UV irradiation induces histone variant H2AX phosphorylated on serine 139 (γH2AX) foci and high levels of pan-nuclear γH2AX staining without foci, but the significance of this finding is still uncertain. We examined the formation of γH2AX and 53BP1 that coincide at sites of double-strand breaks (DSBs) after ionizing radiation. We compared UV irradiation and treatment with etoposide, an agent that causes DSBs during DNA replication. We found that during DNA replication, UV irradiation induced at least three classes of γH2AX response: a minority of γH2AX foci colocalizing with 53BP1 foci that represent DSBs at replication sites, a majority of γH2AX foci that did not colocalize with 53BP1 foci, and cells with high levels of pan-nuclear γH2AX without foci of either γH2AX or 53BP1. Ataxia-telangiectasia mutated kinase and JNK mediated the UV-induced pan-nuclear γH2Ax, which preceded and paralleled UV-induced S phase apoptosis. These high levels of pan-nuclear γH2AX were further increased by loss of the bypass polymerase Pol η and inhibition of ataxia-telangiectasia and Rad3-related, but the levels required the presence of the damagebinding proteins of excision repair xeroderma pigmentosum complementation group A and C proteins. DSBs, therefore, represent a small variable fraction of UV-induced γH2AX foci dependent on repair capacity, and they are not detected within high levels of pan-nuclear γH2AX, a preapoptotic signal associated with ATM-and JNK-dependent apoptosis during replication. The formation of γH2AX foci after treatment with DNA-damaging agents cannot, therefore, be used as a direct measure of DSBs without independent corroborating evidence.T o maintain the integrity of genomic information under threat of DNA damage, cells employ a range of responses including DNA repair, replication bypass, recombination, cell-cycle checkpoints, and senescence or apoptosis (1, 2). These responses are described by the all-embracing concept of the DNA damage response (DDR) (1). DNA double-strand breaks (DSBs) are important but not the only starting lesion for the DDR.In eukaryotic cells, the DDR is rapidly initiated by the PI3K kinases ataxia-telangiectasia and Rad3-related (ATR) and ataxiatelangiectasia mutated kinase (ATM) (3, 4). ATR is recruited to single-stranded DNA regions at stalled replication forks in response to replication stress (5-8); ATM is activated primarily in response to DSBs (3, 9-11). ATR and ATM phosphorylate serine threonine protein kinase and CHK2, respectively, which activate cell-cycle checkpoints and p53, leading to a p53-dependent apoptotic pathway (12). This kinase cascade phosphorylates serine 139 and tyrosine 142 of the histone variant H2AX. After ionizing radiation accumulates in foci, phosphorylated H2AX (γH2AX) serine threonine protein kinase colocalizes with other markers of DSBs (53BP1, pNBS1, MDC1, and Brca1) in immunofluorescent microscopy (IF) (13-16). γH2AX foci are frequently adopted as quantitative markers for DSBs in IF (17, 18). However, the exact correspondence between γH2AX and D...

The histopathology of DRESS syndrome highlights various associated inflammatory patterns in a single biopsy. Cutaneous effector lymphocytes comprise a high proportion of polyclonal CD8(+) granzyme B(+) T lymphocytes.

