Researchers at Harvard Medical School say the active component of marijuana may enhance the virus that causes a rare type of skin cancer called Kaposi's sarcoma. While most people are not at risk of developing this cancer, AIDS patients are transplant recipients are. It's the weakened immune system that puts some at risk for this disease. And these are the people who should discuss with their doctors the costs of using marijuana medicinally or recreationally.

It may take only small doses of tetrahydrocannabinol (THC) -- the ingredient that gives marijuana users a "high" -- to cause cells to become infected and then multiply, according to a study reported in the August 1 issue of Cancer Research.

Previous studies have indicated this very same association between marijuana use and Kaposi's sarcoma. But this study shows THC itself is the driving force.

Kidney transplants can save lives. They can also increase the risk of developing a variety of cancers, according to Australian researchers who report a risk 300 percent higher than in the general population.

Most cancers developed in kidney transplant patients have a known or suspected viral origin, suggesting the weakened immune systems in these patients limit protection against cancer.

"The immunosuppressive drugs transplant patients take lower their ability to fight off infections that can trigger malignancy", the lead researcher said. "We believe the increased incidence of infection leads to the infection that results in cancer." She also notes there is probably an even greater risk of cancer among heart and lung transplant patients because these patients receive more powerful immunosuppressive drugs.

Researchers gathered their findings by comparing the incidence of cancer in 29,000 patients with end-stage kidney disease who received kidney transplants. Data was collected beginning five years prior to transplantation, during dialysis, and after transplantation. Researchers then consulted an Australian registry to identify cancers occurring between the years of 1982-2003. They compared the statistics with the number of cancers seen among transplant patients.

These cancers included melanoma, Kaposi's sarcoma, non-Hodgkin's lymphoma, Hodgkin's disease, leukemia and cancers of the lip, tongue, mouth, salivary gland, esophagus, stomach, colon, anus, liver, gallbladder, lung, connective and other soft tissue, vulva, cervix, penis, eye and thyroid. There was also an increase in nasal cavity and vaginal cancers.

This study has important implications for future immosuppression. Patients should give considerable thought to quality-of-life transplants -- such as face transplants and hand transplants -- and should carefully weigh the risks of weakened immunity. On a brighter note, this study might help prompt research on medication that can selectively target the part of the body responsible for rejecting a transplant. Because right now, medications affect the entire immune system -- and this is what makes patients more prone to developing cancer.

I'm headed for a Saturday morning workout with my fitness trainer. For one hour, I will physically challenge my body and emotionally charge my spirits. I will sweat and pant and if I am required to do the inner thigh exercise, I will scream. I will also whine -- it's in my nature -- and I will push, pull, bounce, balance, lift, squat, lunge, and run until it's quitting time. I will fall short on some of my exercise expectations. And I will surprise myself and exceed others. In the end, I will feel accomplished, strong, motivated, and ready to tackle the day.

I'm making a comeback. I have come back from the depths of cancer and all of its accompanying treatment, and I have invited this powerhouse of a girl to transform me. She has accepted the challenge -- and she has helped me evolve from a weak, shaky, dizzy cancer patient to a semi-strong, 5K-running breast cancer survivor with biceps that are almost visible at a close distance.

This spunky fitness girl -- also an accomplished kick boxer, wife, and mom of two little ones -- has accepted another one of my challenges. I asked her to share some of her health and fitness expertise so that we all may reap the benefits. And so she kindly extracted some important tidbits from her vast library of knowledge and concisely crafted the responses that follow.

Take it from Fitz Koehler -- exercise and healthy eating habits are key for survival. For all of us. Cancer survivors included.

Why is fitness important for everyone?

100% of the population needs to exercise in some way. For the most part, if you're not working to get stronger, you're going to get weaker. Whether it's tummy time as an infant, gym class as a kid, weight training as an adult, or short walks as a senior, in order to live well and live long, we must eat well and exercise. Plus, a fit lifestyle prevents so many horrible ailments and diseases -- heart disease, some cancers, diabetes, GERD. Who wants any of that?

The overall cure rate for the 20,000 children diagnosed with cancer in the United States each year is more than 75 percent. Sounds good -- especially when 50 years ago, most children diagnosed with cancer died. But considering that only one in three childhood cancer survivors remain healthy, perhaps this is not such good news.

Thirty years after diagnosis, about 40 percent of survivors have a serious health problem and one-third have multiple problems. Strokes, heart disease, and kidney failure are just a few of the major health concerns that plague many survivors who have entered adulthood.

Doctors have long known that cancer treatments can cause new cancers later in life. But the Childhood Cancer Survivor Study -- the largest ever childhood study of its kind -- shows there are other long-term health problems. Researchers studied 10,000 survivors -- past studies examined 200-300 survivors -- and found these survivors were eight times as likely as their siblings to develop severe and life-threatening conditions. They found survivors of bone tumors, nerve and brain cancer, and Hodgkin's disease faced the highest risk.

