Since its discovery as a CDKI (cyclin-dependent kinase inhibitor) in 1993, the tumor suppressor p16 (INK4A/MTS-1/CDKN2A) has gained widespread importance in cancer. The frequent mutations and deletions of p16 in human cancer cell lines first suggested an important role for p16 in carcinogenesis. This genetic evidence for a causal role was significantly strengthened by the observation that p16 was frequently inactivated in familial melanoma kindreds. Since then, a high frequency of p16 gene alterations were observed in many primary tumors. In human neoplasms, p16 is silenced in at least three ways: homozygous deletion, methylation of the promoter, and point mutation. The first two mechanisms comprise the majority of inactivation events in most primary tumors. Additionally, the loss of p16 may be an early event in cancer progression, because deletion of at least one copy is quite high in some premalignant lesions. p16 is a major target in carcinogenesis, rivaled in frequency only by the p53 tumor-suppressor gene. Its mechanism of action as a CDKI has been elegantly elucidated and involves binding to and inactivating the cyclin D-cyclin-dependent kinase 4 (or 6) complex, and thus renders the retinoblastoma protein inactive. This effect blocks the transcription of important cell-cycle regulatory proteins and results in cell-cycle arrest. Although p16 may be involved in cell senescence, the physiologic role of p16 is still unclear. Future work will focus on studies of the upstream events that lead to p16 expression and its mechanism of regulation, and perhaps lead to better therapeutic strategies that can improve the clinical course of many lethal cancers.

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Murine long-term bone marrow cultures (LTBMCs) were used to generate hematopoietic cells free from marrow stromal cells. These progenitor cells were treated with GM-CSF (5 U/ml) with or without rat bone osteocalcin or rat serum albumin in either alpha-MEM with 2% heat-inactivated horse serum alone (alpha) or supplemented with 10% L-cell-conditioned medium (as a source of M-CSF) (L10). Few substrate-attached cells survived in basal alpha medium, but when treated with L10 medium or GM-CSF, they survived and proliferated. Osteocalcin did not significantly affect survival or proliferation. Subcultures of cells treated with GM-CSF had large numbers of multinucleated cells, more than half of which were tartrate-resistant acid phosphatase-positive (TRAP). Osteocalcin further promoted the development of TRAP-positive multinucleated cells; a dose of 0.7 microgram/ml osteocalcin promoted osteoclastic differentiation by 60%. Using a novel microphotometric assay, we detected significantly more tartrate-resistant acid phosphatase activity in the osteocalcin plus GM-CSF group (75.6 +/- 14.2) than in GM-CSF alone (53.3 +/- 7.3). In the absence of M-CSF, GM-CSF stimulated tartrate-resistant acid phosphatase activity, but osteocalcin did not have an additional effect. These studies indicate that osteocalcin promotes osteoclastic differentiation of a stromal-free subpopulation of hematopoietic progenitors in the presence of GM-CSF and L-cell-conditioned medium. These results are consistent with the hypothesis that this bone-matrix constituent plays a role in bone resorption.

Although the hematopoietic origin of the osteoclast is generally accepted, the precise phenotype of the progenitor and the regulation of its differentiation are unclear. This study compares proliferation and differentiation of progenitors in response to macrophage colony stimulating factor (M-CSF) and granulocyte macrophage colony stimulating factor (GM-CSF). Nonadherent progenitor cells from murine long-term bone marrow cultures (LTBMC) (as a source of osteoclast progenitors) demonstrated a significant proliferative response to M-CSF. In addition, M-CSF increased the number of multinucleated cells, only a small percent of which (14-16%) were tartrate-resistant, acid phosphatase (TRAP)-positive. In contrast, cells cultured with GM-CSF generated more TRAP-positive multinucleated cells even at concentrations less stimulatory of proliferation than M-CSF. The osteoclast phenotype of these multinucleated cells was also assessed by ultrastructural characterization of ruffled borders in association with bone fragments. The bone-active hormone 1,25-dihydroxyvitamin D3 inhibited the proliferation of this subset of progenitor cells in the presence of M-CSF or GM-CSF. All of these results show effects on progenitors in the absence of the stromal cell microenvironment in this system. These results provide evidence for a divergence in the biological responsiveness of osteoclast progenitor cells to M-CSF compared with GM-CSF; they support the notion that M-CSF has a "priming" effect on osteoclast progenitors whose subsequent differentiation to osteoclastic multinucleated cells is promoted by GM-CSF.

