The multi-faceted nature of 15 CFTR exonic variations: Impact on their functional classification and perspectives for therapy

BACKGROUND

The majority of variants of unknown clinical significance (VUCS) in the CFTR gene are missense variants. While change on the CFTR protein structure or function is often suspected, impact on splicing may be neglected. Such undetected splicing default of variants may complicate the interpretation of genetic analyses and the use of an appropriate pharmacotherapy.

METHODS

We selected 15 variants suspected to impact CFTR splicing after in silico predictions on 319 missense variants (214 VUCS), reported in the CFTR-France database. Six specialized laboratories assessed the impact of nucleotide substitutions on splicing (minigenes), mRNA expression levels (quantitative PCR), synthesis and maturation (western blot), cellular localization (immunofluorescence) and channel function (patch clamp) of the CFTR protein. We also studied maturation and function of the truncated protein, consecutive to in-frame aberrant splicing, on additional plasmid constructs.

RESULTS

Six of the 15 variants had a major impact on CFTR splicing by in-frame (n = 3) or out-of-frame (n = 3) exon skipping. We reclassified variants into: splicing variants; variants causing a splicing defect and the impairment of CFTR folding and/or function related to the amino acid substitution; deleterious missense variants that impair CFTR folding and/or function; and variants with no consequence on the different processes tested.

CONCLUSION

The 15 variants have been reclassified by our comprehensive approach of in vitro experiments that should be used to properly interpret very rare exonic variants of the CFTR gene. Targeted therapies may thus be adapted to the molecular defects regarding the results of laboratory experiments.

DRESS (Drug reaction with eosinophilia and systemic symptoms) après traitement par imatinib (Glivec)

BACKGROUND

Imatinib (Gleevec) is a tyrosine kinase inhibitor used to treat chronic myeloid leukemia. We describe a case of drug reaction with eosinophilia and systemic symptoms (DRESS) after institution of treatment with imatinib.

PATIENT AND METHODS

A 78-year-old woman was treated with low-dose imatinib for chronic myeloid leukemia since November 2003. A macular and pruritic eruption appeared on the patient's trunk after 7 weeks of treatment and gradually worsened. After 1 month, she was admitted for generalized skin eruption with fever and diffuse lymphadenopathy. Laboratory data showed hypereosinophilia and blood cultures positive for Staphylococcus aureus. Imatinib was stopped and replaced with hydroxyurea (Hydrea). Improved clinical and laboratory results were seen with antibiotics and topical steroids.

DISCUSSION

To our knowledge, this is the first case of DRESS following treatment with imatinib. Cutaneous reactions to imatinib are frequent and are usually mild, comprising maculopapular eruption, pruritus and facial edema. Few cases of serious skin reactions have been reported until now. Several authors suggest that the prevalence and severity of cutaneous manifestations are related to a pharmacologic effect of imatinib. Our observation cannot rule out an underlying immunologic mechanism. Septicemia may also play a part in the development of DRESS.

[Perforating granuloma annulare with transfollicular perforation]

INTRODUCTION

The perforating granuloma annulare is a rare form of granuloma annulare. The clinical diagnosis is difficult and the confirmation is histological. The localisation is unique in less than 10% of all cases. We report a documented case with a histological suspicion of transfollicular perforation.

OBSERVATION

A 36 year-old woman, without any particular antecedent, presented on her upper arm a single ulcerated nodular lesion that had evolved for one year. The clinical examination and biological investigations were normal. The histological examination led to the diagnosis of perforating granuloma annulare with a large epidermic ulceration. Treatment with a topical corticosteroid was disappointing and the removal was decided.

DISCUSSION

In our observation, the single localization of this lesion raises the problem of differential diagnosis such as cutaneous tuberculosis, atypical mycobacteriosis, skin sarcoidosis, foreign body granuloma, epidermoid carcinoma or perforating dermatitis. The histological examination permitted diagnosis of a perforating granuloma annulare with large epidermic ulceration. The infiltration and destruction of a hair follicle evoked the possible transfollicular elimination of the necrotic material. Other pathologies with the histological aspect of a palisading granuloma were excluded from this context. No associated pathology such as diabetes nor any other favouring factors such as ultraviolet light or insect bites or traumas were identified. The physiopathology of perforating granuloma annulare and the process of perforation remain unknown. Numerous therapies have been proposed with variable results.

Intracranial germinoma: the case for lower dose radiation therapy

PURPOSE

To determine the optimal dose and treatment outcome of patients treated with radiation for intracranial germinoma.

METHODS AND MATERIALS

Between 1975 and 1995, 40 patients with the diagnosis of intracranial germinoma were treated with radiation (RT) to the central nervous system. All patients received whole-brain (WB) RT (median dose: 32.4 Gy, range: 15-44.37 Gy) and a boost to the tumor volume (median total tumor volume dose: 52 Gy, range: 45-59.5 Gy). Thirty patients received RT to the spine (median dose: 26 Gy, range: 18.75-37.5 Gy). Four patients were treated with cisplatin-based chemotherapy and WB RT with a boost to the tumor volume (dose range: 51-54 Gy). A low-dose RT only group was defined as < or = 25.5 Gy to the WB (9 patients); < 50 Gy to the primary site (14 patients); and < 22 Gy to the spine (9 patients). Seventeen tumors were biopsy-proven germinoma, and 17 patients presented with multiple midline germinomas (MMG). Among 26 patients who had tumor markers measured, 27% had elevation of beta-human chorionic gonadotropin and by definition, no patient had an elevation of AFP. Twenty-four percent of 26 patients who had spine imaging or cerebral spinal fluid cytology had evidence of tumor seeding at diagnosis. The male to female ratio was 1.9:1. Median age at diagnosis was 14 years for male patients and 9.5 years for female patients (p = 0.02), (overall age ranges: 0.5-31 years). Median follow-up was 62 months (range: 3-226 months). Late effects of 29 patients with follow-up of > or = 20 months and adequate documentation in their medical records were analyzed.

