Molecular genetics and colorectal cancer

GASTROENTEROLOGY 1993;104:1223-1231

ARIES

SELECTEDSU Mark Feldman, M.D. Selected Summaries Editor Dallas Veterans AdmlnlstrationMedicalCenter MedicalService (111) Dallas, Texas 75216

STAFF James L. Achord, Jackson, MS Kim E. Barrett, San Diego, CA Grace H. Elta, Ann Arbor, Ml Lawrence S. Friedman, Philadelphia, Hans Fromm, Washington, DC Fayez K. Ghishan, Nashville, TN John B. Gross, Jr., Rochester, MN Lynn Hornsby-Lewis, New York, NY

MOLECULAR CANCER

Oncology

AND

COLORECTAL

tions

(l-4

13 were

PowelSM, Z&N, more,

Raymond S. Koff, Framingham, MA Ronald L. Koretz, Sylmar, CA Benjamin Krevsky, Philadelphia, PA Loren Laine, Los Angeles, CA William M. Lee, Dallas, TX Thomas A. Miller, Houston, TX Ravinder K. Mittal, Charlottesville, VA Malcolm Robinson, Oklahoma City, OK

PA

GENETICS

OF CONTRIBUTORS

Beazr-Barday Y, et a/. (The Johns

Center, Johns

Maryland).

Hopkins

School of Medicine,

APC mutations

rectal tumorigenesis.

Nature

Hopkins

occur

early during

1992;359:235-237

splice

mutations

in a truncated

APC

determine APC

the role of the candidate

(adenomatous

polyposis

cancers.

APC is abnormal

familial

adenomatous

(GS), inherited mutations

cancers.

more, there was a proclivity at CpG

dinucleotides,

methylcytosine

varying

nomatous

polyps

The entire for mutations.

in Dukes’

DNA then

sequenced

mutation dent

PCR

more,

discovered

mutations

somatic

reaction

sequencing

was confirmed and

APC sequence

(PCR).

by a second

sequence

analysis.

were shown in adjacent

and Each

indepenFurthercolonic

cancers

and

the authors

found

15 of 25 (60%) of colo-

10 of 16 (63%) of adenomatous

polyps

had at least one somatic mutation of the APC gene. There was similarity in the mutations found in the polyps and cancers. Of the 35 total mutations discovered, 6 were inser-

Furtherto occur of 5-

in exon 15 of the APC gene, of the entire

and cancers polyposis

coding

re-

is the same in spoas in the germline

(FAP)

and patients

of with

also found that 31% of the polyps and 35% of

allelic

according noted

in colon

both copies authors.

only one contained indicate noted,

alteration

resulted

a ras mutation,

population

with

APC

from which

likely precede

acid changes. did not differ

and the patient

the potential

functional

were

as well as cancers, is a rather

10 germline

amino

3 variants

progression

mutations

early event

population

significance

mutations, the authors

ras alterations.

APC

were silent polymorphisms

in specific

A or

also to occur in polyps and cancers

enough,

7 of which

alone. polyps

in the ras genes (Ki-ras,

Of five polyps

that APC alterations

Interestingly

APC

polyps

mutations

as well.

for tumor

Because

that this genetic

to the

of the APC gene, although

and large

carcinogenesis,

tested

or mutation

be conferred

may not be necessary

N-ras, and H-ras) known were

mutation,

might

in diminutive

suggesting

of both alleles of their APC gene

loss and

to the

of the latter

In this fashion,

protein. deamination

of mutations

had alterations

by mutating

mucosa. rectal

The authors

cancer

by

mutation, Most of the

GS.

two mutations

by comparison normal

polyps

adenomatous

advantage

The amplified primers.

colorectal

growth

from

that

two-thirds

the pattern

25

and polyps vector

were found

through

15 for the APC

pBluescript

radic

sites.

for the point mutations

implying

about

for

16 ade-

splice sites were amplified

APC mutations

to the wild-type

and

gion. Overall, familial

7 base pairs),

may play a role. Nearly 60% (20 of 35) of the

represents

the cancers

including

from the 41 cancers

internal

amplification

with

syndrome

0.5 cm to 4.5 cm.

