1. Genetics of Gastrointestinal Neoplasia
张咸宁
Tel： ;
Office: A705, Research Building
2014/05

2. Learning Objectives
掌握结直肠癌为模型的恶性肿瘤的多步骤发生模式。
了解APC等相关癌基因。

3. Required Reading
Thompson &Thompson Genetics in Medicine, 7th Ed （双语版，2009）
● pp ；
● Clinical Case Studies-19 Hereditary Nonpolyposis Colon Cancer

4. World Cancer Report 2014, WHO Press.

6. Cancer is a group of genetic diseases affecting fundamental aspects of cellular function, including DNA repair, cell-cycle regulation, apoptosis, and signal transduction.

8. 特点 原癌基因 抑癌基因 正常生长和增殖必需 增殖负调控，分化必需 点突变、染色体重排、基因扩增、病毒插入 点突变、LOH等 显性 隐性
基因功能
正常生长和增殖必需
增殖负调控，分化必需
突变（激活）方式
点突变、染色体重排、基因扩增、病毒插入
点突变、LOH等
致癌方式（They behave as） 显性 隐性
突变蛋白的效应
功能失去突变
功能获得突变
遗传方式
体细胞突变，不遗传
体细胞或生殖细胞突变，可遗传
常见于哪些癌肿
白血病、淋巴瘤
实体瘤

9. LOH (loss of heterozygosity)
Loss of a normal allele from a region of one cs of a pair,allowing a defective allele on the homologous cs to be clinically manifest.
A feature of many cases of retinoblastoma, breast cancer, and other tumors due to mutation in a TSG.

10. LOH (loss of heterozygosity)

11. A and B represent two microsatellite polymorphisms that have been assayed using DNA from a cancer patient's normal cells (N) and tumor cells (T)

12. Tumour suppressor gene (TSG)
Caretaker genes: TSGs that are indirectly involved in controlling cellular proliferation by repairing DNA damage and maintaining genomic integrity, thereby protecting proto-oncogenes and gatekeeper TSGs from mutations that could lead to cancer. E.g., ATM, BRCA1/2, MLH1, MSH2, XPA.
Gatekeeper genes: Tumor-suppressor genes that directly regulate cell proliferation. E.g., APC, CDKN2A, RB, TP53, VHL.

13. “Two-hit” hypothesis: Knudson,1971
“Two-hit” hypothesis: Knudson,1971. This explains why hereditary retinoblastoma usually has an earlier age of onset and exhibits bilateral or multifocal occurrence more often than sporadic retinoblastoma.

15. Colorectal Cancer is a Major Cause of Cancer Deaths in the United States
Men 289,550
Women 270,100
Lung and bronchus 31%
Colon and rectum 9%
Prostate 9%
Pancreas 6%
Leukemia 4%
Esophagus 4%
Liver/intrahepatic bile duct 4%
Non-Hodgkin’s lymphoma 3%
Urinary bladder 3%
Kidney and renal pelvis 3%
All other sites 24%
26% Lung and bronchus
15% Breast
10% Colon and rectum
6% Pancreas
6% Ovary
4% Leukemia
3% Non-Hodgkin’s lymphoma
3% Uterine corpus
2% Liver/intrahepatic bile duct
2% Brain/nervous system
25% All other sites
Colorectal cancer is the third most common cancer in the United States and the third most common both in men and in women.1
Prostate, breast, and lung cancers are more commonly diagnosed.
It is estimated that more than 150,000 new cases of CRC are diagnosed in the United States each year.
Approximately 10% of all cancer deaths in the United States are caused by CRC.
Colorectal cancer is the second most common cause of cancer death in men in the United States.
Lung cancer is the most common cause of cancer death. An estimated 52,000 deaths from CRC (men + women) occur each year.
Lifetime risk of developing the disease is approximately 6%.2
Ninety percent of CRC cases occur in patients over the age of 50.
Jemal et al. CA Cancer J Clin. 2007;57:43.
1. Jemal A et al. CA Cancer J Clin. 2007;57:43-66.
2. Ries LAG et al. SEER Cancer Statistics Review, At: Accessed July 2007. 15

16. Colorectal Cancer (CRC)
Factors associated with increased risk
Age (>90% diagnoses in individuals >50 years old)
Personal or first-degree family history of CRC, or adenomas, polyps or inflammatory bowel disease
Hereditary conditions
Familial adenomatous polyposis (FAP)
Lynch syndrome (Hereditary nonpolyposis colorectal cancer, HNPCC)
Ulcerative colitis
Obesity, physical inactivity
High-fat or low-fiber diet, inadequate intake of fruits and vegetables
American Cancer Society. Cancer Facts & Figures National Cancer Institute. PDQ® Physician Statement.

