Histological types and significance of bronchial epithelial dysplasia

Adenomatous hyperplasia induced by chronic cherry pit retention mimicking an endobronchial tumor-case series and systematic review of literature

Introduction

Endobronchial foreign body aspiration is not common in adults, but it is a life-threatening event. Recurrent pneumonias by chronic retention of foreign body often lead to initial medical presentation of the patient. However, lymphoplasmacellular bronchitis with adenomatous hyperplasia and squamous epithelium metaplasia with complete or partial blockage of lobar bronchus mimicking lung tumor is rare in literature, and this particular condition is often misdiagnosed.

Case presentation

we report our experience in the diagnostic and management of two elderly patients with recurrent pneumonia, admitted in hospital for further examination. In both patients, with no history of aspiration, the cherry pit was detected during bronchoscopy and recanalization with flexible cryoprobe, surrounded by purulent secretion, occluding completely the right upper lobe in the first case, and partially the left lower lobe associated with persistent actinomycosis in the second case, with signs of local inflammation, bronchial adenomatous hyperplasia mimicking lung tumor at initial bronchoscopic examination. Histology showed a lymphoplasmacellullar bronchitis with adenomatous hyperplasia and squamous epithelium metaplasia because of chronic retention of foreign body.

Conclusion

Bronchoscopy examination should be considered in cases where there is an unresolved chronic cough with recurrent pneumonia or persistent actinomycosis in patients with high risk. Cryoprobe is a safe and feasible approach for treatment of airway obstructions due to chronic foreign body retention. Furthermore, relevant findings are discussed here, along with a review of the pathologic alterations and treatment modalities seen in chronic retention of foreign body and airway injury.

Regenerative and progressing lesions in lungs and lung-associated lymph nodes from fourteen 90-day inhalation studies with chemically different particulate materials

Rat lungs and lung-associated lymph nodes from 14 inhalation studies with chemically different particulate materials were histopathologically re-evaluated, and the bronchoalveolar lavage fluid (BALF) data and lung burden analyses were compared. All investigated substances caused similar lesions. For most substances, 1 mg/m3 of respirable particulate matter was established as the borderline for adverse morphological changes after the 90-day exposure period, confirmed by the increase in polymorphonuclear neutrophils in BALF. Possible reversibility was demonstrated when recovery groups are included in the study especially allowing the differentiation between regeneration or progressing of inflammatory changes during the recovery period. It was concluded, that the major driver of toxicity is not an intrinsic chemical property of the particle but a particle effect. Concerning classification for specific target organ toxicant (STOT) repeated exposure (RE), this paper highlights that merely comparing the lowest concentration, at which adverse effects were observed, with the Classification Labelling and Packaging (CLP) regulation (EC) no. 1272/2008 guidance values is inappropriate and might lead to a STOT classification under CLP for a large part of the substances discussed in this paper, on the basis of typically mild to moderate findings in rat lung and lung-associated lymph nodes on day 1 after exposure. An in-depth evaluation of the pathologic findings is required and an expert judgement has to be included in the decision on classification and labeling, evaluating the type and severity of effects and comparing these with the classification criteria.

The predictive value of the change of the number of pixels under different CT value intervals in the CT-occult central lung squamous cell carcinoma and squamous epithelial precancerous lesions

BACKGROUND

Due to the fact that the CT-occult central lung squamous cell carcinoma and squamous epithelial precancerous lesions. (CT-occult CLSCC and SEPL) cannot be detected by lung CT screening, early and timely diagnosis of central lung cancer becomes very difficult, which directly affects the prognosis of patients.

METHODS

We retrospectively review medical records of patients at the Zhejiang Cancer Hospital and enrolled 41 patients with the CT-occult CLSCC and SEPL and 48 patients without the CT-occult CLSCC and SEPL. We compare the clinical characteristics, imaging features and Changes in the number of pixels under different CT value intervals of patients with and without the CT-occult CLSCC and SEPL and we perform univariate and multivariate logistic regression analysis to explore independent factors for the CT-occult CLSCC and SEPL in the patients.

