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Current therapy against colorectal cancer (CRC) is based on DNA-damaging agents that remain ineffective in a proportion of patients. Whether and how non-curative DNA damage-based treatment affects tumor cell behavior and patient outcome is primarily unstudied. Using CRC patient-derived organoids (PDO)s, we show that sublethal doses of chemotherapy (CT) does not select previously resistant tumor populations but induces a quiescent state specifically to TP53 wildtype (WT) cancer cells, which is linked to the acquisition of a YAP1-dependent fetal phenotype. Cells displaying this phenotype exhibit high tumor-initiating and metastatic activity. Nuclear YAP1 and fetal traits are present in a proportion of tumors at diagnosis and predict poor prognosis in patients carrying TP53 WT CRC tumors. We provide data indicating the higher efficacy of CT together with YAP1 inhibitors for eradication of therapy resistant TP53 WT cancer cells. Together these results identify fetal conversion as a useful biomarker for patient prognosis and therapy prescription. The failure of chemotherapy in colorectal cancer is currently unclear. Here, the authors show that upon sub-lethal dose of chemotherapy wild-type p53 colorectal cancers acquire a quiescence-like phenotype and a YAP-dependent fetal-like intestinal stem cell state associated with a higher metastatic activity and poor prognosis in patients.

Selective KRAS G12C inhibitors have been developed to covalently lock the oncogene in the inactive GDP-bound state. Two of these molecules, sotorasib and adagrasib, are approved for the treatment of adult patients with KRAS G12C -mutated previously treated advanced non-small cell lung cancer. Drug treatment imposes selective pressures leading to the outgrowth of drug-resistant variants. Mass sequencing from patients’ biopsies identified a number of acquired KRAS mutations -both in cis and in trans - in resistant tumors. We demonstrate here that disease progression in vivo can also occur due to adaptive mechanisms and increased KRAS-GTP loading. Using the preclinical tool tri-complex KRAS G12C -selective covalent inhibitor, RMC-4998 (also known as RM-029), that targets the active GTP-bound (ON) state of the oncogene, we provide a proof-of-concept that the clinical stage KRAS G12C (ON) inhibitor RMC-6291 alone or in combination with KRAS G12C (OFF) drugs can be an alternative potential therapeutic strategy to circumvent resistance due to increased KRAS-GTP loading. KRAS G12C mutant selective inhibitors targeting inactive state have been approved for use in non-small cell lung cancer (NSCLC). Here, using models derived from a patient with NSCLC who progressed on sotorasib (KRAS G12C inhibitor), the authors identify increased KRAS GTP loading as an adaptive resistance mechanism which could be targeted with KRAS G12C inhibitors selective to the GTP active state.

Maintenance of pluripotency is a multifactorial process in which NF-κB is a negative regulator. Our previous work identified a chromatin role for IκBα, the master regulator of NF-κB signaling, that is critical for the proper regulation of various tissue stem cells. Here, we found that IκBα accumulates specifically in the chromatin fraction of mouse pluripotent stem cells. IκBα depletion does not affect NF-kB-dependent transcription, but causes a profound epigenetic rewiring in pluripotent stem cells, including alterations in H3K27me3, a histone mark catalyzed by Polycomb repression complex 2. Chromatin changes induced by IκBα depletion affect a subset of pluripotency genes and are associated with altered gene transcription. At the cellular level, IκBα-deficient embryonic stem cells are arrested in a naive pluripotency state when cultured in serum/LIF conditions and fail to exit pluripotency under differentiation conditions. By constructing separation-of-function mutants, we show that the effects of IκBα in regulating stem cell pluripotency are NF-κB-independent, but mainly rely on its chromatin-related function. Taken together, our results reveal a novel mechanism by which IκBα participates in the regulation of the pluripotent state of mouse embryonic stem cells and shed light on the interplay between inflammatory signals and the regulation of pluripotency.