17. CRC Risk in Familial Syndromes
100
FAP
HNPCC
Probability of Cancer (%)
Population Risk 30 50 70
Age (y)
Bussey HJR, ed. Familial Polyposis Coli. Baltimore, Md: Johns Hopkins University Press; 1975 [Evidence Level C]; Petersen GM, et al. Gastroenterology. 1991;100:1658–1664. [Evidence Level C]

18. Genetic predisposition to CRC

19. Familial adenomatous polyposis (FAP)
Or adenomatous polyposis coli (APC).
An AD subtype of colon cancer that is characterized by a large number of adenomatous polyps. Typically develop during the 2nd decade of life and number in the hundreds or more (polyposis itself is defined as the presence of >100 polyps). FAP accounts for ~1% of all CRC.
Penetrance of FAP is virtually 100%.
> 700 different germline mutations of the APC gene (5q21), most of which are nonsense or frameshift.
APC: Adhesion molecule. Interacts with β-catenin and when APC is mutated, the complex accumulates in the cell leading to transcriptional activation of other tumor promoting genes.
100% chance of cancer if no surgery.

20. In late childhood and early adulthood, up to 1000 and more polyps develop in the mucous membrane of the colon (1). Each polyp can develop into a carcinoma (2). In about 85% of the affected, small hypertrophic areas not affecting vision are present in the retina (congenital hypertrophy of the retinal pigment epithelium, CHRPE, 3).

21. FAP
Persons with FAP have increased risks of other cancers, including gastric cancer (<1% lifetime risk), duodenal adenocarcinoma (5%-10% lifetime risk), hepatoblastoma (1% risk), and thyroid cancer.
Mutations in APC can also produce a related syndrome, termed attenuated familial adenomatous polyposis. This syndrome differs from FAP in that patients have fewer than 100 polyps (typically 10-20).
FAP can also result from recessive mutations in MUTYH, a gene that encodes a DNA repair protein.

24. CRC
Lynch syndrome or Hereditary nonpolyposis colorectal cancer (HNPCC) comprises 1-3% of CRC and is characterized by early-onset proximal CRC exhibiting MSI (microsatellite instability).
AD, high-penetrance cancer syndrome, HNPCC individuals face a 50-70% lifetime risk of developing CRC, in addition to other malignancies.
HNPCC is caused by mutations in any of 6 genes (MSH2, MLH1, MSH6, MLH3, PMS1/2) involved in DNA mismatch repair.

25. Gel electrophoresis of 3 different microsatellite polymorphic
markers in normal (N) and tumor (T) samples from a patient with
a mutation in MSH2 and microsatellite instability (MSI, MIN). Although marker #2 shows no difference between normal and tumor tissues, genotyping at markers #1 and #3 reveals extra alleles (blue arrows), some smaller, some larger, than the alleles present in normal tissue.

29. Two Pathways to CRC

30. Genetics of Colon Cancer
Mutations in tumor
CIN: K-ras, APC, DCC, p53 (85%)
MIN: DNA MMR (15%)
Mutations in patient
FAP, HNPCC, methylating genes
Approximately 5% of CRC case are caused by inherited genetic mutations
CIN = chromosome instable; APC = adenomatous polyposis coli; DCC = deleted in colon cancer [gene]; MIN = multiple intestinal neoplasia; MMR = mismatch repair; FAP = familial adenomatous polyposis; HNPCC = hereditary nonpolyposis colorectal cancer.

31. CRC: Adenoma-Carcinoma Sequence
32-57%
K-Ras mutant 31 31

32. K-Ras First Biomarker in Colon Cancer Predictive, Possibly Prognostic
Predicts response to anti-EGFR drugs
Is an example of how we can “personalize” cancer therapy

34. Epigenetics of CRC
Epigenetics changes include: (1) altered DNA methylation, (2) chromatin remodeling and (3) non-coding small RNA (miRNAs).
Notable changes in epigenetics have been reported for several age-related diseases, including CRC.

37. Risk Factors of Pancreatic Cancer
Family history (10 %)
familial atypical multiple mole melanoma syndrome
familial breast cancer (BRCA2)
Peutz-Jeghers syndrome
hereditary pancreatitis
Diet
Meat/fats
Advancing age
Male gender
Diabetes
Environmental factors
smoking
alcohol
coffee (?)
asbestos, pesticides, dyes

38. Hereditary Pancreatitis
trypsin
autosomal dominant
early progressive fibrosis
40 x risk pancreatic cancer

39. Progression Model of Pancreatic Cancer
In recent years it has become clear that cyclooxygenase-2 is a critical molecule in tumor biology. COX-2 is over-expressed in many cancers and it contributes to the malignant phenotype of tumors on several levels. For example it can confer resistance to apoptosis, stimulate cell proliferation and invasion. More recently, studies have shown that COX-2 is also critical for tumor angiogenesis. Its expression correlates to …
Bardeesy et al., Nature Rev Cancer 2002 39

40. Gastric Cancer
Diffuse type – linitis plastica
Intestinal type

42. Acknowledge（PPT特别鸣谢！）
UCLA David Geffen School of Medicine
Prof.s Wainberg ZA, Hines J, Hart S,
et al.