Therapeutic and prognostic implications of NOTCH and MAPK signaling in bladder cancer.

Signaling pathways that drive bladder cancer (BC) progression may be promising and specific targets for systemic therapy. Here, we investigated the clinical significance and targetability of NOTCH and mitogen-activated protein kinase (MAPK) signaling for this aggressive malignancy. We assessed NOTCH1 and MAPK activity in 222 stage III and IV BC specimens of patients that had undergone radical cystectomy, and tested for clinical associations including cancer-specific and overall survival. We examined therapeutic effects of NOTCH and MAPK repression in a murine xenograft model of human bladder cancer cells and evaluated tumor growth and tumor cell plasticity. In BC, NOTCH1 and MAPK signaling marked two distinct tumor cell subpopulations. The combination of high NOTCH1 and high MAPK activity indicated poor cancer-specific and overall survival in univariate and multivariate analyses. Inhibition of NOTCH and MAPK in BC xenografts in vivo depleted targeted tumor cell subpopulations and revealed strong plasticity in signaling pathway activity. Combinatorial inhibition of NOTCH and MAPK signaling most strongly suppressed tumor growth. Our findings indicate that tumor cell subpopulations with high NOTCH and MAPK activity both contribute to tumor progression. Furthermore, we propose a new concept for BC therapy, which advocates specific and simultaneous targeting of these different tumor cell subpopulations through combined NOTCH and MAPK inhibition.

In vivo effects of chemotherapy on oncogenic pathways in colorectal cancer.

Patients with advanced colorectal cancer often are treated with systemic cytotoxic therapy using fluorouracil (5-FU), oxaliplatin, irinotecan, and FOLFOX or FOLFIRI combination protocols. Additionally, signaling pathways that are active in colorectal cancer can be therapeutically targeted. Herein, we examined whether chemotherapy impacts on WNT, MAPK and NOTCH signaling pathways in xenograft models of colon cancer. Furthermore, we tested whether combining chemotherapy with MAPK and NOTCH inhibition has superior therapeutic effects. We show that colon cancer cells with high WNT, MAPK and NOTCH activity are variably affected but generally persist in xenograft tumors under different chemotherapeutic regimens, indicating limited effects of cytotoxic therapy on oncogenic signaling pathways. Although these results provided a rationale to additionally target pathway activity, we found no significant increase in therapy response when combining MAPK and NOTCH inhibition with fluorouracil chemotherapy. We attribute this finding to a decrease in tumor cell proliferation upon MAPK and NOTCH inhibition, resulting in reduced effectiveness of cytotoxic treatment. Therapeutic benefits of combining chemotherapy with targeting of oncogenic signaling pathways must therefore be critically evaluated for patients with colorectal cancer.

PBX3 Is Part of an EMT Regulatory Network and Indicates Poor Outcome in Colorectal Cancer.

Purpose: Colorectal cancers are composed of phenotypically different tumor cell subpopulations within the same core genetic background. Here, we identify high expression of the TALE transcription factor PBX3 in tumor cells undergoing epithelial-mesenchymal transition (EMT), analyze PBX3 regulation, and determine clinical associations in colorectal cancer.Experimental design: We used transcriptomic and in situ analyses to identify PBX3 expression in colorectal cancer and cell biology approaches to determine its regulation and function. Clinical associations were analyzed in independent tissue collections and gene expression datasets of colorectal cancers with recorded follow-up data.Results: PBX3 was expressed in tumor cells with high WNT activity undergoing EMT at the leading tumor edge of colorectal cancers, whereas stromal cells were PBX3 negative. PBX3 expression was induced by WNT activation and by the EMT transcription factors SNAIL and ZEB1, whereas these effects were mediated indirectly through microRNA miR-200. PBX3 was required for a full EMT phenotype in colon cancer cells. On the protein level, PBX3 expression indicated poor cancer-specific and disease-free survival in a cohort of 244 UICC stage II colorectal cancers, and was associated with metastasis in a case-control collection consisting of 90 cases with or without distant metastasis. On the mRNA level, high PBX3 expression was strongly linked to poor disease-free survival.Conclusions: PBX3 is a novel indicator of EMT in colorectal cancer, part of an EMT regulatory network, and a promising prognostic predictor that may aid in therapeutic decision making for patients with colorectal cancer. Clin Cancer Res; 24(8); 1974-86. ©2018 AACR.

Targeting tumor cell plasticity by combined inhibition of NOTCH and MAPK signaling in colon cancer.

In colorectal cancer, signaling pathways driving tumor progression are promising targets for systemic therapy. Besides WNT and MAPK signaling, activation of NOTCH signaling is found in most tumors. Here, we demonstrate that high NOTCH activity marks a distinct colon cancer cell subpopulation with low levels of WNT and MAPK activity and with a pronounced epithelial phenotype. Therapeutic targeting of MAPK signaling had limited effects on tumor growth and caused expansion of tumor cells with high NOTCH activity, whereas upon targeting NOTCH signaling, tumor cells with high MAPK activity prevailed. Lineage-tracing experiments indicated high plasticity between both tumor cell subpopulations as a mechanism for treatment resistance. Combined targeting of NOTCH and MAPK had superior therapeutic effects on colon cancer growth in vivo. These data demonstrate that tumor cells may evade systemic therapy through tumor cell plasticity and provide a new rationale for simultaneous targeting of different colon cancer cell subpopulations.

