الفهرس 
Pathogenesis of Mycosis FungoidesOnly 14 pages are availabe for public view
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Abstract
Mycosis fungoides represents the most common type of CTCL. There is continued and substantial increase in the incidence of MF in the last years especially among Arab populations. The diagnosis of early MF (stage I, IIA) is one of the greatest challenges in clinical dermatology and dermatopathology. The lack of a standardized and reliable method for diagnosing MF presents significant difficulties in the assessment and management of patients suspected to have MF.
To solve this problem, the ISCL (2005) has proposed an algorithm for the diagnosis of early MF. This algorithm relies on integration of several diagnostic parameters (clinical, histopathological, immunophenotypical and molecular). This algorithm is based on a scoring system and a score of 4 is considered sufficient for the diagnosis of early MF. Although, the proposed algorithmic scoring provides a degree of diagnostic standardization, it lacks positive identification markers for better establishment of the diagnosis.
The lack of consensus on the diagnosis of MF reflects the unclear and complex pathophysiology. Several signaling pathways may be involved in the pathogenesis of MF. The dysregulation of these pathways may lead to disturbance in the immune biology as well as alteration of the cell cycle control. Several genes have been studied in MF however; none of these genes can be used as diagnostic biological markers.
Matrix metalloproteinase-2 has been found to promote oncogenesis in many tumors. Besides its invasive potential in the late stage, it mediates early tumorigenesis through many mechanisms. It may enhance cell proliferation, suppress tumor apoptosis, induce angiogenic switch and evade the host anti-tumor response. However, scarce data are available about its role in early MF.
Matrix metalloproteinase-2 is regulated at both the transcriptional and post-transcriptional levels. Gene polymorphism is one of the mechanisms regulating the transcription of MMP-2 through its influence on the activity of transcription factors. Sp1 is one of the transcription factors that can be found within the MMP-2 promoter gene. It mediates MMP-2 transcription in many tumors through its association with specific gene polymorphism.
In this study, we investigated MMP-2 gene promoter polymorphism in early MF and the effect of this polymorphism on MMP-2 expression. In addition, we studied the expression of Sp1transcription factor and its relation with that of MMP-2.
This study aimed to find out the role of these molecular and immunohistochemical markers in the diagnosis of early MF by comparing it with inflammatory dermatitis (chronic eczema).
The current study included 25 cases with early MF and 25 age and sex matched controls with chronic eczema (contact dermatitis). All patients were recruited from the dermatology outpatient clinic at Ain Shams university hospital in the period from January 2012 to June 2013.
All MF cases were diagnosed according to the proposed algorithm of the ISCL. They were all subjected to clinical and histopathological examination. The clinical characteristics of the MF group were recorded as regards age, sex, type of MF, recurrence state and age of onset of MF(<30 years or ≥ 30 years). We included both the classical and hypopigmented types in the study. Immunophenotyping (CD3, CD7) and genotyping (TCRγ gene rearrangement) were done for selected patients who didn’t fulfill the 4 points needed for establishment of the diagnosis by clinico-pathological examination only.
For staging purposes, MF patients were further subjected to laboratory (CBC, LFT, RFT and LDH) and radiological investigations (CXR, U/S on peripheral LN and pelvi-abdominal U/S in stage IA/IB or CT scans in extensive IB/IIA). LN biopsy was done if the size of the node >1.5 cm and/or firm, irregular clustered nodes were present. This was followed by histopathological examination and LN staging according to the Dutch system. Only patients who fulfilled the diagnostic algorithm and had early stage (stage I, IIA) were included in the study.
In both cases and controls, two punch skin biopsies were taken. Gene polymorphism of MMP-2 was detected by PCR-RFLP. Three sites were studied (-1575 G/A, -1306 C/T, -790 T/G). The expression of MMP-2 and Sp1 was studied by streptavidin-biotin immunoperoxidase technique.
As regards the molecular study, different genotypes were obtained according to the presence or absence of restriction site. The homozygous genotypes displayed either one or two bands on gel electrophoresis whereas; the heterozygous genotypes displayed three bands.
Regarding the immunohistochemical study, MMP-2 displayed cytoplasmic staining of the lymphocytes, stroma and keratinocytes. Sp1 displayed nuclear staining of the lymphocytes and keratinocytes.
Both MMP-2 and Sp1 were considered negative if <10% of lymphocytes were stained; positive if >10% of lymphocytes stained positive (weak positive: 10-50%; strong positive: >50%).
This study revealed no significant statistical difference between MF patients and eczema controls in the genotype (separate or combined) and allele distribution. Thus, MMP-2 gene polymorphism could not be used as a diagnostic biomarker in our study. Similar studies are lacking in the literature.
Moreover, patients with MF showed no significant difference as regards the different clinical characteristics (gender, age of onset, MF type and recurrence state). However, significant difference was found between classical and hypopigmented MF as regards -1306 C/T polymorphism. CC genotype was associated with classical MF whereas; CT was more common in hypopigmented MF. CC genotype was found to be associated with several malignancies and considered as a marker for aggressiveness. This may reflect the difference in the biological behavior between the classical and hypopigmented MF and provides new insight for the different molecular characteristics in both types.
Regarding MMP-2 expression, immunohistochemical study revealed a highly significant difference between MF group and eczema group. Both lymphocytes and stroma of MF lesions displayed higher expression of MMP-2 than controls. This may highlight the role of MMP-2 in promoting early lymphogenesis in MF through a crosstalk between stroma and neoplastic cells. All the previous studies investigated the role of MMP-2 in the late stage disease. However, the role of MMP-2 in early MF had not been studied before.
Our study could not find a relation between MMP-2 genotype and immunophenotype. This could be attributed to the complex regulatory mechanisms that govern MMP-2 expression. Besides transcriptional regulation, MMP-2 expression may be regulated at the protein level through various inhibitors and activators. This may be a subject for further studies in early MF.
Regarding Sp1 immunostaining, MF patients showed higher expression than eczema controls. This may point to the role of Sp1 in the pathogenesis of early MF. Its role in carcinogenesis has been proven in various tumors but still needs to be investigated in MF.
Moreover, no significant difference in MMP-2 or SP1 expression was found among MF patients as regards sex, age of onset, recurrence and type of MF. Also, the expression of these markers by the keratinocytes was non-significant between cases and controls.
In addition, no relation was found between Sp1 and MMP-2 expression. MMP-2 was found to be more specific and less sensitive than Sp1. This may be attributed to the involvement of Sp1 in inflammatory conditions as well as carcinogenesis.
In this study, MMP-2 was found to be more effective than Sp1 in differentiating MF cases from eczema controls. It appears that MMP-2 and Sp1immunohistochemical markers may be of interest for the dermatologist to differentiate between early MF and inflammatory dermatoses.