The expression of S100A8/S100A9 is inducible and regulated by the Hippo/YAP pathway in squamous cell carcinomas.

BACKGROUND: S100A8 and S100A9, two heterodimer-forming members of the S100 family, aberrantly express in a variety of cancer types. However, little is known about the mechanism that regulates S100A8/S100A9 co-expression in cancer cells. METHODS: The expression level of S100A8/S100A9 measured in three squamous cell carcinomas (SCC) cell lines and their corresponding xenografts, as well as in 257 SCC tissues. The correlation between S100A8/S100A9, Hippo pathway and F-actin cytoskeleton were evaluated using western blot, qPCR, ChIP and Immunofluorescence staining tests. IncuCyte ZOOM long time live cell image monitoring system, qPCR and Flow Cytometry measured the effects of S100A8/S100A9 and YAP on cell proliferation, cell differentiation and apoptosis. RESULTS: Here, we report that through activation of the Hippo pathway, suspension and dense culture significantly induce S100A8/S100A9 co-expression and co-localization in SCC cells. Furthermore, these expressional characteristics of S100A8/S100A9 also observed in the xenografts derived from the corresponding SCC cells. Importantly, Co-expression of S100A8/S100A9 detected in 257 SCC specimens derived from five types of SCC tissues. Activation of the Hippo pathway by overexpression of Lats1, knockdown of YAP, as well as disruption of F-actin indeed obviously results in S100A8/S100A9 co-expression in attached SCC cells. Conversely, inhibition of the Hippo pathway leads to S100A8/S100A9 co-expression in a manner opposite of cell suspension and dense. In addition, we found that TEAD1 is required for YAP-induced S100A8/S100A9-expressions. The functional studies provide evidence that knockdown of S100A8/S100A9 together significantly inhibit cell proliferation but promote squamous differentiation and apoptosis. CONCLUSIONS: Our findings demonstrate for the first time that the expression of S100A8/S100A9 is inducible by changes of cell shape and density through activation of the Hippo pathway in SCC cells. Induced S100A8/S100A9 promoted cell proliferation, inhibit cell differentiation and apoptosis.

Chronological protein synthesis in regenerating rat liver.

Liver regeneration has been studied for decades; however, its regulation remains unclear. In this study, we report a dynamic tracing of protein synthesis in rat regenerating liver with a new proteomic technique, (35) S in vivo labeling analysis for dynamic proteomics (SiLAD). Conventional proteomic techniques typically measure protein alteration in accumulated amounts. The SiLAD technique specifically detects protein synthesis velocity instead of accumulated amounts of protein through (35) S pulse labeling of newly synthesized proteins, providing a direct way for analyzing protein synthesis variations. Consequently, protein synthesis within short as 30 min was visualized and protein regulations in the first 8 h of regenerating liver were dynamically traced. Further, the 3.5-5 h post partial hepatectomy (PHx) was shown to be an important regulatory turning point by acute regulation of many proteins in the initiation of liver regeneration.

S100A7 acts as a dual regulator in promoting proliferation and suppressing squamous differentiation through GATA-3/caspase-14 pathway in A431 cells.

S100A7 is expressed in many squamous cell carcinomas (SCCs), such as SCC of the skin, and well-differentiated SCC always displays stronger staining of this protein. A431 cells, an epidermal cancer cell line, were selected as a cell model to investigate the roles and mechanism of S100A7 in SCC of the skin. In this study, we demonstrated that the overexpression of S100A7 in A431 cells significantly promoted cell proliferation in vitro and tumor growth in vivo, whereas it suppressed the expression of GATA-3, caspase-14 and three squamous differentiation markers, keratin-1, TG-1 and involucrin. Conversely, the overexpression of caspase-14 not only significantly decreased cell proliferation and delayed tumor growth but also markedly induced the expression of three squamous differentiation markers, whereas S100A7 and GATA-3 were not influenced. Further evidence showed that silencing GATA-3 greatly inhibited the expression of caspase-14 and three differentiation markers, while the expression of S100A7 was not changed; contrary results were obtained when overexpressing GATA-3. Importantly, restoring the expression of GATA-3 and caspase-14 in A431-S100A7 cells could bypass the ability of S100A7 to increase cell viability and repress squamous differentiation. These data suggested that S100A7 expression in SCC may play an important role in the maintenance of SCC cell dedifferentiation, at least in SCC of the skin.

miR-137 inhibits proliferation of melanoma cells by targeting PAK2.

