1. Molecular Pathological Classification Of Colorectal Cancer (CRC) Dr
Molecular Pathological Classification Of Colorectal Cancer (CRC) Dr. Calypso Barbatis MD, FRCPath, PhD HBD Histobiodiagnosis ATHENS
HSGO / May 2018
ATHENS

3. Frequent malignancy 3rd cause of cancer-related mortality worldwide Sporadic, Hereditary, Familial Related to IBD Precursor Lesions Almost perfect stepwise model of carcinogenesis Conventional adenoma Serrated lesions CRC

5. Specific features of CRC Heterogeneous Diseasein
morphology
site
gender
age
response to treatment
Source: Pol J Path. 2014; 65(4): Bosman FT, Yan P.

6. Does CRC fit to the P4 medicine
Predictive
Personalised
Preventive
Participatory
Source: Hood L, Friend SH. Nat Rev Clin Oncol 2011;8:

7. Clinicopathological parameters Still determine treatment
 Classical evidence-based
Clinicopathological parameters
Still determine treatment
But
The road to molecular classification has opened and awaits full
implementation
when
clinical translation and precision medicine are approved

8. The classification of CRC
is based on
clinical
morphological
molecular features
and
available markers
prognostic
preventive

9. Current non-molecular classification
of CRC
Site
Subsite (the most involved)
Rectal: Inferior margin <16 cm from the anal verge or
if any part of the tumor is located within the supply of the superior rectal artery

10. WHO Histological types
Conventional adenocarcinoma
Mucinous (colloid) adenocarcinoma ( > 50% mucin)
Signet-ring cell carcinoma ( > 50% signet-ring cells)
Medullary carcinoma
Micropapillary
Serrated
Squamous cell carcinoma
Adenosquamous
Spindle cell
Poorly differentiated neuroendocrine carcinoma
Large cell neuroendocrine carcinoma
Small cell neuroendocrine carcinoma
Mixed adenoneuroendocrin
Undifferentiated

12. Histological Grade TNM Stage (T0, T1,T2, T3, T4) Tumor budding Margins
Grade 1,2,3,4 (Undifferentiated)
TNM Stage (T0, T1,T2, T3, T4)
Nx, N0, N1, N2
M: M0, M1a, b, c (metastasis to the peritoneum with or without other organ involvement
Tumor budding
Perineural/Lympho-vascular invasion
Perforation
Assesment of mesorectal envelope
Margins
Treatment effect (Tumor regression score)
0 Complete response
1 Near complete response
2 Partial response
3 Poor non response
Source: Amin MB et al eds. AJCC Staging manual 8th edition 2017

13. Basic pathways in colorectal cancer
East et al, British Society of Gastroenterology position statement on serrated polyps in the colon and rectum.GUT 2017

14. Pathogenesis of colorectal cancer GENETIC AND EPIGENETIC CHANGES
A.GENETIC EVENTS
1.CHROMOSOMAL INSTABILITY (65-70% of sporadic CRC)
a)Aneuploidy
Chromosomal gains
Chromosomal losses
b)LOH=loss of the entire gene and the surrounding chromosomal region.
CAUSES:Chromosomal segregation defects,DNA damage repair,telomere dysfunction, point mutations of oncogene or tumor suppressor genes.
Mutational status:APC,K- RAS,SMAD2-SMAD4,p53
Mc Granahan et al,2012 EMBO Reports
Fredericks et al, J Cancer Biol Res 3(1): 1057

15. GENETIC AND EPIGENETIC CHANGES
B.EPIGENETIC EVENTS
Epigenetic changes are those inheritable changes in gene expression with no alterations in DNA sequences.
DNA methylation
Histone modification
Micro-RNAs (non coding RNAs)
Chen et al,Oncology reports,2013 

16. Molecular pathways of CRC carcinogenesis
1. Classical carcinogenetic model
Chromosomal instability (CIN)
Marked aneuploidy
1st pathogenetic event
APC gene mutations
Allelic loss
Somatic gene amplification
Translocation
Activation
WNT signaling pathway

17. Apc/B-CATENIN PATHWAY
CIN MECHANISMS=APC MUTATIONS Wnt/pathway activation
B-catenin in cytoplasm and in nucleus
Trascription factors promote proliferation
Accumulation of mutations/EGFR activation Kras mutations
Loss of SMAD2 SMAD4
Loss of p53
EMT mechanisms activation
Slaby et al,Molecular Cancer2009

18. 2nd Pathway (MMR gene system or MSI) Inactivation of MMR genes
Inactivation of suppressor genes
Lynch syndrome
(Diploid tumors with MSI)

