Abstract

Anticancer agents are effective in the treatment of malignant or cancerous diseases. There are basically two main classifications.

Firstly, Cytotoxic drug- which involve the action of drugs directly on cells. There are four main groups involved namely: (i) Alkylating agents e.g. Nitrogen mustards ( Cyclophosphamide, Ifosfamide, Chlorambucil and Melphalan), Ethylenimine (Thio-TEPA), Alkyl sulfonate (Busulfan), Nitrosoureas (Carmustine and Lomustine) and Triazine (Dacabazine), (ii) Antimetabolites e.g. Folate antagonist ( Methotrexate, 6-mercaptopurine), Pyrimidine antagonists (5-Fluorouracil and Cytarabine), (iii) Plant alkaloids e.g. Vinca alkaloids (Vincristine and Vinblastine), Epipodophyllo toxin (Etoposide), Taxanes (Paclitaxel and Docetaxel), Camptothecin analogues (Topotecan and Irinotecan) and (iv) Cytotoxic antibiotics ( Dactinomycin, doxorubicin, Daunorubicin and Bleomycin).

Secondly, drugs altering hormonal milieu.

There are nine main groups involved namely: Glucocorticoids, Estrogens, Selective estrogen receptor modulators, Selected estrogen receptor down regulator, Aromatase inhibitors, Antiandrogen, 5-α reductase inhibitors, GnRH analogues and Progestins.

This review provides a brief route of the causes, risk factors, signs and symptoms, nutritional requirement of cancer and their possible treatments, the classification of anticancer agents, the mechanism of action and structure activity relationship for the different classes of anticancer agents and finally, the resistance to anticancer agents and some strategies to overcome it.

CHAPTER ONE

INTRODUCTION

Cancer is a major cause of morbidity and mortality in developed countries. In generic term, cancer is often used to denote a group of malignant neoplastic diseases originating in a variety of sites, tissues and cell types. The branch of medicine concerned with the study, diagnosis, treatment and prevention of cancer is Oncology. It affects people of all ages, even fetuses but the risk of most varieties increases with age. All cancer begins in cells, the body’s basic unit of life.

Cancer is the uncontrolled growth of abnormal cells anywhere in the body. However, it is a disease characterized by uncontrolled multiplication and spread of abnormal forms of the body’s own cells. These abnormal cells are termed cancer cells, malignant cells or tumor cells. These cells can infiltrate normal body tissues. Many cancers and the abnormal cells that compose the cancer tissues are further identified by the name of the tissue that the abnormal cells originated from (for example, breast cancer, lung cancer, and colorectal cancer).

When damaged or unrepaired pairs do not die and become cancer cells and show uncontrolled division and growth – a mass of cancer cells develop. Frequently, cancer cells can break away from this original mass of cells, travel through the blood and lymph systems, and lodge into other organs where they can again repeat the uncontrolled growth cycle.

This process of cancer cells leaving an area and growing in another body area is termed metastatic spread or metastasis. For example, if breast cancer cells spread to a bone, it means that the individual has metastatic breast cancer to bone. However, when cells become damaged, they die and are replaced with new cells. The genetic material (DNA) of a cell can become damaged, producing mutations that affect normal cell growth and division. When this happens, cells do

 

not die when they should and new cells form when the body does not need them. The extra cells may form a mass of tissue called tumor.

Classification of tumors

❖Tumor is generally termed for any abnormal mass or growth of tissues which is not necessarily  life  threatening,  whereas  cancerous  tumor  is  a malignant neoplasm, which is highly dangerous.

❖ Tumor is classified into 2 categories:

1. Malignant tumor (a disease or growth that is likely to get uncontrollably worse and lead to death).
2. Non-malignant tumor or benign tumor (a growth that is not likely to cause death) or also known as non-cancerous tumor which does not metastasize.
3. Metastasis is secondary tumor or growth originating from the primary tumor and may grow elsewhere in the body.

1 .1 Aim

To review the anticancer agents and their mechanism of action.

1.2 Main Objective

To review the agents affecting cancer and their mechanism of action.

1.3 Specific Objective

1. To review the causes, risk factors, signs and symptoms, nutritional requirement of cancer and their possible treatments.
2. To review the classification of anticancer agents
3. To review the mechanism of action and structure activity relationship for the different classes of anticancer agents.
4. A review of the resistance to anticancer agents and some strategies to overcome it.