MUC1-C dictates neuroendocrine lineage specification in pancreatic ductal adenocarcinomas.

Pancreatic ductal adenocarcinomas (PDAC) and poorly differentiated pancreatic neuroendocrine (NE) carcinomas are KRAS mutant malignancies with a potential common cell of origin. PDAC ductal, but not NE, lineage traits have been associated with cell-intrinsic activation of interferon (IFN) pathways. The present studies demonstrate that the MUC1 C-terminal subunit (MUC1-C), which evolved to protect mammalian epithelia from loss of homeostasis, is aberrantly overexpressed in KRAS mutant PDAC tumors and cell lines. We show that MUC1-C is necessary for activation of the type I and II IFN pathways and for expression of the Yamanaka OCT4, SOX2, KLF4 and MYC (OSKM) pluripotency factors. Our results demonstrate that MUC1-C integrates IFN signaling and pluripotency with NE dedifferentiation by forming a complex with MYC and driving the (i) achaete-scute homolog 1 and BRN2/POU3F2 neural, and (ii) NOTCH1/2 stemness transcription factors. Of translational relevance, targeting MUC1-C genetically and pharmacologically in PDAC cells (i) suppresses OSKM, NE dedifferentiation and NOTCH1/2, and (ii) inhibits self-renewal capacity and tumorigenicity. In PDAC tumors, we show that MUC1 significantly associates with activation of IFN signaling, MYC and NOTCH, and that upregulation of the MUC1-C → MYC pathway confers a poor prognosis. These findings indicate that MUC1-C dictates PDAC NE lineage specification and is a potential target for the treatment of recalcitrant pancreatic carcinomas with NE dedifferentiation.

Addiction of Cancer Stem Cells to MUC1-C in Triple-Negative Breast Cancer Progression.

Triple-negative breast cancer (TNBC) is an aggressive malignancy with limited treatment options. TNBC progression is associated with expansion of cancer stem cells (CSCs). Few insights are available regarding druggable targets that drive the TNBC CSC state. This review summarizes the literature on TNBC CSCs and the compelling evidence that they are addicted to the MUC1-C transmembrane protein. In normal epithelia, MUC1-C is activated by loss of homeostasis and induces reversible wound-healing responses of inflammation and repair. However, in settings of chronic inflammation, MUC1-C promotes carcinogenesis. MUC1-C induces EMT, epigenetic reprogramming and chromatin remodeling in TNBC CSCs, which are dependent on MUC1-C for self-renewal and tumorigenicity. MUC1-C-induced lineage plasticity in TNBC CSCs confers DNA damage resistance and immune evasion by chronic activation of inflammatory pathways and global changes in chromatin architecture. Of therapeutic significance, an antibody generated against the MUC1-C extracellular domain has been advanced in a clinical trial of anti-MUC1-C CAR T cells and in IND-enabling studies for development as an antibody-drug conjugate (ADC). Agents targeting the MUC1-C cytoplasmic domain have also entered the clinic and are undergoing further development as candidates for advancing TNBC treatment. Eliminating TNBC CSCs will be necessary for curing this recalcitrant cancer and MUC1-C represents a promising druggable target for achieving that goal.

The evolution of surgical treatment for gastrointestinal cancers.

INTRODUCTION: According to the latest Japanese nationwide estimates, over a million Japanese people are newly diagnosed with cancer each year. Since gastrointestinal cancers account for more than 40% of all cancer-related deaths, it is imperative to formulate effective strategies to control them. MATERIALS AND METHODS, AND RESULTS: Basic drug discovery research Our research has revealed that the abnormal expression of regulators of chromosomal stability is a cause of cancers and identified an effective compound against cancers with chromosomal instability. We revealed the molecular mechanism of peritoneal dissemination of cancer cells via the CXCR4/CXCL12 axis to CAR-like cells and identified an MEK inhibitor effective against these tumors. Residual tumor cells after chemotherapy in colorectal cancer are LGR5-positive cancer stem cells and their ability to eliminate reactive oxygen species is elevated. The development of surgical procedures and devices In cases of gastric tube reconstruction for esophageal cancer, we determined the anastomotic line for evaluating the blood flow using ICG angiography and measuring the tissue O2 metabolism. We established a novel gastric reconstruction method (book-binding technique) for gastric cancer and a new rectal reconstruction method focusing on the intra-intestinal pressure resistance for rectal cancer. We established a novel tissue fusion method, which allows contact-free local heating and retains tissue viability with very little damage, and developed an understanding of the collagen-related processes that underpin laser-induced tissue fusion. Strategy to prevent carcinogenesis We succeeded in cleaving hepatitis B virus DNA integrated into the nucleus of hepatocytes using genome editing tools. The development of HCC from non-alcoholic steatohepatitis (NASH) may be prevented by metabolic surgery. CONCLUSION: We believe that these efforts will help to significantly improve the gastrointestinal cancer treatment and survival.

