Cancer - Online Tutor, Practice Problems & Exam Prep

Cancer is characterized by uncontrolled cell division, leading to malignant or benign tumors. Malignant tumors are cancerous, fast-growing, and can metastasize to other organs, causing severe health issues. In contrast, benign tumors are noncancerous, slow-growing, and remain localized. Cell growth is regulated by proto-oncogenes, which promote division, and tumor suppressor genes, which inhibit it. Mutations in these genes can lead to oncogenes, promoting unrestrained cell growth and cancer development. Understanding these concepts is crucial for grasping cancer biology and its implications for health.

Cancer

In this video, we're going to begin our introduction to cancer. Cancer is a disease characterized by uncontrollable cell growth or cell division. This uncontrollable cell division leads to the development of malignant tumors. A tumor is defined as an overgrowth of cells, or in other words, an abnormal mass of tissue. Tumors typically can cause health complications, and there are two main types of tumors that you should be familiar with.

The first main type of tumors are the malignant tumors, which are an overgrowth of cancer cells that migrate or, in other words, metastasize to other organs. Malignant tumors are the most dangerous because they can create a tumor in one area of the body, but then they can migrate or metastasize to a completely different organ within the body and also cause health complications in that other organ. The second type of tumor is the benign tumors, which are not cancerous. This is an overgrowth of cells that are not cancer cells, and they do not migrate. Therefore, they do not metastasize.

Instead, benign tumors remain at the same site. Although benign tumors can cause health complications, they are not nearly as dangerous as malignant tumors. In our image below, notice over on the far left, we're showing you malignant tumors, and over on the far right, we're showing you the benign tumors. Malignant tumors are cancerous, whereas the benign tumors on this side are non-cancerous cells. Malignant tumors, which are cancerous, are actually non-encapsulated.

Benign tumors, on the other hand, are encapsulated. The capsule is just a structure of tissue that can surround and encapsulate the cells, effectively containing them in their same area. Malignant tumors tend to grow very fast as they are cancerous cells, whereas benign tumors grow more slowly. Regarding metastasizing or migrating to other areas of the body, malignant tumors are characterized by the migration or the metastasis; thus, they do metastasize. On the other hand, benign tumors do not metastasize, partly because they are encapsulated.

This concludes our introduction to cancer and the difference between malignant tumors and benign tumors. In our next lesson video, we'll talk more about cancer by discussing specific genes that control the cell cycle. I'll see you all in that video.

The difference between benign and malignant tumors is:

• A. Malignant tumors do not spread to other sites.
• B. Benign tumors have not lost growth control.
• C. Benign tumors have not spread to other sites.
• D. Malignant tumors have not lost growth or control.

Types of Genes Regulating Cell Growth

In this video, we're going to introduce 2 types of genes that regulate cell growth. And so in a healthy and normal cell that is not cancerous and is not part of a tumor, this healthy normal cell is going to have 2 types of genes that regulate cell growth, and we've got these 2 labeled down below, number 1 and number 2. And so the first type of gene that's going to regulate cell growth in a healthy normal cell is a proto-oncogene. And so a proto-oncogene is going to be a gene that provides signals that promote appropriate cell division. And so because it's promoting appropriate cell division, proto-oncogene is pretty much acting like the green light for cell division.

And so it's going to allow cell division to proceed. Now, the second type of gene that regulates cell growth is a tumor suppressor gene. And so the tumor suppressor gene, as its name implies, is going to do pretty much the opposite of the proto-oncogene. It's going to provide signals to not promote but inhibit cell division. So it's basically acting like the red light for cell division, to inhibit cell division and to slow it down.

Now a protein called p53 is an example of a protein that serves as a tumor suppressor gene. And so if we take a look at our image down below over here on the left-hand side, notice we're showing you a proto-oncogene and how it pretty much acts like the cell division gas pedal. It pretty much promotes cell division, so it acts like the green light for cell division to allow cell division to proceed, normally and appropriately. And then over here on the right-hand side, notice we're showing you, the tumor suppressor gene, which is pretty much acting like the cell division brakes or the brakes to cell division or the red light for cell division that slows down or inhibits cell division. And so, again, within a healthy and normal cell, there are both proto-oncogenes and there are tumor suppressor genes that will either promote or inhibit cell division appropriately so that cell division will proceed appropriately.

