Pathogenesis of metastasis formation

Current

Concepts

101

in Cancer

Pathogenesis of Metastasis Formation

I\

A

1972 symposium

therapy

of cancer,’

S. Garattini, ority hc

stated

a\vay

been

“the

heart

not

by the

itself

that

be aimed the

imply

that

prevented

blood

clotting

phasis clot

of and

effect

old

attention

tumor

spread.

ainount

of

intriguing

two

Since

tindinga doxical,

same

ha\ e

been

doubt

and

approachus

the

models

cmploycd

appropriate coherent

picture

still

available

not

be

t\vo the

human

the

cancer

of cancer

nc\‘eI.

human

can-

not

cancel-

a clearI>

progression the

sum

of

or

is the

” Department of Pathology, Uliiversit\, of Southern California School %f Medicine, ‘2025 Zonal Avenue, Los Angeles, California.

of

ing

one

the

never

may

hasis

ht

prcssurc I’UKCS

of the and

the as well

\vith

early

orientation a\va>

A murc the

Similarly, blood

as neoplastic

invasion cancers

response,

tissue

breakdown.

and

macrophages

mav

and

lead

cell break-

acute

intlammaoften

putatively also

Similarly, present

inflammation

mass into

mass

of melanoma, may

the

internal

pressure

tumor of

pas-

OCCUI- on

inflammation,

inunc

chronic

fail-

basement

migrating

complicating

A chronic

of

mobilit!

of

that

Ilow

a

of an-

esample

loss.

the

one

cohesion,

may

tissue. outside

lion.

other

an

and

concept

at

the growing tumor peripheral cance1‘ cells

compromise with

it would

primarily

part

01 invasion old

give

cellular

switching-

losing

tissue,

an

thus

action

and

01 its direction

t\,pe

can-

the

be

synthesis,

special

of the

ccl1 gaining its

body.

host

be

pos-

the

but

inhibiting

its adhesion

\ivc

and

have,

may

the

contribute

hecausc

of

to the

cancerous

to

rvithin

not

function

from

to its

and

cells

and

Further,

Invasion

this,

and

meta-

the normal

known

another.

release

do\vn

cxper-

obvi-

and

genome

that

lvould

to normal

particularI> cancer

be given

their

those

cells

in the

neighboring

can

animal

anticipated, from

to

of

one

arc

to the

As might

due

para-

muthodolopical

no that

dc-

01’ the or

kinds

Further,

and

been

many

contlicting the

that

alike

hah

time

cancer

be dercpressed

niembrane and

accr~ied,

time,

different

used.

overemphasize are

has

primarily in

01

the elements will

beyond

to a function

1~~ losing

giving

a wluminous

hnuwlcdgc

the

di\ersit\,

studied

ihen.

inlormation

no

all

the

mechanisms

rise

on

mag-

example

invasive

other

program

other.

in 1967 with

the

some

counterpart

and

and

by

he a function

intci.-

svrnposia’,”

to

ne\\ At

ence.

in\,asivc

to the

as is known,

ccr ccl1 may

the

in

great

despite

capabilities

of blood

prog-

for

and

can

of the of

system,

mention

Some

fal-orablc

review

as

factors

defense

OI em-

rencwcd

01 a mo&graph.~

strung

cers

The apparent

ot

publication

the

ot the

noticeably

st’ssed

new

interest

aspects

\vhich

linking

has had

restimulating

holding

rived.

This

a brief areas

processes.

As far acquire

manipulation

concept

processes.

was

sreat

the

been

subjects

relationship

from

be reduced

ques-

have

importance,

host

\latic

of the

data

Some

passing

ous

contro-

stems

can

by

science

the

and Much

lactors.‘~’

an

mclastatic est

chemothcrap!

clinical

metastasis of

basic

orlly

is no

limited

ct>ll proliferation

it has

there

advances

to say,

on

and

Accordingly,

metastascs

even

nitude

disscmina-

approach

and

Needless

I-VW made.

this

y-owth

but

significant

touch

of the

process.” this

of

made. onlv

nii?bt

reports,

that

invad-

at confining

for

experimental

by its

cancer.

metastatic

enthusiasm

studies

tion

mctastases

of

body.

suggested

ling

but

Dr.

