inside a cell (see sidebar on Genetic and Epigenetic Control of Cell Function). A mutation is a change in the type or order of the four deoxyribonucleic acid (DNA) units, called bases, that make up the genetic material of a cell. The sequence of DNA bases determines what proteins are produced by a cell and how much of each protein is produced, thereby defining cellular function. Many different types of mutation can lead to cancer, largely by altering the amount or function of certain proteins (see sidebar on Genetic Mutations), although it is important to note that not all mutations result in cancer.

Most cancer cells have not only numerous genetic mutations, but also profound abnormalities in their epigenomes when compared with normal cells of the same tissue. In many cases, epigenetic alterations and genetic mutations work in conjunction to promote cancer development. Of immense therapeutic interest is the discovery that although genetic mutations are permanent, some epigenetic abnormalities may be reversible. In fact, the FDA has already approved six therapeutics that cause changes in the epigenome (see Targeting the Epigenome​).


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Cancer Development: Influences Outside​ the Cell

Genetic mutations underpin cancer initiation and development in most cases. However, interactions between cancer cells and their environment—known as the tumor microenvironment—as well as interactions with systemic factors, also play an important role in cancer development (see sidebar on Cancer Growth: Local and Global Influences​). Therefore, developing a more comprehensive, whole-patient understanding of cancer has the potential to provide novel approaches to cancer prevention and treatment.

Cancer Development: Exploiting ​Our Expanding Knowledge to Improve Health Care

Research has significantly increased our knowledge of the processes by which cancer starts, progresses, and results in disease. It also has expanded our ability to exploit this knowledge to develop new and better approaches to cancer prevention, detection, diagnosis, and treatment. Most of the new treatments are more precise than traditional therapies, providing patients with not just longer but also higher-quality lives, and researchers are beginning to use the same precision strategy to develop new cancer prevention and interception interventions (see Special Feature on Five Years of Progress Against Cancer​).

In the United States, the research that fuels advances against cancer is largely supported by the NIH and NCI. Given that continued progress will be made only through additional research, it is vital that the administration and Congress increase investments in the NIH and NCI, as well as the FDA, which assures the safety and efficacy of advances.


Cancer Progress Report 2015 Contents

American Association for Cancer Research Foundation
The AACR Cancer Progress Report is published by the American Association for Cancer Research (AACR). The mission of the AACR is to prevent and cure cancer through research, education, communication, and collaboration.

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