Correction: Soung et al. Therapeutic Potential of Chemically Modified MiR-489 in Triple-Negative Breast Cancers. Cancers 2020, 12, 2209.

In the original publication [...].

The role of c-Src in integrin (α6ß4) dependent translational control.

BACKGROUND: Integrin α6ß4 contributes to cancer progression by stimulating transcription as well as translation of cancer related genes. Our previous study demonstrated that α6ß4 stimulates translation initiation of survival factors such as VEGF by activating mTOR pathway. However, the immediate early signaling events that link α6ß4 to mTOR activation needs to be defined. RESULTS: In the current studies, we demonstrated that c-Src is an immediate early signaling molecule that acts upstream of α6ß4 dependent mTOR activation and subsequent translation of VEGF in MDA-MB-435/ß4 and MDA-MB-231 cancer cells. m7GTP-Sepharose-binding assay revealed that Src activity is required to form eIF4F complex which is necessary for Cap-dependent translation in α6ß4 expressing human cancer cells. CONCLUSIONS: Overall, our studies suggest that integrin ß4 and c-Src activation is important early signaling events to lead mTOR activation and cap-dependent translation of VEGF.

Combination Treatment Strategies to Overcome PARP Inhibitor Resistance.

Poly(ADP-ribose) polymerase (PARP) enzymes have been shown to be essential for DNA repair pathways, including homologous recombination repair (HRR). Cancers with HRR defects (e.g., BRCA1 and BRCA2 mutations) are targets for PARP inhibitors (PARPis) based on the exploitation of "synthetic lethality". As a result, PARPis offer a promising treatment option for advanced ovarian and breast cancers with deficiencies in HRR. However, acquired resistance to PARPis has been reported for most tumors, and not all patients with BRCA1/2 mutations respond to PARPis. Therefore, the formulation of effective treatment strategies to overcome resistance to PARPis is urgently necessary. This review summarizes the molecular mechanism of therapeutic action and resistance to PARPis, in addition to emerging combination treatment options involving PARPis.

The Sensitization of Triple-Negative Breast Cancers to Poly ADP Ribose Polymerase Inhibition Independent of BRCA1/2 Mutation Status by Chemically Modified microRNA-489.

Chemoresistance and inefficient therapeutic efficacies in triple-negative breast cancers (TNBCs) are among the major clinical problems in breast cancers. A potential new method to sensitize these tumors to current treatment options is, therefore, urgent and necessary. Our previous studies demonstrated that miR-489 serves as one of the top tumor-suppressing miRs and features downregulated expression in metastatic TNBCs and that the restoration of miR-489 expression in TNBCs effectively inhibits the metastatic potentials of TNBCs both in vitro and in vivo. The chemical modification of miR-489 (CMM489) through the replacement of uracil with 5-FU further enhances the therapeutic potential of miR-489. In the present study, we tested the effects of CMM489 in synergizing DNA damage response (DDR) inhibitors such as PARP inhibitors. CMM489 is particularly effective in sensitizing TNBC cell lines with inherent resistance to PARP inhibitors regardless of BRCA mutation status. One of the anti-cancer mechanisms through which CMM489 synergizes with PARP inhibitors is the blockade of homologous recombination (HR) in TNBC cells upon DNA damage. The results of this study highlight the potential use of CMM489 in combination treatments with PARP inhibitors in TNBCs.

Therapeutic Potential of Chemically Modified miR-489 in Triple-Negative Breast Cancers.

Triple-negative breast cancers (TNBCs) lack ER, PR and her2 receptors that are targets of common breast cancer therapies with poor prognosis due to their high rates of metastasis and chemoresistance. Based on our previous studies that epigenetic silencing of a potential metastasis suppressor, arrestin domain-containing 3 (ARRDC3), is linked to the aggressive nature of TNBCs, we identified a sub-group of tumor suppressing miRNAs whose expressions were significantly up-regulated by ARRDC3 over-expression in TNBC cells. Among these tumor suppressing miRs, we found that miR-489 is most anti-proliferative in TNBC cells. miR-489 also blocked DNA damaging responses (DDRs) in TNBC cells. To define the mechanism by which miR-489 inhibits TNBC cell functions, we screened the potential target genes of miR-489 and identified MDC-1 and SUZ-12 as novel target genes of miR-489 in TNBC cells. To further exploit the therapeutic potentials of miR-489 in TNBC models, we chemically modified the guide strand of miR-489 (CMM489) by replacing Uracil with 5-fluorouracil (5-FU) so that tumor suppressor (miR-489) and DNA damaging (5-FU) components are combined into a single agent as a novel drug candidate for TNBCs. Our studies demonstrated that CMM489 shows superior effects over miR-489 or 5-FU in inhibition of TNBC cell proliferation and tumor progression, suggesting its therapeutic efficacy in TNBC models.