in pri-

that

entire

should

a change

in

formation

the

con\‘encr,

cycle

tumor

and

iny

that

published

chemo-

cell

is represented

of the tion

the

the

from

indicated

disease

on

seen breast, an

contribute

imto

granulocytcs in subacute \vhich can be

102

found at the periphery of some cancers can also be expected to release hydrolases. Should the hydrolases overwhelm the antiproteolytic enzymes of the interstitial fluid, normal tissues as well as cell debris would be digested. Cancer cells themselves are another source of hydrolases since they, like most cells, contain lysosomal “suicide bags” for their own autophagic destruction. Since cancer cells may have leaky membranes, it would seem that they should be particularly vulnerable to high levels of hydrolases in the interstitial fluid. Perhaps the massive necrosis of cancer that sometimes occurs is a reflection of this. Another point not very clear is why regressing mammary cancers of the rat do not show a high level of interstitial fluid hydrolases in the face of high intracellular levels and cell death.s,9 Answers to these and other questions, not the least of which is the fact that most invasive cancer masses arc not accompanied by either inflammatory cells or overt evidence of a tumor proteolytic effect, must await studies on anti-enzvmes, enzyme clearance factors, rate of necrobiosis, and of course the ITalidity of the different testing methodologies themselves. Recent summaries of the hydrolasecancer relationship1’1,11 arc available for further insight into the progress made. Invasion of the tissues, lymphatics, and blood stream is not a property belonging exclusively to cancer cells. Lymphocytes. granulocytes. and macrophages are more “invasive” than most cancer cells that have been studied despite their “normal” physiological status, in particular an absence of high surface charge.lg Their rapid penetration of tissues also does not appear to be related to proteolytic mechanisms. Both leukocytes, and apparentl! some cancer cells, seem to be capable of penetrating other cells directly, and perhaps may use this mechanism exclusively rather than to pass through intercellular junctions.‘,’ In some instances, cancer cell “invasion” is probably passive, bearing in mind the totally passive movement of red blood cells through tissue-

Current

Concepts

in Cancer

lymphatic-blood vessel interconnections, and also diapedesis. Nonneoplastic trophoblasts and megakaryocytcs both invade and metastasize, with the former sometimes producing massive “benign” lung metastases that fortunately tend to regress completely. Neuroblasts “home-in” and invade the adrenal cortex of the fetus, later matur-= ing to form the adrenal medulla, an event complicating the diagnosis of ncuroblastoma for the pathologist. Attention to the “dropping off” phenomenon of the junctional nevus was the key to recognizing the relatively benign invasion of the “carof the oropharynx, now cinosarcoma” identified as a combination of low grade cancer, pseudosarcoma, and junctional change involI:ing nonpigmented cell~.~’ With two other examples, the keloid that fails to stop proliferating, and endometrial glands that commonlv “metastasize” to pelvic lymph nodes in the absence of cancer, it becomes clear that no single explanation will be found for invasion and metastasis. Many avenues arc open to the cancer ccl1 for entering blood vessels and lymphatics. It can take advantage of temporal-v damage to capillary and venular entering through small rents, walls, thanks to its deformable property’” and pseudopodial movements. Intcrcellula~ junctions may open up during division of the conjoined cells, or gaps may form in the absence of a platelet cell-cemcntCancer cells might even ing factor.“; follow lymphocytes and macrophagcs through cellsl; or through intercullular junctions. An increase in capillary permeability, by widening cell ,junctions, \vould favor. invasion, and this could be a conscqucnce of congestion and stasis or a direct noxious effect on the endothelium. Histamine can increase metastases expctimcntally and antihistamines appear to play a preventive role.‘* Endothelial fenestrations and “open” tumor sinusoids may lead to hemorrhage as well as to me;astasis.“’ Little attention has been gi\,en to the

Current

Concepts

in Cancer

direction of cancer cell movement. While our own studies of histocu1tures’9 and the studies of others20.‘7 have noted random movements, we have film recordings sho\ving very purposeful locomotion, e.g., migration of a cancer cell out of a glandular structure followed by division of the cell, and then forceful rc-entrv of the t\vo daughter cells into the gland to form a propct-ly aligned acinus. Time lapse filmin? is espcciall!; useful for demonstrating ameboid motion of cancer cells and the extraordinary deformability of not on]! single cancer (~11s but aggregratcs as \VCll. No one questions that the cancer cells of a primary tumor enter the blood stream at one time or another, influenced bv manv factors2’ and not nccessaril\, follo\vcd bv mctastases. There is some debate as ‘to the frequency of the finding, due mainly to the difficulty in distinguishing cancer cells from a number of nonmalignant cells, especially megakaryocytes and immature bone marrow cell~.~~ There tnay bc a continuous seeding of the blood stream bv tumor cells and tumor cell anrrregates, or a periodic showering. Anti2c c.oagulant drugs might relcuse showers of cells from tumor thrombi by decreasing aclhesi\~eness of cancer cell~,~’ perhaps at the same time preventing their lodging in other vessels. Other agents, heparinoid,” protcolytic,‘” and surfactant”: ma\ also increase tumor cell release by decreasing cell surface stickiness, increasing surface electrostatic charges to cffcct tnutual repulsion of cells, or altering the host and its defense mechanisms in a way that favors tumor cell release and vessel lodgement. Hellmann2” has actuallv reported [hat Triton, a detergent, facilitates the spread of hamster Iym phoma, in contrast to earlier findings.27 Cancer necrosis, vessel rupture, and hemorrhage certainly contribute to seeding of the blood. The benign pheochromocytoma is a good example of this since the sudden release of hormonal pools and cellular aggregates present in poorly defined vascular channels has been impli-