Protein Expression of Programmed Death 1 Ligand 1 and HER2 in Gastric Carcinoma.

OBJECTIVES: Programmed death 1 (PD-1) is an immunoinhibitory receptor and has been identified as a new target for immunotherapy in cancer. Here we report the expression of PD-1 ligand 1 (PD-L1) in surgically resected gastric cancer. MATERIALS AND METHODS: We examined formalin-fixed tumor samples from 144 gastric cancer patients with a primary diagnosis of gastric carcinoma. Immunohistochemistry was used to detect PD-L1. Human epidermal growth factor receptor 2 (HER2) expression and phosphatase and tensin homolog (PTEN) loss of heterozygosity were investigated in these patients. RNA interference was used to downregulate HER2 expression, and PD-L1 protein expression was assessed by flow cytometry using the gastric cancer cell line MKN45. RESULTS: Overexpression of PD-L1 was significantly correlated with tumor invasion (p = 0.011) and associated with poor survival. The number of PD-L1-positive cases increased according to the HER2 score in clinical samples. siRNA-mediated downregulation of HER2 significantly decreased PD-L1 protein expression in MKN45 cells. CONCLUSIONS: PD-L1 expression was associated with poor survival of gastric cancer, and HER2 signaling affects the expression of PD-L1 in gastric cancer. In gastric cancer, PTEN and HER2 are potential candidate biomarkers for developing human antibodies that block PD-L1.

High expression of the Notch ligand Jagged-1 is associated with poor prognosis after surgery for colorectal cancer.

The importance of Notch signaling in colorectal cancer (CRC) carcinogenesis and progression has previously been presented. Increased expression of Jagged-1 (JAG1), a Notch ligand, in CRC has been revealed, but the detailed prognostic significance of JAG1 in CRC has not been determined. Protein expression of JAG1 was examined using immunohistochemistry in 158 CRC specimens. Expression of JAG1 and E-cadherin and their associations with clinicopathologic characteristics, overall survival (OS) and relapse-free survival (RFS) were evaluated. In vitro studies using compounds to regulate intracellular signaling and small interfering RNA to silence JAG1 were performed in a colon cancer cell line. JAG1 expression in cancerous tissues was weak, moderate or strong in 32%, 36% and 32% of specimens, respectively, and correlated with histologic type and T stage. In multivariate analysis, JAG1 expression, histologic type and lymphatic invasion independently correlated with OS and RFS. The combination of high JAG1 expression and low E-cadherin expression had an additive effect toward poorer OS and RFS compared with the low JAG1/high E-cadherin expression subtype. A significant correlation between JAG1 expression and KRAS status was detected in groups stratified as high E-cadherin expression. In vitro studies suggested that RAS-MEK-MAP kinase and the Wnt pathways positively regulated JAG1 expression. Gene silencing with siJAG1 indicated that JAG1 promotes the transition from epithelial to mesenchymal characteristics and cell growth. High expression of JAG1 is regulated by various pathways and is associated with poor prognosis through promoting the epithelial to mesenchymal transition and cell proliferation or maintaining cell survival in CRC.

Molecular mechanisms regulating the hormone sensitivity of breast cancer.