Arrestin Domain Containing 3 Reverses Epithelial to Mesenchymal Transition and Chemo-Resistance of TNBC Cells by Up-Regulating Expression of miR-200b.

Our previous studies demonstrated the importance of arrestin domain containing 3 (ARRDC3), a metastasis suppressor, in inhibiting invasive and metastatic potential of triple negative breast cancer (TNBC) in vitro and in vivo. However, little is known about ARRDC3 mediated transcriptional control and its target genes that are implicated in its metastatic suppressing activity. In this study, we used miRNA array and subsequent functional analyses to identify miRNAs whose expression are significantly regulated by ARRDC3 in TNBC cells. We identified miR-200b as a major target gene of ARRDC3. miR-200b played an essential role in mediating ARRDC3 dependent reversal of EMT phenotypes and chemo-resistance to DNA damaging agents in TNBC cells. Expression of miR-200b also increased the expression of ARRDC3 as well in TNBC cells, suggesting a positive feedback loop between these two molecules. In addition, we combined the therapeutic powers of miR-200b and 5-fluorourancil (5-FU) into a single compound (5-FU-miR-200b) to maximize the synergistic effects of these compounds. Chemically modified miR-200b (5-FU-miR-200b mimic) was more effective in inhibiting metastatic potentials of TNBC cells than unmodified miR-200b and does not require transfection reagents, implying its therapeutic potential in TNBC. Our studies showed the importance of therapeutic targeting ARRDC3/miR-200b pathway in TNBC.

Interactions of acetylcholinesterase with caveolin-1 and subsequently with cytochrome c are required for apoptosome formation.

Acetylcholinesterase (AChE) is emerging as an important component in leading to apoptosis. Our previous study demonstrated that silencing of the AChE gene blocked the interaction between cytochrome c and apoptotic protease-activating factor-1 (Apaf-1) in etoposide-induced apoptosis of HT-29 cells. We undertook this study to further dissect the molecular role of AChE in apoptosome formation. The present study elicited that small interfering RNA (siRNA) to cytochrome c gene blocked the interaction of AChE with Apaf-1, whereas siRNA to Apaf-1 gene did not block the interaction of AChE with cytochrome c, indicating that the interaction of AChE with cytochrome c is required for the interaction between cytochrome c and protease-activating factor-1. We further observed that AChE is localized to caveolae via interacting with caveolin-1 during apoptosis and that the disruption of caveolae prevented apoptosome formation. These data indicate that the interactions of AChE with caveolin-1 and subsequently with cytochrome c appear to be indispensable for apoptosome formation.

The Role of Arrestin Domain-Containing 3 in Regulating Endocytic Recycling and Extracellular Vesicle Sorting of Integrin ß4 in Breast Cancer.

Despite the established role of integrin ß4 (ITG ß4) in breast cancer progression, the importance of endocytic recycling of ITG ß4 and its regulatory mechanism are poorly understood. Here, we found that a sub-population of ITG ß4 is sorted into early endosomes, recycled back to the plasma membrane, and secreted in the form of extracellular vesicles (EVs) upon EGF treatment in triple negative breast cancer (TNBC) cells. A metastasis suppressor, ARRDC3 (arrestin domain-containing 3) prevents EGF-driven endocytic recycling of ITG ß4 by inducing NEDD4-dependent ubiquitination of ITG ß4 and targeting endosomal ITG ß4 into lysosomes. Endocytic recycling of ITG ß4 is linked to sorting of ITG ß4 into EVs (ITG ß4+ EVs). ITG ß4+ EVs are mainly detectable from supernatants of TNBC cells and their production is inhibited by ARRDC3 expression. ARRDC3 reduces the metastatic potentials of breast cancer cell-derived EVs by reducing ITG ß4 levels in EVs. Overall, current studies provide novel mechanistic insights on the regulatory mechanism of ITG ß4 recycling, and its importance in invasive potentials of TNBC EVs, thus providing the basis for therapeutic targeting of the ARRDC3/ITG ß4 pathway in TNBC.

