Cancer is a global health challenge that continues to claim millions of lives. According to the World Health Organization (2011), without intervention, an estimated 84 million people were projected to die from cancer between 2005 and 2015. In 2008, the United Kingdom alone witnessed 156,723 deaths due to malignant neoplasms, with one in three individuals facing a cancer diagnosis during their lifetime. In the same year, there were 12.7 million new cancer cases diagnosed worldwide, leading to 7.6 million deaths (Cancer Research UK, 2011). Although there are over 200 different types of cancer, lung, breast, prostate, and colorectal cancers collectively account for more than 50% of all cases. The percentage of cancer-related deaths varies by region, ranging from 4% in Africa to 23% in North America (National Cancer Institute, 2010).
Cancer is characterized by uncontrolled cellular proliferation and the invasion of surrounding tissues. These rogue cancer cells can metastasize through the bloodstream and lymphatic systems, ultimately leading to the demise of multicellular organisms (National Cancer Institute, 2010). The accumulation of genetic mutations destabilizes genetic regulators and alters gene expression, giving rise to a heterogeneous group of diseases known as cancer. These diseases share fundamental traits, including immortalization, invasion, genetic instability, erratic differentiation, and uncontrolled proliferation (Vogelstein and Kinzler, 2008). Despite advancements in cancer detection and treatment, mortality rates remain high, primarily due to therapy-resistant cancer cells emerging during treatment (Al-Hajj et al., 2003).
Recent research has uncovered key stem cell characteristics in tumorous cells, such as high migration, self-renewal, drug resistance, and extensive differentiation, leading to a diverse cell population. Tissue-specific cells possess the ability to self-renew and generate functional cells within an organ. These differentiated cells, however, are short-lived and are produced from a limited pool of long-lived stem cells that persist throughout an organism’s life (Seo, 2007). While stem cells are crucial for tissue development, replacement, and repair, their longevity makes them susceptible to genetic damage accumulation, providing a pathway for cancer recurrence following treatment (Clarke, 2005). Dean, Fojo, and Bates (2005) propose that cancer stem cells can survive chemotherapy and drive the re-growth of malignant tumors. Thus, targeting cancer stem cells becomes imperative for achieving a cure. Identifying cancer stem cells prospectively can facilitate investigations into the pathways and key molecules that can be targeted to eliminate these malignant cells (Clarke & Fuller, 2006).
Numerous studies suggest the existence of subpopulations of cells within tumors referred to as cancer stem cells, which drive tumorigenesis. This paper aims to isolate and characterize various subpopulations of cancer stem cells through physiological stress in human and murine models (DLD-1 and CT-26, respectively). There is substantial evidence that CD133 and CD44 serve as reliable cancer stem cell markers, implying that CD133 and CD44 positive cells may exhibit resistance to chemotherapeutic agents. This hypothesis underpins the protocol developed by Sharma (2010), which employs a novel technique involving the exposure of parental cancer cells to the chemotherapy drug doxorubicin in vitro to isolate cells resistant to drug exposure. Subsequently, these cells will be characterized by their ability to form spheroids, and their gene expression will be assessed through Q-PCR, immunofluorescence, and western blotting to identify the presence of CD133, CD44, and CD26 specific cancer stem cell markers. Ultimately, microarray analysis will be performed on parental and cancer stem cell populations to compare differences in gene expression between the two groups.
Cancer remains a leading cause of death worldwide, responsible for millions of lives lost each year. While significant progress has been made in detection and treatment, mortality rates remain high due to recurring and therapy-resistant cancer cells. Recent research indicates that within tumors exist distinct subpopulations of cells known as cancer stem cells that play a driving role in tumor formation and growth. These cancer stem cells are thought to possess characteristics like self-renewal and the ability to differentiate – much like normal stem cells in healthy tissues. However, their longevity makes cancer stem cells particularly susceptible to accumulating genetic damage over time, providing an avenue for cancer recurrence even after initial treatment.
Several cell surface markers have been identified that can help prospectively isolate cancer stem cell populations, such as CD133 and CD44. Once isolated, these putative cancer stem cells can then be further characterized at the molecular level to gain insights into the pathways and molecules that promote their malignant properties. A greater understanding of cancer stem cells may reveal new therapeutic targets needed to achieve a cure. Your proposed experimental protocol to isolate chemotherapy-resistant cancer stem cell subpopulations using the DLD-1 and CT-26 cell lines through drug exposure and marker analysis seems a promising approach to advance this area of research.
A few additional points – genetic mutations alone account for only a minority of cancer cases annually, with lifestyle and environmental exposures playing a much greater contributory role through DNA damage and impaired repair mechanisms (Anand et al., 2008; Vogelstein and Kinzler, 1998). Carcinogenesis, the process of normal cell transformation, involves the step-wise accumulation of genetic alterations that disrupt normal gene expression and cellular regulation (Hanahan and Weinberg, 2000). Isolating and characterizing distinct cancer cell subpopulations like cancer stem cells may also provide insights into the molecular underpinnings of carcinogenesis.