Breast cancer is a heterogeneous disease. Approximately 70% of breast cancers are estrogen receptor (ER) positive. Endocrine therapy has dramatically improved the prognosis of ER-positive breast cancer; however, many tumors exhibit de novo or acquired resistance to endocrine therapy. A thorough understanding of the molecular mechanisms regulating hormone sensitivity or resistance is important to improve the efficacy of and overcome the resistance to endocrine therapy. The growth factor receptor signaling pathways, particularly the phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) pathway can mediate resistance to all forms of endocrine therapy. In contrast, FOXA1 transcription factor is a key determinant of ER function and endocrine response. Intriguingly, a link between hormone resistance induced by the PI3K/Akt/mTOR pathway and the function of FOXA1 has been suggested. In this review, we focus on the PI3K/Akt/mTOR pathway and functions of FOXA1 in terms of the molecular mechanisms regulating the hormone sensitivity of breast cancer.

Technical improvement of total pharyngo-laryngo-esophagectomy for esophageal cancer and head and neck cancer.

PURPOSE: Total pharyngo-laryngo-esophagectomy (PLE) is highly invasive, and the subsequent reconstruction is difficult. The purpose of this study was to clarify the techniques that can decrease the surgical stress and allow for safe reconstruction after this operation. METHODS: The surgical method and clinical outcomes of total PLE were reviewed in 12 patients with either cervicothoracic esophageal cancer or double cancer of the esophagus and pharynx. Microscopic venous anastomosis was principally performed, and arterial anastomosis was added, if needed. RESULTS: A narrow gastric tube was used in ten patients, including two patients who underwent free jejunal interposition, while the colon was used as the main reconstructed organ in two other patients. Staged operations were performed in three high-risk patients. All six patients treated after 2010 were able to undergo thoracoscopic and/or laparoscopic surgery. No critical postoperative complications developed, although minor anastomotic leakage developed in two patients who were successfully treated conservatively. CONCLUSION: When performing PLE, it is important to decrease the surgical stress and ensure a reliable reconstruction by adopting techniques that are appropriate for each case, such as thoracoscopic and laparoscopic surgery, staged operations, microvascular anastomosis, and muscular flaps.

A case of invasive micropapillary carcinoma of the breast involving extensive lymph node metastasis.

We herein report a case of invasive micropapillary carcinoma (IMPC) involving extensive lymph node metastasis with no recurrence for over 7 years. A 41-year-old female presented with pain and a swelling mass in the left axillary region, which had been present for several months. The tumor measured 1.6 cm in diameter in the middle of upper area of the left breast. Based on the findings of a core needle biopsy the pathological diagnosis was IMPC or mucinous carcinoma. The cytology of the left axillary lymph node was positive for metastatic carcinoma. The patient underwent a left mastectomy and a left axillary dissection (level I to III). The postoperative pathological diagnosis was IMPC with mucin production, and the number of metastatic lymph nodes was 59. The patient was given adjuvant chemotherapy (four courses of 5-fluorouracil, epirubicin and cyclophosphamide (FEC) and four courses of docetaxel), radiation for the left chest wall, supraclavicular and internal thoracic area, and then received tamoxifen for 5 years. The patient has remained recurrence-free for over 7 years. IMPC is known to be an aggressive histological type associated with a high incidence of lymph node metastasis and a poor prognosis. It seems that long-term survival was obtained by performing sufficient medical treatment. Prognostic factors other than the number of lymph node metastases may also exist.

Luteinizing hormone-releasing hormone agonist plus an aromatase inhibitor as second-line endocrine therapy in premenopausal females with hormone receptor-positive metastatic breast cancer.

PURPOSE: The aim of the current study was to explore the efficacy and safety of combination therapy using a luteinizing hormone-releasing hormone (LHRH) agonist plus an aromatase inhibitor (AI) as second-line therapy in premenopausal females with hormone receptor (HR)-positive recurrent or metastatic breast cancer (MBC). METHODS: A retrospective analysis was conducted in patients registered in the breast cancer database of our institution between January 2001 and December 2012. The breast cancer database identified 14 premenopausal patients who had been treated with an LHRH agonist plus AI for HR-positive recurrent or MBC. RESULTS: Fourteen patients with recurrent breast cancer (N = 10) or metastatic disease at primary diagnosis (N = 4) were included in the present study. All patients had previously been treated with an LHRH agonist plus tamoxifen. The clinical benefit rate was 71.4% and the median TTP was 11 months (95% confidence interval 1.7-20.3 months). One patient discontinued treatment because of liver dysfunction (grade 3). CONCLUSIONS: The combination of an LHRH agonist plus an AI is a treatment option for premenopausal females with HR-positive MBC that can prolong the chemotherapy-free interval and yield effective disease stabilization.