totalling

into a T-tailed

using

lesions,

classification

exons,

chain

was subcloned

of patients

of the APC gene was sequenced

Individual

using the polymerase

gene

colorectal

to the development

in size from

region

extracted

to

APC gene was investigated

gene, and their neighboring DNA

suppressor

Gardner’s

colorectal

varying

coding

and

predisposing

The

sought

in sporadic

in the germline

in 41 sporadic

carcinomas

tumor

coli)

polyposis

conditions

of colorectal

genomic

et al., the authors

resulted

colo-

(September

(l-l

1 was a missense

2 had altered

which Powell

12 were deletions

mutations,

and the remaining

somatic from

base pairs), nonsense

Balti-

17). In this report

Anil K. Rustgi, Boston, MA Mitchell L. Schubert, Richmond, VA Konrad Schulze-Delrieu, Iowa City, IA Fergus Shanahan, Los Angeles, CA Joseph Sweeting, New York, NY Richard C. Thirlby, Seattle, WA M. Michael Wolfe, Boston, MA

variants

were

and 3 actually

The allele frequency between

the normal

in the study. Thus, of these

3 variants

re-

mains unclear. Overall, the authors indicate that they may be underestimating the true prevalence of somatic APC alterations

in sporadic

colorectal

polyps

and cancers,

because

1224

SELECTED

the analysis intron

SUMMARIES

GASTROENTEROLOGY

did not include

regions

mutations

and large deletions

in the promoter

as detected

When the latter is taken into account, rectal cancers

contained

but no detectable

and

by allelic loss.

three additional

colo-

loss of one copy of the APC gene

APC germline shifts,

mutations

i.e.,

truncated

Comment.

It is estimated

cases of colorectal Cancer

every

Inst 1991;83:243-253).

tous polyposis the

cancer

that there

annual

cancer

FAP,

syndromes,

The

preponderance from

alterations

mechanisms

involved

that

primarily

suppressor

colonic

progression

to

Thus,

research

the

arising

has uncov-

genes in colo-

may help to elucidate

in normal

and the subsequent

1% to

colorectal

also contribute

genetic

and tumor

(J Nat1

about

is unclear.

are sporadic,

Molecular

in oncogenes

cancer,

ation

cancers

polyps.

ered alterations rectal

I and II syndromes,

new

adenoma-

nonpolyposis

the exact percentage

of colorectal

adenomatous

States

dominant

and GS, contribute

hereditary

or Lynch

the new cases, although

60,000

year in the United Theautosomal

syndromes, prevalence.

are 150,000-I

epithelial

fundamental

cellular

to adenomatous

and

cancer. Insights cancer

into the molecular

have

pathogenesis

in part been gleaned

The first clue to the location the discovery

from

deletion

in a GS patient

(Am J Med Genet

fragment

length

polymorphism

identified

several

that

chromosome

30%40%

losses

of sporadic

sporadic

colorectal

tosomal

colorectal

(N

1989;244:207-211). blood

lymphocytes inactivation

pressor

gene on 5q21.

the remaining thereby

1971;820-822). tivation tions on

199 I ;25 1: 1366-l found

cancers

tations

called

polyposis

DP2.5

(Cell

8972 nucleotides

showed

germ-

hypothesis

region

resides

15. There

daltons.

Not only were somatic colorectal

and GS patients,

cancers

investiga-

suppressor deletions cancer

Further

was termed

and

are 2843 amino

1991;253:665-669;

of the coding

acids in the open

cancers

at the germline Cell

310 kiloin spoarising

in

level were

1991;66:601-613).

paper

it functions

underestimation promoter

because

splice

sites were

analysis

gene

APC pro-

However,

and function

large

of the protein:

in signal

organization?

have

transduction?