103

cated as one of the causes of hypertensive criscs.2X Verv pertinently, a “new type of drug action” is said to have a “normalizing” or “angiometamorphic” effect on the blood vessels of tumors.2!‘.:‘0 With a better blood supply, the cancer undergoes less necrosis and there are fewer defects in the \~~sel walls to permit spillage of cells into the circulation. The application of this principle contrasts with present attempts to control tnetastasis through a rcltlrrctior7 in blood supply, bearing in mind recent interest in an agent to countcract the tumor angiogenesis factor?’ and a linear relationship between vessel density and effluent tumor ~~11s.‘:~ Once seeding of the blood has occurred, it is dell appreciated that this may or may not lead to lodgement and growth. cancer cells in the blood Pertinently, stream of an animal can be successfully transplanted to another animal, yet the donor fails to develop organ metastases with this particular tumor mode1 svstern? When metastases do develop, they arc not necessarily of great biological significancc. The mouse mammary carcinoma often metastasizes to the lung, but rarely elsewhere, and with relatively little effect on the life span of the animal-a finding that cautions against cxtrapolations to the human form of breast cancer. Much work has been done in an attempt to explain preferential organ localization and a central theme, cancer cell trapping by the organ, has just recently been chalIengcd.“’ Since lodgement of cancer cells prccedcs metastasis, the mechanism by which this occurs has been the subject of an intensive search. Long suspcctcd as the prime factor giving cancer cells a toe hold in distant organs is a local disturbance in the clotting mechanism.“,? There arc a number of ways a blood coagulum would favor lodgement and growth. Obviously, a clot can enmesh cancer cells and the resulting aggregate would fail to pass small vessel channels. There would also be a restricted microenvironment, a factor tending to exclude elements of the host defense system as

104

Current

well as to retain key growth substances. A fibrin or fibrin-like network would not only offer strength to the clot but would furnish a needed latticework upon which the cells can proliferate.:“; But why does clotting occur in the first place? O’Meara postulated a “cancer coagulative factor.” However, it is now known that thromboplastin-like substances can be produced by nonneoplastic cells, and some cancers have been reported to produce fibrinolysins.“’ A more appealing first step is a defect in the endothelial lining. This can simply be “normal” wear and tear at a particularly vulnerable site, bearing in mind that endothelial cells have a high turnover rate, that patchy areas of cell loss are said to be common, and that platelets provide a temporary patch for the missing lining.“* Thus, the lodgement of a cancer cell aggregate on a platelet coagulum and structural-chemical interactions of platelets with tumor cells:‘5,39 could be the “crucial” first step. Of clinical interest, thrombocytopenia induced by neuraminidase 40 decreases metastasis, and a similar result via an aspirin medi-

Concepts

in Cancer

ated effect on platelets has been claimed41 and questioned.” Two other endothelial cell considerations have been brought out. The cells are a source of plasminogen activator;? thus their local loss could lead to a microenvironment which accentuates or even initiates clotting at the site of the lining defect. Secondly, endothelial cell injury clearly occurs in radiation damage to the lung, and there is both clinical and experimental evidence that prophylactic irradiation of the chest increases the frequency and the rate of growth of lung and other metastases.13m45 Earlier we mentioned that fibrinolysins might accentuate metastases by freeing cancer cells bound in clots. However, studies with fibrinolysins, including plasmin, tend to indicate that the prevention of clotting may be their dominant seemed to role inasmuch as metastases be fairly consistently Other covered

aspects

reduced.

of metastases

are

being

elsewhere

in this section; in particular, those concerning the relationship of metastasis to activated macrophages, tumor glycocalyx, and temperature.

