Huei-Chi Wen

ERK1/2 and p38α/β Signaling in Tumor Cell Quiescence: Opportunities to Control Dormant Residual Disease

Systemic minimal residual disease after primary tumor treatment can remain asymptomatic for decades. This is thought to be due to the presence of dormant disseminated tumor cells (DTC) or micrometastases in different organs. DTCs lodged in brain, lungs, livers, and/or bone are a major clinical problem because they are the founders of metastasis, which ultimately kill cancer patients. The problem is further aggravated by our lack of understanding of DTC biology. In consequence, there are almost no rational therapies to prevent dormant DTCs from surviving and expanding. Several cancers, including melanoma as well as breast, prostate, and colorectal carcinomas, undergo dormant periods before metastatic recurrences develop. Here we review our experience in studying the cross-talk between ERK1/2 and p38α/β signaling in models of early cancer progression, dissemination, and DTC dormancy. We also provide some potential translational and clinical applications of these findings and describe how some currently used therapies might be useful to control dormant disease. Finally, we draw caution on the use of p38 inhibitors currently in clinical trials for different diseases as these may accelerate metastasis development. Clin Cancer Res; 17(18); 5850–7. ©2011 AACR.

p38α Signaling Induces Anoikis and Lumen Formation During Mammary Morphogenesis

The kinase p38α may suppress breast cancer by promoting formation of the proper architecture of mammary glands. Illuminating Lumen Formation The normal architecture of the mammary gland, which contains ductal and acinar structures in which polarized epithelial cells surround a hollow lumen, is disrupted in early neoplastic lesions, such as ductal carcinoma in situ (DCIS). Loss of signaling through the protein kinase p38 can promote breast cancer progression, but exactly where and how p38 inhibits tumor formation has been unclear. Wen et al. used three-dimensional cultures of mammary epithelial cells to explore the role of p38 in lumen formation, which depends on the death of cells that have become detached from the basement membrane, and found that it depended on opposing signals mediated by p38 and extracellular signal–regulated kinase. Cell detachment stimulated p38 signaling, leading to an increase in the abundance of the death-promoting protein BimEL and, thereby, luminal cell death. Moreover, p38 inhibition accelerated the development of DCIS-like lesions in a mouse model of breast cancer. The authors thus conclude that p38 is crucial to lumen formation during mammary gland development and may act at this stage to inhibit tumorigenesis. The stress-activated protein kinase (SAPK) p38 can induce apoptosis, and its inhibition facilitates mammary tumorigenesis. We found that during mammary acinar morphogenesis in MCF-10A cells grown in three-dimensional culture, detachment of luminal cells from the basement membrane stimulated mitogen-activated protein kinase (MAPK) kinases 3 and 6 (MKK3/6) and p38α signaling to promote anoikis. p38α signaling increased transcription of the death-promoting protein BimEL by phosphorylating the activating transcription factor 2 (ATF-2) and increasing c-Jun protein abundance, leading to cell death by anoikis and acinar lumen formation. Inhibition of p38α or ATF-2 caused luminal filling reminiscent of that observed in ductal carcinoma in situ (DCIS). The mammary glands of MKK3/6 knockout mice (MKK3−/−/MKK6+/− ) showed accelerated branching morphogenesis relative to those of wild-type mice, as well as ductal lumen occlusion due to reduced anoikis. This phenotype was recapitulated by systemic pharmacological inhibition of p38α and β (p38α/β) in wild-type mice. Moreover, the development of DCIS-like lesions showing marked ductal occlusion was accelerated in MMTV-Neu transgenic mice treated with inhibitors of p38α and p38β. We conclude that p38α is crucial for the development of hollow ducts during mammary gland development, a function that may be crucial to its ability to suppress breast cancer.