RESULTS

We demonstrate that pack-years ≥ 20 (OR: 3.848, 95% CI: 1.086 ~ 13.633), the number of pixels change of CT value in interval [-850 ~ -750HU] (OR: 5.302, 95% CI: 1.122 ~ 25.057) and in interval [-900 ~ -850HU] (OR: 3.478, 95% CI: 1.167 ~ 10.365) are independently associated with the CT-occult CLSCC and SEPL in the patients. Ultimately, the logistic model obtained is statistically significant (p < 0.05) and an area under the ROC curve is 0.776 (95% CI: 0.682-0.870). The sensitivity of this model is 90.2% and the specificity is 52.1%.

CONCLUSION

The results of this study indicate that in the CT value range [-950 ~ -750HU], when the total number of lung pixels tend to increase towards the region with high CT value, the probability of the occurrence of CT-occult CLSCC and SEPL lesions also increases. Meanwhile, these results have guiding significance for the further study of radiomic.

Expression of Markers Ki-67, Nestin, VEGF, CD34 and Apoptosis in Relatively Healthy Lung Tissue with Non-Changed and Metaplastic Bronchial Epithelium

BACKGROUND

Knowledge about the occurrence of processes such as proliferation, apoptosis and angiogenesis in healthy lung tissues with different bronchial epitheliums is limited, and further exploration can contribute to a better understanding of the physiological renewal of lung tissues. The processes mentioned above occur with the help of important tissue factors; therefore, the aim of the study was to determine the expression of markers Ki-67, nestin, CD34 and vascular endothelial growth factor (VEFG) and detect apoptotic cells in relatively healthy lung tissue.

METHODS

Samples of relatively healthy lung tissue were obtained from 19 patients and divided into groups of patients with non-changed and patients with metaplastic bronchial epithelium. Tissue samples were examined by hematoxylin and eosin staining. Ki-67, nestin, VEGF and CD34-positive cells were detected by the immunohistochemistry method. Terminal deoxynucleotidyl transferase (TdT) dUTP nick-end labeling (TUNEL) assay was carried out to detect apoptotic cells. The number of positive structures was counted semi-quantitatively by microscopy.

RESULTS

Ki-67-positive cells were detected in only one case. An occasional to moderate number of nestin-positive structures was found in various tissues of relatively healthy lungs with different bronchial epitheliums. No apoptotic cells were seen in non-changed bronchial epithelium, compared with few apoptotic cells in metaplastic bronchial epithelium. Metaplastic bronchial epithelium contained more VEGF-positive cells than non-changed bronchial epithelium. Samples with non-changed, and metaplastic bronchial epithelium both contained a similar number of CD34-positive structures.

CONCLUSIONS

Proliferative activity and programmed cell death are not prominent events in normal lung tissue. A moderate number of nestin-positive cells in the alveolar epithelium and cartilage of bronchi with pseudostratified ciliated epithelium suggests a significant role of neuronal origin cells in these structures, to be intensified in metaplastic bronchial epithelium. A practically non-changed number of CD34-positive cells excludes any difference in stimulation of endothelial origin cells between lungs with different types of epithelium, while an increase in VEGF in structures with metaplastic epithelium suggests the presence/influence of tissue ischemia impact on possible development/maintenance of metaplasia.

Dermal and Intraepidermal Merkel Cell Carcinoma With Squamous Cell Carcinoma: A Report of a Rare Case With Special Reference to the Touch Dome

ABSTRACT

In skin containing hair follicles, specialized epithelial structures known as "touch domes (TDs)" are located where the Merkel cells are clustered. We explored the histogenetic relationship between intraepidermal and dermal Merkel cell carcinomas (MCCs) and investigated which transformed progenitor cells can develop into intraepidermal MCC. We encountered an association between an extremely rare case of dermal and intraepidermal MCC with squamous cell carcinoma, which was examined using standard immunohistochemical methods with various epithelial, neuroendocrine, and TD markers including several immunohistochemical markers. Differential expression levels of CK20 and CD56 were found between intraepidermal and dermal MCCs, indicating molecularly distinct MCC populations. CK15 and CK17, expressed in TDs, were partially expressed in the intraepidermal neuroendocrine component at the tumor periphery in intraepidermal MCC with squamous cell carcinoma. These differences may suggest that the origin of dermal and intraepidermal MCCs is different under pathological conditions. We hypothesize that intraepidermal MCC is derived from tissue-specific stem cells localized within TDs.