Immunohistochemical and mutational analysis of FLASH in gastric carcinomas.

FLASH was initially identified as a pro-apoptotic protein that transmits an apoptosis signal during death receptor-induced apoptosis. Additionally, diverse biologic roles of FLASH, including TNF-induced NF-kappaB activation, cell-cycle progression and cell division, have been identified. Although such functions are important in cancer pathogenesis, little is known about the alterations of FLASH gene and FLASH protein expression in human cancers. In this study, we analyzed the expression of FLASH protein in 60 gastric adenocarcinomas by immunohistochemistry. We furthermore analyzed mutation of FLASH in exon 8, where two polyadenine tracts ((A)8 and (A)9) are present, by single-strand conformation polymorphism (SSCP) assay in 184 gastric adenocarcinomas. By immunohistochemistry, FLASH protein expression in cancer cells was detected positively in 42 gastric carcinoma tissues (70%), whereas its expression in epithelial cells of normal gastric mucosa was shown as no or very weak intensity. Mutational analysis detected one FLASH mutation in the gastric carcinomas (0.5%). The increased expression of FLASH in the malignant gastric epithelial cells compared to the normal mucosal epithelial cells suggests that FLASH expression may play a role in gastric tumorigenesis. Also, the data suggest that somatic mutation of FLASH is a rare event in gastric carcinomas.

Mutational analysis of caspase-14 gene in common carcinomas.

AIMS: Whereas most caspases play roles in apoptosis and/or inflammation, caspase-14 plays a main role in epithelial differentiation. In cancers, expression of caspase-14 is frequently altered and is associated with some clinicopathological characteristics, suggesting caspase-14 might contribute to the pathogenesis of cancers. As a potential mechanism of caspase-14 alterations in cancers, we explored the possibility that mutation of caspase-14 gene is a characteristic of human cancers. METHODS: We analysed the entire coding region and all splice sites of human caspase-14 gene for the detection of somatic mutations in a series of 345 cancers, including 105 colorectal, 60 gastric, 60 hepatocellular, 60 breast and 60 lung carcinomas, by a single-strand conformation polymorphism (SSCP) assay. RESULTS: Overall, we detected two somatic mutations of caspase-14 gene, which consisted of one missense mutation (S32Y) and one silent mutation (T234T). The caspase-14 mutations were detected in two of 105 colorectal carcinomas (1.9%), but not in other carcinomas. CONCLUSION: These data indicate that caspase-14 gene is rarely mutated in colorectal carcinomas, but not mutated in gastric, lung, breast and hepatocellular carcinomas. The data also suggest that the caspase-14 mutation may not be a direct target of inactivation in tumorigenesis of common carcinomas.

Somatic mutations of ERBB2 kinase domain in gastric, colorectal, and breast carcinomas.

PURPOSE: Recent reports revealed that the kinase domain of the ERBB2 gene is somatically mutated in lung adenocarcinoma, suggesting the mutated ERBB2 gene as an oncogene in human cancers. However, because previous reports focused the mutational search of ERBB2 primarily on lung cancers, the data on ERBB2 mutations in other types of human cancers have been largely unknown. EXPERIMENTAL DESIGN: Here, we did a mutational analysis of the ERBB2 kinase domain by PCR single-strand conformational polymorphism assay in gastric, colorectal, and breast carcinoma tissues. RESULTS: We detected the ERBB2 kinase domain mutations in 9 of 180 gastric carcinomas (5.0%), in 3 of 104 colorectal carcinomas (2.9%), and in 4 of 94 breast carcinomas (4.3%). All of the detected ERBB2 mutations except for one in-frame deletion mutation were missense mutations. Of the 16 ERBB2 mutations detected, 4 affected Val777 in the exon 20 site, and 3 affected Leu755 in the exon 19 site. We simultaneously analyzed the somatic mutations of EGFR, K-RAS, PIK3CA, and BRAF genes in the 16 samples with ERBB2 mutations, and found that all of the 3 colorectal carcinoma samples with ERBB2 mutations harbored K-RAS mutations. CONCLUSION: This study showed that in addition to lung adenocarcinomas, ERBB2 kinase domain mutation occurs in other common human cancers such as gastric, breast, and colorectal cancers, and suggested that alterations of ERBB2-mediated signaling pathway by ERBB2 mutations alone or together with K-RAS mutations may contribute to the development of human cancers.

