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Principles of Cancer: Classification, Etiology and Pathogenesis of Cancer

Carcinoma, Leukemia, Lymphoma, Mixed types, Myeloma, Sarcoma

Principle of Cancer

It has been demonstrated that cancer is a highly complex disease that has several hallmarks, including unrelenting proliferation, avoidance of growth suppression signals, apoptosis resistance, neovascularization, and the ability to invade and metastasize. During the past several years, conceptual progress has led to the concept of reprogramming cell energy metabolism and immune escape. The tumor microenvironment consists of "normal" neighboring cells like fibroblasts, endothelial, nerve, and immune cells, which are responsible for the cancer-like characteristics acquired by the tumor. Inducing angiogenesis and immune escape, both of which are mediated by surgical stress responses, are believed to be the most significant of these processes during the perioperative period.

Cancer biology is increasingly recognized as being influenced by the non-malignant stromal cells within the tumor microenvironment. In addition to tumor associated macrophages (TAM), fibroblasts, and inflammatory cells, there are important groups of cells that regulate the growth of tumors through secreted factors. Besides influencing cancer growth, tumor microenvironments also impact tumor initiation, metastasis, and therapy. Researchers have shown that perioperative factors and surgical excision of the primary tumor can affect a patient's long-term survival for more than a decade.

Classification

The following types of cancer are classified according to their tissues:
  • Carcinoma - In epithelial tissues, such as the mucous membranes in the mouth and the gastrointestinal tract, carcinoma cancer occurs. A cancer case is estimated to be carcinoma 80 to 90% of the time, according to the National Cancer Institute.
  • Leukemia - In the bone marrow, where blood cells are produced, leukemia develops.
  • Lymphoma - Spleens, tonsils, and thymus comprise the lymphatic system. Immune function and hormone activity are related in this system.
  • Mixed types - In mixed cancers, two different types of cells can be involved, from the same category or from different categories.
  • Myeloma - Originating in plasma cells that circulate as part of the blood, this type of cancer occurs predominantly in the bone marrow.
  • Sarcoma - All of these substances are produced by connective tissues in skeletal structures, muscles, fat, and cartilage. Sarcomas generally occur as you age.
It is possible for a doctor to distinguish tumors of one type from those of another by their distinct appearance.

Etiology

The term cancer describes a broad range of diseases characterized by uncontrolled cell divisions, invasions of normal tissues, and destructions of them. The human body is prone to spreading cancerous cells. There has been an improvement in cancer survival rates due to screening, treatment, and prevention.

A cell's DNA is mutated when it becomes cancerous. Each gene inside a cell contains instructions about the functions the cell should perform and how it should divide and grow. Hundreds of genes can be found inside each cell of the body. A cell that receives an incorrect instruction may not function properly, resulting in cancer.

How do gene mutations affect the body?

Mutations in genes can cause healthy cells to:
  • Allow rapid growth - Gene mutations can cause cells to divide more rapidly and grow faster. A new cell with that mutation is created.
  • The cells grow uncontrollably - Normally, your cells stop growing at the right time so that there are just the right number of each type of cell. A cancer cell loses tumor suppressor genes (those that control cell growth). Cancer cells can grow and accumulate if a tumor suppressor gene is mutated.

Mutations in genes are caused by what?

Several reasons can lead to the mutation of genes, for example:
  • Mutations that your parents pass on to you. Some mutations are inherited from your parents. These mutations are responsible for a small proportion of cancer cases.
  • After-birth mutations of genes lead to cancer. Genetic mutations usually take place after birth and aren't inherited. A number of factors can lead to gene mutations, including smoking, radiation, viruses, chemicals that cause cancer (carcinogens), hormones, obesity, lack of exercise and chronic inflammation.
  • It is common for genes to mutate during normal cell growth. Nevertheless, cells contain mechanisms that recognize and repair mistakes when they occur. Mistakes may be missed occasionally. The result can be cancerous cells.

What is the interaction between gene mutations?