Screening and identification of the tumor-associated antigen CK10, a novel potential liver cancer marker

Hepatocellular carcinoma (HCC) is a malignancy that is associated with high mortality rates in Asia. These tumors are highly invasive and their etiology is frequently unknown. Thus, most patients are diagnosed in the middle and late stages of the disease, and thus do not have sufficient time for therapy. Therefore, it is essential to study the early diagnosis and treatment of HCC; in this regard, the study of tumor‐associated antigens has received much attention. Here, antigens from the human primary HCC cell line, QGY‐7703, were used to immunize mice in order to prepare monoclonal antibodies. The specific antigen recognized by antibody 11C3 was purified from total protein lysates of QGY‐7703 by immunoaffinity chromatography. The validity of the candidate antigen as a new HCC‐associated marker was tested using SDS/PAGE, western blot, HPLC‐ESI‐MS/MS, and RT‐qPCR. Our results showed that the levels of CK10 in HCC‐derived cell lines were significantly higher than those in normal liver cells. Thus, we suggest that CK10 may be involved in the formation and development of HCC, and may be a therapeutically targetable tumor‐associated antigen.

Cytokeratin 17 immunoexpression in actinic keratosis (bowenoid and nonbowenoid) and in Bowen disease

Cytokeratin (CK) 17 immunoexpression has been investigated in nonmelanoma skin cancer as well as in many preinvasive epithelial malignancies. However, there is not any previous study of CK17 immunoexpression in actinic keratosis (AK) or Bowen disease in nonimmunocompromised patients. We evaluated CK17 immunoexpression in 20 cases of AK (10 nonbowenoid and 10 bowenoid) as well as in 10 cases of Bowen disease. We identified expression of CK17 in the superficial layers above the atypical foci. In some cases, there were foci of expression by the full thickness of the epidermis, which was the predominant pattern in very few cases (1 Bowen disease and 1 bowenoid AK). In addition, 1 case of bowenoid AK showed CK17 expression in a "skyline" pattern in the basal layer of the epidermis. Cytokeratin 17 immunostaining did not allow us to distinguish between the 3 entities studied. However, the immunostaining allowed us to distinguish atypical foci in the biopsies, even if atypicality was minimal. In addition, CK17 was useful in identifying surgical borders involved by disease in cases in which the hematoxylin-eosin was difficult to evaluate. Cytokeratin 17 immunoexpression might have a role in evaluating surgical borders in some cases of AK and Bowen disease.

Recurrence of squamous cell lung carcinoma is associated with the co-presence of reactive lesions in tumor-adjacent bronchial epithelium

Recurrences occur in 30 % of lung cancer patients after radical therapy; however, known prognostic factors are not always effective. In this study, we investigated whether the frequency of squamous non-small cell lung cancer (NSCLC) recurrence depends on the presence of reactive lesions in tumor-adjacent bronchial epithelium. Specimens of adjacent lung tissue from 104 patients with squamous NSCLC were used for the determination of basal cell hyperplasia (BCH) and squamous metaplasia (SM) and for the analysis of the expression of Ki-67, p53, Bcl-2, and CD138. We found that recurrence was observed in 36.7 % of patients with BCH combined with SM (BCH + SM+) in the same bronchus, compared with 1.8 % in patients with isolated BCH (BCH + SM-; odds ratio (OR) 31.26, 95 % confidence interval (CI) 3.77-258.60; p = 0.00002). The percentage of Ki-67-positive cells was significantly higher in BCH + SM+ than in BCH + SM- (34.9 vs. 18.3 %; effect size 2.86, 95 % CI 2.23-3.47; p = 0.003). P53 expression was also more significant in BCH + SM+ than in BCH + SM- (14.4 vs. 9.6 %; effect size 1.22, 95 % CI 0.69-1.76; p = 0.0008). In contrast, CD138 expression was lower in BCH + SM+ than in BCH + SM- (21.8 vs. 38.5 %; effect size -6.26, 95 % CI -7.31 to -5.22; p = 0.003). Based on our results, we concluded that the co-presence of reactive bronchial lesions is associated with the development of recurrent squamous NSCLC and may be a negative prognostic indicator. In addition, significant differences in Ki-67, p53, and CD138 expression exist between isolated BCH and BCH combined with SM that probably reflect part of biological differences, which could relate to the mechanism of lung cancer recurrence.