Colorectal cancer (CRC) frequently develops aggressive metastatic disease, yet the cellular features that enable dissemination remain poorly defined. IKKα, a kinase traditionally linked to stress and inflammatory signaling, is increasingly recognized for broader functions in cancer. Here, we show that loss of IKKα unexpectedly promotes metastasis in CRC. Using patient-derived organoids, we find that genetic or pharmacological inhibition of IKKα stabilizes tight-junction components, leading to the emergence of compact epithelial clusters with a heightened ability to spread and colonize the liver. Single-cell transcriptomics reveals expansion of a CDH17⁺/CLDN2⁺ epithelial subpopulation that dominates metastatic lesions, a finding validated by tissue staining. Remarkably, disrupting CLDN2 completely eliminates the metastatic advantage caused by IKKα loss. These results identify a metastasis-competent epithelial state driven by tight-junction remodeling and uncover a vulnerable node that may be exploited therapeutically in aggressive colorectal cancer.

Maintenance of pluripotency is a multifactorial process in which NF-κB is a negative regulator. Our previous work identified a chromatin role for IκBα, the master regulator of NF-κB signaling, that is critical for the proper regulation of various tissue stem cells. Here, we found that IκBα accumulates specifically in the chromatin fraction of mouse pluripotent stem cells. IκBα depletion does not affect NF-kB-dependent transcription, but causes a profound epigenetic rewiring in pluripotent stem cells, including alterations in H3K27me3, a histone mark catalyzed by Polycomb repression complex 2. Chromatin changes induced by IκBα depletion affect a subset of pluripotency genes and are associated with altered gene transcription. At the cellular level, IκBα-deficient embryonic stem cells are arrested in a naive pluripotency state when cultured in serum/LIF conditions and fail to exit pluripotency under differentiation conditions. By constructing separation-of-function mutants, we show that the effects of IκBα in regulating stem cell pluripotency are NF-κB-independent, but mainly rely on its chromatin-related function. Taken together, our results reveal a novel mechanism by which IκBα participates in the regulation of the pluripotent state of mouse embryonic stem cells and shed light on the interplay between inflammatory signals and the regulation of pluripotency.

Maintenance of pluripotency is a multifactorial process in which NF-κB is a negative regulator. Our previous work identified a chromatin role for IκBα, the master regulator of NF-κB signaling, that is critical for the proper regulation of various tissue stem cells. Here, we found that IκBα accumulates specifically in the chromatin fraction of pluripotent embryonic stem cells. IκBα depletion does not affect NF-kB-dependent transcription, but causes a profound epigenetic rewiring in pluripotent stem cells, including alterations in H3K27me3, a histone mark catalyzed by Polycomb repression complex 2. Chromatin changes induced by IκBα depletion affect a subset of pluripotency genes and are associated with altered gene transcription. At the cellular level, IκBα-deficient embryonic stem cells are arrested in a naive pluripotency state when cultured in serum/LIF conditions and fail to exit pluripotency under differentiation conditions. By constructing separation-of-function mutants, we show that the effects of IκBα in regulating stem cell pluripotency are NF-κB-independent, but mainly rely on its chromatin-related function. Taken together, our results reveal a novel mechanism by which IκBα participates in the regulation of the pluripotent state of embryonic stem cells and shed light on the interplay between inflammatory signals and the regulation of pluripotency.

We previously demonstrated that the NF-κB inhibitor IκBα binds the chromatin together with PRC2 to regulate a subset of developmental- and stem cell-related genes. This alternative function has been elusive in both physiological and disease conditions because of the predominant role of IκBα as a negative regulator of NF-κB. We here uniquely characterize specific residues of IκBα that allow the generation of separation-of-function (SOF) mutants that are defective for either NF-κB-related (SOFΔNF-κB) or chromatin-related (SOFΔH2A,H4) activities. Expression of IκBα SOFΔNF-κB, but not SOFΔH2A/H4, is sufficient to negatively regulate a specific stemness program in intestinal cells, thus rescuing the differentiation blockage imposed by IκBα deficiency. In contrast, full IκBα activity is required for regulating clonogenic/tumor-initiating activity of colorectal cancer cells. Our data indicate that SOF mutants represent an exclusive tool for studying IκBα functions in physiology and disease, and identified IκBα as a robust prognosis biomarker for human cancer.

