p53 AutoAntobodies as Pancreatic Cancer Biomarkers

Collaborators:  Michael (Tony) Hollingsworth, Ph.D. (University of Nebraska)

Disease Background

Who gets it?
What are the symptoms?
How do we detect it now?
How is it currently treated?
What are the current challenges?
  • The pancreas is a gland located in the abdomen that is responsible for producing enzymes that help with digestion and regulate blood sugar.
  • 45,220 Americans will be diagnosed with pancreatic cancer this year, and 38,460 are expected to die from the disease.
  • Lifetime risk of the disease is about 1 in 78, but can increase with risk factors (such as drinking alcohol or smoking).
  • 5 year survival rates of the disease is only 20% and worsens as time continues.
  • Pancreatic cancer is extremely difficult to detect. Symptoms are not always obvious and can develop slowly.
  • Pancreatic cancer is probably present for 15 years or more before these symptoms occur
  • Benign pancreatic cysts look like cancer by X-ray.
  • Currently, only surgery can distinguish them.
  • Treatment for the cancer can vary, but is often worse when the disease is in advanced stages.
  • There is a critical need to identify biomarkers to detect early stage pancreatic cancer and to be able to distinguish between benign and malignant cysts.
  • Current clinical methods of the early detection of pancreatic cancer are extremely limited in specificity and sensitivity.
  • p53 is a tumor suppressor protein
  • When a mutation occurs in p53 it fails to stop cancer.
  • A large percentage of pancreatic tumors harbor some kind of p53 mutation
  • If we can target this mutant gene, we may be able to detect these deadly diseases much early than current methods.

 


Our Approach

Autoantibodies (AAb) found in the serum of patients to tumor-derived proteins offer patients a minimally invasive option for the diagnosis of numerous cancers. p53-AAbs have been studied as biomarkers in thousands of patients with a wide variety of tumors and correlate strongly both with cancer, and with somatic TP53 mutation. Despite the strong specificity of p53-AAb for cancer patient sera, only 20-40% of patients with cancers harboring TP53 missense mutations will have detectable p53-AAb by traditional ELISA assays, which has limited their use as diagnostic markers.

Our unique method of conformational protein display and detection, Nucleic Acid Programmable Protein Array (NAPPA) allows us to simultaneously detect autoantibodies for 52 of the most common p53 point mutations associated with cancer. Further validation is performed using the Luminex technology of programmable magnetic bead arrays. This will allow us to screen each p53 mutation as well as validate each sample with high sensitivity and specificity over traditional ELISA techniques. Over 70% of ovarian cancer patients harbor mutation to p53. As validation, using our mammalian in vitro protein display, we found p53-AAb in 41% of cases at 91% specificity in ovarian cancer.

Pancreatic cancer has a 5-year survival rate of 2-5%. An impediment to the increase in these survival rates is the lack of established biomarkers for the early detection of pancreatic cancer. In addition there are no established sera biomarkers for the differentiation of benign pancreatic diseases compared to metastatic pancreatic cancer. The prevalence of TP53 mutations in pancreatic tumors is 50-75%. This suggests that p53-AAb could have similar sensitivities in pancreatic as in ovarian cancer. Our project aims to identify and validate p53-AAb found in patient sera that can be used for early diagnosis and differentiation of pancreatic cancer.

Thus far, we have screened sera from 60 cases of pancreatic cancer and 60 controls to identify autoantibodies to 52 of the most common p53 mutations. We have completed the statistical analysis to identify potential autoantibodies to mutant p53 for further screening. AAb to at least 2 specific p53 point mutations were identified in 10/60 cases ( 17% Sensitivity) and 2/63 controls (96% Specificity). All of these were confirmed visually as well as statistically. Further analysis using a separate validation set will help us verify if these specific mutations will have value as biomarkers to identify patients with pancreatic cancer.

 


Publications

Anderson KS, Wong J, Vitonis A, Crum CP, Sluss PM, Labaer J, Cramer D. (2010) P53 Autoantibodies As Potential Detection And Prognostic Biomarkers In Serous Ovarian Cancer. Cancer Epidemiology, Biomarkers, and Prevention Mar;19(3):859-68. PMID: 20200435

Wong, J., Sibani, S., Lokko, N. N., LaBaer, J., and Anderson, K. S. (2009) Rapid detection of antibodies in sera using multiplexed self-assembling bead arrays. Journal of Immunological Methods 350, (1-2), 171-182. Abstract

Anderson KS, Ramachandran N, Wong J, Raphael JV, Hainsworth E, Demirkan G, Cramer D, Aronzon D, Hodi FS, Harris L, Logvinenko T, LaBaer J. (2008) Application of protein microarrays for multiplexed detection of antibodies to tumor antigens in breast cancer. J Proteome Res. 7(4):1490-9. Epub 2008 Feb 27. PMID: 18311903