Facts and fiction: premalignant lesions of lung tissues

Lung cancer is now the leading cause of death from cancer in Australia. Most patients are diagnosed with late-stage disease. Although diagnosis at pre-invasive stages could theoretically improve outcomes, mooted precursor lesions are often asymptomatic and often undetectable by non-invasive investigations. Nonetheless, they merit study to identify early and essential molecular steps involved in lung carcinoma pathogenesis, with the aim of developing therapies targeted against one or more such steps. Some lung cancers appear to develop via a series of progressive morphological changes with correlating molecular alterations, but others seem to arise in histologically normal epithelium, and these differences may reflect anatomically and functionally distinct epithelial compartments of the respiratory tract. Pre-invasive precursor lesions recognised by the World Health Organization (WHO) include squamous metaplasia with dysplasia and carcinoma in situ, atypical adenomatous hyperplasia, and diffuse idiopathic pulmonary neuroendocrine cell hyperplasia. Other lesions that likely represent pre-invasive lesions, but which are not currently WHO-listed, include human papillomavirus (HPV)-related respiratory papillomatosis and mesothelioma in situ. No single cancer stem cell marker has been identified. Field cancerisation plays an important role in lung cancer development, and includes the spread of pre-invasive clones along the respiratory epithelium or the occurrence of multiple separate foci of pre-invasive abnormalities such as squamous dysplasia and carcinoma in situ.In addition to well-characterised step-wise progression in squamous cell carcinomas and some adenocarcinomas, alternative pathways exist, and are currently being investigated. In addition, molecular techniques, including miRNA screening on blood samples or cytology samples--such as sputum samples--may become clinically relevant and more accurate in predicting lung cancer progression.

The expression of cytokeratin 19 in lymph nodes was a poor prognostic factor for hepatocellular carcinoma after hepatic resection

BACKGROUND

The expression of CK19 in primary hepatocellular carcinoma (HCC) is associated with a poor outcome. However, few studies have investigated the expression profile of CK19 in regional lymph nodes (LNs) of HCC after hepatic resection. The purpose of this study was to evaluate the expression of CK19 in primary liver tumor and regional LNs of HCC with and without lymph node metastasis (LNM).

METHODS

The expression of CK19 in patients with (n = 16) and without LNM (n = 26) was examined using immunohistochemical staining. Both the primary tumor and LN specimen were studied for their CK19 expression. Clinico-pathological variables and prognostic significance were analyzed.

RESULTS

Immunopositivity of CK19 in primary liver tumor was significantly correlated with LNM (P = 0.005) and tumor non-encapsulation (P <0.005). Univariate analysis showed that CK19 expression in primary liver tumor, CK19 expression in regional LN, vascular invasion, daughter nodules, positive resection margin and American Joint Committee on Cancer (AJCC) tumor stage significantly decreased overall survival. Multivariate analysis demonstrated that daughter nodules (P = 0.001) and CK19 expression in regional LN (P = 0.002) were independent prognostic factors for overall survival.

CONCLUSIONS

This study showed that CK19 expression in regional LN of HCC was associated with LNM and an extremely poor outcome after operation. It is of clinical significance to identify these patients at risk for more aggressive HCC, and multi-modality treatment could be helpful to improve their dismal outcome.

Serpin B4 isoform overexpression is associated with aberrant epithelial proliferation and lung cancer in idiopathic pulmonary fibrosis

AIMS

The aim of the study was to evaluate the role of Serpin B3/B4 in advanced idiopathic pulmonary fibrosis (IPF) patients, mainly focusing on epithelial proliferation.

METHODS

Lungs from 48 IPF patients (including cases with cancer or high-grade epithelial dysplasia) were studied and compared with other diffuse parenchymal diseases and normal lungs. Immunohistochemistry for Serpin B3/B4 and Ki-67 was quantified in all cases, distinguishing stained metaplastic cells. In IPF patients correlations between Serpin expression and several clinicopathological data, including fibrotic remodelling [fibrosis extension and transforming growth factor β expression (TGF-β)] were performed. Molecular analysis was used for Serpin isoform characterisation.

RESULTS

In IPF patients Serpin B3/B4 and Ki-67 were significantly overexpressed in many metaplastic cells (mainly squamous type) compared to control cases. Higher Serpin B3/B4 was found in older patients and cases with more impaired respiratory function. Serpin B3/B4 expression was related to both TGF-β and Ki-67 and was higher in patients with cancer/high-grade dysplasia. Serpin B3 was expressed in all cases, whereas Serpin B4 was expressed only in IPF.