Analysis of Marker-Defined HNSCC Subpopulations Reveals a Dynamic Regulation of Tumor Initiating Properties

Head and neck squamous carcinoma (HNSCC) tumors carry dismal long-term prognosis and the role of tumor initiating cells (TICs) in this cancer is unclear. We investigated in HNSCC xenografts whether specific tumor subpopulations contributed to tumor growth. We used a CFSE-based label retentions assay, CD49f (α6-integrin) surface levels and aldehyde dehydrogenase (ALDH) activity to profile HNSCC subpopulations. The tumorigenic potential of marker-positive and -negative subpopulations was tested in nude (Balb/c nu/nu) and NSG (NOD.Cg-Prkdcscid Il2rgtm1Wjl/SzJ) mice and chicken embryo chorioallantoic membrane (CAM) assays. Here we identified in HEp3, SQ20b and FaDu HNSCC xenografts a subpopulation of G0/G1-arrested slow-cycling CD49fhigh/ALDH1A1high/H3K4/K27me3low subpopulation (CD49f+) of tumor cells. A strikingly similar CD49fhigh/H3K27me3low subpopulation is also present in primary human HNSCC tumors and metastases. While only sorted CD49fhigh/ALDHhigh, label retaining cells (LRC) proliferated immediately in vivo, with time the CD49flow/ALDHlow, non-LRC (NLRC) tumor cell subpopulations were also able to regain tumorigenic capacity; this was linked to restoration of CD49fhigh/ALDHhigh, label retaining cells. In addition, CD49f is required for HEp3 cell tumorigenicity and to maintain low levels of H3K4/K27me3. CD49f+ cells also displayed reduced expression of the histone-lysine N-methyltransferase EZH2 and ERK1/2phosphorylation. This suggests that although transiently quiescent, their unique chromatin structure is poised for rapid transcriptional activation. CD49f− cells can “reprogram” and also achieve this state eventually. We propose that in HNSCC tumors, epigenetic mechanisms likely driven by CD49f signaling dynamically regulate HNSCC xenograft phenotypic heterogeneity. This allows multiple tumor cell subpopulations to drive tumor growth suggesting that their dynamic nature renders them a “moving target” and their eradication might require more persistent strategies.

Stress signaling and the shaping of the mammary tissue in development and cancer

The postnatal mammary gland develops extensively through cycles of proliferation, branching, involution and remodeling. We review recent advances made in the field of stress signaling pathways and its roles in mammary gland organogenesis, how they contribute to normal organ specification and homeostasis and how its subversion by oncogenes leads to cancer. We analyze stress signaling in mammary gland biology taking into account the interrelationship with the extracellular matrix and adhesion signaling during morphogenesis. By integrating the information gathered from in vivo and three dimensional in vitro organogenesis studies, we review the novel contribution of p38SAPK, c-Jun NH2-terminal kinase and PKR-like endoplasmic reticulum kinase (PERK) signaling pathways to the timely activation of cell death, correct establishment of polarity and growth arrest and autophagy, respectively. We also review the evidence supporting that the activation of the aforementioned stress kinases maintain breast acinar structures as part of a tumor suppressive program and that its deregulation is commonplace during breast cancer initiation.

The atopic dermatitis blood signature is characterized by increases in inflammatory and cardiovascular risk proteins

Beyond classic “allergic”/atopic comorbidities, atopic dermatitis (AD) emerges as systemic disease with increased cardiovascular risk. To better define serum inflammatory and cardiovascular risk proteins, we used an OLINK high-throughput proteomic assay to analyze moderate-to-severe AD (n = 59) compared to psoriasis (n = 22) and healthy controls (n = 18). Compared to controls, 10 proteins were increased in serum of both diseases, including Th1 (IFN-γ, CXCL9, TNF-β) and Th17 (CCL20) markers. 48 proteins each were uniquely upregulated in AD and psoriasis. Consistent with skin expression, AD serum showed up-regulation of Th2 (IL-13, CCL17, eotaxin-1/CCL11, CCL13, CCL4, IL-10), Th1 (CXCL10, CXCL11) and Th1/Th17/Th22 (IL-12/IL-23p40) responses. Surprisingly, some markers of atherosclerosis (fractalkine/CX3CL1, CCL8, M-CSF, HGF), T-cell development/activation (CD40L, IL-7, CCL25, IL-2RB, IL-15RA, CD6) and angiogenesis (VEGF-A) were significantly increased only in AD. Multiple inflammatory pathways showed stronger enrichment in AD than psoriasis. Several atherosclerosis mediators in serum (e.g. E-selectin, PI3/elafin, CCL7, IL-16) correlated with SCORAD, but not BMI. Also, AD inflammatory mediators (e.g. MMP12, IL-12/IL-23p40, CXCL9, CCL22, PI3/Elafin) correlated between blood and lesional as well as non-lesional skin. Overall, the AD blood signature was largely different compared to psoriasis, with dysregulation of inflammatory and cardiovascular risk markers, strongly supporting its systemic nature beyond atopic/allergic association.

