Overexpression of Chromatin Assembly Factor-1/p60 helps to predict the prognosis of melanoma patients

Abstract

Background: Cutaneous melanoma (CM) is the most lethal form of skin malignancy, which registers a constant increase in incidence worldwide. The identification of molecular alteration(s) involved in its biological aggressiveness represents a major challenge for researchers, considering that existing therapies are ineffective to treat metastasizing cases. The epigenetic control of chromatin dynamics during DNA synthesis, replication, and repair is fundamental for the orderly progression of cell proliferation. The Chromatin Assembly Factor 1 (CAF-1) complex acts as a major regulator of this process; its intermediate (p60) subunit has been recently proposed as a novel proliferation and prognostic marker for several tumors. We aimed to establish if the evaluation of the expression of CAF-1/p60 in primary CM may help define the prevision of outcome of patients.

Methods: Immunohistochemistry with anti-CAF-1/p60 was performed on paraffin-embedded tissue sections of 130 cases of primary CM retrieved from the archive files of the Department of Biomorphological and Functional Sciences, Section of Pathology, University "Federico II" of Naples, Italy. Results were compared with histopathological and follow-up data of patients.

Results: CAF-1/p60 was expressed in all CM. A significant statistical association between the overexpression of the protein and the occurrence of skin, node and/or distant metastases (P < 0.05) emerged, independently from histopathological prognostic factors.

Conclusions: CAF-1/p60 looks promising as a new prognostic marker for CM and sheds new light on the molecular events associated with photocancerogenesis and melanoma biology.The screening for CAF-1/p60 might contribute to the molecular sub-classification of CM, with improved translational outcomes.

Figure 1

Positive controls for CAF-1/p60 immunostaining. A case of breast carcinoma (1A, ×400) and a case of squamous cell carcinoma (1B, ×400) showing a strong expression of CAF-1/p60.

Figure 2

CAF-1 expression in "thin" cutaneous melanoma. A case of primary "thin" cutaneous melanoma (< 1 mm Breslow depth) showing over-expression of CAF-1/p60. This patient experienced node metastasis 7 years from diagnosis (2A: original magnification, ×150; 2B: ×200); "Thin" cutaneous melanoma, disease-free 11 years from surgery: low expression of CAF-1/p60; (2C: original magnification, ×200; 2D, ×250). Arrows indicate the immunostained melanocytes.

Figure 3

CAF-1 expression in thick cutaneous melanoma. Thick cutaneous melanoma (Breslow thickness: > 4 mm) with diffuse over-expression of CAF-1/p60. This patient developed nodal and distant metastases and died for disease 2 years from diagnosis (3A: original magnification, ×150; 3B, ×200); Thick cutaneous melanoma, disease-free 12 years after surgery: moderate expression of CAF-1/p60 (3C: original magnification, ×150; 3D, ×200).

Figure 4

Log-rank testing analysis. The incidence of recurrence (4A) and death for disease (4B) of patients is significantly associated with the highest level (+++) of CAF-1/p60 expression in the vertical phase of CM (P = 0,001);

Figure 5

Receiver operating characteristic (ROC) curve. ROC curve evidence an excellent performance of CAF-1/p60 +++ expression level in the vertical phase both in terms of sensitivity and specificity (area under curve: 0,92).