Atypical fibroxanthoma (AFX) (dermal pleomorphic sarcoma) remains a somewhat controversial entity. Some authors have averred that AFX is a fiction, suggesting that such lesions merely represent misclassified examples of spindled squamous cell carcinoma. In addition, the immunoperoxidase confirmation of AFX has been less than straightforward and has historically been approached as a diagnosis of exclusion because of the lack of sensitivity and specificity of available "positive" reagents. Procollagen 1 (PC1) and CD10 represent recently developed immunoperoxidase reagents that have been forwarded as useful in this setting, and we sought to characterize our experience, both to confirm the utility of these antibodies and to compare them. Our investigation included 3 separate data sets. Group 1 consisted of a retrospective review of 98 consecutive cases in which PC1 was used in the evaluation of dermatopathology specimens in routine practice during a 13-month interval. Group 2 consisted of a direct comparison of 11 AFX, 11 dermatofibroma (DF), and 7 epithelioid dermatofibroma (EDF) using the CD10 reagent on cases identified by database search. Group 3 consisted of a retrospective review of 47 cases in which CD10 was used in routine practice during a 10-month interval. Group 1 included 47 AFX, 13 carcinomas, and 6 melanomas. PC1 expression was observed in 45 of 47 AFX (96%), with a strong reaction in 78% of cases. Among a comparison group of carcinomas, 13 of 13 displayed strong keratin immunopositivity and 11 of 13 (85%) lacked PC1 expression whereas 2 showed focal weak labeling. Six of six melanomas exhibited avid S100 expression and none labeled with PC1. In group 2, strong CD10 immunoreactivity was present in 11 of 11 AFX. Similarly, 11 of 11 DFs were also positive. In contrast, 6 of 7 cases of EDF lacked CD10 expression. Group 3 included 38 AFX and 9 miscellaneous spindle cell proliferations. Of the 38 AFX, 37 (97%) labeled with CD10 and in 34 (92%) the reaction was strong. PC1 immunostaining was also completed in 34 of 38 AFX from group 3 and 27 (79%) cases showed positive labeling. Our results confirm that both PC1 and CD10 can be used as positive markers of AFX. We believe that CD10 and PC1 immunostaining can be used as a useful adjunct to supplement the diagnosis of AFX, within the context of an immunoperoxidase panel. Not surprisingly, CD10 expression is also common in DF, a benign analog of AFX, with the exception of its epithelioid variant. In direct head-to-head comparison, our experience indicates that the staining of AFX with CD10 is more avid than that observed with PC1. Lastly, out data includes over 80 examples of AFX, <5% of which showed keratin labeling. Given a general lack of keratin expression, it seems unlikely that AFX merely represents poorly differentiated squamous carcinoma.

Patients with lung cancer often present with metastatic disease and therefore have a very poor prognosis. The recent discovery of several novel ROS receptor tyrosine kinase molecular alterations in non-small-cell lung cancer (NSCLC) presents a therapeutic opportunity for the development of new targeted treatment strategies. Here, we report that the NSCLC-derived fusion CD74-ROS, which accounts for 30% of all ROS fusion kinases in NSCLC, is an active and oncogenic tyrosine kinase. We found that CD74-ROS expressing cells were highly invasive in vitro and metastatic in vivo. Pharmacological inhibition of CD74-ROS kinase activity reversed its transforming capacity by attenuating downstrream signaling networks. Using quantitative phosphoproteomics, we uncovered a mechanism by which CD74-ROS activates a novel pathway driving cell invasion. Expression of CD74-ROS resulted in the phosphorylation of the extended synaptotagmin-like protein E-Syt1. Elimination of E-Syt1 expression drastically reduced invasiveness both in vitro and in vivo without modifying the oncogenic activity of CD74-ROS. Furthermore, expression of CD74-ROS in non-invasive NSCLC cell lines readily confered invasive properties that paralleled the acquisition of E-Syt1 phosphorylation. Taken together, our findings indicate that E-Syt1 is a mediator of cancer cell invasion and molecularly define ROS fusion kinases as therapeutic targets in the treatment of NSCLC.

A 6-month-old boy was referred to our burn unit with a recurrent bullous dermatitis, fever, and emesis, originally diagnosed as staphylococcal scalded skin syndrome (SSSS) at an outside hospital. Infectious workup was negative and shave biopsy revealed a dense, diffuse dermal infiltrate of mast cells, consistent with diffuse cutaneous bullous mastocytosis-a rare variant of cutaneous mastocytosis. Treatment included a prolonged course of corticosteroids and antihistamines. Recognition of this rare form of mastocytosis is important, as it can be easily mistaken for other pediatric bullous diseases and is associated with life-threatening complications including vasodilation, anaphylactic shock, gastrointestinal bleeding, and death.