MicroRNAs (miRNA) are key players in a variety of cancers including malignant melanoma. miR-137 has been reported to be a tumor suppressor in melanoma and several targets have been identified for this miRNA. We previously developed a novel proteomics technology, (35) S in vivo/vitro labelling analysis for dynamic proteomics (SiLAD). Because of its high sensitivity in analysing protein expression rates, SiLAD has the potential to unravel miRNA effects on mRNAs coding for proteins with long half-lives or high abundance. Using SiLAD, we discovered that miR-137 significantly downregulated the expression rate of p21-activated kinase 2 (PAK2) in melanoma cells. Bioinformatics analysis predicted PAK2 as a direct target of miR-137, which was confirmed by luciferase reporter assay and Western blot analysis. We found that overexpression of miR-137 inhibited the proliferation of melanoma cells, which could be phenocopied by knockdown of PAK2 using siRNAs. Furthermore, overexpression of PAK2 restored miR-137-mediated suppression of cell proliferation. These findings indicate that miR-137 could inhibit proliferation through targeting PAK2 in melanoma cells.

High-confidence de novo peptide sequencing using positive charge derivatization and tandem MS spectra merging.

De novo peptide sequencing holds great promise in discovering new protein sequences and modifications but has often been hindered by low success rate of mass spectra interpretation, mainly due to the diversity of fragment ion types and insufficient information for each ion series. Here, we describe a novel methodology that combines highly efficient on-tip charge derivatization and tandem MS spectra merging, which greatly boosts the performance of interpretation. TMPP-Ac-OSu (succinimidyloxycarbonylmethyl tris(2,4,6-trimethoxyphenyl)phosphonium bromide) was used to derivatize peptides at N-termini on tips to reduce mass spectra complexity. Then, a novel approach of spectra merging was adopted to combine the benefits of collision-induced dissociation (CID) and electron transfer dissociation (ETD) fragmentation. We applied this methodology to rat C6 glioma cells and the Cyprinus carpio and searched the resulting peptide sequences against the protein database. Then, we achieved thousands of high-confidence peptide sequences, a level that conventional de novo sequencing methods could not reach. Next, we identified dozens of novel peptide sequences by homology searching of sequences that were fully backbone covered but unmatched during the database search. Furthermore, we randomly chose 34 sequences discovered in rat C6 cells and verified them. Finally, we conclude that this novel methodology that combines on-tip positive charge derivatization and tandem MS spectra merging will greatly facilitate the discovery of novel proteins and the proteome analysis of nonmodel organisms.

Selective expression of S100A11 in lung cancer and its role in regulating proliferation of adenocarcinomas cells.

S100A11, one secreted protein, is overexpressed in certain cancers. We investigated S100A11 expression in various subtypes of lung cancer and explored its role in cell proliferation. S100A11 mRNA level was examined in 45 pairs of frozen lung cancer tissues by reverse transcriptase PCR (RT-PCR). The specific expression and subcellular distribution of S100A11 were examined in 78 paraffin-embedded lung cancers, 2 benign lung diseases as well as 22 healthy lung tissues by immunohistochemistry. S100A11 protein level was further analyzed in the sera of 86 lung cancer patients and 50 healthy individuals by enzyme-linked immunosorbent assay. We found that both mRNA and protein levels of S100A11 were overexpressed in adenocarcinomas (ADC) and squamous cell carcinomas (SCC) compared with paired non-cancerous lung tissues, while S100A11 was detected downregulated in small cell lung cancers (SCLC). Further immunohistochemistry staining was positive for S100A11 only in non-small cell lung cancer (NSCLC) (ADC, SCC, large cell carcinomas, et al.), but not SCLC. Conclusively, we found S100A11 protein level increased in the sera of NSCLC patients. Furthermore, when S100A11 expression was knocked down in lung adenocarcinoma cells A549 and LTEP-a-2, the cell proliferation was significantly inhibited in vitro and in vivo.

A combined biomarker pattern improves the discrimination of lung cancer.

A total of 227 sera were analysed using surface-enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF MS) to find novel serum biomarkers for lung cancer. The results showed that the 11.53, 11.70, 13.78, 13.90 and 14.07 k m/z peaks identified as native serum amyloid A (SAA), SAA with N-terminal Arg cleaved, native transthyretin (TTR) and its two variants significantly differentiated lung cancer sera from normal control sera (p <0.01). A 'biomarker pattern' combining SAA and TTR was tested to distinguish lung cancer patients from normal control individuals, and the diagnostic positive rate of lung cancer was improved to 91.6%.

