Activation of CCR9/CCL25 in cutaneous melanoma mediates preferential metastasis to the small intestine.
OBJECTIVE
Specific chemokines and their respective receptors have been implicated in distant tumor cell metastasis. Cutaneous melanoma has a distinct pattern of metastasis, preferentially targeting the submucosa of the small intestine. However, the underlying pathogenic mechanism remains unknown. Migration of CCR9(+) lymphocytes to the small intestine is known to occur in response to the chemoattractant effects of CCL25 (thymus-expressed chemokine). The integrin heterodimers alphabeta are also known to be important mediators of cellular adhesion. We hypothesize that the mechanism of small intestinal metastasis by melanoma is via the CCR9-CCL25 axis and specific integrins.


METHODS
Quantitative reverse transcription-PCR, flow cytometry, and immunohistochemistry were used to assess melanoma tumors for CCR9 and CCL25. Integrin expression was assessed using flow cytometry. CCR9 expression by quantitative reverse transcription-PCR was assessed in primary (n = 23) and metastatic (n = 198) melanomas, and melanoma lines derived from small intestinal metastases (n = 23).


RESULTS
We showed CCR9 expression in 88 of 102 paraffin-embedded metastatic melanomas from the small intestine, 8 of 8 melanoma lines derived from metastases in the small intestine, and 0 of 96 metastatic melanomas from other sites. In vitro migration and invasion studies done on CCR9(+) melanoma lines showed migration in response to CCL25 that was inhibited by anti-CCR9 antibody or by short interfering RNA CCR9. Flow cytometric analysis confirmed CCR9 expression by melanomas to the small intestine and showed concomitant alpha(4)beta(1) integrin expression.


CONCLUSIONS
Our findings show that functionally active CCR9 on melanoma cells facilitates metastasis to the small intestine. The CCR9-CCL25 axis may explain the high incidence of melanoma metastasis to this specific location.
Amersi
Farin F
FF
Department of Molecular Oncology, John Wayne Cancer Institute, Santa Monica, California 90404, USA.
Terando
Alicia M
AM
Goto
Yasufumi
Y
Scolyer
Richard A
RA
Thompson
John F
JF
Tran
Andy N
AN
Faries
Mark B
MB
Morton
Donald L
DL
Hoon
Dave S B
DS
D045744:Cell Line, Tumor; D019742:Chemokines, CC / Q000235:genetics*; D017931:DNA Primers; D005091:Exons; D005434:Flow Cytometry; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007414:Intestinal Neoplasms / Q000473:pathology / Q000556:secondary*; D008545:Melanoma / Q000235:genetics / Q000473:pathology*; D012334:RNA, Neoplasm / Q000235:genetics / Q000302:isolation & purification; D034741:RNA, Small Interfering / Q000235:genetics; D054388:Receptors, CCR / Q000235:genetics*; D012189:Retrospective Studies; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012878:Skin Neoplasms / Q000235:genetics / Q000473:pathology*
C119309:CC chemokine receptor 9; C108074:CCL25 protein, human; D019742:Chemokines, CC; D017931:DNA Primers; D012334:RNA, Neoplasm; D034741:RNA, Small Interfering; D054388:Receptors, CCR