Expression of nuclear and cytoplasmic phosphorylated FADD in gastric cancers.

Fas-associated death domain (FADD) plays a crucial role during death receptor-mediated apoptosis. In addition, FADD possesses apoptosis-independent activities, including cell-cycle regulation and cell proliferation regulated by the phosphorylation of FADD at Ser194. The aim of this study was to explore the possibility whether alteration of phosphorylated FADD (p-FADD) expression might be a characteristic of gastric cancer. We analyzed the expression of p-FADD protein in 60 gastric adenocarcinomas by immunohistochemistry using a tissue microarray approach. In the normal gastric mucosal cells, surface and glandular epithelial cells evenly expressed p-FADD in the nuclei but not in the cytoplasm. In the cancers, p-FADD expression was detected in 38 cases (63%) of the gastric carcinomas, but there was no p-FADD immunostaining in the remaining 22 cancers (37%). Of note, p-FADD immunostaining was observed in cytoplasm/nuclei (20 cancers; 33%) and cytoplasm (18 cancers; 30%). There was no significant association of p-FADD expression with clinocopathological characteristics, including invasion, metastasis, and stage. Our data showed that the expression of p-FADD in gastric cancers was heterogenous in its location compared to the uniform nuclear expression of p-FADD in normal gastric cells. Many of the cancers (67%) were devoid of nuclear p-FADD, suggesting that p-FADD functions in the nucleus may be perturbed in the cancers. Also, p-FADD expression in the cytoplasm in a large fraction of the cancers (63%), not seen in the normal cells, suggested that the cell death functions of p-FADD could be altered in the cancer cells.

Mutational analysis of proapoptotic integrin beta 3 cytoplasmic domain in common human cancers.

AIMS: Mounting evidence indicates that deregulation of apoptosis is involved in the mechanisms of cancer development. Integrins are cell adhesion receptors that mediate cell survival and migration. A recent study showed that unligated integrin beta 3 (ITGB3) induced apoptosis by recruitment of caspase-8. The aim of the present study was to explore the possibility that genetic alteration of the ITGB3 gene is involved in the development of human cancers possibly by inactivating the apoptosis function of ITGB3. METHODS: We analyzed the coding region of the cytoplasmic domain of the human ITGB3 gene for the detection of somatic mutations in 100 gastric, 90 colorectal, 100 non-small cell lung, 43 urinary bladder and 50 head-neck cancers by a polymerase chain reaction-based, single-strand conformation polymorphism. RESULTS: We found an identical ITGB3 mutation in two unrelated patient samples (one in colorectal and the other in bladder cancer). The ITGB3 mutation was a missense mutation which would substitute an amino acid (E757K). CONCLUSIONS: The data suggested that the proapoptotic ITGB3 cytoplasmic domain is rarely mutated in common human cancers and may not play an important role in the development of the cancers.

Mutational analysis of the BH3 domains of proapoptotic Bcl-2 family genes Bad, Bmf and Bcl-G in laryngeal squamous cell carcinomas.

AIMS: There is mounting evidence that deregulation of apoptosis is involved in the mechanisms of cancer development. Somatic mutations of apoptosis-related genes have been reported in many human cancers. The aim of this study was to explore the possibility that mutation of the BH3 domains of the proapoptotic Bcl-2 genes Bad, Bmf and Bcl-G might be involved in the development of laryngeal cancer. METHODS: We analyzed the BH3 domains of Bad, Bmf and Bcl-G for the detection of somatic mutations in 33 squamous cell carcinomas of the larynx by a polymerase chain reaction-based single-strand conformation polymorphism assay. RESULTS: There were no somatic mutations of the BH3 domains of Bad, Bmfand BcI-G in the laryngeal squamous cell carcinoma samples. CONCLUSIONS: The data presented here indicate that BH3 domain mutation of the proapoptotic genes Bad, Bmf and Bcl-G is rare in laryngeal squamous cell carcinoma and may not contribute to the apoptosis-resistance mechanisms of laryngeal squamous cell carcinoma.

CASPASE-8 gene is inactivated by somatic mutations in gastric carcinomas.