REFERENCES 1. S. Garattini and G. Franchi (Eds). Chemotherapy of Cancer Dissemination and Metastasis. New York: Raven Press, 1973. 2. D. Ogston, N. B. Bennett, and C. M. Ogston. The fibrinolytic enzyme system in hepatic cirrhosis and malignant metastases. J. Clin. Pathol. 24:822-826, 1971. 3. L. Michaels. The incidence and course of cancer in patients receiving anticoagulant theranv. J. Med. 5:98-106. 1974. 4. 6.’ E. Clifton and C.’ E. Grossi. The rationale of anticoagulanjts in treatment of cancer. J. Med. 5:107-113, 1974. 5. R. W. Wissler, T. L. Dao, and S. Wood, Jr. Endogenous Factors Influencing Host-Tumor Balance. Chicago: Univ. of Chicago Press, 1967. 6. B. Fisher and E. R. Fisher. Studies of metastatic mechanisms employing labeled tumor cells. In: The Proliferation and Spread of Neoplastic Cells. Baltimore: Williams and Wilkins, 1968, pp. 552-582. 7. P. Denoix (Ed). Mechanisms of Invasion in Cancer. UICC Monograph Vol 6. BerlinHeidelberg: Springer-Verlag, 1967. 8. P. M. Gullino and R. H. Lanzerotti. Maminary tumor regression. II. Autophagy of neo-

plastic cells. J. Nat. Cancer Inst. 49: 1349-1356, 1972. 9. R. H. Lanzerotti and P. M. Gullino. Activities and quantities of lysosomal enzymes during mammary tumor regression. Cancer Res. 3212679-2685, 1972. 10. A. C. Allison. Lysosomes in cancer cells. J. Clin. Pathol. 27 (Suppl 7): 43-50, 1974. 11. B. Sylven. Biochemical and enzymatic factors involved in cellular detachment. In: Chemotherapy of Cancer Dissemination and Metastasis. S. Garattini and G. Franchi (Eds). New York: Raven Press, 1973, pp. 129-138. 12. L. Weiss. The cell periphery, metastasis and other contact phenomena, In: Frontiers of Biology, vol. 7, A. Neuberger and E. L. Tatu (Eds.). Amsterdam: North-Holland Pub]., 1967, p. 338. 13. J. Dingemans. Behaviour of intravenously injected malignant lymph cells: A morphologic study. J.-Nat. Cancer Inst. 51: 1883-1887. 1973. 14. R. P. Sherwin, M. S. Strong, and C. W. Vaughn, Jr. Polypoid and ,junctional squamous cell carcinoma of the tongue and larynx with spindle cell carcinoma (“pseudosarcoma”). Cancer 16: 51-60, 1963.

Current

Concepts

in Cancer

15. E. Shelton and M. E. Rice. Studies on mouse lymphomas. II. Behavior of three lymphomas in diffusion chambers in relation to their invasive capacity in the host. J. Nat Cancer VInst. 21: 137-149, 1958. 16. J. F. Mustard, H. C. Rowsell, E. A. Murphy, and M. F. Glynn. The platelet and endothelium. Blood 25:613, 1965 (Abstra.). 17. R. P. Sherwin and A. Richters. Patho biologic nature of lymphocyte interaction\ \vith human breast cancer. J. Nat. Cancel. Insl. 48:1111-1115, 1972. 18. T. Takahashi, Y. Okamoto, R. Nakamura, and S. Majima. Influence of vasculatpermeability on blood-borne metastasis. Gann 64: l-5, 1973. 19. R. P. Sherxvin and A. Richters. The dotumentation of human breast cancer in tissue culture. Cancer 34: 1943-1955, 1974. 20. S. Wood, Jr. and P. Strauli. Tumor illvasion and metastasis. In: Cancer Medicinc J. F. Holland and E. Frei, III (Eds.). Philatlelphia: Lea & Febiger, 1973, pp.140-151. 21. R. A. Malmgren. Studies of circulalin? cancer cells in cancer patients. In: Mechanisms of In\raslons in Cancer. P. Denoix (Ed.). UICC Monograph, vol. 6, Berlin Heidelberg: Springer-Vcrlag, New York, 1967, pp. 108-l 17. 22. M. R. Rilelamed, E. E. Clifton, and S. H. Seal. Cancer cells in the peripheral l’enous blood: A quantitative study of problematic origin. Amer. J. Clin. Pathol. 37:381-388, 1962. 23. R. C. Millar and A. S. Ketcham. The effect of heparin and Warfarin on primary and metastatic tumors. J. Med. 5:23-31, 1974. 24. W. Regelson. The antimitotic activity of polyanions: Heparin and hcparinoids. J. Med. 5: 50-68, 1974. 25. R. D. Thornes, H. Smylh, 0. Bro\+ne, M. O’Gorman, D. J. Reen, D. Farrell, and P. D. Holland The effects of proteolysis on the human immune mechanism in cancer: A pre liminary communication. J. Med. 5:92-97, 1974. 26. K. Hellman. Metastasis and Triton WR 1339. Eur. J. Cancer 9:153-154, 1973. 27. G. Franchi, L. Morasca, I. Reyera-DegliInnocenti and S. Garattini. Triton WR 1339 (TWR), an inhibitor of cancer dissemination and metastases. Eur. J. Cancer 7: 533-544, 1971. 28. R. P. Sherwin. The adrenal medulla, paraganglia and related tissues. In: Endocrine Pathology. W. Bloodworth (Ed,). Baltimore: Williams and Wilkins, 1968, pp. 256-315. 29. A. W. LeServe and K. Hellmann. Metastases and normalization of tumor blood vesSCIS BY ICRF 159: A new type of drug action. Brit. Med. J. 1:597-601, 1972. 30. S. E. James and A. J. Salsbury. Effect of t-1.2-bis(3,5-dioxopiperazin-l-yl) propane on tumor blood vessels and its relationship to the antimetastatic effect in the Lewis lung carcinoma. Cancer Res. 34: 839-842, 1974.