CONCLUSIONS

Serpin B3/B4, particularly Serpin B4, appears to play an important role in aberrant epithelial proliferation. Evaluation of Serpin B3/B4 could have prognostic value in predicting disease progression, especially in patients with increased susceptibility to lung cancer.

Short-term exposure to tobacco toxins alters expression of multiple proliferation gene markers in primary human bronchial epithelial cell cultures

The biological effects of only a finite number of tobacco toxins have been studied. Here, we describe exposure of cultures of human bronchial epithelial cells to low concentrations of tobacco carcinogens: nickel sulphate, benzo(b)fluoranthene, N-nitrosodiethylamine, and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). After a 24-hour exposure, EGFR was expressed in cell membrane and cytoplasm, BCL-2 was expressed only in the irregular nuclei of large atypical cells, MKI67 was expressed in nuclei with no staining in larger cells, cytoplasmic BIRC5 with stronger nuclear staining was seen in large atypical cells, and nuclear TP53 was strongly expressed in all cells. After only a 24-hour exposure, cells exhibited atypical nuclear and cytoplasmic features. After a 48-hour exposure, EGFR staining was localized to the nucleus, BCL-2 was slightly decreased in intensity, BIRC5 was localized to the cytoplasm, and TP53 staining was increased in small and large cells. BCL2L1 was expressed in both the cytoplasm and nuclei of cells at 24- and 48-hour exposures. We illustrate that short-termexposure of a bronchial epithelial cell line to smoking-equivalent concentrations of tobacco carcinogens alters the expression of key proliferation regulatory genes, EGFR, BCL-2, BCL2L1, BIRC5, TP53, and MKI67, similar to that reported in biopsy specimens of pulmonary epithelium described to be preneoplastic lesions.

Immunochemistry and lung cancer: application in diagnosis, prognosis and targeted therapy

Immunochemistry is now an established ancillary technique in lung cancer diagnosis. Not only does it help in supporting the morphological diagnosis of malignancy, but its role now extends to the determination of cell lineage, ascertaining the primary site of tumour origin and contributing to decisions on prognosis and treatment. Early detection and confirmation of lung cancer facilitate early treatment decisions. Lung cancer management now has a multidisciplinary approach which includes cytopathologists and clinicians. Some clinicians may not understand what immunochemistry is and what its role is in lung cancer diagnosis, prognosis and therapy. The purpose of this paper is to define immunochemistry, on the background of basic respiratory airway epithelial structure and cancer biology, and discuss its application in the diagnosis, treatment and determination of prognosis of lung cancer.

Identification of proteomic differences between squamous cell carcinoma of the lung and bronchial epithelium

Proteins that exhibit different expression levels in normal and malignant lung cells are good candidate biomarkers to improve early diagnosis and intervention. We used a quantitative approach and compared the proteome of microdissected cells from normal human bronchial epithelium and squamous cell carcinoma tumors of histopathological grades G2 and G3. DIGE analysis and subsequent MS-based protein identification revealed that 32 non-redundant proteins were differentially regulated between the respective tissue types. These proteins are mainly involved in energy pathways, cell growth or maintenance mechanisms, protein metabolism, and the regulation of DNA and RNA metabolism. The expression of some of these proteins was analyzed by immunohistochemistry using tissue microarrays containing tissue specimen of 55 patients, including normal bronchial epithelium, squamous cell carcinomas, adenocarcinomas, and large cell carcinomas. The results of the immunohistochemical studies correlated with the proteome study data and revealed that particularly HSP47 and a group of cytokeratins (i.e. cytokeratins 6a, 16, and 17) are significantly co-regulated in squamous cell carcinoma. Furthermore cytokeratin 17 showed significantly higher abundance in G2 grade compared with G3 grade squamous cell carcinomas in both the gel-based and the immunohistochemical analysis. Therefore this protein might be used as a marker for stratification between different tumor grades.