Early discontinuation of adjuvant hormone therapy is associated with a poor prognosis in Japanese breast cancer patients.

PURPOSE: It is important for patients to complete the planned hormone therapy to reduce both the recurrence and mortality rates of hormone receptor-positive breast cancer. We investigated the rates and factors related to the early discontinuation of adjuvant hormone therapy at our institution. METHODS: We identified 145 females prescribed adjuvant hormone therapy who were followed up for longer than 5 years. The rate of completing the planned hormone therapy and factors related to early discontinuation were examined. The relapse-free survival rate was examined between the completion group and the discontinuation group. RESULTS: The completion rate was 90.6 %. The primary reason for discontinuing hormone therapy within 5 years was side effects, such as arthritic pain. The primary factor related to early discontinuation was a significantly younger age. The relapse-free survival rate was significantly lower in the discontinuation group (p = 0.025). CONCLUSIONS: More than 90 % of the patients completed the planned adjuvant hormone therapy, and early discontinuation was related to a shorter RFS. To improve the rate of the successful completion of adjuvant hormone therapy, it is important to provide supportive care to reduce the occurrence of side effects and to care for young females with a desire to become pregnant.

Surgical strategies for esophageal cancer associated with head and neck cancer.

Esophageal cancer is frequently associated with squamous cell carcinoma in the head and neck. Both cigarette smoking and alcohol consumption are risk factors for multiple cancers of the head and neck, as well as the esophagus. Routine screening and close follow-up for second cancers are important in patients with esophageal cancer or head and neck cancer. For this purpose, endoscopy with Lugol's staining, as well as narrow-band imaging combined with magnifying endoscopy, is a powerful tool for the early detection of esophageal cancer. Multimodal therapy is essential for patients with double cancers. When considering surgical treatment, the curability of both cancers must be carefully evaluated. If both tumors are potentially curable, each lesion should be treated individually. In patients with metachronous double cancers, the prior treatment of the first primary carcinoma often affects the treatment of the second cancer. Close cooperation among medical staff members is essential for complicated surgeries for double cancers. Techniques that are appropriate for each case must be adopted, such as careful dissection, staged operations, muscular flaps and microvascular anastomosis.

A novel system to provide information via online YouTube videos and an evaluation of current online information about hereditary breast cancer.

BACKGROUND: The internet, especially YouTube, has become a prominent source of health information. However, the quality and accuracy of medical content on YouTube vary, posing concerns about misinformation. This study focuses on providing reliable information about hereditary breast cancer on YouTube, given its importance for decision-making among patients and families. The study examines the quality and accessibility of such content in Japanese, where limited research has been conducted. METHODS: A nonprofit organization called BC Tube was established in May 2020 to create informative videos about breast cancer. The study analyzed 85 YouTube videos selected using the Japanese keywords "hereditary breast cancer" and "HBOC", categorized into six groups based on the source of upload: BC Tube, hospitals/governments, individual physicians, public-interest organizations/companies, breast cancer survivors, and others. The videos were evaluated based on various factors, including content length, view counts, likes, comments, and the presence of advertisements. The content was evaluated using the PEMAT and DISCERN quality criteria. RESULTS: BC Tube created high-quality videos with high scores on PEMAT understandability, significantly outperforming other sources. Videos from public-interest organizations/companies received the most views and likes, despite their lower quality. Videos from medical institutions and governments were of superior quality but attracted less attention. CONCLUSIONS: Our study emphasizes the importance of promoting accessible, easy-to-understand, and widely recognized medical information online. The popularity of videos does not always correspond to their quality, emphasizing the importance of quality evaluation. BC Tube provides a peer-reviewed platform to disseminate high-quality health information. We need to develop high-quality online health information and encourage the promotion of evidence-based information on YouTube.

MUC1-C is a target of salinomycin in inducing ferroptosis of cancer stem cells.

