Ron Yaar

Animal models for the study of adenosine receptor function

Adenosine receptors represent a family of G‐protein coupled receptors that are ubiquitously expressed in a wide variety of tissues. This family contains four receptor subtypes: A1 and A3, which mediate inhibition of adenylyl cyclase; and A2a and A2b, which mediate stimulation of this enzyme. Currently, all receptor subtypes have been genetically deleted in mouse models except for the A2b adenosine receptor, and some have been overexpressed in selective tissues of transgenic mice. Studies involving these transgenic mice indicated that receptor levels are rate limiting, as effects were amplified upon increases in receptor level. The knockout models pointed to clusters of activities related to the physiologies of the cardiovascular and the nervous systems, which are either reduced or enhanced upon specific receptor deletion. Interestingly, the trend of effects on these systems is similar in the A1 and A3 adenosine receptor knockout mice and opposite to the effects observed in the A2a adenosine receptor knockout model. This review summarizes in vitro studies on pathways affected by each adenosine receptor, and primarily focuses on the above in vivo models generated to investigate the physiologic role of adenosine receptors. Furthermore, it illustrates the need for multiple adenosine receptor subtype deficiency studies in mice and the deletion of the A2b subtype.

Regional recurrence after negative sentinel lymph node biopsy for melanoma.

Objective:Sentinel lymph node (SLN) biopsy has shown great utility in the management of melanoma. An analysis of regional recurrence in previously mapped negative SLN basins as the first site of relapse is performed. Methods:A retrospective query of a prospective melanoma database from 1994 to 2006 identified 1287 patients who underwent successful SLN biopsy. One thousand sixty patients (82.4%) were SLN negative and 227 (17.6%) patients SLN positive. Clinical variables were examined for the impact on regional recurrence by multivariate analysis. Results:Mean follow-up was 44.3 months (range 3–155 months). Thirty-five patients (3.3%) presented with false-negative (FN) SLN biopsy. Pathologic review of the SLNs harvested from these basins found 7 (20.0%) samples positive for metastatic melanoma. Multivariate analysis found head and neck site [hazard ratio 3.67; 95% confidence interval (CI), 1.77–7.60, P < 0.001] and tumor thickness (hazard ratio 1.16; 95% CI, 1.04–1.30, P = 0.01) to be predictive of FN SLN biopsy. The 5-year melanoma specific survival calculated from the date of the SLN biopsy was 57.6% (95%CI, 35.7–41.9) in the FN group, which was not statistically different than the SLN positive group 60.0% (95% CI, 29.6–40.1; P = 0.14). Conclusions:Head and neck tumor site and tumor thickness are predictors of a FN SLN biopsy. Mechanisms other than pathologic SLN sampling error may contribute to the failure of the SLN biopsy in some patients. Patients with regional recurrence after negative SLN biopsy have a similar 5-year survival compared with patients with positive SLNs.

Stem cell markers (cytokeratin 15, cytokeratin 19 and p63) in in situ and invasive cutaneous epithelial lesions

The inherent longetivity of stem cells causes them to be susceptible to multiple genetic hits. Thus, it is not surprising that stem cells are implicated in the etiopathogenesis of select cutaneous neoplasms. However, most studies to date are restricted to the use of a single marker (p63, cytokeratin-15 or cytokeratin-19) and do not appear to compare distribution of stem cell markers in a spectrum of cutaneous in situ versus invasive epithelial malignancies. In this study, we evaluate expression of cytokeratin-15, cytokeratin-19, and p63 in a series of primary cutaneous epithelial lesions that include actinic keratosis (n=29), squamous cell carcinoma in situ (n=30), bowenoid papulosis (n=15) and squamous cell carcinoma, well differentiated (n=29) in order to evaluate the role of stem cell marker expression in the grading and development of in situ and invasive malignancies. For cytokeratin-15, expression was retained in actinic keratosis (38%), squamous cell carcinoma in situ (53%) and bowenoid papulosis (60%) but appeared to be lost in squamous cell carcinoma (3%) with statistically significant differences observed between groups that retained versus those that did not (P<0.05 for all three); for cytokeratin-19, patchy yet basal expression was noted in actinic keratosis (21%), patchy and suprabasal expression was noted in squamous cell carcinoma in situ (37%), bowenoid papulosis (13%) and squamous cell carcinoma (24%) with no statistically significant differences between groups; for p63, expression was retained in actinic keratosis (90%), squamous cell carcinoma in situ (87%), bowenoid papulosis (60%) and squamous cell carcinoma (100%) with no statistically significant differences between groups. In summary, our findings expand the neoplasms which involve stem cells to include cutaneous epithelial malignancies. Differential localization of each of these markers argues in favor of stem cell heterogeneity.

