Breast Cancer: Searching for the Mean Genes

¶ … cancer genes that are associated with breast cancer. Scientists have known for years that the most common breast cancer genes are BRCA1 AND BRCA2, but there are many more than those two genes that scientists now much cope with. Another aspect of the focus is on whether or not to tell a woman that she has genes that might lead to breast cancer; the ethical questions are serious and this is complicated by the fact that ovarian cancer and breast cancer "share genetic risk factors."

The overall problem is breast cancer, but within the problem of breast cancer is determining which genes are likely to cause tumors and which are present but do not necessarily lead to breast cancer. The identification of BRCA1 and BRCA2 was thought to hold the keys to identifying those women who had those genes as possible breast cancer victims. But with the "rapid expansion of next-generation DNA sequencing," scientists have learned that there are perhaps "dozens" of additional genes that could be linked to breast cancer (Kean, 2014, p. 1457). What is being investigated is why certain genes "shut down" and why the DNA can't repair a double strand break. Also being investigated is why certain mutations increase a woman's chance of cancer two and three-fold in terms of risk (Kean, 1458).

THREE: Experiment: There is no one specific experiment in this article to report, but there are results of research that are key to understanding the difficulty scientists have in finding the right key to unlock the mystery of why certain genes lead to breast cancer in women. In laboratory work scientists have learned that a gene called PALB2, which, on the one hand, works with PRCA2 in repairing breaks in the DNA double-strand, but on the other, can cause mutations that mean a two-fold to three-fold chance of becoming cancerous. But coming up with a theory or strategy to deal with PALB2 is difficult because it appears very rarely (Kean, 1458).

FOUR: Measurement / Data Collection: It is very difficult to measure the impacts of various mutations because "huge numbers" of these mutations exist and each one "requires independent evaluation"; they are "variants of uncertain significance," the article explains (Kean, 1459). About half of the genetic mutations "are still unexplained," so there is a dearth of pertinent data (Kean, 1459). It should be pointed out that six years ago scientists thought they had found the main source of breast cancer in BRCA1 and BRCA2, but new and expanded panels (which are genetic tests) continue to be discovered, Kean continues on page 1459.

FIVE: Mathematical Analysis: The data that is being presented is not always easy to evaluate because there are numerous companies involved in the research and their panels (genetic tests) are unique from company to company. "The field has not settled on consistent, evidence-based guidelines," hence it is problematic as to decisions about which panels to test (Kean, 1459). Moreover, there are 100 genes that "might or might not" lead to breast cancer, and mathematically separating the "rogue" genes from the "pretenders" will take more time and add to the mystery of why certain gene mutations cause breast cancer (Kean, 1459).

SIX: Evaluation of Evidence: The author (Kean) does present information that a lay person can understand. In particular, Kean points out the ethical issues involved when doctors have to decide whether to tell a woman about "ambiguous mutations" that may or may not lead to cancer. There is a "moral hazard here," said geneticist Matthew Ellis (quoted by Kean) (1459).