The WW domains dictate isoform-specific regulation of YAP1 stability and pancreatic cancer cell malignancy.

YAP1 is a key mediator of the Hippo pathway capable of exerting a profound effect on organ size as well as tumorigenesis. Alternative mRNA splicing of human YAP1 results in at least 8 protein isoforms that differ within the 2nd WW motif and the transcriptional activation domain. Methods: To investigate the isoform-specific differences in their mRNA expression, transcriptional activity and tumor-promoting function, we cloned cDNA encoding all of the eight YAP1 protein isoforms. Then, we examined their mRNA expression, subcellular localization, transcriptional regulation properties, interactions with key regulatory partners, and protein stability in response to changes in cell density, as well as their effects on pancreatic cancer cell malignancy both in vitro and in vivo. Results: Multiple YAP1 mRNA isoforms are expressed in commonly used pancreatic cancer lines as well as human pancreatic cancer PDX lines. Based on the analysis of heterologous reporter and endogenous target genes, all YAP1 isoforms are capable of activating transcription, albeit to a different extent. Importantly, we unveiled a marked discrepancy between the mRNA and protein expression levels of the YAP1-1 and YAP1-2 isoforms. We further discovered that the YAP1-2 isoform, which contains two tandem WW motifs, is less stable at the protein level, particularly at high cell densities. Mechanistically, we found that the presence of the 2nd WW motif in YAP1-2 facilitates the de novo formation of the YAP1-2/AMOT/LATS1 complex and contributes to a stronger binding of YAP1-2 to LATS1 and subsequently increased YAP1-2 ubiquitination and degradation by ß-TRCP. Conclusion: Our data reveals a potent effect of YAP1-1 on pancreatic cancer malignancy in vitro and in vivo and provides novel mechanistic insight into isoform-specific and cell density-dependent regulation of YAP1 stability, as well as its impact on cancer malignancy.

Erratum: The WW domains dictate isoform-specific regulation of YAP1 stability and pancreatic cancer cell malignancy: Erratum.

[This corrects the article DOI: 10.7150/thno.42795.].

Doxycycline enhances the Ras-MAPK signaling and proliferation of mouse thymic epithelial cells.

Depletion of T-cell-dependent immunity is a major consideration for patients suffering from infections of human immunodeficiency virus (HIV), those undergoing organ transplantation, and those receiving anti-cancer chemotherapy and/or radiotherapy. In general, T-cell regeneration occurs in the thymus through thymopoiesis. We have found that doxycycline (Dox), a tetracycline derivative, enhances the proliferation of mouse thymic epithelial cells, which are unique in their capacity to support positive selection and are essential throughout the development of thymocytes. Cell cycle analysis indicates that the increased cell proliferation is due to a shortened G(0)/G(1) phase. To reveal the underlying mechanisms, we examined the expression of an array of molecules that regulate the cell cycle. The results show that in mouse thymic medullary-type epithelial cell line 1 (MTEC1) Dox leads to elevated levels of H-Ras, phosphorylated extracellular signal-regulated kinase 1/2 (p-ERK1/2), cyclin E, cyclin dependent kinase 4/2 (CDK4/CDK2), E2F3, and c-myc. These data, and the observation that the proliferation-enhancing effect is largely abolished following treatment with an ERK inhibitor support an active role of the Ras-ERK/mitogen-activated protein kinase (MAPK) signaling pathway. In conclusion, the present study reveals a new activity of an old family of antibiotics. The in vivo effect of Dox on immune reconstitution warrants further exploration.

Serum levels of variants of transthyretin down-regulation in cholangiocarcinoma.

BACKGROUND: Cholangiocarcinoma (CC) is devastating neoplasm and very few specific biomarkers could be used in clinical diagnosis. A study was taken to find novel serum biomarkers for CC. METHODS: Surface enhanced laser desorption/ionization (SELDI) technology was used to analyze 427 serum samples including 56 CCs, 49 hepatobiliary diseases, 269 other cancer control, and 53 healthy individuals. The candidates were isolated and identified by SDS-PAGE, ESI/MS-MS, Western blot, and immunoprecipitation. Liver functions of CC patients were examined and enzyme-linked immunosorbent assay (ELISA) of transthyretin (TTR) and CA19-9 were further performed in some sets of serum samples. RESULTS: 13.76, 13.88, and 14.04 k m/z peaks in sera were significantly decreased in CC compared with the control groups (P < 0.001). Subsequently, these three peaks were identified as native TTR and its two variants. ELISA assay indicated that TTR levels were consistent with SELDI analysis in CC compared with healthy control and benign diseases of hepatobiliary (P < 0.001). Liver function test levels were obviously elevated for CC patients. TTR combining with CA19-9 to differentiate CC from benign hepatobiliary diseases showed sensitivity and specificity were 98.2% and 100%, respectively. CONCLUSION: The levels of TTR were significantly down-regulated in sera of CC patients and may be complementary markers of CA19-9 in diagnosis for CC.