105

31. J. Folkman. Tumor angiogenesis factor. Cancer Res. 34:2109-2113, 1974. 32. L. A. Liotta, J. Kleinerman, and G. M. Saidel. Quantitative relationships of intravascular tumor cells, tumor vessels, and pulmonary metastases following tumor implantation. Cancer Res. 34:997-1004, 1974. 33. G. Crile, Jr., W. Ibister, and S. D. Deodhar. Lack of correlation between the presence of circulating tumor cells and the development of pulmonary metastascs. Cancer 28:655-656, 1971. 34. M. M. Zatz and E. M. Lance. Distribution of “‘Cr labeled lymphocytes into antigen stimulated mice: Lymphocyte trapping. J. Exp. Med. 134:244-254, 1971. 35. L. Weiss. Separation of malignant cells from the primary tumor. In: Frontiers ot Biology. A. Neuberger and E. L. Tatum Publ., (Eds.). Amsterdam: North-Holland 1967, pp. 289-338. 36. K. Laki. Fibrinogen and mctastases. J. Med. 5: 32-37, 1974. 37. E. D. Holyoke, A. L. Frank, and L. Weiss. Tumor thromboplastin activity in vitro. Int J. Cancer 9: 258-263, 1972. 38. B. A. Warren and 0. Vales. The adhesion of thromboplastic tumor emboli to vessel walls in viva. Brit. J. Exp. Pathol. 53:301-312, 1972. 39. B. A. Warren. The ultrastructurc of platelet pseudopodia and the adhesion of homologous platelets to tumor cells. Brit. J. Esp. Pathol. 51: 570-578, 1970. 40. G. J. Gasic, T. B. Gasic, and C. C. Stewart Antimetastatic effects associated \vith platelet reduction. Proc. Nat. Acad. Sci. 61: 46-52, 1968. Jl. G. J. Gasic, T. B. Gasic, and S. Murphv. Anti-metastatic effect of aspirin. Lance; I: 932-933. 1972. 42. S: Wood, Jr. and P. Hilgard. Aspirin and tumor metastasis. Lancet 2: 1416-14 t7, 1972. 43. M. J. Brown. The effect of lung irradiation on the incidence of pulmonary metastases in mice. Brit. J. Radiol. 46:613-618, 1973. 44. P. W. Sheldon and J. F. Fowler. The effect of irradiating a transplanted murine Iymphosarcoma on the subsequent developmcnt of metastases. Brit. J. Cancer 28:508514, 1973. 45. H. A. S. Brenck and H. Kelly. Stimulation of growth metastases by local x-irradiation in kidney and liver. Brit. J. Cancer 28: 349-353, 1973. 46. J. D. Ward, M. G. Hadfield, D. P. Becker, and E. T. Lovings. Endothelial fenestrations and other vascular alterations in primar! melanoma of the central nervous system. Cancer 34: 1982-1991, 1974. 47. J. Leighton. The Spread of Cancer. Pathogenesis, Experimental Methods, Interpretations. New York and London: Academic Press, 1967.