MULTIDRUG RESISTANT TUBERCULOSIS – BIOMECHANISM,EPIDEMIOLOGY AND MANAGEMENT STRATEGIES

Muitidrug resistant tuberculosis has shown an alarming increase and this assumes added importance in view of the increasing number of HIV infected patients. This article reviews the biomechanism of resistance and discusses the present stategies that are available and recommended to tackle the rising incidence of tuberculosis due to resistant mycobacteria.KEYWORDS: Antitubereular drugs, Drug resistance, Mycobacterium tuberculosis     

RECENT ADVANCES IN THE MEDICAL MANAGEMENT OF PROSTATE CANCER

SUMMARY Prostate cancer is a 20th century seedling which, because of its attendant morbidity and mortality and the increased longevity of the population, is set to germinate into a substantial economic burden in the next millennium. Most patients with prostatic cancer present with either locally advanced or metastatic disease, for which palliative endocrine therapies are the first-line treatment. The increasingly sophisticated and selective hormonal methods available today, such as the longer-acting formulations of luteinizing hormone-releasing hormone (LH-RH) analogues and newer, better-tolerated, once-daily, non-steroidal anti-androgens, have increased the therapeutic options and improved patient quality of life. Maximum androgen blockade, combining medical or surgical castration with an anti-androgen, is an increasingly accepted therapy, and offers the greatest efficacy, particularly for patients with a lesser disease burden. The development of hormone-refractory tumours is still a problem in advanced prostate cancer, although elucidation of the mechanisms involved should offer many potentially fruitful avenues for new therapies.     

Long-term follow-up of juvenile-onset cutaneous polyarteritis nodosa associated with streptococcal infection

Polyarteritis nodosa (PAN) is a multisystem inflammatory disease associated with necrotizing vasculitis of small and medium arteries. Although predominantly an adult disease, PAN is well described in children. It can occur in a systemic form with manifestations in skin, joints, heart, nervous system, gastrointestinal tract, lungs and kidneys, and a limited form in which disease is confined to the skin, muscles, joints and peripheral nerves. In either case, streptococcal infection has been implicated by a positive throat swab or a significant increase in either antistreptolysin O (ASOT) or antihyaluronidase titres. The limited form is thought to run a benign course, but little has been written about its long-term outcome. We describe two patients who developed a cutaneous vasculitis following a probable streptococcal infection. Both have run a relapsing and remitting course with significant elevations of ASOT and in one, at least, prophylactic penicillin has had a strikingly beneficial effect. In both patients, the disease seems to have receded during childhood, only to recur, retaining its original form, in adult life. Their current ages are 22 and 19 yr, respectively.      

P-glycoprotein expression in human plasma cell myeloma: correlation with prior chemotherapy

Multidrug-resistant (MDR) myeloma patients failing chemotherapy may express P-glycoprotein (PGP), which serves as an efflux pump protecting the neoplastic cells. Unknown is whether PGP expression might relate to prior cytotoxic drug exposure. To address this question, we studied 106 consecutive bone marrow samples from 104 myeloma patients with samples studied either before or after therapy and at the time of relapse. We performed an established immunocytochemical assay of PGP using an MDR-1- specific monoclonal antibody and correlated PGP status with prior chemotherapy dosage. Myeloma patients with no prior therapy had a low incidence of PGP expression (6%, 3/47), whereas those receiving chemotherapy had a significantly higher incidence (43%, 21/49) (P < .0001). A substantially higher incidence of PGP expression (50%, 83%, respectively) occurred when the total vincristine dose exceeded 20 mg and when doxorubicin exceeded 340 mg. In the 11 patients who received both high vincristine and doxorubicin dosages (> 20 mg, > 340 mg total dose) there was 100% incidence of PGP expression in the tumor cells. These data provided the basis for a predictive mathematical model from which dose-related PGP expression normograms were generated. Time with myeloma for PGP-negative patients (mean 33 months) had overlapping confidence limits with PGP-positive patients (mean 42 months), suggesting that disease duration was not a significant variable. PGP expression did not correlate with other clinical factors or immunophenotypic factors. Our findings indicate a strong correlation between PGP expression in myeloma and past chemotherapy in myeloma, in particular, related to prior exposure to the natural product agents vincristine and doxorubicin. Additionally, the proportion of PGP- positive plasma cells was significantly higher in the doxorubicin- treated patients than the nondoxorubicin-treated patients (87.7% v 65.17%; P = .013). Combined high vincristine and doxorubicin total dosage appear highly predictive of PGP expression.     

p53 overexpression as a marker of poor prognosis in mantle cell lymphomas with t(11;14)(q13;q32)

The t(11;14)(q13;q32) translocation, which juxtaposes the BCL1 oncogene with the Ig heavy chain locus, has been associated with an uncommon subtype of non-Hodgkin's lymphoma (NHL) termed mantle cell lymphoma (MCL). To date, no molecular marker that serves as an indicator of tumor progression or clinical prognosis has been described for NHLs with this translocation. We examined a panel of NHLs with t(11;14) for overexpression of p53 and correlated the results with single-strand conformation polymorphism (SSCP) analysis, karyotypic features, and clinical course. NHLs with t(11;14) were identified from 30 patients. The diagnosis was MCL for 23 of 30, small lymphocytic lymphoma for 4 of 30, and diffuse large-cell lymphoma for 3 of 30 cases. The results of immunohistochemistry analysis using a monoclonal anti-p53 antibody on paraffin-embedded specimens were compared with the SSCP data, the tumor karyotypes, and clinical course of each patient. DNA sequencing of exons was performed on cases that showed conformational changes by SSCP analysis. NHLs from 5 of 23 patients with MCL were positive for p53 overexpression. Deletions of chromosome 17p were identified in 2 of 30 cases, both of which were MCLs showing p53 overexpression. Two of the five MCLs with p53 overexpression showed evidence for TP53 mutations. None of the 18 MCLs negative for p53 overexpression showed conformational changes by SSCP. For these 18 patients with MCLs that did not overexpress p53, the median survival was 63 months, compared with 12 months for the 5 patients with MCLs positive for p53 overexpression (P < .001). These results suggest that p53 overexpression in MCL with t(11;14)(q13;q32) may serve as a marker of poor prognosis.