Elevated expression of UBE2T in lung cancer tumors and cell lines.

The aim of this study was to investigate the association between UBE2T, a member of the ubiquitin-conjugating E2 family, and lung cancer, which has never been reported to date. Therefore, the expression of UBE2T mRNA was examined in normal human tissues and 8 lung cancer cell lines. Subsequently, UBE2T expression was analyzed in 41 lung cancer tissues by PCR and Western blots, as well as in 103 lung cancer specimens by immunohistochemistry. To further elucidate the possible functional role of UBE2T, the protein was overexpressed in NIH3T3 cells. UBE2T mRNA was highly expressed in all lung cancer cell lines examined, while it could not be detected in normal lung tissue. UBE2T was detected in 75.6% of primary lung cancer tissue samples (n = 41) at mRNA level and in 60.9% at protein level. In addition, positive UBE2T staining was observed in 61% of lung cancer specimens (n = 103), particularly in all immunohistochemically stained small cell carcinoma tissues. In normal lung tissue, only weak staining was observed in the basal cells of bronchial epithelium. Overexpression of UBE2T in NIH3T3 cells significantly promoted colony formation in soft agar medium (p < 0.001). In conclusion, UBE2T was significantly upregulated in lung cancer tissue and cell lines, suggesting involvement of UBE2T in the malignant cell phenotype.

CABYR is a novel cancer-testis antigen in lung cancer.

PURPOSE: Cancer-testis (CT) antigens are often expressed in a proportion of tumors of various types. Their restricted normal tissue expression and immunogenicity make them potential targets for immunotherapy. CABYR is a calcium-binding tyrosine phosphorylation-regulated fibrous sheath protein initially reported to be testis specific and subsequently shown to be present in brain tumors. This study was to determine whether CABYR is a novel CT antigen in lung cancer. EXPERIMENTAL DESIGN: mRNA expression of CABYR-a/b (combination of CABYR-a and CABYR-b) and CABYR-c was examined in 36 lung cancer specimens, 14 cancer cell lines, and 1 normal cell line by conventional and real-time reverse transcription-PCR. Protein expression of CABYR was analyzed in 50 lung cancer tissues by immunohistochemistry. Antibodies specific to CABYR were analyzed in sera from 174 lung cancer patients and 60 healthy donors by ELISA and Western blot. RESULTS: mRNA expression of CABYR-a/b and CABYR-c was observed, respectively, in 13 and 15 of 36 lung cancer tissues as well as in 3 and 5 of 14 cancer cell lines, whereas neither of them was observed in adjacent noncancerous tissues or the normal cell line. Protein expression of CABYR-a/b and CABYR-c was observed, respectively, in 20 and 19 of 50 lung cancer tissues. IgG antibodies specific to CABYR-a/b and CABYR-c were detected, respectively, in 11% and 9% of sera from lung cancer patients but not from the 60 healthy donors. CONCLUSION: CABYR is a novel CT antigen in lung cancer and may be a promising target for immunotherapy for lung cancer patients.

miR-137 inhibits melanoma cell proliferation through downregulation of GLO1.

Late-stage melanoma is refractory to current therapies. MicroRNAs (miRNAs) can modulate many physiological and pathological processes of melanoma. Studies have demonstrated that miR-137 acts as a tumor suppressor by inhibiting the proliferation of melanoma cells through targeting multiple mRNAs. The glyoxalase system member glyoxalase 1 (GLO1) is the principal scavenging enzyme of methylglyoxal (MG), a toxic byproduct of glycolysis. Using 35S in vivo/vitro labelling analysis for dynamic proteomics (SiLAD), we found that miR-137 downregulated the expression of GLO1 in melanoma cells. Bioinformatics analysis predicted that GLO1 is a direct target of miR-137. This was validated by dual luciferase reporter assay. Quantitative RT-PCR (qRT-PCR) and western blot analysis indicated that miR-137 could decrease endogenous GLO1 expression. Furthermore, siRNA targeting of GLO1 mimicked inhibition of melanoma cell proliferation caused by miR-137 overexpression. Re-expression of GLO1 was able to restore miR-137-mediated suppression of melanoma cell proliferation. Therefore, these results suggest that miR-137 inhibits the proliferation of melanoma cells by targeting GLO1.

