10.5: Cancer Treatments

Learning Objectives

By the end of this section, you will be able to do the following:

• Explain how alterations in gene regulation at multiple levels contribute to cancer development.
• Describe how biotechnology is used to identify molecular changes in cancer cells and guide treatment decisions.
• Explain how targeted therapies and personalized medicine use knowledge of gene regulation to improve cancer treatment.

Cancer: Disease of Altered Gene Expression

Throughout this chapter, we have seen that cancer develops through the gradual accumulation of DNA mutations that disrupt the normal regulation of cell growth, division, and survival. These mutations alter the activity of proteins that regulate the cell cycle, allowing cells to acquire the hallmarks of cancer. However, DNA mutations are only part of the story. Ultimately, cancer develops because these genetic changes alter how genes are expressed and how proteins function within the cell.

Modern biotechnology has transformed our understanding of these molecular changes. Today, scientists can analyze DNA sequences, measure gene expression, identify abnormal proteins, and detect epigenetic changes within individual tumors. These technologies allow researchers and physicians to better understand why cancers develop, predict how they may behave, and select therapies that specifically target the molecular abnormalities driving a patient's disease.

Cancer can therefore be viewed as a disease of altered gene regulation. Changes in gene expression can occur at nearly every step of the pathway that converts genetic information into functional proteins. Mutations may alter the DNA sequence itself, while changes in epigenetic regulation, transcription, RNA processing, translation, or post-translational modification can all influence which proteins are produced and how they function. Different cancers disrupt different parts of this pathway, but the result is the same: proteins that normally regulate cell growth, DNA repair, apoptosis, or differentiation no longer function properly.

Because these changes occur at multiple levels, researchers investigate each step of gene regulation for potential biomarkers that can improve diagnosis or serve as targets for new therapies.

Link to Learning

Watch this animation(opens in new window) to learn more about the use of p53 in fighting cancer.

Cancer and Epigenetic Alterations

Not all changes that contribute to cancer involve mutations in DNA. Some involve epigenetic modifications that alter whether genes are turned on or off without changing the DNA sequence itself. These changes can silence important tumor suppressor genes or activate genes that promote cancer development.

Silencing genes through epigenetic mechanisms is common in many cancers. DNA within promoter regions may become methylated, while histone proteins lose acetyl groups. Together, these modifications reduce gene expression and can prevent cells from producing proteins needed to regulate growth or repair DNA.

Unlike DNA mutations, many epigenetic modifications are reversible. This has made epigenetics an exciting area of biotechnology research. Scientists have developed drugs that inhibit DNA methyltransferases or histone deacetylases, allowing previously silenced genes to become active again. These therapies demonstrate that understanding gene regulation can lead directly to new treatment strategies.

Cancer and Transcriptional Control

Cancer can also result from changes in transcription—the process of copying DNA into RNA. Many cancers contain mutations that increase the activity of transcription factors or signaling pathways that regulate gene expression. These changes can dramatically increase the production of proteins that stimulate cell growth and division.

One example is the epidermal growth factor receptor (EGFR) signaling pathway. Some cancers produce unusually high levels of EGFR, leading to continuous activation of genes involved in cell proliferation. Biotechnology has enabled scientists to develop drugs that specifically block EGFR signaling, slowing the growth of tumors that depend on this pathway. Rather than affecting every rapidly dividing cell, these targeted therapies focus on the molecular abnormalities driving a particular cancer.

Cancer and Post-transcriptional Control

Gene regulation continues even after RNA has been produced. Small RNA molecules called microRNAs (miRNAs) help determine whether messenger RNAs are translated into proteins or degraded before they can be used.

Many cancers produce abnormal patterns of miRNA expression. Some miRNAs are overproduced, reducing the expression of proteins that normally suppress tumors, while others are underproduced, allowing cancer-promoting proteins to accumulate.

Researchers are now exploring whether specific miRNA "signatures" can serve as biomarkers for early cancer detection or as targets for future therapies.

Cancer and Translational and Post-translational Regulation

The final stages of gene expression also influence cancer development. Proteins can be produced in abnormal amounts, modified by phosphorylation, or processed into alternative forms that behave differently from their normal counterparts.

For example, cyclin proteins, which regulate progression through the cell cycle, are controlled by phosphorylation. Abnormal phosphorylation can keep these proteins active longer than they should be, allowing cells to continue dividing despite DNA damage.

Similarly, different forms of the c-FLIP protein can either promote apoptosis or allow damaged cells to survive. In some colon cancers, expression shifts toward the form that prevents cell death, contributing to continued tumor growth.

These examples illustrate that cancer is not simply a disease of mutated genes—it is also a disease of altered protein activity.

Biotechnology, Targeted Therapies, and Personalized Medicine

Perhaps the greatest impact of understanding gene regulation has been the development of targeted therapies. Traditional chemotherapy attacks rapidly dividing cells, affecting both cancerous and healthy tissues. In contrast, targeted therapies are designed to interfere with specific molecules or signaling pathways that are essential for a particular cancer.

Examples include drugs that block EGFR, inhibit overactive protein kinases, or restore signaling pathways that normally limit cell growth. Before these treatments are prescribed, many patients undergo molecular testing to determine whether their tumors contain the specific genetic or molecular changes that the therapy targets.

This approach has led to the growth of personalized medicine, in which treatments are selected based on the unique molecular characteristics of an individual's tumor rather than solely on where the cancer originated in the body.

Advances in DNA sequencing, molecular diagnostics, and biotechnology continue to improve our ability to identify these molecular differences. As researchers gain a deeper understanding of how gene regulation becomes disrupted in cancer, new therapies are being developed that are increasingly precise, effective, and tailored to individual patients.

Career Connection

Clinical Trial Coordinator

A clinical trial coordinator is the person managing the proceedings of the clinical trial. This job includes coordinating patient schedules and appointments, maintaining detailed notes, building the database to track patients (especially for long-term follow-up studies), ensuring proper documentation has been acquired and accepted, and working with the nurses and doctors to facilitate the trial and publication of the results. A clinical trial coordinator may have a science background, like a nursing degree, or other certification. People who have worked in science labs or in clinical offices are also qualified to become a clinical trial coordinator. These jobs are generally in hospitals; however, some clinics and doctor’s offices also conduct clinical trials and may hire a coordinator.

Summary

Cancer develops because mutations and changes in gene regulation alter the expression and function of proteins that control cell growth, DNA repair, and cell survival. Modern biotechnology allows scientists to identify these molecular changes, leading to more accurate diagnosis, improved understanding of cancer biology, and the development of targeted therapies and personalized medicine. As our knowledge of gene regulation continues to expand, so does our ability to develop more effective strategies for preventing, detecting, and treating cancer.

Key Terms

DNA methylation

An epigenetic modification involving the addition of methyl groups to DNA that can reduce or silence gene expression.

epigenetic modification

A change in gene activity that does not alter the DNA sequence but affects how genes are turned on or off.

gene silencing

The process of preventing a gene from being expressed or producing its RNA/protein product.

histone deacetylation

An epigenetic process that removes acetyl groups from histone proteins, often resulting in tighter DNA packaging and reduced gene expression.

microRNA (miRNA)

A small RNA molecule that regulates gene expression by binding to messenger RNA and affecting its stability or translation.

post-translational modification

A chemical change made to a protein after it is produced that can alter its activity, location, or function.

targeted therapy

A treatment designed to specifically block molecules or pathways involved in disease while minimizing effects on healthy cells.

therapeutic target

A specific molecule, gene, or pathway that can be acted upon by a drug to treat a disease.