Activation of the IKK kinase complex has recurrently been linked to colorectal cancer (CRC) initiation and progression. However, identification of downstream effectors other than NF-κB has remained elusive. Analysis of IKK-dependent substrates after UV-treatment revealed that BRD4 phosphorylation by IKKα is required for chromatin-binding dynamics upon damage. Moreover, IKKα induces the NF-κB-dependent transcription of LIF leading to STAT3 activation, association of BRD4 to STAT3 and recruitment to specific target genes. IKKα abrogation results in defective BRD4 and STAT3 function leading to irreparable DNA damage and apoptotic cell death upon different stimuli. Simultaneous inhibition of BRAF-dependent IKKα activity or BRD4 and the JAK/STAT pathway enhanced the therapeutic potential of 5-FU plus irinotecan in CRC cells, and is curative in a chemotherapy-resistant CRC xenograft model. Coordinated expression of LIF and IKKα is a poor prognosis marker for CRC patients. Our data uncover a functional link between IKKα, BRD4 and JAK/STAT signaling with clinical relevance.

ABSTRACT IκBs exert a principal function as cytoplasmic inhibitors of the NF-kB transcription factors. Additional functions for IκB homologues have been described including association to chromatin and transcriptional regulatioin. Phosphorylated and SUMOylated IκBα (pS-IκBα) binds histones H2A and H4 in the stem and progenitor compartment of skin and intestine, but the mechanisms controlling its recruitment to chromatin are largely unstudied. We here show that serine 32-36 phosphorylation of IκBα favors its binding with nucleosomes and demonstrated that p-IκBα association to H4 is favored by acetylation at specific H4 lysine residues. N-terminal tail of H4 is lost during intestinal cell differentiation by proteolytic cleavage at residues 17-19 imposed ny trypsin or chymotrypsin, which interferes p-IκBα binding. Paradoxically, inhibition of trypsin and chymotrypsin activity in HT29 cells increased p-IκBα chromatin binding and impaired goblet cell differentiation, comparable to IκBα deletion. Together our results indicate that dynamic binding of IκBα to chromatin is a requirement for intestinal cell differentiation and provide a molecular base for the restricted nuclear distribution of p-IκBα at specific stem cell compartments.

Cancer homeostasis depends on a balance between activated oncogenic pathways driving tumorigenesis and engagement of stress-response programs that counteract the inherent toxicity of such aberrant signaling. While inhibition of oncogenic signaling pathways has been explored extensively, there is increasing evidence that overactivation of the same pathways can also disrupt cancer homeostasis and cause lethality. We show here that inhibition of Protein Phosphatase 2A (PP2A) hyperactivates multiple oncogenic pathways and engages stress responses in colon cancer cells. Genetic and compound screens identify combined inhibition of PP2A and WEE1 as synergistic in multiple cancer models by collapsing DNA replication and triggering premature mitosis followed by cell death. This combination also suppressed the growth of patient-derived tumors in vivo. Remarkably, acquired resistance to this drug combination suppressed the ability of colon cancer cells to form tumors in vivo. Our data suggest that paradoxical activation of oncogenic signaling can result in tumor suppressive resistance.Competing Interest StatementR.B., J.K. and M.H.D are listed as inventors of a patent describing the drug combinations discovered here. R.B. is a member of the board of directors of Lixte Biotechnology. R.B and M.H.D. are shareholders of Lixte Biotechnology. J.K. is employee of Lixte and shareholder in the company. This work was supported in part by a research grant for Lixte Biotechnology. A.V. and A.Vil. are co-founders of Xenopat S.L.