Identification and validation of S100A7 associated with lung squamous cell carcinoma metastasis to brain.

To identify potential markers associated with non-small cell lung cancer (NSCLC) metastasis to brain, comparative proteome analysis on two lung squamous cell carcinoma (SCC) cell lines, NCI-H226 and H226Br (the brain metastatic cell line of NCI-H226), was performed using two-dimensional electrophoresis (2-DE) followed by a tandem mass spectrometer with a matrix-assisted laser desorption/ionization (MALDI) source. Twenty differential proteins were identified, of which 6 proteins were up-regulated in H226Br cell compared with NCI-H226 cells, whereas 14 proteins were down-regulated. S100A7 and 14-3-3sigma, two of candidate proteins significantly upregulated and downregulated in H226Br cell, were selected to verify the liability of the differential proteins by Western blot. The results were in accordance with 2-D data. To determine whether S100A7 overexpression is actually associated with SCC metastasis to brain, S100A7 protein was testified in 10 brain metastasis tissues from NSCLC, 38 primary NSCLC tissues including half matched local positive lymph nodes, 5 primary brain tumors and 2 non-cancer brain tissues by immunohistochemistry. Of particular interest to us was that the positive staining of S100A7 could be found in 3/5 (60%) brain metastases tissue from SCC and 8/21 (38%) the primary lung SCC tissues, while no positive staining was observed in the brain metastases tissue from Ad (n=5), the primary adenocarcinoma (Ad) tissues (n=17), the primary brain tumors (n=5), all local positive lymph nodes from the primary NSCLC (n=19) and non-cancer brain tissues (n=2). These findings suggest that S100A7 expression is closely associated with SCC metastasis to brain and may be a potential biomarker for monitoring the development of SCC.

Protein profile of human lung squamous carcinoma cell line NCI-H226.

OBJECTIVE: To construct a database of human lung squamous carcinoma cell line NCI-H226 and to facilitate discovery of novel subtypes markers of lung cancer. METHOD: Proteomic technique was used to analyze human lung squamous carcinoma cell line NCI-H226. The proteins of the NCI-H226 cells were separated by two-dimensional gel electrophoresis and identified by mass spectrometry. RESULTS: The results showed that a good reproducibility of the 2-D gel pattern was attained. The position deviation of matched spots among three 2-D gels was 1.95 +/- 0.53 mm in the isoelectric focusing direction, and 1.73 +/- 0.45 mm in the sodium dodecyl sulfate-polyacrylamide gel electrophoresis direction. One hundred and twenty-seven proteins, including enzymes, signal transduction proteins, structure proteins, transport proteins, etc. were characterized, of which, 29 identified proteins in NCI-H226 cells were reported for the first time to be involved in lung cancer carcinogenesis. CONCLUSION: The information obtained from this study could provide some valuable clues for further study on the carcinogenetic mechanism of different types of lung cancer, and may help us to discover some potential subtype-specific biomarkers of lung cancer.

Serum amyloid A protein: a potential biomarker correlated with clinical stage of lung cancer.

OBJECTIVE: To identify serum diagnosis or progression biomarkers in patients with lung cancer using protein chip profiling analysis. METHOD: Profiling analysis was performed on 450 sera collected from 213 patients with lung cancer, 19 with pneumonia, 16 with pulmonary tuberculosis, 65 with laryngeal carcinoma, 55 with laryngopharyngeal carcinoma patients, and 82 normal individuals. A new strategy was developed to identify the biomarkers on chip by trypsin pre-digestion. RESULTS: Profiling analysis demonstrated that an 11.6 kDa protein was significantly elevated in lung cancer patients, compared with the control groups (P < 0.001). The level and percentage of 11.6 kDa protein progressively increased with the clinical stages I-IV and were also higher in patients with squamous cell carcinoma than in other subtypes. This biomarker could be decreased after operation or chemotherapy. On the other hand, 11.6 kDa protein was also increased in 50% benign diseases of lung and 13% of other cancer controls. After trypsin pre-digestion, a set of new peptide biomarkers was noticed to appear only in the samples containing a 11.6 kDa peak. Further identification showed that 2177 Da was a fragment of serum amyloid A (SAA, MW 11.6 kDa). Two of the new peaks, 1550 Da and 1611 Da, were defined from the same protein by database searching. This result was further confirmed by partial purification of 11.6 kDa protein and MS analysis. CONCLUSION: SAA is a useful biomarker to monitor the progression of lung cancer and can directly identify some biomarkers on chip.

