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Researchers find prostate cancer stem cell

in.reuters.com

Researchers find prostate cancer stem cell

Cancer stem cells (CSCs) are cancer cells (found within tumors or hematological cancers) that possess characteristics associated with normal stem cells, specifically the ability to give rise to all cell types found in a particular cancer sample. CSCs are therefore tumorigenic (tumor-forming), perhaps in contrast to other non-tumorigenic cancer cells. CSCs may generate tumors through the stem cell processes of self-renewal and differentiation into multiple cell types. Such cells are proposed to persist in tumors as a distinct population and cause relapse and metastasis by giving rise to new tumors. Therefore, development of specific therapies targeted at CSCs holds hope for improvement of survival and quality of life of cancer patients, especially for sufferers of metastatic disease.

Existing cancer treatments have mostly been developed based on animal models, where therapies able to promote tumor shrinkage were deemed effective. However, animals could not provide a complete model of human disease. In particular, in mice, whose life spans do not exceed two years, tumor relapse is exceptionally difficult to study.

The efficacy of cancer treatments is, in the initial stages of testing, often measured by the ablation fraction of tumor mass (fractional kill). As CSCs would form a very small proportion of the tumor, this may not necessarily select for drugs that act specifically on the stem cells. The theory suggests that conventional chemotherapies kill differentiated or differentiating cells, which form the bulk of the tumor but are unable to generate new cells. A population of CSCs, which gave rise to it, could remain untouched and cause a relapse of the disease.

Researchers have found a stem cell, a kind of master cell, that may cause at least some types of prostate cancer.

Their findings are only experimental — the stem cells were found in mice — but could explain at least some types of prostate cancer and eventually offer new ways to treat it, they reported on Wednesday in the journal Nature.

The findings also show a potential new source for prostate tumors — so-called luminal cells, which secrete various compounds used in the prostate.

“The role of stem cells in the development of prostate cancer has been a focus of speculation for many years,” Dr. Helen Rippon of Britain’s Prostate Cancer Charity said in a statement.

“Importantly, this new stem cell does not rely on androgens — the male sex hormones that control prostate growth — to survive and grow. This may give a clue as to why prostate cancer often becomes resistant to treatments designed to regulate these androgens in the later stages of the disease,” added Rippon, who was not involved in the research.

“This improved knowledge will also be a step forward in learning how we might help to prevent the disease from developing in men in the first place.”

Michael Shen of Columbia University Medical Center and colleagues named the new stem cells CARNs, for castration-resistant Nkx3.1-expressing cells.

They normally regenerate part of the tissue that lines the inside of the gland, which produces semen. But the cells can also form tumors if certain genes meant to stop out-of-control growth get turned off.

Shen said researchers had believed that tumors arise from a different layer of cells in the prostate, called basal cells.

“Previous research suggested that prostate cancer originates from basal stem cells, and that during cancer formation these cells differentiate into luminal cells,” Shen said in a statement. “Instead, CARNs may represent a luminal origin for prostate cancer.”

Prostate cancer is the second most common cancer in men worldwide after lung cancer, killing 254,000 men a year globally.

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Cancer

A young woman exhales cigarette smoke in Shanghai, China. The People’s Republic of China is both the world’s largest producer and largest consumer of tobacco, which has led to an impending cancer epidemic in the most populous country on Earth.

Cancer is a disease that begins as a renegade human cell over which the body has lost control. In order for the body and its organs to function properly, cell growth needs to be strictly regulated. Cancer cells, however, continue to divide and multiply at their own speed, forming abnormal lumps, or tumors. An estimated 6.7 million people currently die from cancer every year.

Not all cancers are natural-born killers. Some tumors are referred to as benign because they don’t spread elsewhere in the body. But cells of malignant tumors do invade other tissues and will continue to spread if left untreated, often leading to secondary cancers.

Cancers can start in almost any body cell, due to damage or defects in genes involved in cell division. Mutations build up over time, which is why people tend to develop cancer later in life. What actually triggers these cell changes remains unclear, but diet, lifestyle, viral infections, exposure to radiation or harmful chemicals, and inherited genes are among factors thought to affect a person’s risk of cancer.

Lung cancer is the world’s most killing cancer. It claims about 1.2 million victims a year. Most of those victims are smokers, who inhale cancer-causing substances called carcinogens with every puff. Experts say around 90 percent of lung cancer cases are due to tobacco smoking.

Breast cancer now accounts for almost one in four cancers diagnosed in women. Studies suggest the genes you inherit can affect the chances of developing the illness. A woman with an affected mother or sister is about twice as likely to develop breast cancer as a woman with no family history of the disease. Lifestyle may also have an influence, particularly in Western countries where many women are having children later. Women who first give birth after the age of 30 are thought to have a three times greater risk of breast cancer than those who became mothers in their teens.

Geographical Distinctions

There are also stark geographic differences, with incidence rates varying by as much as thirtyfold between regions. In much of Asia and South and Central America, for example, cervix cancer is the most deadly in females. However, in North America and Europe another kind of gynecological cancer, ovarian cancer, is a more serious threat.

Among males, southern and eastern Africa record the second and third highest rates of oesophageal, or gullet, cancer after China, but western and central regions of Africa have the lowest incidence in the world. Differences in diet may explain this.

Nevertheless, the reasons why many cancers develop remain elusive. Brain cancer, leukemia (blood cancer), and lymphoma (cancer of the lymph glands) are among types that still mystify scientists.

Treatments

Yet ever more people are surviving diagnosis thanks to earlier detection, better screening, and improved treatments. The three main treatment options are surgery, radiotherapy and chemotherapy. Radiotherapy, also called radiation therapy, involves blasting tumors with high-energy x-rays to shrink them and destroy cancerous cells. Chemotherapy employs cancer-killing drugs.

Even so, future cancer cases are predicted to climb, since the world’s population is aging. The proportion of people over age 60 is expected to more than double by 2050, rising from 10 percent to 22 percent. This will add an estimated 4.7 million to the cancer death toll by 2030.