Is it a dominant

mutations

the entire

polymorphisms,

the more prominent

remain

practical

ples, allowing particular

region

denaturing

for screening

a mutation

region

gradient

PCR

gel electropho-

for screening

However,

these

DNA

techniques

in large clinical

of a particular followed

is

and neighboring

such as single-strand

of mutations

and then

Nonethe-

in independent

techniques

mutations.

the identification

may contain

coding

in the

and large de-

in the coding

and confirmed

resis, to name

slightly

may be an

that mutations

in this study. Methods,

miss

This

of APC were not analyzed.

sequenced

may

mutations. indicate

APC muta-

Indeed,

were not investigated,

region

because

for mutations,

and cancers.

the authors

of somatic

by the authors

study of somatic

APC

conformation

DNA

sam-

segment

by sequencing

that

of that

segment.

Among

the tenets

progression namely,

in the Vogelstein

in the colon

of alterations

in critical

oncogenes

suppressor which

cancer

adenomas

and tumor

in 70%80% (Cell

previous

colonic

contributing

though

that

indicates,

both

before

Ultimately, exhaustive

number

such

study

risk for developing

of children

at average

colorectal

al-

also

with known

1992;256:102-105). and therefore,

some. To that end, strategies

from an to the

arena.

The

for APC mutations and siblings

Such

in

of individ-

for APC mutations

risk, moderate

cancer.

on a preliminary

the stool of individuals

gained

as the one discussed,

FAP and GS, (2) Searching

in the stool of individuals

(Science

states,

This

of cases, that APC gene alter-

(1) Screening

lymphocytes

APC gene is large,

state, perof diminuitive

as well as to the clinical

be forthcoming

been performed

the progres-

sporadic

state.

to apply knowledge

study

of the APC protein

with

and

in the inherited

one is compelled

blood

formation

study are in-

ras gene mutations.

and thorough

should

present

alterations

in particular,

in inherited

accelerated

of colon

to a hyperproliferative for

in

in colon

stages

The

APC gene

milieu

albeit in a limited

occur

biology

mucosa

to the

polyps,

clearly

later

1990;61:759-767).

indications

genes,

mutation

and the inactivation

of the

in the early stages of colon cancer,

sion of normal

suppressor

by point

and cancers

for tumor

and aggregation

genes, such as p53 and DCC (deletion

occur

development

confirms

model

sequence

of the ras oncogene

40% of sporadic

of tumor

genetic

is the essential

the activation

cancer),

cancer

disrupt

suppressor

cell proliferation.

introns

of the coding accurate

latter

could

have yet to be

then a truncated

adenomas

lesions

and various

highly

ations

as a tumor

is an exhaustive

less, the frequency

haps

USA amino

homodimerizes.

protein

Is it involved

colorectal

60% of such

volved

Sci

the MCC and APC proteins

as to localization

tions in sporadic

nearly

Acad

protein?

The present

uals affected

contains

described

negative

frame-

termination

of the APC protein

it play a role in cytoskeletal

No. 4

of the predicted

to a truncated

is it in the cytoplasm?

Does

that

to abnormal

remain

peripheral

alternately

mass of about

in the colorectal

but mutations

mu-

research

The APC cDNA

APC mutations

were and in

APC (ade-

1991;253:661-665),

molecular

gene

MCC germline

where

Natl

cell proliferation,

tein may contribute questions

mutations,

that the APC protein

The functions

but if indeed

adenomatous

(Science

and

15 exons; over two-thirds

a predicted

radic

mutation,

colon

were not found.

1991;66:589-600).

FAP

point

cancer)

mutations

inac-

Initial

tumor colon

of the gene that

frame

(Science

(acquired).

of

gene locus, cancers,

genes through

coli) (Science

cancers

Acad Sci USA

colorectal

i.e., in sporadic

reading

described

Natl

in FAP and GS patients,

in exon with

suppressor

of a putative

sup-

with inactivation

(Proc

in

tumor

that colorectal

in sporadic

Although

spanning

Science

of one copy of a candidate

(mutated

the identification

nomatous

and sporadic

in FAP and GS patients

in FAP and GS patients

yielded

au-

or pe-

level,

arising

30% of

inherited

syndromes

allele at the tumor

MCC 370).

in both

1988;525-531;

