Bruce Lipton is a biologist who now teaches new age ideas about spirituality and medicine. There is a lot of bunk surrounding this guy, here is one of his lectures.
He also has written two books, The Biology of Belief and Spontaneous Evolution. Both say generally the same thing and have a lot of pseudoscience but here I want to focus on his claim that you can heal incurable diseases with your beliefs and mind. He argues that DNA is more plastic than we are lead to believe, claiming that mutations are not random and that we do have control over our genomes. He also points to epigenetics, the study of how proteins regulate gene expression, as evidence to his claim.
His first claim of mutations not being random has no evidence whatsoever to support it. In his Spontaneous Evolution book, he points to a paper published in Nature in 1988 written by John Cairns. The paper describes an experiment where E. coli with a defective mutant gene for breaking down lactose are placed in a medium containing nothing but lactose. Results were that the bacteria had mutated and were able to break down the lactose and grow. Cairns concluded that the mutation was not random and Lipton claims that we can do similar things when our health is compromised. This idea has huge problems because not only was the experiment flawed but there are perfectly good explanations. All of it is discussed rather thoroughly on Wiki.
Lipton's second claim is where the bulk of his ideas come from. He asserts that since proteins control gene expression that we somehow have power over that mechanism with our consciousness and proceeds to tell stories of miracle cures via hypnosis and meditation that can most likely be explained by cases of misdiagnosis or a very lucky recovery. The problem here is that proteins are made with instruction from DNA and specific proteins regulate the expression of certain genes. No gene, no regulatory protein, so genes indirectly control their own expression. As discussed in the previous point, changes in DNA are random, so we cannot control which gene is going to change to produce which protein unless we use genetic engineering. The misconception comes with epigenetics. The most dramatic epigenetic changes are permanent and happen early in development. Epigenetic changes in mature individuals are usually superficial, such as eye color changes, hormone levels, sleep cycle, and other processes that are already very self-regulated. More can be read on that topic here and here. Lipton claims that these processes can somehow be controlled with our beliefs and be used to unlock DNA that can help us live healthy and peacefully without the help from government or pharmaceutical companies. A classic snake-oil salesman who sells false hope to sick patients.