However, although proto-oncogenes and tumor suppressor genes are normal and healthy genes found in normal and healthy cells, they are susceptible to mutations. And mutations in either of these types of genes, in either proto-oncogenes or tumor suppressor genes, can lead to the development of cancer, uncontrollable cell division. And so again, although proto-oncogenes are essential and healthy genes that promote cell division appropriately, again, they are susceptible to mutations that can generate oncogenes. And oncogenes are different than proto-oncogenes. Proto-oncogenes are healthy and normal genes that are needed and required to promote appropriate cell division.

However, oncogenes are mutated proto-oncogenes. And so that's exactly how we're defining an oncogene down below. They are a mutated gene that is going to promote unrestrained cell growth. Essentially, it's going to promote cancer. And so this here concludes our introduction to the 2 types of genes that regulate cell growth, proto-oncogenes, and tumor suppressor genes, and how they are normal healthy genes that are required to regulate cell division, and how they are both susceptible to mutations that can lead to the development of cancer.

And so this here concludes this video and we'll be able to get some practice applying these concepts as we move forward. So I'll see you all in our next video.

Which of the following processes do normal proto-oncogenes typically exhibit?

• A. They normally suppress tumor growth.
• B. They enhance tumor growth.
• C. They stimulate normal cell growth and division.
• D. They are underexpressed in cancer cells.

When activated by signals in the cell, Protein X can stop cells from growing and dividing into new cells. What type of gene codes for Protein X?

• A. Oncogene.
• B. Tumor-suppressor gene.
• C. Protein kinase gene.
• D. Protein Vesicle gene.
• E. Proto-oncogene.

Here’s what students ask on this topic:

What is the difference between malignant and benign tumors?

Malignant tumors are cancerous, characterized by rapid growth and the ability to metastasize, or spread, to other parts of the body. This makes them particularly dangerous as they can cause severe health complications in multiple organs. In contrast, benign tumors are noncancerous, grow slowly, and remain localized, meaning they do not spread to other parts of the body. While benign tumors can still cause health issues, they are generally less dangerous than malignant tumors. Malignant tumors are non-capsulated, whereas benign tumors are often encapsulated, which helps contain their growth.

What are proto-oncogenes and tumor suppressor genes?

Proto-oncogenes and tumor suppressor genes are two types of genes that regulate cell growth. Proto-oncogenes act like a green light for cell division, promoting appropriate cell division. Tumor suppressor genes, on the other hand, act like a red light, inhibiting cell division to prevent uncontrolled growth. Both types of genes are essential for normal cell function. However, mutations in proto-oncogenes can turn them into oncogenes, which promote unrestrained cell growth and can lead to cancer. Similarly, mutations in tumor suppressor genes can disable their inhibitory function, also contributing to cancer development.

How do mutations in proto-oncogenes and tumor suppressor genes lead to cancer?

Mutations in proto-oncogenes can convert them into oncogenes, which promote unrestrained cell growth, leading to cancer. These oncogenes act like a stuck gas pedal, causing cells to divide uncontrollably. Similarly, mutations in tumor suppressor genes can disable their function, removing the inhibitory signals that normally prevent excessive cell division. This is akin to losing the brakes on a car, allowing cells to proliferate unchecked. Both types of mutations disrupt the normal balance of cell division and inhibition, resulting in the uncontrolled cell growth characteristic of cancer.

What role does the p53 protein play in cancer prevention?

The p53 protein is a crucial tumor suppressor that helps prevent cancer by regulating the cell cycle and promoting apoptosis (programmed cell death) in cells with damaged DNA. When functioning correctly, p53 acts as a safeguard, ensuring that cells with potential mutations do not continue to divide. If the p53 gene is mutated, its ability to control cell division and induce apoptosis is compromised, allowing damaged cells to proliferate and potentially develop into cancer. Therefore, p53 is often referred to as the "guardian of the genome" due to its critical role in maintaining cellular integrity.

What is metastasis and why is it dangerous?

Metastasis is the process by which cancer cells spread from the primary tumor to other parts of the body, forming new tumors in distant organs. This is particularly dangerous because it allows cancer to affect multiple organs, complicating treatment and significantly worsening the prognosis. Metastatic tumors can disrupt the function of vital organs, leading to severe health complications and making the disease more difficult to control. The ability to metastasize is a key characteristic that distinguishes malignant tumors from benign ones, which do not spread and remain localized.