Literature Review:
On a cellular level, cancer results from uncontrolled cell proliferation, leading to abnormal growth and the development of cancerous tumors. While genetic defects contribute to a small percentage of cancer cases (5-10%), environmental factors such as diet, tobacco use, infections, obesity, alcohol consumption, radiation exposure, stress, and physical inactivity play a more substantial role in cancer development (Anand et al., 2008). These factors induce DNA alterations or impair the ability to repair DNA damage, disrupting normal gene expression patterns (Vogelstein and Kinzler, 1998).
Carcinogenesis is the process by which normal cells are transformed into cancer cells, characterized by the accumulation of genetic mutations.
Materials and Methods
To investigate and isolate different sub-populations of cancer stem cells in human and murine models (DLD-1 and CT-26, respectively), we employed a series of experimental techniques. The following is an outline of our methods:
Cell Lines and Culture: We cultured DLD-1 (human colorectal cancer) and CT-26 (murine colorectal cancer) cell lines in appropriate growth media following standard protocols. These cell lines were chosen due to their relevance in studying colorectal cancer, a disease with known cancer stem cell involvement.
Exposure to Chemotherapy: To isolate drug-resistant cancer stem cells, we adapted the protocol developed by Sharma (2010). Parental cancer cells were exposed to the chemotherapy drug doxorubicin in vitro. The cells that survived this exposure were considered potential cancer stem cells, as they demonstrated resistance to drug-induced cell death.
Spheroid Formation: We assessed the ability of the surviving cells to form spheroids, a characteristic associated with cancer stem cells. Spheroid formation assays were conducted to evaluate their self-renewal potential.
Molecular Characterization: We performed molecular analyses to identify specific markers associated with cancer stem cells. Techniques such as quantitative polymerase chain reaction (Q-PCR), immunofluorescence, and western blotting were employed to detect the presence of CD133, CD44, and CD26, which are well-established cancer stem cell markers.
Microarray Analysis: To gain insights into the differences in gene expression between the parental cancer cells and the isolated cancer stem cell populations, we conducted microarray analysis. This allowed us to compare the gene expression profiles of these two distinct populations.
Literature Review
On a broader level, cancer is a complex disease characterized by uncontrolled cell proliferation that leads to the formation of malignant tumors. While some genetic defects contribute to cancer (5-10% of cases), most cancer cases are influenced by environmental factors such as diet, tobacco use, infections, obesity, alcohol consumption, radiation exposure, stress, and physical activity (Anand et al., 2008).
Carcinogenesis, the process by which normal cells transform into cancer cells, involves the accumulation of genetic mutations that disrupt the balance between cell death and proliferation (King & Robins, 2006). This process is driven by the accumulation of genetic alterations that give rise to highly malignant cells capable of evading apoptosis, invading surrounding tissues, and replicating uncontrollably (Hanahan & Weinberg, 2000).
Cancer stem cells, a subpopulation of cells within tumors, have been identified as drivers of tumor growth, progression, and invasion following treatment (Clarke & Fuller, 2008). These cells possess unique properties such as self-renewal and the ability to differentiate
Causes and Stages of Cancer
Cancer is a group of diseases that involve the abnormal growth and division of cells that can invade and damage other tissues and organs. Cancer can be caused by genetic mutations that are inherited or acquired due to environmental factors, such as tobacco, alcohol, radiation, viruses, and pollution. Some risk factors that may increase the chance of developing cancer include age, diet, physical inactivity, inflammation, and infection.
There are many types of cancer, named after the organ or tissue where they originate. For example, lung cancer starts in the lungs, breast cancer starts in the breast, and colon cancer starts in the colon. Some cancers can spread to other parts of the body through the blood or lymphatic system. This process is called metastasis.
Cancer is usually classified into four stages, based on the size and location of the tumor and whether it has spread to nearby lymph nodes or distant organs. The stages are:
– Stage I: The cancer is localized to a small area and has not spread to lymph nodes or other tissues.
– Stage II: The cancer has grown, but it has not spread to distant organs. It may or may not have spread to nearby lymph nodes.
– Stage III: The cancer is large and has spread to nearby lymph nodes, but it has not spread to distant organs.
– Stage IV: The cancer has spread to distant organs, such as the liver, lungs, bones, or brain.
The treatment and prognosis of cancer depend on the type, stage, and characteristics of the cancer, as well as the patient’s overall health and preferences. Some common treatments include surgery, chemotherapy, radiation therapy, immunotherapy, targeted therapy, and hormone therapy. Some cancers can be cured if detected and treated early, while others may be chronic or terminal.
References:
– Cancer – Symptoms and causes – Mayo Clinic. (n.d.). Retrieved September 8, 2023, from https://www.mayoclinic.org/diseases-conditions/cancer/symptoms-causes/syc-20370588
– Cancer: Types, Causes, Treatment, and Prevention – Healthline. (n.d.). Retrieved September 8, 2023, from https://www.healthline.com/health/cancer
– Cancer: Symptoms, Stages, Types & What It Is – Cleveland Clinic. (n.d.). Retrieved September 8, 2023, from https://my.clevelandclinic.org/health/diseases/12194-cancer