Several lines of evidence indicate that deregulation of apoptosis is involved in the mechanisms of cancer development. Caspase-8 activation plays a central role in the initiation phase of apoptosis. The aim of this study was to explore the possibility that genetic alteration of CASPASE-8 gene is involved in the development of human cancers, including gastric cancers. We have analyzed the entire coding region of human CASPASE-8 gene for the detection of somatic mutations in 162 gastric carcinomas (40 early and 122 advanced cancers), 185 non-small cell lung cancers, 93 breast carcinomas, and 88 acute leukemias by PCR-single-strand conformation polymorphism. Of the cancers analyzed, 13 cancers harbored CASPASE-8 somatic mutations. Interestingly, all of the mutations were detected in the advanced gastric cancers (10.7% of the 122 samples). We expressed the tumor-derived caspase-8 mutants in 293T, 293, and HT1080 cells and found that most of the mutants (9 of the 10 mutations tested) markedly decreased the cell death activity of caspase-8. In addition, in the cells with the inactivating caspase-8 mutants, cleavage of poly(ADP-ribose)polymerase was markedly reduced compared with that of wild-type caspase-8. The occurrence of CASPASE-8 mutation and the inactivation of cell death activity by the mutants suggest that CASPASE-8 gene mutation may affect the pathogenesis of gastric cancers, especially at the late stage of gastric carcinogenesis.

Exosomes in Cancer Diagnostics.

Exosomes are endosome derived extracellular vesicles of 30-120 nm size ranges. Exosomes have been identified as mediators of cell-to-cell communication by transferring bioactive molecules such as nucleic acids, proteins and lipids into recipient cells. While exosomes are secreted by multiple cell types, cancer derived exosomes not only influence the invasive potentials of proximally located cells, but also affect distantly located tissues. Based on their ability to alter tumor microenvironment by regulating immunity, angiogenesis and metastasis, there has been growing interest in defining the clinical relevance of exosomes in cancers. In particular, exosomes are valuable sources for biomarkers due to selective cargo loading and resemblance to their parental cells. In this review, we summarize the recent findings to utilize exosomes as cancer biomarkers for early detection, diagnosis and therapy selection.

Selective Inhibitors of Nuclear Export (SINE) compounds block proliferation and migration of triple negative breast cancer cells by restoring expression of ARRDC3.

Arrestin-related domain-containing protein-3 (ARRDC3) is one of 6 mammalian arrestins, which suppresses metastasis by inducing degradation of phosphorylated ß2-adrenergic receptor (ß2 AR) and integrin ß4 (ITG ß4). Our previous studies demonstrated that expression of ARRDC3 is epigentically silenced in Triple Negative Breast Cancer (TNBC) cells, and the forced expression of ARRDC3 significantly reduced the invasive potential of TNBC cells. In the current study, we found that Selective Inhibitors of Nuclear Export (SINE) compounds (KPT-185 and selinexor (KPT-330)) restore ARRDC3 expression in TNBC cell lines (MDA-MB-231 and MDA-MB-468) at both the mRNA and protein level in a dose and time course dependent manner. SINE compounds inhibit the proliferation, pro-invasive migration and anchorage independent growth of the TNBC cells by restoring ARRDC3 expression. We found that ARRDC3 expression is lower in TNBC cell lines than those of luminal breast cancer cell lines, and inversely correlated with IC50s of selinexor. Analysis of tissue microarray confirmed that ARRDC3 expression in patient samples is significantly lower in the majority of TNBC tumors relative to normal tissue. In vivo, selinexor inhibited the tumor growth of MDA-MB-231 xenografts by nearly 100% compared with vehicle treated animals. Furthermore, immunohistochemical analysis of TNBC tumors from selinexor treated mice revealed increased ARRDC3 expression versus vehicle treated animals. Our results suggest that restoration of ARRDC3 expression is an important antineoplastic mechanism of SINE compounds in TNBC, and therefore selinexor could be an effective treatment option for breast tumors with down-regulated ARRDC3.

PIK3CA gene is frequently mutated in breast carcinomas and hepatocellular carcinomas.