Med

suppressor

at the somatic

colon

region

in

a role for the

polyposis

loss was somatic

called

present

mucosa

led to the identification 5q21

to disNature

were

suggesting

of normal

Alternatively,

or allelic

linked

colonic

Knudson’s

of both tumor

deletion,

groups

and approximately

arose to a large extent

wild-type

fulfilling

region

It was hypothesized

in FAP and GS patients

tightly

J

Evaluation

line (inherited)

Restriction

by several

It was subsequently

same

polyps,

Engl

band 5q21

1987;328:614-616;

cancers

adenomatous

cancer

ripheral

the

gene in the 5q21

dominant

colorectal

(Nature

adenomatous

yet to be identified

analysis

1987;1411-1413). from

for FAP was

1986;25:473-476).

5q21 markers

Science

allelic

of FAP and GS.

and/or

by regulating

letions

colorectal

of chromosome

(RFLP)

ease in FAP and GS kindreds found

the study

of the gene responsible

of an interstitial

1987;328:616-618;

of sporadic

product

(Proc

it is speculated

such interactions.

over

prolifer-

polyps

protein

APC gene leading

delineated,

encompass

lead to translational

Based on comparison

may heterodimerize A mutated

that

APC

1992;89:4452-4455). acid sequences,

APC mutation.

generally

and microdeletions

Vol. 104,

risk, and high

analysis

has already

basis for ras gene mutations adenomatous

polyps

As mentioned mutational

(e.g., Western

previously,

analysis blot analysis)

in

or colon the

is cumberthat take

SELECTED SUMMARIES

April 1993

advantage

of the fact that nearly

greatly.

Obvious

ity would

questions

have

augment

survival

with

respect

to sensitivity

and

clinical

for screening

measures

how

such

and specific-

strategies would

studies

of APC as an actual

such as the reintroduction

could

be of para-

into colon

cancer

phenotype

as well as tumorigenicity

tumor

suppressor

cells and observing

its effects

gene

APC gene

of the normal

on the malignant

in normal cell proliferation and how alterations of it contribute to dysregulated cell growth are areas of intensive and exciting research.

PREDICTING RECURRENCE CANCER PATIENTS

M.D.

General

Surgery

metastatic

tumour

patients.

Lancet

1992;340:685-689

At the time

of diagnosis,

or clinical

this study, presence

the authors

is a significant surgery.

cancer

tumor

prognostic

indicator

bone marrow.

metastases The

confirmed cluded

aspirates

elective

preoperative

tients during chest

the

physical

firsr year

radiography,

measurements, Bone marrow

with

every

ultrasonography,

were initially

tal cancer

showed

computed analyzed

patients (32%). Previous the absence of epithelial

Within

3-year

relapse-free

cells.

relapse

with a

Within

the CKS

of disease recur-

(30%) who were CK-

with

tumor

recurrence,

and the remaining

22 had dis-

the group with distant

survival

whereas

had 12 pa-

metastases,

13 were CK-.

9 The

rates were also calculated

for a

subgroup of 54 patients who underwent surgery at least 36 months earlier. Within the group without tumor cells in the this rate was 71%, whereas

it was 36% in those with

bone marrow. conclude

munocytochemical bone marrow

of tumor

as an independent

radical surgery. Further-

of tumor

histological

the

factor for recur-

value of bone marrow

to be independent

the im-

cells within

prognostic

cancer following

more, the prognostic found

that their work established

demonstration

rence of colorectal

Comment.

Current

mostly

the

upon

tumor

extension,

grading,

Staging

in colorectal

cancer

postoperative

cells was

lymph

node

age, and localization.

prognostic

in-

most

extensive

and

marrow

with

detection

con-

thelial value

tomography. for the presfor CK-

have shown

This paper

with colorecin 28

studies by the authors had shown cells in 102 patients with nonma-

was found

lignant disease. At the time of diagnosis, no statistically significant correlation was found between tumor extension, lymph node involvement, or histological grading and the

cancer

disease

marrow

neuroblastoma

extension

the predictive

(N

recurrence Engl

cancer

in

J

Med

(Int J Cancer

monoclonal

Suppl

antibodies, cell in 200,000

of the authors’

of epithelial

in patients

patients The

for epi-

1988;61:2407-2411).