The oncogenic MUC1-C transmembrane protein is a critical effector of the cancer stem cell (CSC) state. Addiction to MUC1-C for self-renewal in the progression of human cancers has emphasized the need for development of anti-MUC1-C agents. However, there are presently no approved small molecules for targeting MUC1-C-dependent CSCs. In screening for small molecules, we identified salinomycin (SAL), an inducer of ferroptosis, as a potent inhibitor of MUC1-C signaling. We demonstrate that SAL suppresses MUC1-C expression by disrupting a NF-κB/MUC1-C auto-inductive circuit that is necessary for ferroptosis resistance. Our results show that SAL-induced MUC1-C suppression downregulates a MUC1-C→MYC pathway that activates genes encoding (i) glutathione-disulfide reductase (GSR), and (ii) the LDL receptor related protein 8 (LRP8), which inhibit ferroptosis by generating GSH and regulating selenium levels, respectively. GSR and LRP8 contribute to the function of glutathione peroxidase 4 (GPX4), an essential negative regulator of ferroptotic cell death. We demonstrate that targeting MUC1-C genetically or with the GO-203 peptide inhibitor suppresses GPX4 expression and GPX activity in association with the induction of ferroptosis. Studies of CSCs enriched by serial passage as tumorspheres further demonstrate that the effects of SAL are mediated by downregulation of MUC1-C and thereby overcoming resistance to ferroptosis. As confirmation of these results, rescue of MUC1-C downregulation with the MUC1-C cytoplasmic domain (i) reversed the suppression of GSR, LRP8 and GPX4 expression, and (ii) attenuated the induction of ferroptosis. These findings identify SAL as a unique small molecule inhibitor of MUC1-C signaling and demonstrate that MUC1-C is an important effector of resistance to ferroptosis.

MUC1-C Is a Common Driver of Acquired Osimertinib Resistance in NSCLC.

INTRODUCTION: Osimertinib is an irreversible EGFR tyrosine kinase inhibitor approved for the first-line treatment of patients with metastatic NSCLC harboring EGFR exon 19 deletions or L858R mutations. Patients treated with osimertinib invariably develop acquired resistance by mechanisms involving additional EGFR mutations, MET amplification, and other pathways. There is no known involvement of the oncogenic MUC1-C protein in acquired osimertinib resistance. METHODS: H1975/EGFR (L858R/T790M) and patient-derived NSCLC cells with acquired osimertinib resistance were investigated for MUC1-C dependence in studies of EGFR pathway activation, clonogenicity, and self-renewal capacity. RESULTS: We reveal that MUC1-C is up-regulated in H1975 osimertinib drug-tolerant persister cells and is necessary for activation of the EGFR pathway. H1975 cells selected for stable osimertinib resistance (H1975-OR) and MGH700-2D cells isolated from a patient with acquired osimertinib resistance are found to be dependent on MUC1-C for induction of (1) phospho (p)-EGFR, p-ERK, and p-AKT, (2) EMT, and (3) the resistant phenotype. We report that MUC1-C is also required for p-EGFR, p-ERK, and p-AKT activation and self-renewal capacity in acquired osimertinib-resistant (1) MET-amplified MGH170-1D #2 cells and (2) MGH121 Res#2/EGFR (T790M/C797S) cells. Importantly, targeting MUC1-C in these diverse models reverses osimertinib resistance. In support of these results, high MUC1 mRNA and MUC1-C protein expression is associated with a poor prognosis for patients with EGFR-mutant NSCLCs. CONCLUSIONS: Our findings reveal that MUC1-C is a common effector of osimertinib resistance and is a potential target for the treatment of osimertinib-resistant NSCLCs.

Identification of MUC1-C as a Target for Suppressing Progression of Head and Neck Squamous Cell Carcinomas.

The MUC1-C protein is aberrantly expressed in adenocarcinomas of epithelial barrier tissues and contributes to their progression. Less is known about involvement of MUC1-C in the pathogenesis of squamous cell carcinomas (SCC). Here, we report that the MUC1 gene is upregulated in advanced head and neck SCCs (HNSCC). Studies of HNSCC cell lines demonstrate that the MUC1-C subunit regulates expression of (i) RIG-I and MDA5 pattern recognition receptors, (ii) STAT1 and IFN regulatory factors, and (iii) downstream IFN-stimulated genes. MUC1-C integrates chronic activation of the STAT1 inflammatory pathway with induction of the ∆Np63 and SOX2 genes that are aberrantly expressed in HNSCCs. In extending those dependencies, we demonstrate that MUC1-C is necessary for NOTCH3 expression, self-renewal capacity, and tumorigenicity. The findings that MUC1 associates with ∆Np63, SOX2 and NOTCH3 expression by single-cell RNA sequencing analysis further indicate that MUC1-C drives the HNSCC stem cell state and is a target for suppressing HNSCC progression. SIGNIFICANCE: This work reports a previously unrecognized role for MUC1-C in driving STAT1-mediated chronic inflammation with the progression of HNSCC and identifies MUC1-C as a druggable target for advanced HNSCC treatment.