19. The Serrated pathway Hypermethylation of specific DNA regions near
the “promoter genes” the CpG islands
Diploid tumors
Silence of Tumor Suppressor Genes

21. Msi pathway (1) MICROSATELLITE INSTABILITY (15% of colorectal cancer)
Inactivating mutations in the DNA mismatch repair genes (MMR) or methylation of the gene promoter that codify for ATPases such as hMLH1,hMSH2 hPMS2,
MSH6,MSH3.
10-15% of sporadic colorectal carcinoma CIMP-H frequent BRAF mutated.
Lynch syndrome 3-5% of all colorectal carcinomas.No BRAF mutations.
Imai et al,Carcinogenesis vol.29 no.4 pp.673–680, 2008

22. The cimp pathway CIMP stands for CpG island methylator phenotype.
1. Transcriptional inactivation of genes that have tumor suppressive roles or they are involved in cell cycle.
2.BRAF mutation is an early genetic event in this pathway
3.MLH1 hypermethylation is commonly seen.
4.Other promoters also hypermethylated are:CDKN2A,MGMT tumor suppressor genes,MUYTH polyposis syndrome-BER genes,TIMP3 ecc.
5.CIMP-H,CIMP-L,CIMP-normal classification.
Tariq et al, Cancer Biol Med 2016
Schaafsma et al, Biol Med 2016

23. Classification by molecular subtypes
The Cancer Genome Atlas (TCGA)
Consensus Molecular Subtypes (CMS)
Sources: Nature. 2012; 487: (TCGA)
Comprehensive molecular characterization
of human colon and rectal cancer
Nat Med. 2015; 21:
The consensus molecular subtypes
of colorectal cancer. Guinney J et al.

24. Purpose of classification
“To correlate cancer cell phenotype
with
clinical behavior and provide guidance to rational treatment
with specific targeted therapies”
(CRC subtyping Concortium)
This was attempted by the knowledge of gene expression data
based on
“epigenomic, transcriptomic, microenviromental, genetic
and clinical characteristics of tumors’’

27. Consensus Molecular Subtypes of colorectal cancer (CMS)
Assessment methods
Mutations
Chromosomal number alterations
Methylation status
Posttranslational
Gene regulation
Clinical analysis (site, gender, grade, stage)
DFS (Disease Free Survival)
RFS (Relapse Free Survival)
SAR (Survival After Relapse)
IMPORTANT!!
“No subtype was solely defined
by a genetic aberration”
wild-type KRAS may be found in all subtypes

28. Clinical implications of CMS
CMS1 (MSI)
Better prognosis before dissemination
Worst prognosis after relapse
Stages 1,2 perhaps no adjuvant chemotherapy
Stage 3 no response to 5-FU
Importance of the immunogenic microenvironment
Treatment? Check point inhibitors

29. CONSENSUS MOLECULAR GROUP 1

31. CMS2 Canonical (adenoma – CRC sequence)
APC loss
KRAS activation
P53 loss
CIN increased copies of oncogenes
reduced copies of suppressor genes
low mutation rate ( < 8 mutations / 106 bases)
adjuvant chemotherapy

32. Consensus MOLECULAR GROUP 2

33. Tubulovillous adenoma with serration
CMS3 metabolic subtype
30% hypermutated
KRAS mutation
Tubulovillous adenoma with serration
Precursor lesion (?)
Enriched in RNA (9-10 metabolic pathways)
Glutamine, fatty acid, phospholipid metabolism
Poor prognosis of KRAS mutated cases
Her-2 mutations
Resistance to EGFR mAb

34. CONSENSUS MOLECULAR GROUP 3

35. Resistant to anti-EGFR Regardless of KRAS mutation status
CMS4 (mesenchymal)
Advanced stage in diagnosis
Poor survival (62% in 5 years)
Resistant to anti-EGFR
Regardless of KRAS mutation status
Difficult to treat
? use of microenvironment features
? anti avβ6 integrin
Anti-CAF
Anti-macrophage
Source: Thanki K et al. IBBJ 2017; 3(3)

36. CONSENSUS MOLECULAR GROUP 4
DAWSON et al Reviews in medicine 2015

37. Molecular features of CRC
Molecular Heterogeneity
Genomic, epigenomic
define
Molecular subtypes
Implementation of
Personalized therapies
Improvement of management

38. Acknowledgement
My gratitude to Dr.Bouklas for providing some of the tables and additional literature

39. Thank You For Your Attention