RESULTS

The 5-year actuarial rate of disease-free survival (DFS) and overall survival (OS) for biopsy-proven germinomas and presumed germinomas was 97%. No patient died of germinoma. There were no local failures regardless of the dose of RT, elevation of HCG tumor marker, or CSF dissemination at presentation. At presentation 22 patients had evidence of at least one endocrine abnormality. At follow-up there were no new patients diagnosed with an endocrine abnormality; however, 13 out of 22 patients had an increase in the number of endocrine deficiencies requiring hormone replacement. At presentation, 14 patients showed evidence of growth retardation. At follow-up there were no new cases of growth failure in the remaining patients.

CONCLUSIONS

Germinomas are highly curable with RT alone. Lower doses of RT to the craniospinal axis without chemotherapy appear to produce equally effective DFS and OS as do higher doses of RT or combination chemotherapy and RT. Craniospinal RT may be indicated for patients with MMG or patients with evidence of spinal seeding. Long-term effects of growth retardation, and other endocrine deficiencies appear to be correlated with disease at presentation rather than solely with treatment.

Pre-B acute lymphoblastic leukemia cells may induce T-cell anergy to alloantigen

Even if neoplastic cells express tumor associated antigens they still may fail to function as antigen presenting cells (APC) if they lack expression of one or more molecules critical for the induction of productive immunity. These cellular defects can be repaired by physiologic activation, transfection, or fusion of tumor cells with professional APC. Although such defects can be repaired, antitumor specific T cells may still fail to respond in vivo if they may have been tolerized. Here, human pre-B cell acute lymphoblastic leukemia (pre-B ALL) was used as a model to determine if primary human tumor cells can function as alloantigen presenting cells (alloAPC) or alternatively whether they induce anergy. In the present report, we show that pre-B cell ALL express alloantigen and adhesion molecules but uniformly lack B7-1 (CD80) and only a subset express B7-2 (CD86). Pre-B ALL cells are inefficient or ineffective alloAPC and those cases that lack expression of B7-1 and B7-2 also induce alloantigen specific T-cell unresponsiveness. Under these circumstances, T-cell unresponsiveness could be prevented by physiologic activation of tumor cells via CD40, cross-linking CD28, or signaling through the common gamma chain of the interleukin-2 receptor on T cells. Taken together, these results suggest that pre-B ALL may be incapable of inducing clinically significant T-cell-mediated antileukemia responses. This defect may be not only due to their inability to function as APC, but also due to their potential to induce tolerance. Attempts to induce clinically significant antitumor immune responses may then require not only mechanisms to repair the antigen presenting capacity of the tumor cells, but also reversal of tolerance.

The vascular steal phenomenon: an experimental model

A model for the vascular steal phenomenon was designed and evaluated in 10 mongrel dogs in which the aortic bifurcation was used to represent a parent artery with two distal vascular beds. Right lower extremity flow was increased with a femoral arteriovenous fistula, and progressively greater stenoses were applied to the distal abdominal aorta. Significant decreases in left lower extremity flow (a steal) occurred only when the stenosis of the aorta exceeded 60%. There was a direct relationship between the pressure drop across the aortic stenosis and the degree of steal from the left lower extremity. The stenosis required for a steal phenomenon to occur is analogous to a critical arterial stenosis for a given velocity of flow and the specific cross-sectional area of the distal arterial bed.

The effects of bilateral renal transplantation on pelvic hemodynamics and sexual function

Sexual function and internal iliac artery (IIA) patency were determined in 24 patients who had received at least two renal transplants, one in each iliac fossa, at the University of Maryland and Johns Hopkins Hospitals from 1975 to 1979. The pelvic hemodynamics of each patient were assessed with a penile/brachial blood pressure index (PBI). The rate of sexual dysfunction, as determined by questionnaires and personal interviews, was 46% (11 of 24 patients) compared with only 21% (five of 24 patients) after a single transplant. Nine of the 11 patients who were impotent had bilateral IIA occlusion and four of these nine had a PBI less than 0.70. One of the four patients regained full sexual function after a revascularization procedure, which confirmed that this impotence had a vascular etiology. Results of this study show that vascular insufficiency, but not necessarily vasculogenic impotence, was present in at least four of the 11 patients who were impotent (36%) and may have been avoidable by sparing at least one IIA during renal transplant procedures.

Surgical correction of vasculogenic impotence in a patient after bilateral renal transplantation

This article documents a vascular cause of erectile dysfunction in a patient with ligation of both internal iliac arteries after bilateral renal transplantation. The diagnosis was made by the noninvasive measurement of the penile arterial systolic pressure and confirmed by pelvic arteriography. Correction of the patient's impotence was accomplished by restoration of penile blood flow by a saphenous vein bypass graft between the external iliac and internal iliac arteries.