Cytokeratin 10 and cytokeratin 19: predictive markers for poor prognosis in hepatocellular carcinoma patients after curative resection

PURPOSE

Cytokeratin 10 (CK10) was found to be expressed differently in human hepatocellular carcinoma (HCC) cell lines with different metastatic potentials in our previous research. The aim of this study was to assess the value of CK10 alone or in combination with cytokeratin 19 (CK19) in predicting tumor recurrence after curative resection in HCC patients.

EXPERIMENTAL DESIGN

CK10 expression in stepwise metastatic HCC cell lines and tumor tissues from 50 HCC patients was investigated using immunofluorescence assay, quantitative real-time reverse transcription-PCR, and Western blot analyses. Tumor tissue microarrays of 300 HCC patients who underwent curative resection between 1997 and 2000 were used to detect the expressions of CK10 and CK19. Clinicopathologic data for these patients were evaluated. The prognostic significance was assessed using Kaplan-Meier survival estimates and log-rank tests.

RESULTS

CK10 was overexpressed in the high metastatic HCC cell line and in tumor tissues of recurrent patients. Both univariate and multivariate analyses revealed that CK10 was a significant predictor for overall survival (OS) and disease-free survival, and that CK19 was a significant predictor for OS. CK10 expression was correlated with poor prognosis regardless of alpha-fetoprotein, tumor-node-metastasis stage, and vascular invasion. The 7-year OS and disease-free survival rates in CK10+ and/or CK19+ patients were 30.0% and 37.6%, respectively, which were significantly lower than that of CK10-/CK19- patients (56.1% and 60.0%, respectively; P < 0.001).

CONCLUSION

CK10 is associated with HCC invasiveness. CK10 alone, or in combination with CK19, can be a novel predictor for poor prognosis of HCC patients after curative resection.

Automated detection of genetic abnormalities combined with cytology in sputum is a sensitive predictor of lung cancer

Detection of lung cancer by sputum cytology has low sensitivity but is noninvasive and, if improved, could be a powerful tool for early lung cancer detection. To evaluate whether the accuracy of diagnosing lung cancer by evaluating sputa for cytologic atypia and genetic abnormalities is greater than that of conventional cytology alone, automated scoring of genetic abnormalities for 3p22.1 and 10q22.3 (SP-A) by fluorescence in situ hybridization (FISH) and conventional cytology was done on sputa from 35 subjects with lung cancer, 25 high-risk smokers, and 6 healthy control subjects. Multivariate analysis was performed to select variables that most accurately predicted lung cancer. A model of probability for the presence of lung cancer was derived for each subject. Cells exfoliated from patients with lung cancer contained genetic aberrations and cytologic atypias at significantly higher levels than in those from control subjects. When combined with cytologic atypia, a model of risk for lung cancer was derived that had 74% sensitivity and 82% specificity to predict the presence of lung cancer, whereas conventional cytology achieved only 37% sensitivity and 87% specificity. For diagnosing lung cancer in sputum, a combination of molecular and cytologic variables was superior to using conventional cytology alone.

Loss of Nkx2.8 deregulates progenitor cells in the large airways and leads to dysplasia

Nkx2.8, a homeodomain transcription factor, has been characterized in liver cancer and in the developing central nervous system. We now show that this factor is also expressed in the lung, where it localizes in adults to a discrete population of tracheobronchial basal cells. To target the mouse gene, the first exon was replaced by a LacZ marker gene joined to the intact 5'-untranslated region. Marker expression was observed throughout the lower respiratory tract, beginning on E11 in a few cells of the distal lung buds. The region of expression then spread upward. By neonatal day 1, expression was greatest in the large airways and the Nkx2.8-/- mice exhibited generalized tracheobronchial hyperplasia. Bromodeoxyuridine (BrdUrd) labeling studies showed that a higher rate of bronchial cell proliferation persisted at 6 to 8 months. In adults, Nkx2.8 marker expression decreased with progressive differentiation into ciliated and secretory cells. The cell localizations and patterns of coexpression with BrdUrd and differentiation markers suggest a progenitor relationship: the cells that most strongly express Nkx2.8 seem to function as tracheobronchial stem cells. Moreover, Nkx2.8 acts to limit the number of these progenitor cells because the marker-expressing population was greatly expanded in Nkx2.8-/- mice. Increased proliferation and an altered progenitor relationship caused progressive bronchial pathology, which manifested as widespread dysplasia in the large airways of 1-year-old Nkx2.8-/- mice.