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In the title compound, C9H9NO3·H2O, the plane of the acetamide group is oriented at 20.52 (8)° with respect to the benzene ring, whereas the plane of the carb-oxy-lic acid group is essentially coplanar with the benzene ring [maximum deviation = 0.033 (1) Å]. In the crystal, classical O-H⋯O and N-H⋯O hydrogen bonds and weak C-H⋯O hydrogen bonds link the organic mol-ecules and water mol-ecules of crystallization into a three-dimensional supra-molecular architecture.

In the title adduct, C11H11N3O·C2H4O2, all non-H atoms of the acetamide mol-ecule are roughly coplanar, with an r.m.s. deviation of 0.0720 Å. The dihedral angle between the ring plane and the acetamide group is 8.5 (2)°. In the crystal, O-H⋯N and N-H⋯O hydrogen bonds link the acetamide and acetic acid mol-ecules.

In the title co-crystal, C(12)H(11)Br(2)N(3)O·C(4)H(5)NO(2), the naphthyridine derivative and the pyrrolidine-2,5-dione mol-ecules have crystallographic mirror-plane symmetry with all non-H atoms, except the Br atom, located on the mirror plane. In the crystal, N-H⋯N, N-H⋯O and C-H⋯O hydrogen bonds link the mol-ecules into heterodimers. These dimers are further linked into a one-dimensional structure along [010] by weak C-Br⋯O inter-actions [Br⋯O = 3.028 (5) Å and C-Br⋯O = 158.52 (4)°].

Cancer has been considered to be the result of accumulated gene mutations, which result in uncontrolled cell proliferations for a long time. Cancers are also regarded to be capable of immune evasion. Furthermore, resistance to apoptosis was recognized as an important trait of cancer in the last score of years. However, there are numerous paradoxical issues in this whole set of theory. For example, there is no known set of genes of which mutations are responsible for human cancers. As for the trait of 'resistance to apoptosis', the fact is that cancer has increased frequency of apoptosis. The more malignant the tumour is, the more apoptosis shows. In this study, we propose a new theory that apoptosis plays a key role in the malignant progression and metastasis of cancer. The growth of tumour is the difference between tumour cell proliferation and attrition plus the hyperplastic growth of stroma. Increased and unpreventable death caused by innate or environmental factors such as ischaemia and inflammation drives the tumour cells to proliferate relentlessly, move to new lands to establish colonies. In short, increased cell death is the origin of malignancy., (© 2012 The Authors. Published by Foundation for Cellular and Molecular Medicine/Blackwell Publishing Ltd. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.)