We have reported a rare case of expansion of a CD4+ CD8+ double-positive cell population in a Caribbean male with a complex male karyotype, infected with HTLV-1. The disease was first described in Kyushu, in southwestern Japan, and it occurs most frequently in endemic areas such as Japan, the Caribbean basin, West Africa, Brazil, Central and South America and northern Iran [
2,
4]. The disease is considered a fatal malignant post-thymic lymphoproliferative disorder and is characterized by the presence of leukemic cells with highly convoluted nuclei (so-called 'flower-like cells'), lymphadenopathy, hepatosplenomegaly, skin lesions, and hypercalcemia.
The involvement of CD4+ cells in the development of ATLL is indisputable; however, few case reports have noticed an unusual phenotype of double-positive CD4+ and CD8+ expression in patients with an extremely aggressive course.
Kim et al. [
8] reported an extremely aggressive course with poor survival in a patient with CD4+ CD8+ double-positive acute adult T-cell leukemia with skin manifestations. Kamihira et al. [
7] reported a poorer prognosis with a median survival of 7.8 months as compared to patients with the typical CD4- CD8- phenotype. Ciminale et al. [
9] describe a CD4+ CD8+ phenotype acute lymphoma in a Greek patient with an aggressive clinical course of refractory hypercalcemia. Several authors have implicated a high proliferation index (>18%), and large cells are suggestive of a poor prognosis in these patients [
10].
Although HTLV-1 infects both CD4+ and CD8+ T cells, leukemogenic potential of the virus is restricted to the CD4+ subset. The dynamic relationship between the co-expansion of two cell populations of CD4+ and CD8+ in the course of the disease is still unclear. However, since the CD4/CD8 double-positive phenotype is characteristically associated with the majority of immature thymic precursors, it is hypothesized that the infection with HTLV-1 and expansion of CD8+ cells plays a helper role in the selection of specific CD4+ cell clones, and thus, during intrathymic ontogeny, immature CD4+/CD8+ thymocytes develop into functionally competent CD3+/CD4+/CD8- or CD3+/CD4-/CD8+ T cells after transient expression of the CD4/CD8 double-positive phenotype [
11]. Sibon et al. [
12] have shown that infected CD4+ and CD8+ cells displayed the same pattern of clonal expansion in vivo, and both subsets of T cells disseminated the virus at a proviral state, although the degree of clonal expansion was higher in CD4+ than in CD8+ lymphocytes, which accounted for the significantly higher proviral loads harbored by the CD4+ subset of T cells. Alternatively, the viral infection may alter the expression of interleukin-4, which can modulate the expression of CD8 on the surface of CD4+ T cells, resulting in a concomitant expression of both markers [
13].
Another possible mechanism includes clonal expansion of a less differentiated cell population which is immortalized by HTLV-1 infection; however, the finding that terminal deoxynucleotidyl transferase, which is a marker for thymic T-cell precursors, is usually not expressed in the infiltrative tumor cells opposes this hypothesis [
7,
11,
12,
13].
One of the distinct features of the disease is refractory hypercalcemia, which requires frequent hospitalization and aggressive hydration. This phenomenon has been studied previously by Prager et al. [
14] and other study groups [
15,
16,
17,
18,
19]. They have shown increased bone resorption mediated by parathyroid hormone-related protein (PTHrP), transactivated by the HTLV-1 tax and HTLV-11 tax proteins, which mediates its effects on PTHrP via cellular transcription factors activator protein (AP)-2 and AP-1. Transactivation via an AP-2 motif represents a novel interaction of tax with a cellular transcription factor or lymphokines such as interleukin 1 (IL-1), IL-2, IL-6 and tumor necrosis factor (TNF), and dysregulation of cellular gene transcription by viral proteins. Interestingly, the hypercalcemia in our patient occurred in the setting of normal PTHrP and low 1,25(OH)
2D levels, supporting the role for cytokines in the development of HTLV-1-related hypercalcemia [
20].
Another interesting feature are the clonal chromosome abnormalities along with clinical heterogeneity and a plethora of secondary abnormalities in our patient. Interestingly, we noticed a hyperdiploid male karyotype, monosomy of chromosome 12 and an unbalanced translocation on the long arm of chromosomes 5 and 13, additional material on the long arm of chromosomes 5, 7, 12, 14 (14q+ chromosome) and 17 and on the short arm of 2 of the 3 copies of chromosome 4, and a marker chromosome in 16 of 20 metaphases, suggesting a partial trisomy or inactive genetic material. Five of these metaphases also showed a second copy of the marker chromosome. Interestingly, only 4 metaphases showed a normal karyotype. Complex cytogenetic characteristics are presented in fig. .
Itoyama et al. [
21] reveal cytogenetic findings in 50 cases of ATLL where multiple breaks (at least 6), abnormalities of chromosomes 1p, 1p22, 1q, 1q10-21, 2q, 3q, 3q10-12, 3q21, 14q, 14q32 and 17q, and partial loss of chromosomes 2q, 9p, 14p, 14q and 17q regions correlated with shorter survival [
19]. The most frequent gains include trisomy 3, trisomy 8, trisomy 9 and trisomy 21. Monosomies involve chromosomes 4, 8, 10 and 22.
Several authors have also suggested that 14q32 translocations were the most common abnormalities and are consistently observed in human T-cell tumors [
22,
23]. To date, this is the only report which showed monosomy of chromosome 12 and complex cytogenetic chromosomal abnormalities with a male karyotype in HTLV-1 CD4+ CD8+ double-positive lymphoma.
We believe that despite the aggressive course of the disease, the current treatment has allowed the patient to live longer. We used EPOCH chemotherapy with a 4-day infusion schedule of cyclophosphamide, vincristine, doxorubicin and etoposide, followed by antiretroviral therapy and successful autologous bone marrow transplantation with BEAM therapy. The patient remained in complete remission for 13 months after bone marrow transplantation with no evidence of recurrent HTLV-1 infection on PCR testing and on flow cytometry. However, salvage regimen which included gemcitabine and vinorelbine and, later on, hyper-cyclophosphamide, vincristine, adriamycin and dexamethasone resulted in a transient response after relapse.
In conclusion, we have shown that double-positive ATLL is an aggressive form of lymphoma associated with refractory hypercalcemia. Despite recent advances in treatment, information about this rare disease is still limited. In connection with the multiple chromosomal aberrations and complex cytogenetic characteristics observed in our patient, further investigation into the role of HTLV-1 in these lymphomas and clinical trials are warranted.