Activity of the A3 adenosine receptor gene promoter in transgenic mice: characterization of previously unidentified sites of expression.

Sites of A3 adenosine receptor gene expression have not been fully explored nor has this genes promoter activity been confirmed in vivo. Transgenic mice were generated in which 2.3 kb upstream of the transcriptional start site of the mouse A3 adenosine receptor was coupled to a β‐galactosidase reporter gene. Selective transgene expression was detected in testis and brain as well as at other sites in which A3 adenosine receptor message has not been previously reported, including retinal ganglion cells and smooth muscle cells of the cerebrospinal vasculature. Our study suggests that this promoter may be useful in the selective targeting of gene expression to specific tissues.

Cutaneous metastasis of prostatic adenocarcinoma: a cautionary tale.

With the exception of skin cancer, prostatic adenocarcinoma represents the most common cancer among men in the United States and the second most common cause of cancer mortality. Mortality is often associated with metastatic disease, which in the case of prostatic adenocarcinoma typically involves bones and only rarely affects the skin. Although clinical history and examination, laboratory tests and routine pathology can suggest the prostate as a source of metastatic disease, immunohistochemistry – specifically, for prostate‐specific antigen (PSA) – is often used to help establish the diagnosis. We report a case of cutaneous metastatic prostatic adenocarcinoma presenting in the inguinal region of a 78‐year‐old man 5 years after his initial diagnosis. The case is unusual in that the clinical appearance mimicked a vascular proliferation and in that the metastatic prostatic adenocarcinoma failed to express PSA. Rather, expression of prostatic acid phosphatase was observed.

Microvessel density, lymphovascular density, and lymphovascular invasion in primary cutaneous melanoma - Correlation with histopathologic prognosticators and BRAF status

The relationship between microvessel density (MVD), lymphovascular density (LVD), and lymphovascular invasion (LVI) in primary cutaneous melanoma (PCM) remains unclear. Given this, a total of 102 PCMs were assessed for MVD (vascular endothelial growth factor receptor 2 and Endocan), LVD (D2-40), and LVI (immunostaining with D2-40/S-100 and hematoxylin and eosin); tumoral S-100A13, vascular endothelial growth factor receptor 2, and Endocan; and BRAF status. LVD was associated with MVD (P = .01). MVD was higher in PCMs with depth greater than or equal to 2 mm and ulceration (P = .04, .05), whereas LVD was higher in PCMs with depth greater than or equal to 2 mm and mitoses (P = .03, .02). After adjusting for MVD and LVD, only ulceration was associated with LVI (P < .02). A BRAF mutation was seen in 30.4% cases, and when present, both LVD and host response (P = .0008 and .04, respectively) were significantly associated with MVD. Immunostaining with S-100A13 was noted in 99% of cases and a significant association noted only with ulceration (P = .05). Immunostaining increased LVI positivity (46.5% versus 4.9% by hematoxylin and eosin, P < .0001). MVD and LVD are not associated with LVI, appear to be closely related with each other, and are associated with select markers of poor prognosticative value. The association between a host response and LVD and MVD in PCMs with a BRAF mutation suggests that they exhibit potential for strategizing immunotherapies.

Tumoral PD-L1 expression in desmoplastic melanoma is associated with depth of invasion, tumor-infiltrating CD8 cytotoxic lymphocytes and the mixed cytomorphological variant

Recently, patients with metastatic desmoplastic melanoma (DM) have been shown to respond more favorably to anti-PD1/PD-L1 therapy than other melanoma subtypes. Given this, we evaluated PD-L1/2 expression in primary DM samples and correlated these with subtype, CD8+ lymphocyte status, histopathological prognosticators, and select genetic alterations. Eighty-six (36 mixed DM, 50 pure DM) archival annotated samples met inclusion criteria and were immunohistochemically semiquantitatively evaluated. Per established criteria, for PD-L1/L2, cases with ⩾5% tumoral expression, and for CD8, cases with a predominantly peri/intratumoral CD8+ infiltrate were scored positive. Univariate analysis (chi-square and Wilcoxon) identified potential confounders and a nested case–control study was accomplished using multiple logistic regression. For PD-L1, 49% of cases were positive and 71% of cases with thickness >4 mm were positive; PD-L1 expression differed by median depth (3.29 mm, interquartile range=3.58 mm for PD-L1 positives vs 1.75 mm, interquartile range=2.04 mm for PD-L1 negatives, P=0.0002) and was linearly associated with increasing depth of invasion (P=0.0003). PD-L1-positive cases were more likely to display CD8+ lymphocytes (60 vs 28% P=0.0047).The presence of CD8+ lymphocytes correlated significantly with depth of invasion >1 mm (P=0.022). On multivariate analysis, PD-L1 was 6.14 × more likely to be expressed in mixed DM than pure DM (P=0.0131), CD8+ staining was 6.22 × more likely in PD-L1 positive cases than in PD-L1 negative (P=0.0118), and tumor depth was associated with greater odds of PD-L1 expression (OR=1.61, P=0.0181). PD-L2 expression was observed in 48% of cases but did not correlate with any variables. Correlation of tumoral PD-L1 with increased depth and CD8+ lymphocytes implicates the tumoral immune microenvironment with advancing disease in DM. Enhanced tumoral PD-L1 expression in the mixed cytomorphological variant provides an insight into the differential pathogenesis of the subtypes and suggests that these patients are likely better candidates for anti-PD/PD-L1 therapy.