A recent report revealed that phosphoinositide-3-kinase, catalytic, alpha (PIK3CA) gene is somatically mutated in several types of human cancer, suggesting the mutated PIK3CA gene as an oncogene in human cancers. However, because the previous report focused the mutational search primarily on colon cancers, the data on PIK3CA mutations in other types of human cancers have been largely unknown. Here, we performed mutational analysis of the PIK3CA gene by polymerase chain reaction-single-strand conformation polymorphism assay in 668 cases of common human cancers, including hepatocellular carcinomas, acute leukemias, gastric carcinomas, breast carcinomas, and non-small-cell lung cancers. We detected PIK3CA somatic mutations in 26 of 73 hepatocellular carcinomas (35.6%), 25 of 93 breast carcinomas (26.9%), 12 of 185 gastric carcinomas (6.5%), one of 88 acute leukemias (1.1%), and three of 229 non-small-cell lung cancers (1.3%). Some of the PIK3CA mutations were detected in the early lesions of breast cancer carcinoma, hepatocellular carcinoma, and gastric carcinomas, suggesting that PIK3CA mutation may occur independent of stage of the tumors. The high incidence and wide distribution of PIK3CA gene mutation in the common human cancers suggest that alterations of lipid kinase pathway by PIK3CA mutations contribute to the development of human cancers.

Caspase-8 gene is frequently inactivated by the frameshift somatic mutation 1225_1226delTG in hepatocellular carcinomas.

Evidence exists that alterations of the genes encoding apoptosis-related proteins contribute to either development or progression of human cancers. Caspase-8 plays a crucial role in the initiation phase of apoptosis. To explore the possibility that the genetic alteration of caspase-8 gene is involved in the development of hepatocellular carcinomas (HCCs), we have analysed the entire coding region of human caspase-8 gene for the detection of somatic mutations by polymerase chain reaction-single-strand conformation polymorphism in 69 HCCs with low-grade dysplastic nodule (LGDN, n=2) or high-grade dysplastic nodule (HGDN, n=2) or without any dysplastic nodules (n=65). Overall, we detected a total of nine somatic mutations in 69 HCCs (13.0%). Interestingly, all of the nine mutations were an identical frameshift mutation with two base-pair deletion (1225_1226delTG), which would result in a premature termination of amino-acid synthesis in the p10 protease subunit. In a patient sample, we detected the 1225_1226delTG mutation both in HCC and LDGN lesions, suggesting that caspase-8 mutation could be involved in the early stage of HCC carcinogenesis. We expressed the tumor-derived caspase-8 mutant in the cells and found that the mutant abolished cell death activity of caspase-8. Our data indicate that caspase-8 gene is frequently mutated in HCC and the majority of the mutations may be the frameshift mutation 1225_1226delTG. Also, the data suggest that caspase-8 gene mutation might lead to the loss of its cell death function and contribute to the pathogenesis of HCC.

ERBB2 kinase domain mutation in the lung squamous cell carcinoma.

Mounting evidence exists that the activation of proto-oncogene by somatic mutation plays an important roles in the development of human cancers. Recent reports revealed that the kinase domain of ERBB2 gene, a proto-oncogene, is somatically mutated in the lung adenocarcinomas, suggesting the mutated ERBB2 gene may act as an oncogene in human cancers. The purpose of this was to see whether the ERBB2 kinase domain is mutated in other lung cancer types besides the adenocarcinoma. Here, we performed mutational analysis of the ERBB2 kinase domain by polymerase chain reaction-single strand conformation polymorphism assay in 114 non-adenocarcinoma type non-small cell lung cancers (NSCLCs) tissue samples, including 100 squamous cell carcinomas, three adenosquamous carcinomas and 11 large cell carcinomas. We detected the ERBB2 kinase domain mutation in one squamous cell carcinoma (1.0%). The detected ERBB2 mutation showed G to C transversion at bp 2305 (2305G>C), which would result in the substitution of Asp to His at codon 769 (D769H). The amino acid D769 is located in the alpha-helix within the kinase domain, which is important in the binding of ATP with ERBB2. We simultaneously analyzed the somatic mutations of EGFR, K-RAS, PIK3CA and BRAF genes in the squamous cell carcinoma with the ERBB2 mutation, and found that the tumor did not harbor any EGFR or ERBB2 or K-RAS or PIK3CA or BRAF gene mutation, either. This study demonstrated that in addition to lung adenocarcinoma ERBB2 kinase domain mutation could occur in lung squamous cell carcinomas, and suggested that alterations of ERBB2-mediated signaling pathway by ERBB2 mutations may occasionally contribute to the development of lung squamous cell carcinomas.