Extended Data Fig. 4 |. L1CAM is dispensable for adenoma formation but required for orthotopic tumour engraftment, local expansion, metastasis and chemoresistance.

Representative sections of colons from APC^ΔIEC and L1CAM/APC^ΔIEC mice stained with hematoxylin & eosin, and antibodies against Ki67, L1CAM or E-cadherin, showing no histopathological differences between the two groups. Representative of 5 mice in each group. (b–g) L1CAM inhibition impairs local tumour expansion and metastasis from murine orthotopic caecal transplants. b, Relative L1cam mRNA expression (mean ± s.e.m) in murine AKP organoids stably transduced with lentivirus directing the expression of doxycycline-inducible shRNA targeting L1cam or control, and treated with or without doxycycline for 48 h. Data were normalized to Gapdh mRNA expression levels. n = 4 organoid cultures, two-sided Student’s t test. c, Dissociated cells derived from AKP organoids transduced with lentivirus directing the expression of tdTomato-luciferase and shRNA against L1cam or control were injected into the caecal submucosa. Mice were monitored until caecal tumours were evident by ex vivo BLI imaging 3 weeks following injection, randomized based on BLI signal, and maintained on or off doxycycline diet for 5 weeks prior to euthanasia. Representative of 7 (−Dox), 13 mice (+Dox). (d–g) Quantification of whole animal or ex vivo BLI signal in each indicated organ per group, normalized to BLI at the time of randomization, is shown. Boxplot, boxes show 25^th–75^th percentile with median, whiskers show min to max, n = 12, 7, 7, 13 mice per group (left to right), two-sided Mann-Whitney U test. h, L1CAM immunohistochemistry in sections of orthotopic rectal xenografts (representative of 3 animals analysed per group) or i, liver metastases (representative of 3 animals analysed per group) from mice injected with cells derived from MSK107Li organoids expressing doxycycline-inducible shRNA targeting L1CAM. Mice were maintained on or off doxycycline (dox) diet as indicated. j, Representative (n = 8 (−Dox), n = 9 (+Dox)) ex vivo liver bioluminescence images related to i. k, Representative (n = 12 (−Dox, n = 11 (+Dox)) bioluminescent images of orthotopic caecal xenografts, liver and lung metastases derived from MSK121Li organoids expressing doxycycline-inducible shRNA targeting L1CAM, and randomized to treatment with or without doxycycline. (l, m) L1CAM immunohistochemistry in sections of subcutaneous xenograft tumours derived from MSK107Li organoids expressing doxycycline-inducible shRNA targeting L1CAM. Mice were treated with doxycycline diet and/or irinotecan chemotherapy as indicated. Mean ± s.e.m, n = 22, 15, 21, 19, 18, 23, 25, 21 fields from 3 mice per group (left to right), two-sided Mann-Whitney U test.