Early-onset pediatric atopic dermatitis is characterized by T H 2/T H 17/T H 22-centered inflammation and lipid alterations

Background: Although atopic dermatitis (AD) often starts in early childhood, detailed tissue profiling of early‐onset AD in children is lacking, hindering therapeutic development for this patient population with a particularly high unmet need for better treatments. Objective: We sought to globally profile the skin of infants with AD compared with that of adults with AD and healthy control subjects. Methods: We performed microarray, RT‐PCR, and fluorescence microscopy studies in infants and young children (<5 years old) with early‐onset AD (<6 months disease duration) compared with age‐matched control subjects and adults with longstanding AD. Results: Transcriptomic analyses revealed profound differences between pediatric patients with early‐onset versus adult patients with longstanding AD in not only lesional but also nonlesional tissues. Although both patient populations harbored TH2‐centered inflammation, pediatric AD also showed significant TH17/TH22 skewing but lacked the TH1 upregulation that characterizes adult AD. Pediatric AD exhibited relatively normal expression of epidermal differentiation and cornification products, which is downregulated in adults with AD. Defects in the lipid barrier (eg, ELOVL fatty acid elongase 3 [ELOVL3] and diacylglycerol o‐acyltransferase 2 [DGAT2]) and tight junction regulation (eg, claudins 8 and 23) were evident in both groups. However, some lipid‐associated mediators (eg, fatty acyl‐CoA reductase 2 and fatty acid 2‐hydroxylase) showed preferential downregulation in pediatric AD, and lipid barrier genes (FA2H and DGAT2) showed inverse correlations with transepidermal water loss, a functional measure of the epidermal barrier. Conclusions: Skin samples from children and adult patients with AD share lipid metabolism and tight junction alterations, but epidermal differentiation complex defects are only present in adult AD, potentially resulting from chronic immune aberration that is not yet present in early‐onset disease.

Alopecia areata is characterized by expansion of circulating Th2/Tc2/Th22, within the skin-homing and systemic T-cell populations

Characterizing blood profile of alopecia areata (AA) is important not only for treatment advancements, but also for possibly identifying peripheral biomarkers that will eliminate the need for scalp biopsies. We aimed to compare frequencies of skin homing (CLA+) vs systemic (CLA−) “polar” CD4+ and CD8+ and activated T‐cell subsets in AA vs atopic dermatitis (AD) and control blood.

Asian atopic dermatitis serum is characterized by Th2/Th22-activation, highly correlated with non-lesional skin measures.

Asian AD serum is characterized by prominent Th2 and Th22 signatures that correlate with the non-lesional skin profile, suggesting that serum phenotyping can serve as a surrogate for assessing disease extent beyond apparent AD lesions.

An integrated model of alopecia areata biomarkers highlights both TH1 and TH2 upregulation

This study expands the current paradigm on AA cytokine profile in serum and scalp, identifying IL-15, and Th1 and Th2 serum cytokines that reflect both tissue activity and clinical disease severity.

Atopic dermatitis in Chinese patients shows TH2/TH17 skewing with psoriasiform features

Our data established the molecular fingerprints of AD and psoriasis in Han Chinese patients, and identified tissue biomarkers of disease that correlated with clinical severity.