Oncogenic Effects of High MAPK Activity in Colorectal Cancer Mark Progenitor Cells and Persist Irrespective of RAS Mutations.

About 40% of colorectal cancers have mutations in KRAS accompanied by downstream activation of MAPK signaling, which promotes tumor invasion and progression. Here, we report that MAPK signaling shows strong intratumoral heterogeneity and unexpectedly remains regulated in colorectal cancer irrespective of KRAS mutation status. Using primary colorectal cancer tissues, xenograft models, and MAPK reporter constructs, we showed that tumor cells with high MAPK activity resided specifically at the leading tumor edge, ceased to proliferate, underwent epithelial-mesenchymal transition (EMT), and expressed markers related to colon cancer stem cells. In KRAS-mutant colon cancer, regulation of MAPK signaling was preserved through remaining wild-type RAS isoforms. Moreover, using a lineage tracing strategy, we provide evidence that high MAPK activity marked a progenitor cell compartment of growth-fueling colon cancer cells in vivo Our results imply that differential MAPK signaling balances EMT, cancer stem cell potential, and tumor growth in colorectal cancer. Cancer Res; 77(7); 1763-74. ©2017 AACR.

Multicolor lineage tracing reveals clonal architecture and dynamics in colon cancer.

Colon cancers are composed of phenotypically heterogeneous tumor cell subpopulations with variable expression of putative stem cell and differentiation antigens. While in normal colonic mucosa, clonal repopulation occurs along differentiation gradients from crypt base toward crypt apex, the clonal architecture of colon cancer and the relevance of tumor cell subpopulations for clonal outgrowth are poorly understood. Using a multicolor lineage tracing approach in colon cancer xenografts that reflect primary colon cancer architecture, we here demonstrate that clonal outgrowth is mainly driven by tumor cells located at the leading tumor edge with clonal axis formation toward the tumor center. While our findings are compatible with lineage outgrowth in a cancer stem cell model, they suggest that in colorectal cancer tumor cell position may be more important for clonal outgrowth than tumor cell phenotype.

ADNP Is a Therapeutically Inducible Repressor of WNT Signaling in Colorectal Cancer.

Purpose: Constitutively active WNT signaling is a hallmark of colorectal cancers and a driver of malignant tumor progression. Therapeutic targeting of WNT signaling is difficult due to high pathway complexity and its role in tissue homeostasis. Here, we identify the transcription factor ADNP as a pharmacologically inducible repressor of WNT signaling in colon cancer.Experimental Design: We used transcriptomic, proteomic, and in situ analyses to identify ADNP expression in colorectal cancer and cell biology approaches to determine its function. We induced ADNP expression in colon cancer xenografts by low-dose ketamine in vivo Clinical associations were determined in a cohort of 221 human colorectal cancer cases.Results: ADNP was overexpressed in colon cancer cells with high WNT activity, where it acted as a WNT repressor. Silencing ADNP expression increased migration, invasion, and proliferation of colon cancer cells and accelerated tumor growth in xenografts in vivo Treatment with subnarcotic doses of ketamine induced ADNP expression, significantly inhibited tumor growth, and prolonged survival of tumor-bearing animals. In human patients with colon cancer, high ADNP expression was linked to good prognosis.Conclusions: Our findings indicate that ADNP is a tumor suppressor and promising prognostic marker, and that ketamine treatment with ADNP induction is a potential therapeutic approach that may add benefit to current treatment protocols for patients with colorectal cancer. Clin Cancer Res; 23(11); 2769-80. ©2016 AACR.

CYB5R1 links epithelial-mesenchymal transition and poor prognosis in colorectal cancer.

Colorectal cancers show significant tumor cell heterogeneity within the same core genetic background. Epithelial-mesenchymal transition (EMT) is an important functional aspect of this heterogeneity and hallmark of colorectal cancer progression. Here, we identify CYB5R1, an enzyme involved in oxidative stress protection and drug metabolism, as an indicator of EMT in colon cancer. We demonstrate high CYB5R1 expression in colorectal cancer cells undergoing EMT at the infiltrative tumor edge and reveal an extraordinarily strong association of CYB5R1 expression with two core EMT gene expression signatures in a large independent colon cancer data set from The Cancer Genome Atlas (TCGA). Furthermore, we demonstrate that CYB5R1 is required for an infiltrative tumor cell phenotype, and robustly linked with poor prognosis in colorectal cancer. Our findings have important implications for colon cancer cells undergoing EMT and may be exploited for diagnostic and therapeutic purposes.