Neurofibromin protein loss in desmoplastic melanoma subtypes: implicating NF1 allelic loss as a distinct genetic driver?

Loss of the NF1 allele, coding for the protein neurofibromin, and polymorphism in the proto-oncogene RET (RETp) are purportedly common in desmoplastic melanoma (DM). DM is categorized into pure (PDM) and mixed (MDM) subtypes, which differ in prognosis. Most NF1 mutations result in a truncated/absent protein, making immunohistochemical screening for neurofibromin an ideal surrogate for NF1 allelic loss. Using antineurofibromin, our aims were to ascertain the incidence of neurofibromin loss in DM subtypes and to evaluate the relationship with RET, perineural invasion (PNI) and established histopathologic prognosticators. A total of 78 archival samples of DM met criteria for inclusion (54 cases of non-DM serving as controls). Immunohistochemistry was performed for neurofibromin, whereas direct DNA sequencing was used for RETp and BRAF mutation status. Statistical analyses included χ(2) test as well as Fisher exact test. Neurofibromin loss was more common in DM than non-DM (69% versus 54%; P=.02). In DM, significant differences in neurofibromin loss were noted in the following: non-head and neck versus head and neck biopsy site (88% versus 55%) and PDM versus MDM variants (80% versus 56%). No significant associations were noted with sex, presence of a junctional component, Breslow depth, ulceration, mitoses, host response, RETp, BRAF status, or PNI. RETp was marginally associated with PNI-positive DM versus PNI-negative DM (36 versus 18%; P=.08). Our findings, the largest to date investigating neurofibromin in DM, validate the incidence of NF1 mutations/allelic loss in DM and suggest that the DM subtypes have distinct genetic drivers.

Melan-A positive dermal cells in malignant melanoma in situ

The presence of Melan‐A positive dermal cells in excisions for melanoma in situ represents a frequent conundrum for pathologists. These cells may represent superficially invasive melanoma, benign, incidental, dermal nevi or non‐specific staining of dermal melanophages. Occasionally, rare, Melan‐A positive dermal cells are present which do not clearly correspond to the above three categories. Our objective was to further characterize these Melan‐A positive dermal cells. To do this, immunoperoxidase staining for Melan‐A and SOX‐10 was performed on 188‐cutaneous excisions, including examples of melanoma in situ, atypical junctional melanocytic hyperplasia and non‐melanocytic tumors. These were evaluated for the presence of Melan‐A and SOX‐10 positive dermal cells. Dermal cells, positive for both markers, were identified in 17% of the excisions. The cells were present in 10% of cases from the melanocytic group and 31% of the cases from the non‐melanocytic group. These cells did not exhibit cytologic atypia and resembled neither the co‐existing neoplasm nor melanophages. We conclude that positivity of these rare Melan‐A positive cells for SOX‐10 argues that they represent true melanocytes and not non‐specific staining. The absence of cytologic atypia in these cells and their presence in excisions of non‐melanocytic neoplasms argues that they are benign, reactive, dermal melanocytes.

In situ detection of tandem DNA repeat length.

A simple method for scoring short tandem DNA repeats is presented. An oligonucleotide target, containing tandem repeats embedded in a unique sequence, was hybridized to a set of complementary probes, containing tandem repeats known lengths. Single-stranded loops structures formed on duplexes containing a mismatched (different) number of tandem repeats. No loop structure formed on duplexes containing a matched (identical) number of tandem repeats. The matched and mismatched loop structures were enzymatically distinguished and differentially labeled by treatment with S1 nuclease and the Klenow fragment of DNA polymerase.