Discovery and identification of Serum Amyloid A protein elevated in lung cancer serum.

Two hundred and eighteen serum samples from 175 lung cancer patients and 43 healthy individuals were analyzed by using Surface Enhaced Laser Desorption/Ionization Time of Flight Mass Spectrome-try (SELDI-TOF-MS). The data analyzed by both Biomarker Wizardtrade mark and Biomarker Patternstrade mark software showed that a protein peak with the molecular weight of 11.6 kDa significantly increased in lung cancer. Meanwhile, the level of this biomarker was progressively increased with the clinical stages of lung cancer. The candidate biomarker was then obtained from tricine one-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis by matching the molecular weight with peaks on WCX2 chips and was identified as Serum Amyloid A protein (SAA) by MALDI/MS-MS and database searching. It was further validated in the same serum samples by immunoprecipitation with commercial SAA antibody. To confirm the SAA differential expression in lung cancer patients, the same set of serum samples was measured by ELISA assay. The result showed that at the cutoff point 0.446 (OD value) on the Receiver Operating Characteristic (ROC) curve, SAA could better discriminate lung cancer from healthy individuals with sensitivity of 84.1% and specificity of 80%. These findings demonstrated that SAA could be characterized as a biomarker related to pathological stages of lung cancer.

[Identification and clinical evaluation of lung cancer serum biomarker L-lactate dehydrogenase B].

OBJECTIVE: To identify potential biomarkers related with lung cancer metastasis. METHODS: Conditional media proteins collected from a primary non-small cell lung cancer cell line (NSCLC) NCI-H226 and its brain metastatic subline H226Br were analyzed by SDS-PAGE and MALDI-TOF-MS. Twelve biomarkers were identified, of which LDHB was significantly up-regulated in H226Br cell and was further validated using ELISA in sera including 105 lung cancer samples, 41 pneumonia and pulmonary tuberculosis samples and 65 healthy samples. RESULTS: The levels of LDHB were specifically elevated in NSCLC sera [A value 0.485 (0 - 1.415)] compared with pneumonia and pulmonary tuberculosis [A value 0.187 (0 - 0.609), P < 0.01] and healthy group [A value, 0.159 (0 - 0.524), P < 0.01] and were progressively increased with the clinical stage. At the cutoff point 0.260 (A value) on the ROC curve, the sensitivity, specificity and total accuracy of LDHB were 81%, 70% and 76% respectively. CONCLUSION: These findings demonstrated that secretome could open up a possibility to identify novel biomarkers related with cancer occurrence and metastasis.

YAP Expression and Activity Are Suppressed by S100A7 via p65/NFκB-mediated Repression of ΔNp63.

In several squamous cell carcinoma (SCC) cells, it has been previously observed that induction of the S100 calcium-binding protein A7 (S100A7) is repressed by YAP via the Hippo pathway. This report now demonstrates that S100A7 also represses YAP expression and activity by ΔNp63 in cancer cells. Stable overexpression of S100A7 activates the NFκB pathway and inhibits the expression of ΔNp63. Caffeic acid phenethyl ester (CAPE), as a specific inhibitor of NFκB, counteracts the inhibitory effect of S100A7 on the expression of ΔNp63 and its target genes. Depletion of S100A7 significantly promotes ΔNp63 expression. These data indicate that S100A7 acts as a suppressor of ΔNp63. Mechanistic examination finds that ΔNp63 not only directly binds to the region of YAP promoter and induces its expression, but also inhibits the Hippo pathway and enhances YAP activity. Importantly, either the positive correlation between S100A7 and YAP phosphorylation at S127 or the negative correlation between S100A7 and ΔNp63 is also observed in skin SCC tissues. Chemosensitivity analysis reveals that S100A7 enhances cancer cells' resistance by inhibition of YAP expression and activity. These results demonstrate that S100A7 is an upstream modulator of the Hippo pathway and extend our understanding of S100A7 functions in cancer.Implications: S100A7 is a new upstream regulator of the Hippo signaling pathway and reduces chemosensitivity of SCC cells through inhibitions of YAP expression and activity. Mol Cancer Res; 15(12); 1752-63. ©2017 AACR.