MUC1-C regulates NEAT1 lncRNA expression and paraspeckle formation in cancer progression.

The MUC1 gene evolved in mammals for adaptation of barrier tissues in response to infections and damage. Paraspeckles are nuclear bodies formed on the NEAT1 lncRNA in response to loss of homeostasis. There is no known intersection of MUC1 with NEAT1 or paraspeckles. Here, we demonstrate that the MUC1-C subunit plays an essential role in regulating NEAT1 expression. MUC1-C activates the NEAT1 gene with induction of the NEAT1_1 and NEAT1_2 isoforms by NF-κB- and MYC-mediated mechanisms. MUC1-C/MYC signaling also induces expression of the SFPQ, NONO and FUS RNA binding proteins (RBPs) that associate with NEAT1_2 and are necessary for paraspeckle formation. MUC1-C integrates activation of NEAT1 and RBP-encoding genes by recruiting the PBAF chromatin remodeling complex and increasing chromatin accessibility of their respective regulatory regions. We further demonstrate that MUC1-C and NEAT1 form an auto-inductive pathway that drives common sets of genes conferring responses to inflammation and loss of homeostasis. Of functional significance, we find that the MUC1-C/NEAT1 pathway is of importance for the cancer stem cell (CSC) state and anti-cancer drug resistance. These findings identify a previously unrecognized role for MUC1-C in the regulation of NEAT1, RBPs, and paraspeckles that has been co-opted in promoting cancer progression.

MUC1-C intersects chronic inflammation with epigenetic reprogramming by regulating the set1a compass complex in cancer progression.

Chronic inflammation promotes epigenetic reprogramming in cancer progression by pathways that remain unclear. The oncogenic MUC1-C protein is activated by the inflammatory NF-κB pathway in cancer cells. There is no known involvement of MUC1-C in regulation of the COMPASS family of H3K4 methyltransferases. We find that MUC1-C regulates (i) bulk H3K4 methylation levels, and (ii) the COMPASS SET1A/SETD1A and WDR5 genes by an NF-κB-mediated mechanism. The importance of MUC1-C in regulating the SET1A COMPASS complex is supported by the demonstration that MUC1-C and WDR5 drive expression of FOS, ATF3 and other AP-1 family members. In a feedforward loop, MUC1-C, WDR5 and AP-1 contribute to activation of genes encoding TRAF1, RELB and other effectors in the chronic NF-κB inflammatory response. We also show that MUC1-C, NF-κB, WDR5 and AP-1 are necessary for expression of the (i) KLF4 master regulator of the pluripotency network and (ii) NOTCH1 effector of stemness. In this way, MUC1-C/NF-κB complexes recruit SET1A/WDR5 and AP-1 to enhancer-like signatures in the KLF4 and NOTCH1 genes with increases in H3K4me3 levels, chromatin accessibility and transcription. These findings indicate that MUC1-C regulates the SET1A COMPASS complex and the induction of genes that integrate NF-κB-mediated chronic inflammation with cancer progression.

MUC1-C is necessary for SHP2 activation and BRAF inhibitor resistance in BRAF(V600E) mutant colorectal cancer.