It has been proven that both the mutations you are born with and those you acquire throughout your life help to cause cancer. If, for example, you inherit a mutation that predisposes you to cancer, it does not guarantee it will manifest in your body. Rather, another gene mutation may be needed to cause cancer. If exposed to cancer-causing substances, the mutation in your gene may increase your risk of getting cancer. Cancer cannot form until enough mutations have accumulated. A cancer's type may affect its prognosis.

Pathogenesis of cancer

Various factors contribute to the pathophysiology of cancer. The primary concern of pathologists is the study of disease in all its facets. The reasons behind a disease, the symptoms, the diagnosis, the pathogenesis, the mechanism, and the natural course of the disease are covered. Furthermore, they address the prognosis or outcome of the disease, as well as the biochemical features of the disease. Molecular biologic approaches, including immunohistochemistry and flow cytometry, have revolutionized cancer pathology and other complex disorders.

Genetic changes

Genes are responsible for regulating cell growth, maturation, and death in normal cells. Genetic changes can occur in a variety of ways. A single point mutation can affect a single DNA nucleotide or affect an entire chromosome. Genes affected by these changes fall into two broad categories:
  • Oncogenes - these are genes that cause cancer. Patients with cancer may have normal genes expressing at excessive levels or normal genes that are altered or changed due to mutations. Either way, these genes cause tumor-producing changes in the tissues.
  • Tumor suppressor genes - DNA damage normally inhibits cell division and prevents cancer cells from surviving. Cancer patients often have tumor suppressor genes disabled. Often this is caused by modifications of the genetic code that promote cancer. Several genes change in normal cells to cause them to become cancerous.

Genomic amplification

Amplification of genomic DNA may sometimes occur. One or more oncogenes are present in the cell, as well as adjacent genetic material, in many copies (often 20 or more).

Point mutations

Mutations at single nucleotides are called point mutations. It is particularly easy for the gene's promoter to be altered by insertions and deletions. When this happens, the protein encoded by the gene is altered. Genomic material from DNA viruses or retroviruses can also lead to the disruption of single genes. Oncogenes are formed as a result.

Translocation

A translocation occurs at a specific location on the chromosome after two chromosomal regions fuse abnormally. Philadelphia chromosomes, or translocations of nine and 22, are frequently found in chronic myelogenous leukemias that cause production of an oncogenic tyrosine kinase, the BCR-abl fusion protein.

Tumors

The Latin word for tumor is swell, but not all swellings are tumors within the modern sense of the term. A benign tumor can develop from an inflammation, an infection, a cyst, a fluid-filled lesion or a benign growth, depending on its cause. A cancerous tumor can metastasize and spread as well as grow rapidly. Solid masses of tissue make up most tumors. However, some tumors, including leukemia, are formed from cells suspended in fluid.

Solid tumor parts

The solid tissue of a tumor divides it into two parts. The parenchyma and the stroma contain a number of cancerous cells and tissues. On the one hand, cancerous cells are found in the parenchyma, and on the other, they are distributed in the stroma. Lamina basal membranes separate epithelial cells from stromal tissues. Occasionally, however, tumors can invade the basal lamina and remove it. In the tumor stroma, malignant cells are juxtaposed with normal host cells, which aid in tumor growth. Stromal cells, blood vessels, connective tissue, and inflammatory cells may be found in the nonmalignant cells.

Stroma significantly contributes to the growth of solid tumors, which can only reach a diameter of about one millimeter or two millimeters if not for it. The growth of new blood vessels is another characteristic of cancerous tumors. There are many components to the stroma, not just blood vessels. In some tumors, the bulk of the stroma consists of interstitial connective tissue, and blood vessels make up only a small fraction of the stroma. The stroma is made up of blood cells, tissues, proteins, water, and inflammatory cells, among other things. Proteoglycans and glycosaminoglycans are not the only interstitials present.
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Ankur Choudhary is India's first professional pharmaceutical blogger, author and founder of Pharmaceutical Guidelines, a widely-read pharmaceutical blog since 2008. Sign-up for the free email updates for your daily dose of pharmaceutical tips.
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