Cancer

Cancer is one of the most common diseases. According to some sources, every third person will eventually develop cancer. This Mini Lecture deals with the causes and therapeutic options of cancer with direct quotes by Nobel Laureates Renato Dulbecco, Howard Temin, and Aaron Ciechanover.

The world faces many challenges not least on the medical front. Among those challenges remains cancer. Some statistics say that one in every three people will eventually develop the disease. The word cancer though is often used in a misleading way as there is no such thing as The Cancer. Rather there exist more than one hundred different kinds of cancer. But regardless of whether the skin, blood, brain or internal organs are affected these different types do have one thing in common and that’s the abnormal growth of cells. Cancer cells develop in an uncontrolled way and often spread to other organs, a process that in many cases leads to death. In Germany for instance the majority of male cancer patients die of lung cancer while breast cancer is the main offender among female patients. What are the causes, the uniqueness? What are the differences between the cancer cell and the normal cell? And this question of course has been asked for many years and people have found lots and lots of differences. But these differences are too many if any and really they don’t make much sense. Some of them can be explained by saying that the cancer cells in their persistent state of growth and therefore, because it never shuts off, never reaches that other stage, that acquiescence which normal cells always have. But actually cell division is a normal process and a necessary one. If there were no cell division, the human body, a highly complex system of organs, could not develop, grow or regenerate nor could genetic information be handed down across the different generations. There are two kinds of cell division. On the one hand meiosis is vital for sexual reproduction and produces gametes with half of the usual set of chromosomes. Mitosis in humans, on the other hand, produces cells with what's known as a diploid set of 46 chromosomes. But cells also need to die, sometimes through a kind of programmed cell suicide known as apoptosis. This process is necessary for the regulation of the cell count and the elimination of sick cells. The division growth and death of cells are tightly regulated by a molecular system of signals, barriers and repair systems. But even though all these internal safeguards exist and usually work well within the human body, sometimes a genetic mistake, a so-called mutation, can occur. Subsequently a cell might alter its usual behaviour and start growing in an uncontrolled way thereby producing a tumour. The genes whose mutations can cause cancer are called oncogenes. Today we know that mutations of genetic information can be triggered by high doses of ultraviolet radiation or by certain mutagenic chemicals. But cancer can also be caused by smoking or an unbalanced and unhealthy diet. An individual’s age also plays a role when it comes to the development of cancer. That’s because the older we get, the more likely it is that a mistake can happen during cell division. And on top of all that viral infections too are strongly linked to the development of the disease. The study of cancer by viruses called highly oncogenic retro viruses has been avidly pursued for a great number of years because of the very simple ability of these viruses to cause cancer. In contradistinction to the usual multi-stage nature of carcinogenesis these viruses can infect a normal cell and in a single step change the normal cell into a cancer cell. Scientific research on cancer has been around for some time. In 1927 Johannes Fibiger was the first researcher to be awarded a Nobel Prize for his work on the disease ironically thanks to a scientific error. Fibiger had fed rats with cockroaches that carried a worm called spiroptera carcinoma. The rats eventually developed stomach cancer and died as a consequence. But when Fibiger could still find the worm in the dead rats, he drew the false conclusion that it must have been the parasite that caused the cancer. It was only later that the real reason for the rats tumour could be identified, a bad diet. But Fibiger was not the only one interested in the field of cancer research. By 1910 Peyton Rous had identified the very first tumour virus. He managed to extract a virus from an infected hen and injected it into healthy chicks. They then developed cancer as a result. But research in the field was just beginning. And even though Rous’s work sparked debate among scientists, it would take over 50 years for him to be awarded a Nobel Prize for his cancer research. Scientists did not let up on the virus front and rightly so. These tiny packets of genetic information are crucial to our understanding of cancer. At the moment it’s estimated that 1:7 to 1:5 tumours is caused by chronic viral infections. Viruses are not able to survive on their own and need host cells in order to reproduce. To achieve this, a virus must take over the host cell injecting its own genetic information into the host. This then dies or starts to run amok on a cellular level. Two different types of viruses are currently known to us. There are those whose genetic information is saved in double helix DNA and those that carry single helix RNA. RNA needs a special enzyme called reverse transcriptase to transform RNA into DNA before viral genes can be reproduced. It was David Baltimore, Renato Dulbecco and Howard Temin who ultimately uncovered how this mechanism works. One widely known tumour virus is HPV, or the human papillomavirus. It causes cervical cancer in women. It was Harald zur Hausen whose scientific studies demonstrated this. Now there exists a wide array of HPV subtypes that we can identify and at least 15 of them are linked to tumour growth. Fortunately though science has made great strides when it comes to cervical cancer treatment. So today HPV vaccines are effective against 2:4 of the high risk strains of these viruses. All the same women over thirty should still have regular check-ups. Despite the intensive research on cancer over the past 100 years, the majority of different cancer types remain incurable. There is simply on one therapy or any one medication that’s effective against the disease. But we are still deeply into cancer. Cancer cells are very sophisticated, they have all kinds of tricks to live under hypoxic conditions, to develop other blood vessels and so on and so forth. So it’s not that simple. So you see again, people did launch major attacks on major diseases but apparently nature tricks us. Therapeutic outcomes for patients have improved markedly though. This is due to advances in surgery, radiation therapy and new forms of medicinal treatment that complement established chemotherapies. On top of this health care providers have dedicated more resources to cancer prevention. The decoding of a human genome opens the way for a more customised treatment, one oriented towards the genetic make-up of the individual patient and that particular disease. There’s increasing hope that cancer may go from being a terminal illness to being a chronic condition.