7085 Background: Targeting VEGF has proven to be an effective tx strategy in many solid tumors including non-small cell lung cancer. VEGF expression in SCLC provides rationale for studying B in addition to chemoradiotherapy. Methods: The endpoints of this multicenter community-based study were to assess the safety, response rate (RR), and progression-free survival (PFS) of I/C/RT followed by B in patients (pts) with LS-SCLC. Tx included: C AUC = 5 IV D1, I 50mg/m2 IV D1,8 Q 21D x 4 cycles, and RT 1.8 Gy daily to a total of 61.2 Gy, beginning with the 3rd cycle. 3rd and 4th cycles were 28D each. Pts were restaged after 4 cycles. If no progressive disease (PD) pts received B 10 mg/kg IV Q 14D x 10 doses. Eligibility included: measurable disease, ECOG PS 0–1, informed consent, and no new brain metastases or bleeding. Results: Fifty-seven pts were enrolled from 8/03 to 10/04. Forty-five pts (79%) and 41 pts (72%) received planned tx with I/C/RT and B, respectively. The range of follow-up is 14–28 months. Baseline features: median age 65 years (42–80); male/female, 37%/63%; ECOG PS 0,1: 26%/74%. Grade (G) 3/4 non-hematologic toxicity: diarrhea (9%), DVT (4%), vomiting (11%), and fatigue (9%). G3/4 hematologic toxicity: neutropenia (37%), anemia (5%), and thrombocytopenia (13%). Only 9% of pts experienced G3/4 toxicity during B tx (1 pt each: DVT, hypokalemia, depression, pain, and colon perforation). There were 2 tx-related deaths (both from respiratory failure; 1 and 2 doses of B had been administered). Complete/partial responses were observed in 15 pts (26%)/31 pts (54%), respectively, for an overall RR of 80% (95% CI 70%-90%). Four pts had stable disease, and 5% had PD (4 pts were unevaluable.) 1- and 2-year PFS rates were 63% and 54%, respectively. 1- and 2- year overall survival (OS) rates were 71% and 29%, respectively. Median OS was 15 months. Conclusions: The safety, RR, and 1- and 2-year survival results of I/C/RT followed by B compare favorably with standard tx for LS-SCLC; and B may improve PFS. Assessing the role of B as maintenance tx in improving OS in this setting will require randomized trials. [Table: see text]

Purpose. Epoetin alfa administered s.c. three times weekly or once weekly increases hemoglobin (Hb) levels, decreases transfusion requirements, and improves quality of life in anemic cancer patients receiving chemotherapy. This study assessed the feasibility of using higher initial doses of once-weekly epoetin alfa followed by less frequent maintenance doses to increase and then maintain adequate Hb levels in this population. Materials and Methods.In this open-label, nonrandomized, pilot study, anemic (baseline Hb ≤11 g/dl) cancer patients undergoing chemotherapy received initial doses of epoetin alfa of 60,000 U s.c. once weekly to increase Hb levels by at least 2 g/dl, followed by 120,000 U s.c. every 3 weeks to maintain Hb levels. The maximum treatment duration was 24 weeks.Results. The mean baseline Hb level was 10.1 ± 0.8 g/dl (n = 20). Once-weekly dosing resulted in mean Hb level increases of 1.0 ± 1.1 g/dl by week 4 and 2.9 ± 1.9 g/dl by week 8; 86% and 79% of patients evaluable at week 8 and week 12, respectively, demonstrated increases of at least 2 g/dl (target Hb level of ≥12 g/dl). Thirteen patients (65%) received at least one maintenance dose; the mean Hb level increased from 12.8 ± 1.1 g/dl before starting maintenance therapy to 13.3 ± 1.4 g/dl at the last maintenance week. Both dosage regimens were well tolerated. TheOncologist ® LEARNING OBJECTIVESAfter completing this course, the reader will be able to:1. List the recommendations in current clinical practice guidelines on epoetin alfa dosing and administration regimens for patients with cancer and chemotherapy-related anemia.2. Discuss the benefits associated with epoetin alfa therapy in cancer patients with anemia receiving chemotherapy, in terms of increased hemoglobin levels, lower transfusion needs, and improved quality of life.3. Explain how higher initial doses of once-weekly epoetin alfa followed by less frequent maintenance dosing with epoetin alfa in anemic cancer patients undergoing chemotherapy may be beneficial, both to the patient and to the health care provider.Access and take the CME test online and receive one hour of AMA PRA category 1 credit at CME.TheOncologist.com CME CME Patton, Kuzur, Liggett et al. 91 Conclusions. Once-weekly epoetin alfa at a dose of 60,000 U effectively increased Hb levels by week 8; 86% of patients achieved rises of at least 2 g/dl or Hb levels ≥12 g/dl. Moreover, epoetin alfa at doses of 120,000 U every 3 weeks maintained or increased Hb levels. Results from this pilot study suggest that higher initial once-weekly dosing of epoetin alfa followed by less frequent maintenance dosing appears to be feasible for treating anemia in cancer patients undergoing chemotherapy. Further evaluation of these and other epoetin alfa dosage regimens is warranted. The Oncologist 2004;9:90-96

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