Cancer is a deadly disease in which disorder occurs in the normal process of cell division, which is controlled by the genetic material (DNA) of the cell (1). There are over 100 different types of cancer, and each is classified by the type of cell that is initially affected. Cancer harms the body when damaged cells divide uncontrollably to form lumps or masses of tissue called tumors. Tumors can grow and interfere with the digestive, nervous, and circulatory systems and they can release hormones that alter body function. Tumors that stay in one spot and demonstrate limited growth are generally considered to be benign .When a tumor successfully spreads to other parts of the body and grows, invading and destroying other healthy tissues, it is said to have metastasized. This process itself is called metastasis, and the result is a serious condition that is very difficult to treat. Cancer occurs under the influence of gene mutations in cell which unable the cell to correct the DNA damage and also resist to killing by apoptosis process. In other words, cancer is a result of mutations that inhibit oncogene and tumor suppressor gene function, leading to uncontrollable cell growth. Tobacco, asbestos, arsenic, radiation such as gamma and x-rays, the sun, and compounds in car exhaust fumes are all known examples of carcinogens. When our bodies are exposed to carcinogens, free radicals are formed that try to steal electrons from other molecules in the body and affect their ability to function normally. In 2007, cancer claimed the lives of about 7.6 million people in the world. Cancers can affect all animals (2). In the present investigation we are mainly focusing on breast cancer based on the survey done by Indian Council of Medical Research, New Delhi in 2009 that India accounts for nearly six percent of deaths due to breast cancer globally and 1 out of every 22 women in India is diagnosed with breast cancer. According to this survey report, the number of breast cancer patients are rapidly increasing as compared to the number of cervical cancer cases among Indian women.

Breast Cancer

Breast cancer is a malignant proliferation of epithelial cells lining the ducts and lobules of the breast. There are different types of breast cancer, on the basis of different stages (spread) I and II, aggressiveness, and genetic makeup. Treatment includes surgery, drugs (hormone therapy and chemotherapy), and radiation therapy. Worldwide, breast cancer is the second most common type of cancer after lung cancer (10.4% of all cancer incidence, both sexes counted) and the fifth most common cause of cancer death.

Women with breast cancer have many treatment options. The treatment that's best for one woman may not be best for another. The options are surgery, radiation therapy, hormone therapy, chemotherapy, and targeted therapy. You may receive more than one type of treatment. The treatment options are described below. Surgery and radiation therapy are types of local therapy. They remove or destroy cancer in the breast. Hormone therapy, chemotherapy, and targeted therapy are types of systemic therapy. The drug enters the bloodstream and destroys or controls cancer throughout the body. The treatment that's right for you depend mainly on the stage of the cancer, the results of the hormone receptor tests, the result of the HER2/neu test, and your general health.

Factors Responsible for Breast Cancer in Human

The responsible factor for the breast cancer is the HER receptor family. HER family receptors are located on the surface of the cell. Each receptor has an extracellular and intracellular domain. These are also known as Human Epidermal Growth Factor Receptor (HER, also known as ErbB) family consists of four receptors HER1 , HER2, HER3 and HER4 binding more than 10 polypeptide ligands between them. The HER receptors play a crucial role in breast cancer and many other types of cancer. These receptors belong to subclass I of the super family of Receptor Tyrosine Kinases (RTKs) which are transmembrane receptors with an intrinsic ability to phosphorylate their tyrosine residues in the cytoplasmic domains to transduce signals. However, HER2 and HER3 are not autonomous since HER2 has no known ligand and the kinase activity of HER3 is defective. These two receptors can form heterodimeric complexes with each other as well as other HER receptors to generate potent signals. Targeting HER2 has been the main focus in breast cancer although increasingly, inhibition of EGFR in combination with HER2 blockage is seen to be important in breast cancer therapy.

Trastuzumab (Herceptin)
Trastuzumab (monoclonal antibody), which specifically targets HER-2, kills these cancer cells and decreases the risk of recurrence. Trastuzumab is often used with chemotherapy. However, it may also be used alone or in combination with hormone-blocking medications, such as an aromatase inhibitor or tamoxifen. Trastuzumab is usually well tolerated, but it does have some potential side effects, such as fever, nausea, vomiting, diarrhea, pain, rash, headache, weakness, hypersensitivity, congestive heart failure, and allergic reaction.

Lapatinib (Tykerb)
Like trastuzumab, lapatinib is a HER-2 specific drug. Lapatinib may be effective for HER-2 positive breast cancer that doesn't respond to trastuzumab. Lapatinib is used in combination with the chemotherapy drug capecitabine (Xeloda) and the aromatase inhibitor letrozole (Femara). Lapatinib is also being studied in combination with trastuzumab. These therapies having a high cost, thus the hand of common person are very far away from these drugs.

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