Colorectal cancers (CRCs) harboring the BRAF(V600E) mutation are associated with aggressive disease and resistance to BRAF inhibitors by feedback activation of the receptor tyrosine kinase (RTK)→RAS→MAPK pathway. The oncogenic MUC1-C protein promotes progression of colitis to CRC; whereas there is no known involvement of MUC1-C in BRAF(V600E) CRCs. The present work demonstrates that MUC1 expression is significantly upregulated in BRAF(V600E) vs wild-type CRCs. We show that BRAF(V600E) CRC cells are dependent on MUC1-C for proliferation and BRAF inhibitor (BRAFi) resistance. Mechanistically, MUC1-C integrates induction of MYC in driving cell cycle progression with activation of the SHP2 phosphotyrosine phosphatase, which enhances RTK-mediated RAS→ERK signaling. We demonstrate that targeting MUC1-C genetically and pharmacologically suppresses (i) activation of MYC, (ii) induction of the NOTCH1 stemness factor, and (iii) the capacity for self-renewal. We also show that MUC1-C associates with SHP2 and is required for SHP2 activation in driving BRAFi-induced feedback of ERK signaling. In this way, targeting MUC1-C in BRAFi-resistant BRAF(V600E) CRC tumors inhibits growth and sensitizes to BRAF inhibition. These findings demonstrate that MUC1-C is a target for the treatment of BRAF(V600E) CRCs and for reversing their resistance to BRAF inhibitors by suppressing the feedback MAPK pathway.

MUC1-C is a master regulator of MICA/B NKG2D ligand and exosome secretion in human cancer cells.

BACKGROUND: The MUC1-C protein evolved in mammals to protect barrier tissues from loss of homeostasis; however, MUC1-C promotes oncogenesis in association with chronic inflammation. Aberrant expression of MUC1-C in cancers has been linked to depletion and dysfunction of T cells in the tumor microenvironment. In contrast, there is no known involvement of MUC1-C in the regulation of natural killer (NK) cell function. METHODS: Targeting MUC1-C genetically and pharmacologically in cancer cells was performed to assess effects on intracellular and cell surface expression of the MHC class I chain-related polypeptide A (MICA) and MICB ligands. The MICA/B promoters were analyzed for H3K27 and DNA methylation. Shedding of MICA/B was determined by ELISA. MUC1-C interactions with ERp5 and RAB27A were assessed by coimmunoprecipitation and direct binding studies. Exosomes were isolated for analysis of secretion. Purified NK cells were assayed for killing of cancer cell targets. RESULTS: Our studies demonstrate that MUC1-C represses expression of the MICA and MICB ligands that activate the NK group 2D receptor. We show that the inflammatory MUC1-C→NF-κB pathway drives enhancer of zeste homolog 2-mediated and DNMT-mediated methylation of the MICA and MICB promoter regions. Targeting MUC1-C genetically and pharmacologically with the GO-203 inhibitor induced intracellular and cell surface MICA/B expression but not MICA/B cleavage. Mechanistically, MUC1-C regulates the ERp5 thiol oxidoreductase that is necessary for MICA/B protease digestion and shedding. In addition, MUC1-C interacts with the RAB27A protein, which is required for exosome formation and secretion. As a result, targeting MUC1-C markedly inhibited secretion of exosomes expressing MICA/B. In concert with these results, we show that targeting MUC1-C promotes NK cell-mediated killing. CONCLUSIONS: These findings uncover pleotropic mechanisms by which MUC1-C confers evasion of cancer cells to NK cell recognition and destruction.

MUC1-C integrates aerobic glycolysis with suppression of oxidative phosphorylation in triple-negative breast cancer stem cells.

Activation of the MUC1-C protein promotes lineage plasticity, epigenetic reprogramming, and the cancer stem cell (CSC) state. The present studies performed on enriched populations of triple-negative breast cancer (TNBC) CSCs demonstrate that MUC1-C is essential for integrating activation of glycolytic pathway genes with self-renewal and tumorigenicity. MUC1-C further integrates the glycolytic pathway with suppression of mitochondrial DNA (mtDNA) genes encoding components of mitochondrial Complexes I-V. The repression of mtDNA genes is explained by MUC1-C-mediated (i) downregulation of the mitochondrial transcription factor A (TFAM) required for mtDNA transcription and (ii) induction of the mitochondrial transcription termination factor 3 (mTERF3). In support of pathogenesis that suppresses mitochondrial ROS production, targeting MUC1-C increases (i) mtDNA gene transcription, (ii) superoxide levels, and (iii) loss of self-renewal capacity. These findings and scRNA-seq analysis of CSC subpopulations indicate that MUC1-C regulates self-renewal and redox balance by integrating activation of glycolysis with suppression of oxidative phosphorylation.