It is both exciting and unnerving to know that so many of our questions have been answered solely within the last couple of decades. Genome-wide association studies (GWAS) have emplaced a drastic amount of knowledge and discovery on aspects of the chromosome that give us a better understanding on genetic contributions to certain diseases processes, which can help us to better prevent, and prophylactically care for those that have a higher susceptibility of certain diagnoses.
When analyzing my family genogram (see Appendix A), there are several cancers on my mother’s side; including non-smokers lung cancer, colon cancer, pancreatic cancer, and uncertainties of cancerous moles and melanomas (not included d/t lack of evidence).
In addition, both the Duchman and Diekmann families have a history of heart disease, specifically coronary artery disease (CAD), with a stronger prevalence on my maternal (Diekmann) side. From this information, I was able to extract more data from the Diekmann side due to better historical recall.
Other diagnoses that are represented in my family genogram are depression and hypertension, which can have genetic influences as well.
From the knowledge gained from my family genogram, I decided to focus the majority of this paper on pancreatic cancer and CAD, as there is a genetic component to both of these disease processes. I feel particularly strongly towards pancreatic cancer as I feel it does not receive the same attention as other cancers do. In addition, after being my grandmother’s nurse in her last days with pancreatic cancer, I feel a strong desire to better understand the disease in hopes that the future will bring more timely screenings and potentially, a cure.
There are many forms of cancer, with various outcomes, and with assorted degrees of familial or hereditary components. Pancreatic cancer is an incredibly aggressive form of cancer, which has genetic mechanisms and multiple lifestyle factors that account for the likelihood of obtaining the disease. “In the United States, it is predicted to become the second leading cause of cancer-related deaths by 2030” (Amundadottir, 2016). Although pancreatic cancer is not as common as breast, lung, prostate, colon, melanoma, or bladder cancer; the growing mortality rate is undeniable.
The most common form of pancreatic cancer is pancreatic ductal adenocarcinoma, which encompasses 95% of pancreatic cancers, with the remaining 5% of pancreatic cancers occurring in the endocrine pancreas (Amundadottir, 2016). The four major genes involved in pancreatic cancer include; KRAS, CDKN2A, TP53, and SMAD4 (Kamisawa, Wood, Itoi, & Takaori, 2016). KRAS works in the pre-cancerous stages, as it increases the amount of preneoplastic pancreatic intraepithelial neoplasia lesions (Amundadottir, 2016). The gene CDKN2A involves a germline mutation, which can cause familial atypical mole melanoma syndrome; increasing the likelihood of both melanoma and pancreatic cancer (Kamisawa et al., 2016). CDKN2A is the most common tumor gene to mutate (Kamisawa et al., 2016). Additionally, TP53 is a frequent gene that changes, and plays a large role in cellular stress reaction (Kamisawa et al., 2016). Lastly, SMAD4 mediates signaling, but often becomes inactivated in pancreatic cancer.
Knowing what genes are involved and obtaining better understanding of the particular roles of these proteins helps to recognize how pancreatic cancer arises, and the familial relationship. There are numerous inherited disorders associated with pancreatic cancer including; familial breast and ovarian cancer, familial atypical multiple mole melanoma syndromes (as previously discussed), Peutz-Jeghers syndrome, hereditary pancreatitis, Lynch syndrome, and familial pancreatic cancer (Amundadottir, 2016). In addition to the genetic component of pancreatic cancer, there are also several well-studied risk factors including a history of tobacco usage, type II diabetes, chronic pancreatitis, obesity, and workplace exposure to carcinogens (Rustgi, 2014).
Unfortunately, “most patients with pancreatic cancer remain asymptomatic until the disease reaches an advanced stage” (Kamisawa et al., 2016). Due to this, and the location of the pancreas within the body, there are limited pre-cancerous and early-cancer signs. After diagnosis of pancreatic cancer through computed tomography (CT), magnetic resonance imaging (MRI), ultrasound (US), or positron emission tomography (PET); the most common treatment is to resect as much of the diseased pancreas as possible and follow with chemotherapy (Amundadottir, 2016). Even after treatment, the “5-year survival in patients with pancreatic cancer remains as low as 6% in the USA” (Kamisawa et al., 2016, p.73). Knowing this, it is imperative to understand family history, and grasp opportunities for any sort of genetic counseling, as there is currently no standard for screening patients at high risk (Rustgi, 2014).
Coronary artery disease (CAD) has been studied for many years and is continuing to show an increase in prevalence globally, due to lifestyle factors, familial factors, and the increase in longevity of humans. “CAD, including myocardial infarction (MI), is a common disease and among the leading cause of death in the world” (Ozaki & Tanaka, 2016, p. 71). Coronary artery disease occurs when there is a presence of damage or disease within the heart’s major vessels (McCance & Huether, 2019).
Plaque and inflammation are often the main culprits and can lead to decreased blow flow to the heart (McCance & Huether, 2019). Some nonmodifiable risk factors include increased age, male gender, women’s post-menopause, and familial influences (McCance & Huether, 2019). Additionally, “modifiable risk factors include dyslipidemia, hypertension, cigarette smoking, type II diabetes, obesity, and an atherogenic diet” (McCance & Huether, 2019, p.1074-1075). Knowing this is imperative in understanding lifestyle changes that can help mitigate this disease process.
Through GWAS we have been able to discover over 50 loci that have genetic significance with CAD (Ozaki & Tanaka, 2016). 9p21 was one of the first locus to be discovered, and it was found to also have a connection with atherosclerosis and multivessel diseases (McPherson & Tybjaerg-Hansen, 2016). Additionally, 9p21 is thought to be a cell cycle kinase inhibitor but could have other compositional purposes (Roberts, 2014). After the initial discovery of 9p21, the Manhattan plot helped to identify many other genetically significant fixed positions on chromosomes including; SORT1, WDR12, PHACTR1, 9P21, and ADAMTS7 (McPherson & Tybjaerg-Hansen, 2016). There is constantly new research in the realm of CAD, along with proper statin therapies to help lessen the likelihood of fatal outcomes.
To conclude, both pancreatic cancer and coronary artery disease have genetic components associated with an increased likelihood of obtaining either disease. There are many other modifiable lifestyle factors and nonmodifiable factors that contribute to these diseases as well. However, without knowing my exact genetic susceptibility to these diseases, as I have never mapped my genes, it will be best to move forward with the awareness that I may have a higher chance of obtaining some type of cancer; specifically, pancreatic or colon, along with post-menopausal CAD. I will continue to live a healthy lifestyle that includes a low-fat, low-cholesterol diet, and an active, non-smoking lifestyle; as I have been.