with

previous

cells in the bone

with

colorectal

nonmalignant

to conventional

of bone marrow of 160 breast Metastases

cancer

patients

were found

histological

techniques

and the authors’

previous

(Cancer studies,

when

(J Clin Oncol staining

histological

micrometastases

work marrow

cancer

disease

use of immunocytochemical

to be superior

biopsies.

ventional

bone

for tumor

has

staining

in colorectal

Nat1 Acad Sci USA 1978;84:8672-8676).

by a study

to the

(J Surg Oncol

confirmed

that as few as one breast

exclusively

the detection

have

immunofluorescent

is a logical

1990;8:831-837).

report

as

(Cancer

with

been shown (Proc

bone

that the presence

compared

of fac-

staining

and small cell lung cancer Using

can be detected showing

for the

marrow

prognostic

micrometastases in breast

studies

well

1991;324:219-226) studies

en-

as

on

performed

Various

cancer

barium

at

therapy.

evidence

cells in the bone

as an independent

work

of micrometastatic

breast

patients

from adjuvant

by immunocytochemical

cells has been

1991;47:32-36).

1988;2:8-10).

level

cancer

surgical-paththose

convincing

tumor

of that

recurrence.

The

3 months

(CK+)

colorectal

subgroups

It is possible

to identify

put forth

importance

in various

likely to benefit

the authors

rely 1979;

that have established

to conventional

clinicians

relapse

cancer

(Cancer

a greater

reports

as effective

in addition

of micrometastatic with

resection

1990;322:352-3580).

will allow

In this report,

for colorectal

have assumed

therapy

J Med

high risk for tumor presence

methods

factors

staging

methods at surgical

since the recent

adjuvant

(N Engl

ological

staging

findings

43:961-968).

6 months),

antibody

origin

patients

had CK+ bone marrow

tor for tumor

for these pa-

antigen

from the 88 patients

cells of epithelial

tumor criteria

(every

subsequently

and in rectal cancer,

aspirates

of micro-

criteria

Follow-up

ence of epithelial cells using a monoclonal 18 (cytokeratin no. 18). Bone marrow

is

of surgery second-

serum carcinoembryonic

aspirates

patients

other

as-

histologically-

Exclusion

2 months

of 35 months.

initial

of tumor

had tumor

(57%) had evidence

had local recurrence,

patients

of this protein

Inclusion

examinations

and

abdominal

ema or colonoscopy,

the

following

as evidence

of the primary

complications.

included

tients

the presence

18 of 60 patients

Of those

tant metastases.

patients

aspirates.

of death within

ary to perioperative

Presence

cancer.

resection

bone marrow

sisted primarily

whether

no. 18), which

88 patients

colorectal

radical

In

cancer.

recruited

primary

metastases.

for relapse

was taken

from colorectal

authors

and

used an immunocytochemical

not found

in normal

relied

histology,

of the bone marrow

(cytokeratin

period

Disease-free

in which

of the prog-

to determine seeding

protein

marrow

cancer

has primarily

of distant

say for an epithelial in bone

rence, whereas

involvement,

stage, tumor

attempt

The investigators

of colorectal

the determination

evidence

of microscopic

of Muof micro-

(Sept).

with colorectal

the surgical-pathological

radiological

University

significance

cells in bone marrow

nosis for patients upon

Clinic,

Prognostic

showed

16 of 28 patients

marrow.

in patients

of all patients

follow-up

group

shorter

aspirates

The authors

and II Medical

Germany).

median

CK+

of

cells in the bone

four percent

marrow,

IN COLORECTAL

Lindemann F, Schlimok G, Dirscbedl P, et al. (Department nich, Munich,

Thirty

relapsed.

in nude mice. The role of APC

h. K. RUSTGI,

of CK+

was significantly

bone marrow

importance.

The demonstration awaits

presence

in the coding

to be addressed,

known

mount

region

protein will facilitate screening

all alterations

of the APC gene lead to truncated

1225

in

cancer

This is supported who

underwent

in only 2 patients

bone by con-

1988;60:96-98). none of the patients

In this with