The source of these later-in-life health problems vary. Kidney failure may result from damage caused by chemotherapy or radiation or the infections children suffer when their immune systems are weakened. Drugs used to treat infections may also be to blame. Strokes may result from head and chest radiation.

Cancer treatment for people of all ages comes with a price. We buy time, we buy life in exchange for the unknown. But for children -- who stand to live longer than adults -- there is a greater unknown. Sadly, there is a dark side to surviving cancer.

Luis Carranza is just eight years old. And he is just a few years -- or perhaps a few months -- away from dying as a result of a weakened immune system due to aggressive treatment for leukemia. The same treatment that at one time brought remission for this boy also attacked his central nervous system, caused seizures, brought on terminal and irreversible brain damage, and eventually sent him into a vegetative state. Luis has traveled a rough road -- and so has his mother who illegally slipped him across the Mexican border into the United States in hopes of treatment to save her young son's life.

Guadalupe Carranza did find salvation for her son in a Texas hospital and for more than one year, Luis received chemotherapy and radiation -- and loads of love from staff and volunteers who helped care for him. Guadalupe was not always there for her son, though, because after locating helpful health care and social services, she was deported to Mexico. She tried to return on many occasions and even received assistance from doctors, nurses, social workers, and attorneys who worked to find a legal way to unite Guadalupe and Luis. But not until Luis fell into a coma did efforts pay off.

After negotiation with border and consulate officials, Guadalupe was granted a humanitarian parole visa and legally crossed into the United States on May 8. The visa allowed her 60 days -- but officials agreed to let her stay until Luis passes away. And so she stays -- by her son's bedside where he rests peacefully in a place that gave him a chance at life. A chance his mother says he never would have had in Mexico.

Need one more reason to calm down? Take it all in stride? Walk on the sunny side of the street?

Boston's Harvard School of Public Health researchers have one more reason for you to let it all go because a new study has shown that being angry and hostile contributes to diminished lung function. During the eight-year study, 670 men -- aged 45 to 86 -- were tracked. Men who exhibited sustained levels of anger and hostility suffered from accelerated lung deterioration.

This study supports further evidence that emotions, and the mind-body connection, have a biological effect that can lead to better or worse health. Negative emotions are known to contribute to heart disease and other diseases. Experts explain that "stress-related factors are known to depress the immune function and increase susceptibility to or exacerbate a host of diseases and disorders."

Grab your coat and get your hat
Leave your worries on the doorstep
Life can be so sweet
On the sunny side of the street -- Louis Armstrong On The Sunny Side Of The Street

In the 11th report of the Committee on Medical Aspects of Radiation in the Environment (COMARE), children growing up in an affluent urban environment and children from rural areas are at higher risk for developing many cancers.

Researchers studied cancer clusters where leukemia and other childhood cancers were reported, and have come to the conclusion that affluent children are being raised in an environment that is too clean. Called the dirty hypothesis, children living in too sterile an environment where they are not exposed to infection have weak immune systems.

For rural children, infection brought in to the rural community by people from larger populated urban areas, might be causing genetic damage that leads to cancer.

With the exception of the processing plant at Sellafield in Cumbria, and Dounreay in Scotland, the researchers also state they found no general pattern of increased cancer incidence around nuclear plants.

The researchers feel confident in the reported results of this study. They invite further study into the hypothesis of their findings. The database was constructed from the National Registry of Childhood Tumours by staff of the Childhood Cancer Research Group in Oxford, and included 12,415 cases of childhood leukemia and non-Hodgkin lymphoma and 19,908 cases of children with solid tumors registered under the age of 15 in England, Wales and Scotland from 1969 to 1993. To download the 160 page report, go here.

Consumer Reports has completed a review of the FDA testing on mercury levels found in canned tuna and issued new safety concerns. While the focus is on a clear alert for pregnant women and the damage mercury-contaminated tuna can cause to a developing fetus, mercury is also known to have an adverse effect on the immune system of adults. For anyone interested in cancer prevention, a healthy immune system is a vital first-line defense to keeping cancer from developing in the first place. Mercury, once consumed, can stay in the body for years.

Because of the new information provided by Consumer Reports regarding the dangers of canned tuna, and because fish is an excellent cancer prevention food, here is a list of fish that have shown consistently low-levels of mercury during testing and are safe to eat daily. Wild salmon and tilapia can be safely eaten every day. Flounder, sole, mullet, Atlantic mackerel and crab can be safely eaten once a week. In addition, Consumer Reports found fish-oil supplements to be a safe, reliable way to get omega-3 fatty acids. You can check state agencies and the Environmental Protection Agency advisories for contaminant levels of fish caught where you live here.